Source: https://profiles.arizona.edu/person/benquist
Timestamp: 2019-04-19 08:32:33+00:00

Document:
On the origin and consequences of allometric scaling in biology.
Elected Chair of GRC meeting "Metabolic Basis of Ecology and Evolution"
Oliveras, I., Roman-Cuesta, R. M., Urquiaga-Flores, E., Loayza, J., Kala, J., Huaman, V., Lizarraga, N., Sans, G., Quispe, K., Lopez, E., Lopez, D., Cuba, T. I., Enquist, B. J., & Malhi, Y. (2018). Fire effects and ecological recovery pathways of tropical montane cloud forests along a time chronosequence. GLOBAL CHANGE BIOLOGY , 24(2), 758-772.
Oliveras, I., Román-Cuesta, R. M., Urquiaga-Flores, E., Quintano Loayza, J. A., Kala, J., Huamán, V., Lizárraga, N., Sans, G., Quispe, K., Lopez, E., Lopez, D., Cuba Torres, I., Enquist, B. J., & Malhi, Y. (2018). Fire effects and ecological recovery pathways of tropical montane cloud forests along a time chronosequence. Global change biology , 24(2), 758-772.
Tropical montane cloud forests (TMCFs) harbour high levels of biodiversity and large carbon stocks. Their location at high elevations make them especially sensitive to climate change, because a warming climate is enhancing upslope species migration, but human disturbance (especially fire) may in many cases be pushing the treeline downslope. TMCFs are increasingly being affected by fire, and the long-term effects of fire are still unknown. Here, we present a 28-year chronosequence to assess the effects of fire and recovery pathways of burned TMCFs, with a detailed analysis of carbon stocks, forest structure and diversity. We assessed rates of change of carbon (C) stock pools, forest structure and tree-size distribution pathways and tested several hypotheses regarding metabolic scaling theory (MST), C recovery and biodiversity. We found four different C stock recovery pathways depending on the selected C pool and time since last fire, with a recovery of total C stocks but not of aboveground C stocks. In terms of forest structure, there was an increase in the number of small stems in the burned forests up to 5-9 years after fire because of regeneration patterns, but no differences on larger trees between burned and unburned plots in the long term. In support of MST, after fire, forest structure appears to approximate steady-state size distribution in less than 30 years. However, our results also provide new evidence that the species recovery of TMCF after fire is idiosyncratic and follows multiple pathways. While fire increased species richness, it also enhanced species dissimilarity with geographical distance. This is the first study to report a long-term chronosequence of recovery pathways to fire suggesting faster recovery rates than previously reported, but at the expense of biodiversity and aboveground C stocks.
Saleska, S. R., Enquist, B. J., Boyle, B., Meir, P., da Costa, A. C., Ferreira, L. V., de Camargo, P. B., Simova, I., Violle, C., Van Haren, J. L., Smith, M. N., McMahon, S. M., & Taylor, T. C. (2018). Isoprene emission structures tropical tree biogeography and community assembly responses to climate. New Phytologist .
Vasseur, F., Exposito-Alonso, M., Ayala-Garay, O. J., Wang, G., Enquist, B. J., Vile, D., Violle, C., & Weigel, D. (2018). Adaptive diversification of growth allometry in the plant. Proceedings of the National Academy of Sciences of the United States of America .
Seed plants vary tremendously in size and morphology; however, variation and covariation in plant traits may be governed, at least in part, by universal biophysical laws and biological constants. Metabolic scaling theory (MST) posits that whole-organismal metabolism and growth rate are under stabilizing selection that minimizes the scaling of hydrodynamic resistance and maximizes the scaling of resource uptake. This constrains variation in physiological traits and in the rate of biomass accumulation, so that they can be expressed as mathematical functions of plant size with near-constant allometric scaling exponents across species. However, the observed variation in scaling exponents calls into question the evolutionary drivers and the universality of allometric equations. We have measured growth scaling and fitness traits of 451accessions with sequenced genomes. Variation among accessions around the scaling exponent predicted by MST was correlated with relative growth rate, seed production, and stress resistance. Genomic analyses indicate that growth allometry is affected by many genes associated with local climate and abiotic stress response. The gene with the strongest effect,, has molecular signatures of balancing selection, suggesting that intraspecific variation in growth scaling is maintained by opposing selection on the trade-off between seed production and abiotic stress resistance. Our findings suggest that variation in allometry contributes to local adaptation to contrasting environments. Our results help reconcile past debates on the origin of allometric scaling in biology and begin to link adaptive variation in allometric scaling to specific genes.
Asner, G. P., Martin, R. E., Anderson, C. B., Kryston, K., Vaughn, N., Knapp, D. E., Bentley, L. P., Shenkin, A., Salinas, N., Sinca, F., Tupayachi, R., Huaypar, K. Q., Pillco, M. M., Alvarez, F., Diaz, S., Enquist, B. J., & Malhi, Y. (2017). Scale dependence of canopy trait distributions along a tropical forest elevation gradient. NEW PHYTOLOGIST , 214(3), 973-988.
Blonder, B., Moulton, D. E., Blois, J., Enquist, B. J., Graae, B. J., Macias-Fauria, M., McGill, B., Nogue, S., Ordonez, A., Sandel, B., & Svenning, J. (2017). Predictability in community dynamics. ECOLOGY LETTERS , 20(3), 293-306.
Blonder, B., Moulton, D. E., Blois, J., Enquist, B. J., Graae, B. J., Macias-Fauria, M., McGill, B., Nogué, S., Ordonez, A., Sandel, B., & Svenning, J. C. (2017). Predictability in community dynamics. Ecology letters , 20(3), 293-306.
The coupling between community composition and climate change spans a gradient from no lags to strong lags. The no-lag hypothesis is the foundation of many ecophysiological models, correlative species distribution modelling and climate reconstruction approaches. Simple lag hypotheses have become prominent in disequilibrium ecology, proposing that communities track climate change following a fixed function or with a time delay. However, more complex dynamics are possible and may lead to memory effects and alternate unstable states. We develop graphical and analytic methods for assessing these scenarios and show that these dynamics can appear in even simple models. The overall implications are that (1) complex community dynamics may be common and (2) detailed knowledge of past climate change and community states will often be necessary yet sometimes insufficient to make predictions of a community's future state.
Blonder, B., Salinas, N., Patrick Bentley, L., Shenkin, A., Chambi Porroa, P. O., Valdez Tejeira, Y., Violle, C., Fyllas, N. M., Goldsmith, G. R., Martin, R., Asner, G. P., Díaz, S., Enquist, B. J., & Malhi, Y. (2017). Predicting trait-environment relationships for venation networks along an Andes-Amazon elevation gradient. Ecology .
Understanding functional trait-environment relationships (TERs) may improve predictions of community assembly. However, many empirical TERs have been weak or lacking conceptual foundation. TERs based on leaf venation networks may better link individuals and communities via hydraulic constraints. We report measurements of vein density, vein radius, and leaf thickness for more than 100 dominant species occurring in ten forest communities spanning a 3300 m Andes-Amazon elevation gradient in Peru. We use these data to measure the strength of TERs at community scale and to determine whether observed TERs are similar to those predicted by physiological theory. We found strong support for TERs between all traits and temperature, as well weaker support for a predicted TER between maximum abundance-weighted leaf transpiration rate and maximum potential evapotranspiration. These results provide one approach for developing a more mechanistic trait-based community assembly theory. This article is protected by copyright. All rights reserved.
Brummer, A. B., Savage, V. M., & Enquist, B. J. (2017). A general model for metabolic scaling in self-similar asymmetric networks. PLOS COMPUTATIONAL BIOLOGY , 13(3).
Brummer, A. B., Savage, V. M., & Enquist, B. J. (2017). A general model for metabolic scaling in self-similar asymmetric networks. PLoS computational biology , 13(3), e1005394.
How a particular attribute of an organism changes or scales with its body size is known as an allometry. Biological allometries, such as metabolic scaling, have been hypothesized to result from selection to maximize how vascular networks fill space yet minimize internal transport distances and resistances. The West, Brown, Enquist (WBE) model argues that these two principles (space-filling and energy minimization) are (i) general principles underlying the evolution of the diversity of biological networks across plants and animals and (ii) can be used to predict how the resulting geometry of biological networks then governs their allometric scaling. Perhaps the most central biological allometry is how metabolic rate scales with body size. A core assumption of the WBE model is that networks are symmetric with respect to their geometric properties. That is, any two given branches within the same generation in the network are assumed to have identical lengths and radii. However, biological networks are rarely if ever symmetric. An open question is: Does incorporating asymmetric branching change or influence the predictions of the WBE model? We derive a general network model that relaxes the symmetric assumption and define two classes of asymmetrically bifurcating networks. We show that asymmetric branching can be incorporated into the WBE model. This asymmetric version of the WBE model results in several theoretical predictions for the structure, physiology, and metabolism of organisms, specifically in the case for the cardiovascular system. We show how network asymmetry can now be incorporated in the many allometric scaling relationships via total network volume. Most importantly, we show that the 3/4 metabolic scaling exponent from Kleiber's Law can still be attained within many asymmetric networks.
Chavana-Bryant, C., Malhi, Y., Wu, J., Asner, G. P., Anastasiou, A., Enquist, B. J., Cosio, C., Doughty, C. E., Saleska, S. R., Martin, R. E., & Gerard, F. F. (2017). Leaf aging of Amazonian canopy trees as revealed by spectral and physiochemical measurements. NEW PHYTOLOGIST , 214(3), 1049-1063.
Csergő, A. M., Salguero-Gómez, R., Broennimann, O., Coutts, S. R., Guisan, A., Angert, A. L., Welk, E., Stott, I., Enquist, B. J., McGill, B., Svenning, J. C., Violle, C., & Buckley, Y. M. (2017). Less favourable climates constrain demographic strategies in plants. Ecology letters , 20(8), 969-980.
Correlative species distribution models are based on the observed relationship between species' occurrence and macroclimate or other environmental variables. In climates predicted less favourable populations are expected to decline, and in favourable climates they are expected to persist. However, little comparative empirical support exists for a relationship between predicted climate suitability and population performance. We found that the performance of 93 populations of 34 plant species worldwide - as measured by in situ population growth rate, its temporal variation and extinction risk - was not correlated with climate suitability. However, correlations of demographic processes underpinning population performance with climate suitability indicated both resistance and vulnerability pathways of population responses to climate: in less suitable climates, plants experienced greater retrogression (resistance pathway) and greater variability in some demographic rates (vulnerability pathway). While a range of demographic strategies occur within species' climatic niches, demographic strategies are more constrained in climates predicted to be less suitable.
Fyllas, N. M., Bentley, L. P., Shenkin, A., Asner, G. P., Atkin, O. K., Díaz, S., Enquist, B. J., Farfan-Rios, W., Gloor, E., Guerrieri, R., Huasco, W. H., Ishida, Y., Martin, R. E., Meir, P., Phillips, O., Salinas, N., Silman, M., Weerasinghe, L. K., Zaragoza-Castells, J., & Malhi, Y. (2017). Solar radiation and functional traits explain the decline of forest primary productivity along a tropical elevation gradient. Ecology letters , 20(6), 730-740.
One of the major challenges in ecology is to understand how ecosystems respond to changes in environmental conditions, and how taxonomic and functional diversity mediate these changes. In this study, we use a trait-spectra and individual-based model, to analyse variation in forest primary productivity along a 3.3 km elevation gradient in the Amazon-Andes. The model accurately predicted the magnitude and trends in forest productivity with elevation, with solar radiation and plant functional traits (leaf dry mass per area, leaf nitrogen and phosphorus concentration, and wood density) collectively accounting for productivity variation. Remarkably, explicit representation of temperature variation with elevation was not required to achieve accurate predictions of forest productivity, as trait variation driven by species turnover appears to capture the effect of temperature. Our semi-mechanistic model suggests that spatial variation in traits can potentially be used to estimate spatial variation in productivity at the landscape scale.
Gallet, R., Violle, C., Fromin, N., Jabbour-Zahab, R., Enquist, B. J., & Lenormand, T. (2017). The evolution of bacterial cell size: the internal diffusion-constraint hypothesis. The ISME journal .
Size is one of the most important biological traits influencing organismal ecology and evolution. However, we know little about the drivers of body size evolution in unicellulars. A long-term evolution experiment (Lenski's LTEE) in which Escherichia coli adapts to a simple glucose medium has shown that not only the growth rate and the fitness of the bacterium increase over time but also its cell size. This increase in size contradicts prominent 'external diffusion' theory (EDC) predicting that cell size should have evolved toward smaller cells. Among several scenarios, we propose and test an alternative 'internal diffusion-constraint' (IDC) hypothesis for cell size evolution. A change in cell volume affects metabolite concentrations in the cytoplasm. The IDC states that a higher metabolism can be achieved by a reduction in the molecular traffic time inside of the cell, by increasing its volume. To test this hypothesis, we studied a population from the LTEE. We show that bigger cells with greater growth and CO2 production rates and lower mass-to-volume ratio were selected over time in the LTEE. These results are consistent with the IDC hypothesis. This novel hypothesis offers a promising approach for understanding the evolutionary constraints on cell size.The ISME Journal advance online publication, 4 April 2017; doi:10.1038/ismej.2017.35.
Garnier, E., Stahl, U., Laporte, M., Kattge, J., Mougenot, I., Kuehn, I., Laporte, B., Amiaud, B., Ahrestani, F. S., Boenisch, G., Bunker, D. E., Cornelissen, J., Diaz, S., Enquist, B. J., Gachet, S., Jaureguiberry, P., Kleyer, M., Lavorel, S., Maicher, L., , Perez-Harguindeguy, N., et al. (2017). Towards a thesaurus of plant characteristics: an ecological contribution. JOURNAL OF ECOLOGY , 105(2), 298-309.
Goldsmith, G. R., Bentley, L. P., Shenkin, A., Salinas, N., Blonder, B., Martin, R. E., Castro-Ccossco, R., Chambi-Porroa, P., Diaz, S., Enquist, B. J., Asner, G. P., & Malhi, Y. (2017). Variation in leaf wettability traits along a tropical montane elevation gradient. NEW PHYTOLOGIST , 214(3), 989-1001.
Kaspari, M., Bujan, J., Weiser, M. D., Ning, D., Michaletz, S. T., Zhili, H., Enquist, B. J., Waide, R. B., Zhou, J., Turner, B. L., & Wright, S. J. (2017). Biogeochemistry drives diversity in the prokaryotes, fungi, and invertebrates of a Panama forest. Ecology , 98(8), 2019-2028.
Humans are both fertilizing the world and depleting its soils, decreasing the diversity of aquatic ecosystems and terrestrial plants in the process. We know less about how nutrients shape the abundance and diversity of the prokaryotes, fungi, and invertebrates of Earth's soils. Here we explore this question in the soils of a Panama forest subject to a 13-yr fertilization with factorial combinations of nitrogen (N), phosphorus (P), and potassium (K) and a separate micronutrient cocktail. We contrast three hypotheses linking biogeochemistry to abundance and diversity. Consistent with the Stress Hypothesis, adding N suppressed the abundance of invertebrates and the richness of all three groups of organisms by ca. 1 SD or more below controls. Nitrogen addition plots were 0.8 pH units more acidic with 18% more exchangeable aluminum, which is toxic to both prokaryotes and eukaryotes. These stress effects were frequently reversed, however, when N was added with P (for prokaryotes and invertebrates) and with added K (for fungi). Consistent with the Abundance Hypothesis, adding P generally increased prokaryote and invertebrate diversity, and adding K enhanced invertebrate diversity. Also consistent with the Abundance Hypothesis, increases in invertebrate abundance generated increases in richness. We found little evidence for the Competition Hypothesis: that single nutrients suppressed diversity by favoring a subset of high nutrient specialists, and that nutrient combinations suppressed diversity even more. Instead, combinations of nutrients, and especially the cation/micronutrient treatment, yielded the largest increases in richness in the two eukaryote groups. In sum, changes in soil biogeochemistry revealed a diversity of responses among the three dominant soil groups, positive synergies among nutrients, and-in contrast with terrestrial plants-the frequent enhancement of soil biodiversity.
Messier, J., Lechowicz, M. J., McGill, B. J., Violle, C., & Enquist, B. J. (2017). Interspecific integration of trait dimensions at local scales: the plant phenotype as an integrated network. JOURNAL OF ECOLOGY , 105(6), 1775-1790.
Messier, J., McGill, B. J., Enquist, B. J., & Lechowicz, M. J. (2017). Trait variation and integration across scales: is the leaf economic spectrum present at local scales?. ECOGRAPHY , 40(6), 685-697.
Zhou, J., Deng, Y., Shen, L., Wen, C., Yan, Q., Ning, D., Qin, Y., Xue, K., Wu, L., He, Z., Voordeckers, J. W., Van Nostrand, J. D., Buzzard, V., Michaletz, S. T., Enquist, B. J., Weiser, M. D., Kaspari, M., Waide, R., Yang, Y., & Brown, J. H. (2017). Correspondence: Reply to 'Analytical flaws in a continental-scale forest soil microbial diversity study'. Nature communications , 8, 15583.
Asner, G. P., Martin, R. E., Anderson, C. B., Kryston, K., Vaughn, N., Knapp, D. E., Bentley, L. P., Shenkin, A., Salinas, N., Sinca, F., Tupayachi, R., Quispe Huaypar, K., Montoya Pillco, M., Ccori Álvarez, F. D., Díaz, S., Enquist, B., & Malhi, Y. (2016). Scale dependence of canopy trait distributions along a tropical forest elevation gradient. The New phytologist .
Average responses of forest foliar traits to elevation are well understood, but far less is known about trait distributional responses to elevation at multiple ecological scales. This limits our understanding of the ecological scales at which trait variation occurs in response to environmental drivers and change. We analyzed and compared multiple canopy foliar trait distributions using field sampling and airborne imaging spectroscopy along an Andes-to-Amazon elevation gradient. Field-estimated traits were generated from three community-weighting methods, and remotely sensed estimates of traits were made at three scales defined by sampling grain size and ecological extent. Field and remote sensing approaches revealed increases in average leaf mass per unit area (LMA), water, nonstructural carbohydrates (NSCs) and polyphenols with increasing elevation. Foliar nutrients and photosynthetic pigments displayed little to no elevation trend. Sample weighting approaches had little impact on field-estimated trait responses to elevation. Plot representativeness of trait distributions at landscape scales decreased with increasing elevation. Remote sensing indicated elevation-dependent increases in trait variance and distributional skew. Multiscale invariance of LMA, leaf water and NSC mark these traits as candidates for tracking forest responses to changing climate. Trait-based ecological studies can be greatly enhanced with multiscale studies made possible by imaging spectroscopy.
Blonder, B., Baldwin, B. G., Enquist, B. J., & Robichaux, R. H. (2016). Variation and macroevolution in leaf functional traits in the Hawaiian silversword alliance (Asteraceae). JOURNAL OF ECOLOGY , 104(1), 219-228.
Buzzard, V., Hulshof, C. M., Birt, T., Violle, C., & Enquist, B. J. (2016). Re-growing a tropical dry forest: functional plant trait composition and community assembly during succession. FUNCTIONAL ECOLOGY , 30(6), 1006-1013.
Carey, J. C., Tang, J., Templer, P. H., Kroeger, K. D., Crowther, T. W., Burton, A. J., Dukes, J. S., Emmett, B., Frey, S. D., Heskel, M. A., Jiang, L., Machmuller, M. B., Mohan, J., Panetta, A. M., Reich, P. B., Reinsch, S., Wang, X., Allison, S. D., Bamminger, C., , Bridgham, S., et al. (2016). Temperature response of soil respiration largely unaltered with experimental warming. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA , 113(48), 13797-13802.
The respiratory release of carbon dioxide (CO2) from soil is a major yet poorly understood flux in the global carbon cycle. Climatic warming is hypothesized to increase rates of soil respiration, potentially fueling further increases in global temperatures. However, despite considerable scientific attention in recent decades, the overall response of soil respiration to anticipated climatic warming remains unclear. We synthesize the largest global dataset to date of soil respiration, moisture, and temperature measurements, totaling >3,800 observations representing 27 temperature manipulation studies, spanning nine biomes and over 2 decades of warming. Our analysis reveals no significant differences in the temperature sensitivity of soil respiration between control and warmed plots in all biomes, with the exception of deserts and boreal forests. Thus, our data provide limited evidence of acclimation of soil respiration to experimental warming in several major biome types, contrary to the results from multiple single-site studies. Moreover, across all nondesert biomes, respiration rates with and without experimental warming follow a Gaussian response, increasing with soil temperature up to a threshold of ∼25 °C, above which respiration rates decrease with further increases in temperature. This consistent decrease in temperature sensitivity at higher temperatures demonstrates that rising global temperatures may result in regionally variable responses in soil respiration, with colder climates being considerably more responsive to increased ambient temperatures compared with warmer regions. Our analysis adds a unique cross-biome perspective on the temperature response of soil respiration, information critical to improving our mechanistic understanding of how soil carbon dynamics change with climatic warming.
Charney, N. D., Babst, F., Poulter, B., Record, S., Trouet, V. M., Frank, D., Enquist, B. J., & Evans, M. (2016). Observed forest sensitivity to climate implies large changes in 21st century North American forest growth. ECOLOGY LETTERS , 19(9), 1119-1128.
Charney, N. D., Babst, F., Poulter, B., Record, S., Trouet, V. M., Frank, D., Enquist, B. J., & Evans, M. E. (2016). Observed forest sensitivity to climate implies large changes in 21st century North American forest growth. Ecology letters , 19(9), 1119-28.
Predicting long-term trends in forest growth requires accurate characterisation of how the relationship between forest productivity and climatic stress varies across climatic regimes. Using a network of over two million tree-ring observations spanning North America and a space-for-time substitution methodology, we forecast climate impacts on future forest growth. We explored differing scenarios of increased water-use efficiency (WUE) due to CO2 -fertilisation, which we simulated as increased effective precipitation. In our forecasts: (1) climate change negatively impacted forest growth rates in the interior west and positively impacted forest growth along the western, southeastern and northeastern coasts; (2) shifting climate sensitivities offset positive effects of warming on high-latitude forests, leaving no evidence for continued 'boreal greening'; and (3) it took a 72% WUE enhancement to compensate for continentally averaged growth declines under RCP 8.5. Our results highlight the importance of locally adapted forest management strategies to handle regional differences in growth responses to climate change.
Charney, N., Babst, F., Poulter, B., Record, S., Trouet, V. M., Frank, D. C., Enquist, B. J., & Evans, M. E. (2016). Observed forest sensitivity to climate implies larger reductions in 21st century forest growth. Ecology Letters .
Charney, N., Babst, F., Poulter, B., Record, S., Trouet, V. M., Frank, D., Enquist, B. J., & Evans, M. E. (2015). Observed forest sensitivity to climate implies larger reductions in 21st century forest growth. Ecology Letters .
Chavana-Bryant, C., Malhi, Y., Wu, J., Asner, G. P., Anastasiou, A., Enquist, B. J., Cosio Caravasi, E. G., Doughty, C. E., Saleska, S. R., Martin, R. E., & Gerard, F. F. (2016). Leaf aging of Amazonian canopy trees as revealed by spectral and physiochemical measurements. The New phytologist .
Leaf aging is a fundamental driver of changes in leaf traits, thereby regulating ecosystem processes and remotely sensed canopy dynamics. We explore leaf reflectance as a tool to monitor leaf age and develop a spectra-based partial least squares regression (PLSR) model to predict age using data from a phenological study of 1099 leaves from 12 lowland Amazonian canopy trees in southern Peru. Results demonstrated monotonic decreases in leaf water (LWC) and phosphorus (Pmass ) contents and an increase in leaf mass per unit area (LMA) with age across trees; leaf nitrogen (Nmass ) and carbon (Cmass ) contents showed monotonic but tree-specific age responses. We observed large age-related variation in leaf spectra across trees. A spectra-based model was more accurate in predicting leaf age (R(2) = 0.86; percent root mean square error (%RMSE) = 33) compared with trait-based models using single (R(2) = 0.07-0.73; %RMSE = 7-38) and multiple (R(2) = 0.76; %RMSE = 28) predictors. Spectra- and trait-based models established a physiochemical basis for the spectral age model. Vegetation indices (VIs) including the normalized difference vegetation index (NDVI), enhanced vegetation index 2 (EVI2), normalized difference water index (NDWI) and photosynthetic reflectance index (PRI) were all age-dependent. This study highlights the importance of leaf age as a mediator of leaf traits, provides evidence of age-related leaf reflectance changes that have important impacts on VIs used to monitor canopy dynamics and productivity and proposes a new approach to predicting and monitoring leaf age with important implications for remote sensing.
Doughty, C. E., Wolf, A., Morueta-Holme, N., Jorgensen, P. M., Sandel, B., Violle, C., Boyle, B., Kraft, N., Peet, R. K., Enquist, B. J., Svenning, J., Blake, S., & Galetti, M. (2016). Megafauna extinction, tree species range reduction, and carbon storage in Amazonian forests. ECOGRAPHY , 39(2), 194-203.
Engemann, K., Sandel, B., Boyle, B., Enquist, B. J., Jørgensen, P. M., Kattge, J., McGill, B. J., Morueta-Holme, N., Peet, R. K., Spencer, N. J., Violle, C., Wiser, S. K., & Svenning, J. C. (2016). A plant growth form dataset for the New World. Ecology , 97(11), 3243.
This dataset provides growth form classifications for 67,413 vascular plant species from North, Central, and South America. The data used to determine growth form were compiled from five major integrated sources and two original publications: the Botanical Information and Ecology Network (BIEN), the Plant Trait Database (TRY), the SALVIAS database, the USDA PLANTS database, Missouri Botanical Garden's Tropicos database, Wright (2010), and Boyle (1996). We defined nine plant growth forms based on woodiness (woody or non-woody), shoot structure (self-supporting or not self-supporting), and root traits (rooted in soil, not rooted in soil, parasitic or aquatic): Epiphyte, Liana, Vine, Herb, Shrub, Tree, Parasite, or Aquatic. Species with multiple growth form classifications were assigned the growth form classification agreed upon by the majority (>2/3) of sources. Species with ambiguous or otherwise not interpretable growth form assignments were excluded from the final dataset but are made available with the original data. Comparisons with independent estimates of species richness for the Western hemisphere suggest that our final dataset includes the majority of New World vascular plant species. Coverage is likely more complete for temperate than for tropical species. In addition, aquatic species are likely under-represented. Nonetheless, this dataset represents the largest compilation of plant growth forms published to date, and should contribute to new insights across a broad range of research in systematics, ecology, biogeography, conservation, and global change science.
Engemann, K., Sandel, B., Enquist, B. J., Jorgensen, P. M., Kraft, N., Marcuse-Kubitza, A., McGill, B., Morueta-Holme, N., Peet, R. K., Violle, C., Wiser, S., & Svenning, J. (2016). Patterns and drivers of plant functional group dominance across the Western Hemisphere: a macroecological re-assessment based on a massive botanical dataset. BOTANICAL JOURNAL OF THE LINNEAN SOCIETY , 180(2), 141-160.
Evans, M., Merow, C., Record, S., McMahon, S. M., & Enquist, B. J. (2016). Towards Process-based Range Modeling of Many Species. TRENDS IN ECOLOGY & EVOLUTION , 31(11), 860-871.
Feakins, S. J., Bentley, L. P., Salinas, N., Shenkin, A., Blonder, B., Goldsmith, G. R., Ponton, C., Arvin, L. J., Wu, M. S., Peters, T., West, A. J., Martin, R. E., Enquist, B. J., Asner, G. P., & Malhi, Y. (2016). Plant leaf wax biomarkers capture gradients in hydrogen isotopes of precipitation from the Andes and Amazon. GEOCHIMICA ET COSMOCHIMICA ACTA , 182, 155-172.
Feakins, S. J., Peters, T., Wu, M. S., Shenkin, A., Salinas, N., Girardin, C., Bentley, L. P., Blonder, B., Enquist, B. J., Martin, R. E., Asner, G. P., & Malhi, Y. (2016). Production of leaf wax n-alkanes across a tropical forest elevation transect. ORGANIC GEOCHEMISTRY , 100, 89-100.
Goldsmith, G. R., Bentley, L. P., Shenkin, A., Salinas, N., Blonder, B., Martin, R. E., Castro-Ccossco, R., Chambi-Porroa, P., Diaz, S., Enquist, B. J., Asner, G. P., & Malhi, Y. (2016). Variation in leaf wettability traits along a tropical montane elevation gradient. The New phytologist .
Leaf wetting is often considered to have negative effects on plant function, such that wet environments may select for leaves with certain leaf surface, morphological, and architectural traits that reduce leaf wettability. However, there is growing recognition that leaf wetting can have positive effects. We measured variation in two traits, leaf drip tips and leaf water repellency, in a series of nine tropical forest communities occurring along a 3300-m elevation gradient in southern Peru. To extend this climatic gradient, we also assembled published leaf water repellency values from 17 additional sites. We then tested hypotheses for how these traits should vary as a function of climate. Contrary to expectations, we found that the proportion of species with drip tips did not increase with increasing precipitation. Instead, drip tips increased with increasing temperature. Moreover, leaf water repellency was very low in our sites and the global analysis indicated high repellency only in sites with low precipitation and temperatures. Our findings suggest that drip tips and repellency may not solely reflect the negative effects of wetting on plant function. Understanding the drivers of leaf wettability traits can provide insight into the effects of leaf wetting on plant, community, and ecosystem function.
Michaletz, S. T., Cheng, D., Kerkhoff, A. J., & Enquist, B. J. (2016). Corrigendum: Convergence of terrestrial plant production across global climate gradients. Nature , 537(7620), 432.
Michaletz, S. T., Weiser, M. D., McDowell, N. G., Zhou, J., Kaspari, M., Helliker, B. R., & Enquist, B. J. (2016). Corrigendum: The energetic and carbon economic origins of leaf thermoregulation. Nature plants , 2, 16147.
Michaletz, S. T., Weiser, M. D., McDowell, N. G., Zhou, J., Kaspari, M., Helliker, B. R., & Enquist, B. J. (2016). The energetic and carbon economic origins of leaf thermoregulation. NATURE PLANTS , 2(9).
Michaletz, S. T., Weiser, M. D., McDowell, N. G., Zhou, J., Kaspari, M., Helliker, B. R., & Enquist, B. J. (2016). The energetic and carbon economic origins of leaf thermoregulation. Nature plants , 2, 16129.
Leaf thermoregulation has been documented in a handful of studies, but the generality and origins of this pattern are unclear. We suggest that leaf thermoregulation is widespread in both space and time, and originates from the optimization of leaf traits to maximize leaf carbon gain across and within variable environments. Here we use global data for leaf temperatures, traits and photosynthesis to evaluate predictions from a novel theory of thermoregulation that synthesizes energy budget and carbon economics theories. Our results reveal that variation in leaf temperatures and physiological performance are tightly linked to leaf traits and carbon economics. The theory, parameterized with global averaged leaf traits and microclimate, predicts a moderate level of leaf thermoregulation across a broad air temperature gradient. These predictions are supported by independent data for diverse taxa spanning a global air temperature range of ∼60 °C. Moreover, our theory predicts that net carbon assimilation can be maximized by means of a trade-off between leaf thermal stability and photosynthetic stability. This prediction is supported by globally distributed data for leaf thermal and photosynthetic traits. Our results demonstrate that the temperatures of plant tissues, and not just air, are vital to developing more accurate Earth system models.
Morueta-Holme, N., Blonder, B., Sandel, B., McGill, B. J., Peet, R. K., Ott, J. E., Violle, C., Enquist, B. J., Jorgensen, P. M., & Svenning, J. (2016). A network approach for inferring species associations from co-occurrence data. ECOGRAPHY , 39(12), 1139-1150.
Neyret, M., Bentley, L. P., Oliveras, I., Marimon, B. S., Marimon-Junior, B. H., Almeida de Oliveira, E., Barbosa Passos, F., Castro Ccoscco, R., Dos Santos, J., Matias Reis, S., Morandi, P. S., Rayme Paucar, G., Robles Cáceres, A., Valdez Tejeira, Y., Yllanes Choque, Y., Salinas, N., Shenkin, A., Asner, G. P., Díaz, S., , Enquist, B. J., et al. (2016). Examining variation in the leaf mass per area of dominant species across two contrasting tropical gradients in light of community assembly. Ecology and evolution , 6(16), 5674-89.
Understanding variation in key functional traits across gradients in high diversity systems and the ecology of community changes along gradients in these systems is crucial in light of conservation and climate change. We examined inter- and intraspecific variation in leaf mass per area (LMA) of sun and shade leaves along a 3330-m elevation gradient in Peru, and in sun leaves across a forest-savanna vegetation gradient in Brazil. We also compared LMA variance ratios (T-statistics metrics) to null models to explore internal (i.e., abiotic) and environmental filtering on community structure along the gradients. Community-weighted LMA increased with decreasing forest cover in Brazil, likely due to increased light availability and water stress, and increased with elevation in Peru, consistent with the leaf economic spectrum strategy expected in colder, less productive environments. A very high species turnover was observed along both environmental gradients, and consequently, the first source of variation in LMA was species turnover. Variation in LMA at the genus or family levels was greater in Peru than in Brazil. Using dominant trees to examine possible filters on community assembly, we found that in Brazil, internal filtering was strongest in the forest, while environmental filtering was observed in the dry savanna. In Peru, internal filtering was observed along 80% of the gradient, perhaps due to variation in taxa or interspecific competition. Environmental filtering was observed at cloud zone edges and in lowlands, possibly due to water and nutrient availability, respectively. These results related to variation in LMA indicate that biodiversity in species rich tropical assemblages may be structured by differential niche-based processes. In the future, specific mechanisms generating these patterns of variation in leaf functional traits across tropical environmental gradients should be explored.
Neyret, M., Bentley, L. P., Oliveras, I., Marimon, B. S., Marimon-Junior, B. H., de, O., Passos, F. B., Castro, C. R., dos, S. J., Reis, S. M., Morandi, P. S., Rayme, P. G., Robles, C. A., Valdez, T. Y., Yllanes, C. Y., Salinas, N., Shenkin, A., Asner, G. P., Diaz, S., , Enquist, B. J., et al. (2016). Examining variation in the leaf mass per area of dominant species across two contrasting tropical gradients in light of community assembly. ECOLOGY AND EVOLUTION , 6(16), 5674-5689.
Tu, Q., Deng, Y. e., Yan, Q., Shen, L., Lin, L. u., He, Z., Wu, L., Van, N., Buzzard, V., Michaletz, S. T., Enquist, B. J., Weiser, M. D., Kaspari, M., Waide, R. B., Brown, J. H., & Zhou, J. (2016). Biogeographic patterns of soil diazotrophic communities across six forests in the North America. MOLECULAR ECOLOGY , 25(12), 2937-2948.
Tu, Q., Deng, Y., Yan, Q., Shen, L., Lin, L., He, Z., Wu, L., Van Nostrand, J. D., Buzzard, V., Michaletz, S. T., Enquist, B. J., Weiser, M. D., Kaspari, M., Waide, R. B., Brown, J. H., & Zhou, J. (2016). Biogeographic patterns of soil diazotrophic communities across six forests in the North America. Molecular ecology , 25(12), 2937-48.
Zhou, J., Deng, Y. e., Shen, L., Wen, C., Yan, Q., Ning, D., Qin, Y., Xue, K., Wu, L., He, Z., Voordeckers, J. W., Van, N., Buzzard, V., Michaletz, S. T., Enquist, B. J., Weiser, M. D., Kaspari, M., Waide, R., Yang, Y., & Brown, J. H. (2016). Temperature mediates continental-scale diversity of microbes in forest soils. NATURE COMMUNICATIONS , 7.
Zhou, J., Deng, Y., Shen, L., Wen, C., Yan, Q., Ning, D., Qin, Y., Xue, K., Wu, L., He, Z., Voordeckers, J. W., Nostrand, J. D., Buzzard, V., Michaletz, S. T., Enquist, B. J., Weiser, M. D., Kaspari, M., Waide, R., Yang, Y., & Brown, J. H. (2016). Temperature mediates continental-scale diversity of microbes in forest soils. Nature communications , 7, 12083.
Climate warming is increasingly leading to marked changes in plant and animal biodiversity, but it remains unclear how temperatures affect microbial biodiversity, particularly in terrestrial soils. Here we show that, in accordance with metabolic theory of ecology, taxonomic and phylogenetic diversity of soil bacteria, fungi and nitrogen fixers are all better predicted by variation in environmental temperature than pH. However, the rates of diversity turnover across the global temperature gradients are substantially lower than those recorded for trees and animals, suggesting that the diversity of plant, animal and soil microbial communities show differential responses to climate change. To the best of our knowledge, this is the first study demonstrating that the diversity of different microbial groups has significantly lower rates of turnover across temperature gradients than other major taxa, which has important implications for assessing the effects of human-caused changes in climate, land use and other factors.
, B. J., , J. N., , S. P., , C. V., , C. T., , A. H., , L. L., & , V. M. (2015). Scaling from traits to ecosystems: Developing a general Trait Driver Theory via integrating trait-based and metabolic scaling theories. , Advances in Ecological Research, .
Blonder, B., Nogues-Bravo, D., Borregaard, M. K., Donoghue, J., Jorgensen, P. M., Kraft, N., Lessard, J., Morueta-Holme, N., Sandel, B., Svenning, J., Violle, C., Rahbek, C., & Enquist, B. J. (2015). Linking environmental filtering and disequilibrium to biogeography with a community climate framework. ECOLOGY , 96(4), 972-985.
Blonder, B., Nogués-Bravo, D., Borregaard, M. K., Donoghue, J. C., Jørgensen, P. M., Kraft, N. J., Lessard, J., Morueta-Holme, N., Sandel, B., Svenning, J., Violle, C., Rahbek, C., & Enquist, B. J. (2015). Linking environmental filtering and disequilibrium to biogeography with a community climate framework. Ecology , 96(4), 972-85.
We present a framework to measure the strength of environmental filtering and disequilibrium of the species composition of a local community across time, relative to past, current, and future climates. We demonstrate the framework by measuring the impact of climate change on New World forests, integrating data for climate niches of more than 14000 species, community composition of 471 New World forest plots, and observed climate across the most recent glacial-interglacial interval. We show that a majority of communities have species compositions that are strongly filtered and are more in equilibrium with current climate than random samples from the regional pool. Variation in the level of current community disequilibrium can be predicted from Last Glacial Maximum climate and will increase with near-future climate change.
Blonder, B., Vasseur, F., Violle, C., Shipley, B., Enquist, B. J., & Vile, D. (2015). Testing models for the leaf economics spectrum with leaf and whole-plant traits in Arabidopsis thaliana. AOB PLANTS , 7.
Duncanson, L. I., Dubayah, R. O., & Enquist, B. J. (2015). Assessing the general patterns of forest structure: quantifying tree and forest allometric scaling relationships in the United States. GLOBAL ECOLOGY AND BIOGEOGRAPHY , 24(12), 1465-1475.
Engemann, K., Enquist, B. J., Sandel, B., Boyle, B., Jorgensen, P. M., Morueta-Holme, N., Peet, R. K., Violle, C., & Svenning, J. (2015). Limited sampling hampers "big data" estimation of species richness in a tropical biodiversity hotspot. ECOLOGY AND EVOLUTION , 5(3), 807-820.
Engemann, K., Enquist, B. J., Sandel, B., Boyle, B., Jørgensen, P. M., Morueta-Holme, N., Peet, R. K., Violle, C., & Svenning, J. (2015). Limited sampling hampers "big data" estimation of species richness in a tropical biodiversity hotspot. Ecology and evolution , 5(3), 807-20.
Macro-scale species richness studies often use museum specimens as their main source of information. However, such datasets are often strongly biased due to variation in sampling effort in space and time. These biases may strongly affect diversity estimates and may, thereby, obstruct solid inference on the underlying diversity drivers, as well as mislead conservation prioritization. In recent years, this has resulted in an increased focus on developing methods to correct for sampling bias. In this study, we use sample-size-correcting methods to examine patterns of tropical plant diversity in Ecuador, one of the most species-rich and climatically heterogeneous biodiversity hotspots. Species richness estimates were calculated based on 205,735 georeferenced specimens of 15,788 species using the Margalef diversity index, the Chao estimator, the second-order Jackknife and Bootstrapping resampling methods, and Hill numbers and rarefaction. Species richness was heavily correlated with sampling effort, and only rarefaction was able to remove this effect, and we recommend this method for estimation of species richness with "big data" collections.
Grady, J. M., Enquist, B. J., Dettweiler-Robinson, E., Wright, N. A., & Smith, F. A. (2015). Response to Comments on "Evidence for mesothermy in dinosaurs". SCIENCE , 348(6238).
Grady, J. M., Enquist, B. J., Dettweiler-Robinson, E., Wright, N. A., & Smith, F. A. (2015). Response to Comments on "Evidence for mesothermy in dinosaurs". Science (New York, N.Y.) , 348(6238), 982.
D'Emic and Myhrvold raise a number of statistical and methodological issues with our recent analysis of dinosaur growth and energetics. However, their critiques and suggested improvements lack biological and statistical justification.
Michaletz, S. T., Weiser, M. D., Zhou, J., Kaspari, M., Helliker, B. R., & Enquist, B. J. (2015). Plant Thermoregulation: Energetics, Trait-Environment Interactions, and Carbon Economics. TRENDS IN ECOLOGY & EVOLUTION , 30(12), 714-724.
Michaletz, S. T., Weiser, M. D., Zhou, J., Kaspari, M., Helliker, B. R., & Enquist, B. J. (2015). Plant Thermoregulation: Energetics, Trait-Environment Interactions, and Carbon Economics. Trends in ecology & evolution , 30(12), 714-24.
Building a more predictive trait-based ecology requires mechanistic theory based on first principles. We present a general theoretical approach to link traits and climate. We use plant leaves to show how energy budgets (i) provide a foundation for understanding thermoregulation, (ii) explain mechanisms driving trait variation across environmental gradients, and (iii) guide selection on functional traits via carbon economics. Although plants are often considered to be poikilotherms, the data suggest that they are instead limited homeotherms. Leaf functional traits that promote limited homeothermy are adaptive because homeothermy maximizes instantaneous and lifetime carbon gain. This theory provides a process-based foundation for trait-climate analyses and shows that future studies should consider plant (not only air) temperatures.
Simova, I., Violle, C., Kraft, N., Storch, D., Svenning, J., Boyle, B., Donoghue, J., Jorgensen, P., McGill, B. J., Morueta-Holme, N., Piel, W. H., Peet, R. K., Regetz, J., Schildhauer, M., Spencer, N., Thiers, B., Wiser, S., & Enquist, B. J. (2015). Shifts in trait means and variances in North American tree assemblages: species richness patterns are loosely related to the functional space. ECOGRAPHY , 38(7), 649-658.
Sloat, L. L., Henderson, A. N., Lamanna, C., & Enquist, B. J. (2015). The Effect of the Foresummer Drought on Carbon Exchange in Subalpine Meadows. ECOSYSTEMS , 18(3), 533-545.
Stark, S. C., Enquist, B. J., Saleska, S. R., Leitold, V., Schietti, J., Longo, M., Alves, L. F., Camargo, P. B., & Oliveira, R. C. (2015). Linking canopy leaf area and light environments with tree size distributions to explain Amazon forest demography. ECOLOGY LETTERS , 18(7), 636-645.
Stark, S. C., Enquist, B. J., Saleska, S. R., Leitold, V., Schietti, J., Longo, M., Alves, L. F., Camargo, P. B., & Oliveira, R. C. (2015). Linking canopy leaf area and light environments with tree size distributions to explain Amazon forest demography. Ecology letters , 18(7), 636-45.
Forest biophysical structure - the arrangement and frequency of leaves and stems - emerges from growth, mortality and space filling dynamics, and may also influence those dynamics by structuring light environments. To investigate this interaction, we developed models that could use LiDAR remote sensing to link leaf area profiles with tree size distributions, comparing models which did not (metabolic scaling theory) and did allow light to influence this link. We found that a light environment-to-structure link was necessary to accurately simulate tree size distributions and canopy structure in two contrasting Amazon forests. Partitioning leaf area profiles into size-class components, we found that demographic rates were related to variation in light absorption, with mortality increasing relative to growth in higher light, consistent with a light environment feedback to size distributions. Combining LiDAR with models linking forest structure and demography offers a high-throughput approach to advance theory and investigate climate-relevant tropical forest change.
Barnagaud, J., Daniel Kissling, W., Sandel, B., Eiserhardt, W. L., Sekercioğlu, C. H., Enquist, B. J., Tsirogiannis, C., & Svenning, J. (2014). Ecological traits influence the phylogenetic structure of bird species co-occurrences worldwide. Ecology letters , 17(7), 811-20.
Barnagaud, J., Kissling, W. D., Sandel, B., Eiserhardt, W. L., Sekercioglu, C. H., Enquist, B. J., Tsirogiannis, C., & Svenning, J. (2014). Ecological traits influence the phylogenetic structure of bird species co-occurrences worldwide. ECOLOGY LETTERS , 17(7), 811-820.
Blonder, B., & Enquist, B. J. (2014). Inferring climate from angiosperm leaf venation networks. NEW PHYTOLOGIST , 204(1), 116-126.
Blonder, B., & Enquist, B. J. (2014). Inferring climate from angiosperm leaf venation networks. The New phytologist , 204(1), 116-26.
Leaf venation networks provide an integrative linkage between plant form, function and climate niche, because leaf water transport underlies variation in plant performance. Here, we develop theory based on leaf physiology that uses community-mean vein density to predict growing season temperature and atmospheric CO2 concentration. The key assumption is that leaf water supply is matched to water demand in the local environment. We test model predictions using leaves from 17 temperate and tropical sites that span broad climatic gradients. We find quantitative agreement between predicted and observed climate values. We also highlight additional leaf traits that may improve predictions. Our study provides a novel approach for understanding the functional linkages between functional traits and climate that may improve the reconstruction of paleoclimate from fossil assemblages.
Blonder, B., Lamanna, C., Violle, C., & Enquist, B. J. (2014). The n-dimensional hypervolume. GLOBAL ECOLOGY AND BIOGEOGRAPHY , 23(5), 595-609.
Abstract: Aim: The Hutchinsonian hypervolume is the conceptual foundation for many lines of ecological and evolutionary inquiry, including functional morphology, comparative biology, community ecology and niche theory. However, extant methods to sample from hypervolumes or measure their geometry perform poorly on high-dimensional or holey datasets. Innovation: We first highlight the conceptual and computational issues that have prevented a more direct approach to measuring hypervolumes. Next, we present a new multivariate kernel density estimation method that resolves many of these problems in an arbitrary number of dimensions. Main conclusions: We show that our method (implemented as the 'hypervolume' R package) can match several extant methods for hypervolume geometry and species distribution modelling. Tools to quantify high-dimensional ecological hypervolumes will enable a wide range of fundamental descriptive, inferential and comparative questions to be addressed. © 2014 John Wiley & Sons Ltd.
Blonder, B., Royer, D. L., Johnson, K. R., Miller, I., & Enquist, B. J. (2014). Plant Ecological Strategies Shift Across the Cretaceous-Paleogene Boundary. PLOS BIOLOGY , 12(9).
Blonder, B., Royer, D. L., Johnson, K. R., Miller, I., & Enquist, B. J. (2014). Plant ecological strategies shift across the Cretaceous-Paleogene boundary. PLoS biology , 12(9), e1001949.
The Chicxulub bolide impact caused the end-Cretaceous mass extinction of plants, but the associated selectivity and ecological effects are poorly known. Using a unique set of North Dakota leaf fossil assemblages spanning 2.2 Myr across the event, we show among angiosperms a reduction of ecological strategies and selection for fast-growth strategies consistent with a hypothesized recovery from an impact winter. Leaf mass per area (carbon investment) decreased in both mean and variance, while vein density (carbon assimilation rate) increased in mean, consistent with a shift towards "fast" growth strategies. Plant extinction from the bolide impact resulted in a shift in functional trait space that likely had broad consequences for ecosystem functioning.
Blonder, B., Sloat, L., Enquist, B. J., & McGill, B. (2014). Separating macroecological pattern and process: comparing ecological, economic, and geological systems. PloS one , 9(11), e112850.
Theories of biodiversity rest on several macroecological patterns describing the relationship between species abundance and diversity. A central problem is that all theories make similar predictions for these patterns despite disparate assumptions. A troubling implication is that these patterns may not reflect anything unique about organizational principles of biology or the functioning of ecological systems. To test this, we analyze five datasets from ecological, economic, and geological systems that describe the distribution of objects across categories in the United States. At the level of functional form ('first-order effects'), these patterns are not unique to ecological systems, indicating they may reveal little about biological process. However, we show that mechanism can be better revealed in the scale-dependency of first-order patterns ('second-order effects'). These results provide a roadmap for biodiversity theory to move beyond traditional patterns, and also suggest ways in which macroecological theory can constrain the dynamics of economic systems.
Blonder, B., Violle, C., Bentley, L. P., & Enquist, B. J. (2014). Inclusion of vein traits improves predictive power for the leaf economic spectrum: a response to Sack et al. (2013). JOURNAL OF EXPERIMENTAL BOTANY , 65(18), 5109-5114.
Blonder, B., Violle, C., Bentley, L. P., & Enquist, B. J. (2014). Inclusion of vein traits improves predictive power for the leaf economic spectrum: a response to Sack et al. (2013). Journal of experimental botany , 65(18), 5109-14.
Our model for the worldwide leaf economics spectrum (LES) based on venation networks (Blonder et al., 2011, 2013) was strongly criticized by Sack et al. (2013) in this journal. Here, we show that the majority of criticisms by Sack et al. are based on mathematical and conceptual misunderstandings. Using empirical data from both our original study as well as others in the literature, we show support for our original hypothesis, that venation networks provide predictive power and conceptual unification for the LES. In an effort to reconcile differing viewpoints related to the role of leaf venation traits for the LES, we highlight several lines of further investigation.
Grady, J. M., Enquist, B. J., Dettweiler-Robinson, E., Wright, N. A., & Smith, F. A. (2014). DINOSAUR PHYSIOLOGY Evidence for mesothermy in dinosaurs. SCIENCE , 344(6189), 1268-1272.
Grady, J. M., Enquist, B. J., Dettweiler-Robinson, E., Wright, N. A., & Smith, F. A. (2014). Dinosaur physiology. Evidence for mesothermy in dinosaurs. Science (New York, N.Y.) , 344(6189), 1268-72.
Lamanna, C., Blonder, B., Violle, C., Kraft, N. J., Sandel, B., Šímová, I., Donoghue, J. C., Svenning, J., McGill, B. J., Boyle, B., Buzzard, V., Dolins, S., Jørgensen, P. M., Marcuse-Kubitza, A., Morueta-Holme, N., Peet, R. K., Piel, W. H., Regetz, J., Schildhauer, M., , Spencer, N., et al. (2014). Functional trait space and the latitudinal diversity gradient. Proceedings of the National Academy of Sciences of the United States of America , 111(38), 13745-50.
The processes causing the latitudinal gradient in species richness remain elusive. Ecological theories for the origin of biodiversity gradients, such as competitive exclusion, neutral dynamics, and environmental filtering, make predictions for how functional diversity should vary at the alpha (within local assemblages), beta (among assemblages), and gamma (regional pool) scales. We test these predictions by quantifying hypervolumes constructed from functional traits representing major axes of plant strategy variation (specific leaf area, plant height, and seed mass) in tree assemblages spanning the temperate and tropical New World. Alpha-scale trait volume decreases with absolute latitude and is often lower than sampling expectation, consistent with environmental filtering theory. Beta-scale overlap decays with geographic distance fastest in the temperate zone, again consistent with environmental filtering theory. In contrast, gamma-scale trait space shows a hump-shaped relationship with absolute latitude, consistent with no theory. Furthermore, the overall temperate trait hypervolume was larger than the overall tropical hypervolume, indicating that the temperate zone permits a wider range of trait combinations or that niche packing is stronger in the tropical zone. Although there are limitations in the data, our analyses suggest that multiple processes have shaped trait diversity in trees, reflecting no consistent support for any one theory.
Lamanna, C., Blonder, B., Violle, C., Kraft, N., Sandel, B., Simova, I., Donoghue, J., Svenning, J., McGill, B. J., Boyle, B., Buzzard, V., Dolins, S., Jorgensen, P. M., Marcuse-Kubitza, A., Morueta-Holme, N., Peet, R. K., Piel, W. H., Regetz, J., Schildhauer, M., , Spencer, N., et al. (2014). Functional trait space and the latitudinal diversity gradient. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA , 111(38), 13745-13750.
Li, Y. M., Dlugosch, K. M., & Enquist, B. J. (2015). Novel spatial analysis methods reveal scale‐dependent spread and infer limiting factors of invasion by Sahara mustard. Ecography , 38(3), 311–320.
Michaletz, S. T., Cheng, D., Kerkhoff, A. J., & Enquist, B. J. (2014). Convergence of terrestrial plant production across global climate gradients. NATURE , 512(7512), 39-+.
Michaletz, S. T., Cheng, D., Kerkhoff, A. J., & Enquist, B. J. (2014). Convergence of terrestrial plant production across global climate gradients. Nature , 512(7512), 39-43.
Variation in terrestrial net primary production (NPP) with climate is thought to originate from a direct influence of temperature and precipitation on plant metabolism. However, variation in NPP may also result from an indirect influence of climate by means of plant age, stand biomass, growing season length and local adaptation. To identify the relative importance of direct and indirect climate effects, we extend metabolic scaling theory to link hypothesized climate influences with NPP, and assess hypothesized relationships using a global compilation of ecosystem woody plant biomass and production data. Notably, age and biomass explained most of the variation in production whereas temperature and precipitation explained almost none, suggesting that climate indirectly (not directly) influences production. Furthermore, our theory shows that variation in NPP is characterized by a common scaling relationship, suggesting that global change models can incorporate the mechanisms governing this relationship to improve predictions of future ecosystem function.
Sides, C. B., Enquist, B. J., Ebersole, J. J., Smith, M. N., Henderson, A. N., & Sloat, L. L. (2014). REVISITING DARWIN'S HYPOTHESIS: DOES GREATER INTRASPECIFIC VARIABILITY INCREASE SPECIES' ECOLOGICAL BREADTH?. AMERICAN JOURNAL OF BOTANY , 101(1), 56-62.
Sides, C. B., Enquist, B. J., Ebersole, J. J., Smith, M. N., Henderson, A. N., & Sloat, L. L. (2014). Revisiting darwins hypothesis: Does greater intraspecific variability increase species ecological breadth?. American Journal of Botany , 101(1), 56-62.
Abstract: Premise of the study: Darwin first proposed that species with larger ecological breadth have greater phenotypic variation. We tested this hypothesis by comparing intraspecific variation in specific leaf area (SLA) to species' local elevational range and by assessing how external (abiotic) filters may influence observed differences in ecological breadth among species. Understanding the patterns of individual variation within and between populations will help evaluate differing hypotheses for structuring of communities and distribution of species. Methods: We selected 21 species with varying elevational ranges and compared the coefficient of variation of SLA for each species against its local elevational range. We examined the influence of external filters on local trait composition by determining if intraspecific changes in SLA with elevation have the same direction and similar rates of change as the change in community mean SLA value. Key results: In support of Darwin's hypothesis, we found a positive relationship between species' coefficient of variation for SLA with species' local elevational range. Intraspecific changes in SLA had the same sign, but generally lower magnitude than the community mean SLA. Conclusions: The results indicate that wide-ranging species are indeed characterized by greater intraspecific variation and that species' phenotypes shift along environmental gradients in the same direction as the community phenotypes. However, across species, the rate of intraspecific trait change, reflecting plastic and/or adaptive changes across populations, is limited and prevents species from adjusting to environmental gradients as quickly as interspecific changes resulting from community assembly. © 2014 Botanical Society of America.
Smith, D. D., Sperry, J. S., Enquist, B. J., Savage, V. M., McCulloh, K. A., & Bentley, L. P. (2014). Deviation from symmetrically self-similar branching in trees predicts altered hydraulics, mechanics, light interception and metabolic scaling. NEW PHYTOLOGIST , 201(1), 217-229.
Smith, D. D., Sperry, J. S., Enquist, B. J., Savage, V. M., McCulloh, K. A., & Bentley, L. P. (2014). Deviation from symmetrically self-similar branching in trees predicts altered hydraulics, mechanics, light interception and metabolic scaling. The New phytologist , 201(1), 217-29.
The West, Brown, Enquist (WBE) model derives symmetrically self-similar branching to predict metabolic scaling from hydraulic conductance, K, (a metabolism proxy) and tree mass (or volume, V). The original prediction was Kα V(0.75). We ask whether trees differ from WBE symmetry and if it matters for plant function and scaling. We measure tree branching and model how architecture influences K, V, mechanical stability, light interception and metabolic scaling. We quantified branching architecture by measuring the path fraction, Pf : mean/maximum trunk-to-twig pathlength. WBE symmetry produces the maximum, Pf = 1.0. We explored tree morphospace using a probability-based numerical model constrained only by biomechanical principles. Real tree Pf ranged from 0.930 (nearly symmetric) to 0.357 (very asymmetric). At each modeled tree size, a reduction in Pf led to: increased K; decreased V; increased mechanical stability; and decreased light absorption. When Pf was ontogenetically constant, strong asymmetry only slightly steepened metabolic scaling. The Pf ontogeny of real trees, however, was 'U' shaped, resulting in size-dependent metabolic scaling that exceeded 0.75 in small trees before falling below 0.65. Architectural diversity appears to matter considerably for whole-tree hydraulics, mechanics, photosynthesis and potentially metabolic scaling. Optimal architectures likely exist that maximize carbon gain per structural investment.
Abstract: Summary: The West, Brown, Enquist (WBE) model derives symmetrically self-similar branching to predict metabolic scaling from hydraulic conductance, K, (a metabolism proxy) and tree mass (or volume, V). The original prediction was K∝V0.75. We ask whether trees differ from WBE symmetry and if it matters for plant function and scaling. We measure tree branching and model how architecture influences K, V, mechanical stability, light interception and metabolic scaling. We quantified branching architecture by measuring the path fraction, Pf: mean/maximum trunk-to-twig pathlength. WBE symmetry produces the maximum, Pf = 1.0. We explored tree morphospace using a probability-based numerical model constrained only by biomechanical principles. Real tree Pf ranged from 0.930 (nearly symmetric) to 0.357 (very asymmetric). At each modeled tree size, a reduction in Pf led to: increased K; decreased V; increased mechanical stability; and decreased light absorption. When Pf was ontogenetically constant, strong asymmetry only slightly steepened metabolic scaling. The Pf ontogeny of real trees, however, was 'U' shaped, resulting in size-dependent metabolic scaling that exceeded 0.75 in small trees before falling below 0.65. Architectural diversity appears to matter considerably for whole-tree hydraulics, mechanics, photosynthesis and potentially metabolic scaling. Optimal architectures likely exist that maximize carbon gain per structural investment. © 2013 New Phytologist Trust.
Violle, C., Reich, P. B., Pacala, S. W., Enquist, B. J., & Kattge, J. (2014). The emergence and promise of functional biogeography. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA , 111(38), 13690-13696.
Violle, C., Reich, P. B., Pacala, S. W., Enquist, B. J., & Kattge, J. (2014). The emergence and promise of functional biogeography. Proceedings of the National Academy of Sciences of the United States of America , 111(38), 13690-6.
Understanding, modeling, and predicting the impact of global change on ecosystem functioning across biogeographical gradients can benefit from enhanced capacity to represent biota as a continuous distribution of traits. However, this is a challenge for the field of biogeography historically grounded on the species concept. Here we focus on the newly emergent field of functional biogeography: the study of the geographic distribution of trait diversity across organizational levels. We show how functional biogeography bridges species-based biogeography and earth science to provide ideas and tools to help explain gradients in multifaceted diversity (including species, functional, and phylogenetic diversities), predict ecosystem functioning and services worldwide, and infuse regional and global conservation programs with a functional basis. Although much recent progress has been made possible because of the rising of multiple data streams, new developments in ecoinformatics, and new methodological advances, future directions should provide a theoretical and comprehensive framework for the scaling of biotic interactions across trophic levels and its ecological implications.
, B. J., , J. N., , S. P., , C. V., , C. T., , A. H., , L. L., & , V. M. (2013). Scaling from traits to ecosystems: Developing a general Trait Driver Theory via integrating trait-based and metabolic scaling theories. , Advances in Ecological Research, .
Bentley, L. P., Stegen, J. C., Savage, V. M., Smith, D. D., I., E., Sperry, J. S., Reich, P. B., & Enquist, B. J. (2013). An empirical assessment of tree branching networks and implications for plant allometric scaling models. Ecology Letters , 16(8), 1069-1078.
PMID: 23800188;Abstract: Several theories predict whole-tree function on the basis of allometric scaling relationships assumed to emerge from traits of branching networks. To test this key assumption, and more generally, to explore patterns of external architecture within and across trees, we measure branch traits (radii/lengths) and calculate scaling exponents from five functionally divergent species. Consistent with leading theories, including metabolic scaling theory, branching is area preserving and statistically self-similar within trees. However, differences among scaling exponents calculated at node- and whole-tree levels challenge the assumption of an optimised, symmetrically branching tree. Furthermore, scaling exponents estimated for branch length change across branching orders, and exponents for scaling metabolic rate with plant size (or number of terminal tips) significantly differ from theoretical predictions. These findings, along with variability in the scaling of branch radii being less than for branch lengths, suggest extending current scaling theories to include asymmetrical branching and differential selective pressures in plant architectures. © 2013 John Wiley & Sons Ltd/CNRS.
Bentley, L. P., Stegen, J. C., Savage, V. M., Smith, D. D., von, A., Sperry, J. S., Reich, P. B., & Enquist, B. J. (2013). An empirical assessment of tree branching networks and implications for plant allometric scaling models. ECOLOGY LETTERS , 16(8), 1069-1078.
Blonder, B., Violle, C., & Enquist, B. J. (2013). Assessing the causes and scales of the leaf economics spectrum using venation networks in Populus tremuloides. JOURNAL OF ECOLOGY , 101(4), 981-989.
Abstract: The leaf economics spectrum (LES) describes global interspecific correlations between leaf traits. Despite recent theoretical advances, the biological scale at which LES correlations emerge and the physiological and climatic causes of these correlations remains partially unknown. Here, we test an extant theory based on universal trade-offs in leaf venation networks that predicts that (i) the LES primarily originates within individuals; (ii) minor vein density drives LES trait correlations; and (iii) between individuals, LES correlations reflects variation in minor vein density driven by water availability. To test these predictions, we sample leaves within and between clones of Populus tremuloides across a wide climate gradient. We show that predictions i) and iii) are supported but ii) is only partially supported. To account for this discrepancy, we develop a more general venation theory. This theory describes linkages between vein density, leaf area and leaf thickness that can modulate LES correlations across scales. This theory helps to identify multiple selective pressures that can drive trait covariation underlying the LES. Synthesis. Our results broaden the range of biological scales at which the leaf economics spectrum (LES) is found and highlight the complex causal roles of venation networks in LES correlations. This study points to the need to better understand the coupling between venation networks, leaf size and climate to fully understand the LES. © 2013 The Authors. Journal of Ecology © 2013 British Ecological Society.
Boyle, B., Hopkins, N., Lu, Z., Garay, J., Mozzherin, D., Rees, T., Matasci, N., Narro, M. L., Piel, W. H., Mckay, S. J., Lowry, S., Freeland, C., Peet, R. K., & Enquist, B. J. (2013). The taxonomic name resolution service: an online tool for automated standardization of plant names. BMC BIOINFORMATICS , 14.
Enquist, B., Boyle, B., Hopkins, N., Lu, Z., Raygoza Garay, J. A., Mozzherin, D., Rees, T., Matasci, N., Narro, M. L., Piel, W. H., McKay, S. J., Lowry, S., Freeland, C., Peet, R. K., & Enquist, B. J. (2013). The taxonomic name resolution service: an online tool for automated standardization of plant names. BMC bioinformatics , 14.
The digitization of biodiversity data is leading to the widespread application of taxon names that are superfluous, ambiguous or incorrect, resulting in mismatched records and inflated species numbers. The ultimate consequences of misspelled names and bad taxonomy are erroneous scientific conclusions and faulty policy decisions. The lack of tools for correcting this 'names problem' has become a fundamental obstacle to integrating disparate data sources and advancing the progress of biodiversity science.
Hulshof, C. M., Violle, C., Spasojevic, M. J., McGill, B., Damschen, E., Harrison, S., & Enquist, B. J. (2013). Intra-specific and inter-specific variation in specific leaf area reveal the importance of abiotic and biotic drivers of species diversity across elevation and latitude. JOURNAL OF VEGETATION SCIENCE , 24(5), 921-931.
Abstract: Questions: Are patterns of intra- and inter-specific functional trait variation consistent with greater abiotic filtering on community assembly at high latitudes and elevations, and greater biotic filtering at low latitudes and elevations? Locations: Area de Conservación Guanacaste, Costa Rica; Santa Catalina Mountains, Arizona; Siskiyou Mountains, Oregon. Methods: We measured woody plant species abundance and a key functional trait associated with competition for resources and environmental tolerance (specific leaf area, SLA) along elevational gradients in low-latitude tropical (Costa Rica), mid-latitude desert (Arizona) and high latitude mediterranean (southern Oregon) biomes. We explored patterns of abiotic and biotic filtering by comparing observed patterns of community-weighted means and variances along elevational and latitudinal gradients to those expected under random assembly. In addition, we related trait variability to niches and explored how total trait space and breadth vary across broad spatial gradients by quantifying the ratio of intra- to inter-specific variation. Results: Both the community-wide mean and variance of SLA decreased with increasing latitude, consistent with greater abiotic filtering at higher latitudes. Further, low-elevation communities had higher trait variation than expected by chance, consistent with greater biotic filtering at low elevations. Finally, in the tropics and across latitude the ratio of intra- to inter-specific variation was negatively correlated to species richness, which further suggests that biotic interactions influence plant assembly at low latitudes. Conclusions: Intra- and inter-specific patterns of SLA variation appeared broadly consistent with the idea that the relative strength of biotic and abiotic drivers on community assembly changes along elevational and latitudinal gradients; evidence for biotic drivers appeared more prominent at low latitudes and elevations and evidence for abiotic drivers appeared more prominent at high latitudes and elevations. © 2013 International Association for Vegetation Science.
Moles, A. T., Peco, B., Wallis, I. R., Foley, W. J., G., A., Seabloom, E. W., Vesk, P. A., Bisigato, A. J., Cella-Pizarro, L., Clark, C. J., Cohen, P. S., Cornwell, W. K., Edwards, W., Ejrnæs, R., Gonzales-Ojeda, T., Graae, B. J., Hay, G., Lumbwe, F. C., Magaña-Rodríguez, B., , Moore, B. D., et al. (2013). Correlations between physical and chemical defences in plants: Tradeoffs, syndromes, or just many different ways to skin a herbivorous cat?. New Phytologist , 198(1), 252-263.
PMID: 23316750;Abstract: Most plant species have a range of traits that deter herbivores. However, understanding of how different defences are related to one another is surprisingly weak. Many authors argue that defence traits trade off against one another, while others argue that they form coordinated defence syndromes. We collected a dataset of unprecedented taxonomic and geographic scope (261 species spanning 80 families, from 75 sites across the globe) to investigate relationships among four chemical and six physical defences. Five of the 45 pairwise correlations between defence traits were significant and three of these were tradeoffs. The relationship between species' overall chemical and physical defence levels was marginally nonsignificant (P = 0.08), and remained nonsignificant after accounting for phylogeny, growth form and abundance. Neither categorical principal component analysis (PCA) nor hierarchical cluster analysis supported the idea that species displayed defence syndromes. Our results do not support arguments for tradeoffs or for coordinated defence syndromes. Rather, plants display a range of combinations of defence traits. We suggest this lack of consistent defence syndromes may be adaptive, resulting from selective pressure to deploy a different combination of defences to coexisting species. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.
Moles, A. T., Peco, B., Wallis, I. R., Foley, W. J., Poore, A., Seabloom, E. W., Vesk, P. A., Bisigato, A. J., Cella-Pizarro, L., Clark, C. J., Cohen, P. S., Cornwell, W. K., Edwards, W., Ejrnaes, R., Gonzales-Ojeda, T., Graae, B. J., Hay, G., Lumbwe, F. C., Magana-Rodriguez, B., , Moore, B. D., et al. (2013). Correlations between physical and chemical defences in plants: tradeoffs, syndromes, or just many different ways to skin a herbivorous cat?. NEW PHYTOLOGIST , 198(1), 252-263.
Morueta-Holme, N., Enquist, B. J., McGill, B. J., Boyle, B., Jorgensen, P. M., Ott, J. E., Peet, R. K., Simova, I., Sloat, L. L., Thiers, B., Violle, C., Wiser, S. K., Dolins, S., Donoghue, J., Kraft, N., Regetz, J., Schildhauer, M., Spencer, N., & Svenning, J. (2013). Habitat area and climate stability determine geographical variation in plant species range sizes. ECOLOGY LETTERS , 16(12), 1446-1454.
Morueta-Holme, N., Enquist, B. J., Mcgill, B. J., Boyle, B., Jørgensen, P. M., Ott, J. E., Peet, R. K., Šímová, I., Sloat, L. L., Thiers, B., Violle, C., Wiser, S. K., Dolins, S., Donoghue, J. C., Kraft, N. J., Regetz, J., Schildhauer, M., Spencer, N., & Svenning, J. (2013). Habitat area and climate stability determine geographical variation in plant species range sizes. Ecology Letters , 16(12), 1446-1454.
Abstract: Despite being a fundamental aspect of biodiversity, little is known about what controls species range sizes. This is especially the case for hyperdiverse organisms such as plants. We use the largest botanical data set assembled to date to quantify geographical variation in range size for ~ 85 000 plant species across the New World. We assess prominent hypothesised range-size controls, finding that plant range sizes are codetermined by habitat area and long- and short-term climate stability. Strong short- and long-term climate instability in large parts of North America, including past glaciations, are associated with broad-ranged species. In contrast, small habitat areas and a stable climate characterise areas with high concentrations of small-ranged species in the Andes, Central America and the Brazilian Atlantic Rainforest region. The joint roles of area and climate stability strengthen concerns over the potential effects of future climate change and habitat loss on biodiversity. © 2013 The Authors. Ecology Letters published by John Wiley & Sons Ltd and CNRS.
Stegen, J. C., Ferriere, R., & Enquist, B. J. (2013). Evolving ecological networks and the emergence of biodiversity patterns across temperature gradients. PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES , 279(1731), 1051-1060.
Stegen, J. C., Swenson, N. G., Valencia, R., Enquist, B. J., & Thompson, J. (2013). Above-ground forest biomass is not consistently related to wood density in tropical forests. GLOBAL ECOLOGY AND BIOGEOGRAPHY , 18(5), 617-625.
Blonder, B., Buzzard, V., Simova, I., Sloat, L., Boyle, B., Lipson, R., Aguilar-Beaucage, B., Andrade, A., Barber, B., Barnes, C., Bushey, D., Cartagena, P., Chaney, M., Contreras, K., Cox, M., Cueto, M., Curtis, C., Fisher, M., Furst, L., , Gallegos, J., et al. (2012). THE LEAF-AREA SHRINKAGE EFFECT CAN BIAS PALEOCLIMATE AND ECOLOGY RESEARCH. AMERICAN JOURNAL OF BOTANY , 99(11), 1756-1763.
Blonder, B., De, C. F., Moore, J., Rivers, M., & Enquist, B. J. (2012). X-ray imaging of leaf venation networks. NEW PHYTOLOGIST , 196(4), 1274-1282.
Enquist, B. J., & Bentley, L. P. (2012). Land Plants: New Theoretical Directions and Empirical Prospects. Metabolic Ecology: A Scaling Approach , 164-187.
Enquist, B., Blonder, B., Buzzard, V., Simova, I., Sloat, L., Boyle, B., Lipson, R., Aguilar-Beaucage, B., Andrade, A., Barber, B., Barnes, C., Bushey, D., Cartagena, P., Chaney, M., Contreras, K., Cox, M., Cueto, M., Curtis, C., Fisher, M., , Furst, L., et al. (2012). The leaf-area shrinkage effect can bias paleoclimate and ecology research. American journal of botany , 99(11).
Leaf area is a key trait that links plant form, function, and environment. Measures of leaf area can be biased because leaf area is often estimated from dried or fossilized specimens that have shrunk by an unknown amount. We tested the common assumption that this shrinkage is negligible.
Enquist, B., Blonder, B., De Carlo, F., Moore, J., Rivers, M., & Enquist, B. J. (2012). X-ray imaging of leaf venation networks. The New phytologist , 196(4).
Enquist, B., Hulshof, C. M., Stegen, J. C., Swenson, N. G., Enquist, C. A., & Enquist, B. J. (2012). Interannual variability of growth and reproduction in Bursera simaruba: the role of allometry and resource variability. Ecology , 93(1).
Plants are expected to differentially allocate resources to reproduction, growth, and survival in order to maximize overall fitness. Life history theory predicts that the allocation of resources to reproduction should occur at the expense of vegetative growth. Although it is known that both organism size and resource availability can influence life history traits, few studies have addressed how size dependencies of growth and reproduction and variation in resource supply jointly affect the coupling between growth and reproduction. In order to understand the relationship between growth and reproduction in the context of resource variability, we utilize a long-term observational data set consisting of 670 individual trees over a 10-year period within a local population of Bursera simaruba (L.) Sarg. We (1) quantify the functional form and variability in the growth-reproduction relationship at the population and individual-tree level and (2) develop a theoretical framework to understand the allometric dependence of growth and reproduction. Our findings suggest that the differential responses of allometric growth and reproduction to resource availability, both between years and between microsites, underlie the apparent relationship between growth and reproduction. Finally, we offer an alternative approach for quantifying the relationship between growth and reproduction that accounts for variation in allometries.
Fuller, M. M., & Enquist, B. J. (2012). Accounting for spatial autocorrelation in null models of tree species association. ECOGRAPHY , 35(6), 510-518.
Abstract: A commonly used null model for species association among forest trees is a well-mixed community (WMC). A WMC represents a non-spatial, or spatially implicit, model, in which species form nearest-neighbor pairs at a rate equal to the product of their community proportions. WMC models assume that the outcome of random dispersal and demographic processes is complete spatial randomness (CSR) in the species' spatial distributions. Yet, stochastic dispersal processes often lead to spatial autocorrelation (SAC) in tree species densities, giving rise to clustering, segregation, and other nonrandom patterns. Although methods exist to account for SAC in spatially-explicit models, its impact on non-spatial models often remains unaccounted for. To investigate the potential for SAC to bias tests based upon non-spatial models, we developed a spatially-heterogeneous (SH) modelling approach that incorporates measured levels of SAC. Using the mapped locations of individuals in a tropical tree community, we tested the hypothesis that the identity of nearest-neighbors represents a random draw from neighborhood species pools. Correlograms of Moran's I confirmed that, for 50 of 51 dominant species, stem density was significantly autocorrelated over distances ranging from 50 to 200 m. The observed patterns of SAC were consistent with dispersal limitation, with most species occurring in distinct patches. For nearly all of the 106 species in the community, the frequency of pairwise association was statistically indistinguishable from that projected by the null models. However, model comparisons revealed that non-spatial models more strongly underestimated observed species-pair frequencies, particularly for conspecific pairs. Overall, the CSR models projected more significant facilitative interactions than did SH models, yielding a more liberal test of niche differences. Our results underscore the importance of accounting for stochastic spatial processes in tests of association, regardless of whether spatial or non-spatial models are employed. © 2011 The Authors. Ecography © 2011 Nordic Society Oikos.
Hulshof, C. M., Stegen, J. C., Swenson, N. G., Enquist, C., & Enquist, B. J. (2012). Interannual variability of growth and reproduction in Bursera simaruba: the role of allometry and resource variability. ECOLOGY , 93(1), 180-190.
I., E., Sperry, J. S., Smith, D. D., Savage, V. M., Enquist, B. J., Reich, P. B., & Bentley, L. P. (2012). A species-level model for metabolic scaling of trees II. Testing in a ring- and diffuse-porous species. Functional Ecology , 26(5), 1066-1076.
Abstract: A 17-parameter 'species model' that predicts metabolic scaling from vascular architecture was tested in a diffuse-porous maple (Acer grandidentatum) and a ring-porous oak (Quercus gambelii). Predictions of midday water transport (Q) and its scaling with above-ground mass (M) were compared with empirical measurements. We also tested the assumption that Q was proportional to the biomass growth rate of the shoot (G). Water transport and biomass growth rate were measured on 18 trees per species that spanned a broad range in trunk diameter (4-26 cm). Where possible, the same trees were used for obtaining the 17 model parameters that concern external branching, internal xylem conduit anatomy, and soil-to-canopy sap pressure drop. The model succeeded in predicting the Q by M b scaling exponent, b, being within 8% (maple) and 6% (oak) of measured exponents from sap flow data. In terms of absolute Q, the model was better in maple (16% Q overestimate) than oak (128% overestimate). The overestimation of Q was consistent with the model not accounting for cavitation, which is reportedly more prevalent in oak than in maple at the study site. The modelled and measured Q by M b exponents averaged within 3·6% of the measured G by M b exponents, supporting the assumption that G ∝ Q 1. The average b exponent was 0·62 ± 0·016 (mean ± SE) across species, rejecting b = 0·75 for intraspecific scaling. The performance of this species model, both for scaling purposes as well as for predicting rates of water consumption within and between species, argues for its further refinement and wider application in ecology and ecosystem biology. © 2012 The Authors. Functional Ecology © 2012 British Ecological Society.
Sperry, J. S., Smith, D. D., Savage, V. M., Enquist, B. J., McCulloh, K. A., Reich, P. B., Bentley, L. P., & I., E. (2012). A species-level model for metabolic scaling in trees I. Exploring boundaries to scaling space within and across species. Functional Ecology , 26(5), 1054-1065.
Abstract: Metabolic scaling theory predicts how tree water flow rate (Q) scales with tree mass (M) and assumes identical scaling for biomass growth rate (G) with M. Analytic models have derived general scaling expectations from proposed optima in the rate of axial xylem conduit taper (taper function) and the allocation of wood space to water conduction (packing function). Recent predictions suggest G and Q scale with M to the ≈ 0·7 power with 0·75 as an upper bound. We complement this a priori optimization approach with a numerical model that incorporates species-specific taper and packing functions, plus additional empirical inputs essential for predicting Q (effects of gravity, tree size, heartwood, bark, and hydraulic resistance of leaf, root and interconduit pits). Traits are analysed individually, and in ensemble across tree types, to define a 2D 'scaling space' of absolute Q vs. its scaling exponent with tree size. ll traits influenced Q and many affected its scaling with M. Constraints driving the optimization of taper or packing functions, or any other trait, can be relaxed via compensatory changes in other traits. The scaling space of temperate trees overlapped despite diverse anatomy and winter-adaptive strategies. More conducting space in conifer wood compensated for narrow tracheids; extensive sapwood in diffuse-porous trees compensated for narrow vessels; and limited sapwood in ring-porous trees negated the effect of large vessels. Tropical trees, however, achieved the greatest Q and steepest size-scaling by pairing large vessels with extensive sapwood, a combination compatible with minimal water stress and no freezing-stress. Intraspecific scaling across all types averaged Q ∝ M 0·63 (maximum = Q ∝ M 0·71) for size-invariant root-shoot ratio. Scaling reached Q ∝ M 0·75 only if conductance increased faster in roots than in shoots with size. Interspecific scaling could reach Q ∝ M 0·75, but this may require the evolution of size-biased allometries rather than arising directly from biophysical constraints. Our species-level model is more realistic than its analytical predecessors and provides a tool for interpreting the adaptive significance of functional trait diversification in relation to whole-tree water use and consequent metabolic scaling. © 2012 The Authors. Functional Ecology © 2012 British Ecological Society.
Sperry, J. S., Smith, D. D., Savage, V. M., Enquist, B. J., McCulloh, K. A., Reich, P. B., Bentley, L. P., & von, A. (2012). A species-level model for metabolic scaling in trees I. Exploring boundaries to scaling space within and across species. FUNCTIONAL ECOLOGY , 26(5), 1054-1065.
Stegen, J. C., Enquist, B. J., & Ferriere, R. (2012). Advancing the metabolic theory of biodiversity. ECOLOGY LETTERS , 12(10), 1001-1015.
Stegen, J. C., Enquist, B. J., & Ferriere, R. (2012). Eco-Evolutionary Community Dynamics: Covariation between Diversity and Invasibility across Temperature Gradients. AMERICAN NATURALIST , 180(4), E110-E126.
Swenson, N. G., Enquist, B. J., Pither, J., Kerkhoff, A. J., Boyle, B., Weiser, M. D., Elser, J. J., Fagan, W. F., Forero-Montana, J., Fyllas, N., Kraft, N., Lake, J. K., Moles, A. T., Patino, S., Phillips, O. L., Price, C. A., Reich, P. B., Quesada, C. A., Stegen, J. C., , Valencia, R., et al. (2012). The biogeography and filtering of woody plant functional diversity in North and South America. GLOBAL ECOLOGY AND BIOGEOGRAPHY , 21(8), 798-808.
Swenson, N. G., Enquist, B. J., Pither, J., Kerkhoff, A. J., Boyle, B., Weiser, M. D., Elser, J. J., Fagan, W. F., Forero-Montaña, J., Fyllas, N., J., N., Lake, J. K., Moles, A. T., Patiño, S., Phillips, O. L., Price, C. A., Reich, P. B., Quesada, C. A., Stegen, J. C., , Valencia, R., et al. (2012). The biogeography and filtering of woody plant functional diversity in North and South America. Global Ecology and Biogeography , 21(8), 798-808.
Abstract: Aim In recent years evidence has accumulated that plant species are differentially sorted from regional assemblages into local assemblages along local-scale environmental gradients on the basis of their function and abiotic filtering. The favourability hypothesis in biogeography proposes that in climatically difficult regions abiotic filtering should produce a regional assemblage that is less functionally diverse than that expected given the species richness and the global pool of traits. Thus it seems likely that differential filtering of plant traits along local-scale gradients may scale up to explain the distribution, diversity and filtering of plant traits in regional-scale assemblages across continents. The present work aims to address this prediction. Location North and South America. Methods We combine a dataset comprising over 5.5 million georeferenced plant occurrence records with several large plant functional trait databases in order to: (1) quantify how several critical traits associated with plant performance and ecology vary across environmental gradients; and (2) provide the first test of whether the woody plants found within 1° and 5° map grid cells are more or less functionally diverse than expected, given their species richness, across broad gradients. Results The results show that, for many of the traits studied, the overall distribution of functional traits in tropical regions often exceeds the expectations of random sampling given the species richness. Conversely, temperate regions often had narrower functional trait distributions than their smaller species pools would suggest. Main conclusion The results show that the overall distribution of function does increase towards the equator, but the functional diversity within regional-scale tropical assemblages is higher than that expected given their species richness. These results are consistent with the hypothesis that abiotic filtering constrains the overall distribution of function in temperate assemblages, but tropical assemblages are not as tightly constrained. © 2011 Blackwell Publishing Ltd.
Vasseur, F., Violle, C., Enquist, B. J., Granier, C., & Vile, D. (2012). A common genetic basis to the origin of the leaf economics spectrum and metabolic scaling allometry. ECOLOGY LETTERS , 15(10), 1149-1157.
PMID: 22856883;Abstract: Many facets of plant form and function are reflected in general cross-taxa scaling relationships. Metabolic scaling theory (MST) and the leaf economics spectrum (LES) have each proposed unifying frameworks and organisational principles to understand the origin of botanical diversity. Here, we test the evolutionary assumptions of MST and the LES using a cross of two genetic variants of Arabidopsis thaliana. We show that there is enough genetic variation to generate a large fraction of variation in the LES and MST scaling functions. The progeny sharing the parental, naturally occurring, allelic combinations at two pleiotropic genes exhibited the theorised optimum 3/4 allometric scaling of growth rate and intermediate leaf economics. Our findings: (1) imply that a few pleiotropic genes underlie many plant functional traits and life histories; (2) unify MST and LES within a common genetic framework and (3) suggest that observed intermediate size and longevity in natural populations originate from stabilising selection to optimise physiological trade-offs. © 2012 Blackwell Publishing Ltd/CNRS.
Violle, C., Enquist, B. J., McGill, B. J., Jiang, L., Albert, C. H., Hulshof, C., Jung, V., & Messier, J. (2012). The return of the variance: Intraspecific variability in community ecology. Trends in Ecology and Evolution , 27(4), 244-252.
PMID: 22244797;Abstract: Despite being recognized as a promoter of diversity and a condition for local coexistence decades ago, the importance of intraspecific variance has been neglected over time in community ecology. Recently, there has been a new emphasis on intraspecific variability. Indeed, recent developments in trait-based community ecology have underlined the need to integrate variation at both the intraspecific as well as interspecific level. We introduce new T-statistics ('T' for trait), based on the comparison of intraspecific and interspecific variances of functional traits across organizational levels, to operationally incorporate intraspecific variability into community ecology theory. We show that a focus on the distribution of traits at local and regional scales combined with original analytical tools can provide unique insights into the primary forces structuring communities. © 2011 Elsevier Ltd.
Violle, C., Enquist, B. J., McGill, B. J., Jiang, L., Albert, C. H., Hulshof, C., Jung, V., & Messier, J. (2012). Viva la variance! A reply to Nakagawa & Schielzeth. Trends in Ecology and Evolution , 27(9), 475-476.
von, A., Sperry, J. S., Smith, D. D., Savage, V. M., Enquist, B. J., Reich, P. B., & Bentley, L. P. (2012). A species-level model for metabolic scaling of trees II. Testing in a ring- and diffuse-porous species. FUNCTIONAL ECOLOGY , 26(5), 1066-1076.
Blonder, B., Violle, C., Bentley, L. P., & Enquist, B. J. (2011). Venation networks and the origin of the leaf economics spectrum. ECOLOGY LETTERS , 14(2), 91-100.
Enquist, B. J., & A., C. (2011). Long-term change within a Neotropical forest: Assessing differential functional and floristic responses to disturbance and drought. Global Change Biology , 17(3), 1408-1424.
Abstract: Disentangling the relative roles of biotic and abiotic forces influencing forest structure, function, and local community composition continues to be an important goal in ecology. Here, utilizing two forest surveys 20-year apart from a Central American dry tropical forest, we assess the relative role of past disturbance and local climatic change in the form of increased drought in driving forest dynamics. We observe: (i) a net decrease in the number of trees; (ii) a decrease in total forest biomass by 7.7Mgha-1 but when calculated on subquadrat basis the biomass per unit area did not change indicating scale sensitivity of forest biomass measures; (iii) that the decrease in the number of stems occurred mainly in the smallest sizes, and in more moist and evergreen habitats; (iv) that there has been an increase in the proportion of trees that are deciduous, compound leaved and are canopy species, and a concomitant reduction in trees that are evergreen, simple-leaved, and understory species. These changes are opposite to predictions based on recovery from disturbance, and have resulted in (v) a uniform multivariate shift from a more mesic to a more xeric forest. Together, our results show that over relatively short time scales, community composition and the functional dominance may be more responsive to climate change than recovery to past disturbances. Our findings point to the importance of assessing proportional changes in forest composition and not just changes in absolute numbers. Our findings are also consistent with the hypothesis that tropical tree species exhibit differential sensitivity to changes in precipitation. Predicted future decreases in rainfall may result in quick differential shifts in forest function, physiognomy, and species composition. Quantifying proportional functional composition offers a basis for a predictive framework for how the structure, and diversity of tropical forests will respond to global change. © 2010 Blackwell Publishing Ltd.
Enquist, B., & Enquist, B. J. (2011). Forest annual carbon cost: comment. Ecology , 92(10).
Enquist, B., Blonder, B., Violle, C., Bentley, L. P., & Enquist, B. J. (2011). Venation networks and the origin of the leaf economics spectrum. Ecology letters , 14(2).
The leaf economics spectrum describes biome-invariant scaling functions for leaf functional traits that relate to global primary productivity and nutrient cycling. Here, we develop a comprehensive framework for the origin of this leaf economics spectrum based on venation-mediated economic strategies. We define a standardized set of traits - density, distance and loopiness - that provides a common language for the study of venation. We develop a novel quantitative model that uses these venation traits to model leaf-level physiology, and show that selection to optimize the venation network predicts the mean global trait-trait scaling relationships across 2548 species. Furthermore, using empirical venation data for 25 plant species, we test our model by predicting four key leaf functional traits related to leaf economics: net carbon assimilation rate, life span, leaf mass per area ratio and nitrogen content. Together, these results indicate that selection on venation geometry is a fundamental basis for understanding the diversity of leaf form and function, and the carbon balance of leaves. The model and associated predictions have broad implications for integrating venation network geometry with pattern and process in ecophysiology, ecology and palaeobotany.
Fuller, M. M., Wagner, A., & Enquist, B. J. (2011). Using network analysis to characterize forest structure. NATURAL RESOURCE MODELING , 21(2), 225-247.
Kattge, J., Díaz, S., Lavorel, S., Prentice, I. C., Leadley, P., Bönisch, G., Garnier, E., Westoby, M., Reich, P. B., Wright, I. J., Cornelissen, J. H., Violle, C., Harrison, S. P., Bodegom, P. V., Reichstein, M., Enquist, B. J., Soudzilovskaia, N. A., Ackerly, D. D., Anand, M., , Atkin, O., et al. (2011). TRY - a global database of plant traits. Global Change Biology , 17(9), 2905-2935.
Abstract: Plant traits - the morphological, anatomical, physiological, biochemical and phenological characteristics of plants and their organs - determine how primary producers respond to environmental factors, affect other trophic levels, influence ecosystem processes and services and provide a link from species richness to ecosystem functional diversity. Trait data thus represent the raw material for a wide range of research from evolutionary biology, community and functional ecology to biogeography. Here we present the global database initiative named TRY, which has united a wide range of the plant trait research community worldwide and gained an unprecedented buy-in of trait data: so far 93 trait databases have been contributed. The data repository currently contains almost three million trait entries for 69000 out of the world's 300000 plant species, with a focus on 52 groups of traits characterizing the vegetative and regeneration stages of the plant life cycle, including growth, dispersal, establishment and persistence. A first data analysis shows that most plant traits are approximately log-normally distributed, with widely differing ranges of variation across traits. Most trait variation is between species (interspecific), but significant intraspecific variation is also documented, up to 40% of the overall variation. Plant functional types (PFTs), as commonly used in vegetation models, capture a substantial fraction of the observed variation - but for several traits most variation occurs within PFTs, up to 75% of the overall variation. In the context of vegetation models these traits would better be represented by state variables rather than fixed parameter values. The improved availability of plant trait data in the unified global database is expected to support a paradigm shift from species to trait-based ecology, offer new opportunities for synthetic plant trait research and enable a more realistic and empirically grounded representation of terrestrial vegetation in Earth system models. © 2011 Blackwell Publishing Ltd.
Kerkhoff, A. J., & Enquist, B. J. (2011). The implications of scaling approaches for understanding resilience and reorganization in ecosystems. BIOSCIENCE , 57(6), 489-499.
McCarthy, M. C., & Enquist, B. J. (2011). Consistency between an allometric approach and optimal partitioning theory in global patterns of plant biomass allocation. FUNCTIONAL ECOLOGY , 21(4), 713-720.
1. Optimal partitioning theory (OPT) suggests that plants should allocate biomass to the organ that acquires the most limiting resource. An implied assumption of this is that there are trade-offs in allocation between leaf, stem and root functions.
Moles, A. T., Wallis, I. R., Foley, W. J., Warton, D. I., Stegen, J. C., Bisigato, A. J., Cella-Pizarro, L., Clark, C. J., Cohen, P. S., Cornwell, W. K., Edwards, W., Ejrnaes, R., Gonzales-Ojeda, T., Graae, B. J., Hay, G., Lumbwe, F. C., Magana-Rodriguez, B., Moore, B. D., Peri, P. L., , Poulsen, J. R., et al. (2011). Putting plant resistance traits on the map: a test of the idea that plants are better defended at lower latitudes. NEW PHYTOLOGIST , 191(3), 777-788.
Moles, A. T., Wallis, I. R., Foley, W. J., Warton, D. I., Stegen, J. C., Bisigato, A. J., Cella-Pizarro, L., Clark, C. J., Cohen, P. S., Cornwell, W. K., Edwards, W., Ejrnæs, R., Gonzales-Ojeda, T., Graae, B. J., Hay, G., Lumbwe, F. C., Magaña-Rodríguez, B., Moore, B. D., Peri, P. L., , Poulsen, J. R., et al. (2011). Putting plant resistance traits on the map: A test of the idea that plants are better defended at lower latitudes. New Phytologist , 191(3), 777-788.
PMID: 21539574;Abstract: It has long been believed that plant species from the tropics have higher levels of traits associated with resistance to herbivores than do species from higher latitudes. A meta-analysis recently showed that the published literature does not support this theory. However, the idea has never been tested using data gathered with consistent methods from a wide range of latitudes. We quantified the relationship between latitude and a broad range of chemical and physical traits across 301 species from 75 sites world-wide. Six putative resistance traits, including tannins, the concentration of lipids (an indicator of oils, waxes and resins), and leaf toughness were greater in high-latitude species. Six traits, including cyanide production and the presence of spines, were unrelated to latitude. Only ash content (an indicator of inorganic substances such as calcium oxalates and phytoliths) and the properties of species with delayed greening were higher in the tropics. Our results do not support the hypothesis that tropical plants have higher levels of resistance traits than do plants from higher latitudes. If anything, plants have higher resistance toward the poles. The greater resistance traits of high-latitude species might be explained by the greater cost of losing a given amount of leaf tissue in low-productivity environments. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.
Riveros, A. J., & Enquist, B. J. (2011). Metabolic scaling in insects supports the predictions of the WBE model. Journal of Insect Physiology , 57(6), 688-693.
PMID: 21296084;Abstract: The functional association between body size and metabolic rate (BS-MR) is one of the most intriguing issues in ecological physiology. An average scaling exponent of 3/4 is broadly observed across animal and plant taxa. The numerical value of 3/4 is theoretically predicted under the optimized version of West, Brown, and Enquist's vascular resource supply network model. Insects, however, have recently been proposed to express a numerically different scaling exponent and thus application of the WBE network model to insects has been rejected. Here, we re-analyze whether such variation is indeed supported by a global deviation across all insect taxa at the order and family levels to assess if specific taxa influence insect metabolic scaling. We show that a previous reported deviation is largely due to the effect of a single insect family (Termitidae). We conclude that the BS-MR relationship in insects broadly supports the core predictions of the WBE model. We suggest that the deviation observed within the termites warrants further investigation and may be due to either difficulty in accurately measuring termite metabolism and/or particularities of their life history. Future work on allometric scaling should assess the nature of variation around the central tendencies in scaling exponents in order to test if this variation is consistent with core assumptions and predictions of the WBE model that stem by relaxing its secondary optimizing assumptions that lead to the 3/4 exponent. © 2011 Elsevier Ltd.
Simova, I., Storch, D., Keil, P., Boyle, B., Phillips, O. L., & Enquist, B. J. (2011). Global species-energy relationship in forest plots: role of abundance, temperature and species climatic tolerances. GLOBAL ECOLOGY AND BIOGEOGRAPHY , 20(6), 842-856.
Stark, S. C., Bentley, L. P., & Enquist, B. J. (2011). Response to Coomes & Allen (2009)'Testing the metabolic scaling theory of tree growth'. JOURNAL OF ECOLOGY , 99(3), 741-747.
Abstract: Coomes & Allen (2009) propose a new statistical method to test the Metabolic Scaling Theory prediction for tree growth rate size scaling (scaling constant α=1/3) presented in Enquist (1999). This method finds values of the scaling constant that yield standardized major axis (SMA) slopes of one in a comparison of allometrically transformed diameter census data. This SMA 'slope-of-one' method produces results that contrast with those generated by maximum-likelihood estimation (MLE; Russo, Wiser & Coomes 2007; Coomes & Allen 2009). We hypothesize that the SMA slope-of-one method is inappropriate for this application because it assumes, unrealistically, that there is no biological or error variance in tree growth size scaling. To test our hypothesis, we simulate 'allometric' tree growth with biological and error variance in parameters and measurements. We find that the SMA slope-of-one method is sensitive to the amount of biological and error variance and consistently returns biassed parameter estimates, while the MLE method displays relatively little bias, particularly at larger sample sizes. Synthesis. The conclusions of Coomes & Allen (2009) should be reconsidered in the light of our findings. Investigations of tree growth rate size scaling must consider the influence of biological and error variance in model-fitting procedures to ultimately unravel the effects of tree architecture and ecological factors on patterns of size-dependent growth. © 2010 The Authors. Journal of Ecology © 2010 British Ecological Society.
Stegen, J. C., Swenson, N. G., Enquist, B. J., White, E. P., Phillips, O. L., Jorgensen, P. M., Weiser, M. D., Monteagudo, M. A., & Vargas, P. N. (2011). Variation in above-ground forest biomass across broad climatic gradients. GLOBAL ECOLOGY AND BIOGEOGRAPHY , 20(5), 744-754.
Stegen, J. C., Swenson, N. G., Enquist, B. J., White, E. P., Phillips, O. L., Jørgensen, P. M., Weiser, M. D., Mendoza, A. M., & Vargas, P. N. (2011). Variation in above-ground forest biomass across broad climatic gradients. Global Ecology and Biogeography , 20(5), 744-754.
Abstract: Aim An understanding of the relationship between forest biomass and climate is needed to predict the impacts of climate change on carbon stores. Biomass patterns have been characterized at geographically or climatically restricted scales, making it unclear if biomass is limited by climate in any general way at continental to global scales. Using a dataset spanning multiple climatic regions we evaluate the generality of published biomass-climate correlations. We also combine metabolic theory and hydraulic limits to plant growth to first derive and then test predictions for how forest biomass should vary with maximum individual tree biomass and the ecosystem water deficit. Location Temperate forests and dry, moist and wet tropical forests across North, Central and South America. Methods A forest biomass model was derived from allometric functions and power-law size distributions. Biomass and climate were correlated using extensive forest plot (276 0.1-ha plots), wood density and climate datasets. Climate variables included mean annual temperature, annual precipitation, their ratio, precipitation of the driest quarter, potential and actual evapotranspiration, and the ecosystem water deficit. The water deficit uniquely summarizes water balance by integrating water inputs from precipitation with water losses due to solar energy. Results Climate generally explained little variation in forest biomass, and mixed support was found for published biomass-climate relationships. Our theory indicated that maximum individual biomass governs forest biomass and is constrained by water deficit. Indeed, forest biomass was tightly coupled to maximum individual biomass and the upper bound of maximum individual biomass declined steeply with water deficit. Water deficit similarly constrained the upper bound of forest biomass, with most forests below the constraint. Main conclusions The results suggest that: (1) biomass-climate models developed at restricted geographic/climatic scales may not hold at broader scales; (2) maximum individual biomass is strongly related to forest biomass, suggesting that process-based models should focus on maximum individual biomass; (3) the ecosystem water deficit constrains biomass, but realized biomass often falls below the constraint; such that (4) biomass is not strongly limited by climate in most forests so that forest biomass may not predictably respond to changes in mean climate. © 2011 Blackwell Publishing Ltd.
Swenson, N. G., Enquist, B. J., Pither, J., Thompson, J., & Zimmerman, J. K. (2011). The problem and promise of scale dependency in community phylogenetics. ECOLOGY , 87(10), 2418-2424.
West, G. B., Enquist, B. J., & Brown, J. H. (2011). A general quantitative theory of forest structure and dynamics. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA , 106(17), 7040-7045.
Šímová, I., Storch, D., Keil, P., Boyle, B., Phillips, O. L., & Enquist, B. J. (2011). Global species-energy relationship in forest plots: Role of abundance, temperature and species climatic tolerances. Global Ecology and Biogeography , 20(6), 842-856.
Abstract: Aim To evaluate the strength of evidence for hypotheses explaining the relationship between climate and species richness in forest plots. We focused on the effect of energy availability which has been hypothesized to influence species richness: (1) via the effect of productivity on the total number of individuals (the more individuals hypothesis, MIH); (2) through the effect of temperature on metabolic rate (metabolic theory of biodiversity, MTB); or (3) by imposing climatic limits on species distributions. Location Global. Methods We utilized a unique 'Gentry-style' 370 forest plots data set comprising tree counts and individual stem measurements, covering tropical and temperate forests across all six forested continents. We analysed variation in plot species richness and species richness controlled for the number of individuals by using rarefaction. Ordinary least squares (OLS) regression and spatial regressions were used to explore the relative performance of different sets of environmental variables. Results Species richness patterns do not differ whether we use raw number of species or number of species controlled for number of individuals, indicating that number of individuals is not the proximate driver of species richness. Productivity-related variables (actual evapotranspiration, net primary productivity, normalized difference vegetation index) perform relatively poorly as correlates of tree species richness. The best predictors of species richness consistently include the minimum temperature and precipitation values together with the annual means of these variables. Main conclusion Across the world's forests there is no evidence to support the MIH, and a very limited evidence for a prominent role of productivity as a driver of species richness patterns. The role of temperature is much more important, although this effect is more complex than originally assumed by the MTB. Variation in forest plot diversity appears to be mostly affected by variation in the minimum climatic values. This is consistent with the 'climatic tolerance hypothesis' that climatic extremes have acted as a strong constraint on species distribution and diversity. © 2011 Blackwell Publishing Ltd.
Elser, J. J., Fagan, W. F., Kerkhoff, A. J., Swenson, N. G., & Enquist, B. J. (2010). Biological stoichiometry of plant production: Metabolism, scaling and ecological response to global change. New Phytologist , 186(3), 593-608.
PMID: 20298486;Abstract: Biological stoichiometry theory considers the balance of multiple chemical elements in living systems, whereas metabolic scaling theory considers how size affects metabolic properties from cells to ecosystems. We review recent developments integrating biological stoichiometry and metabolic scaling theories in the context of plant ecology and global change. Although vascular plants exhibit wide variation in foliar carbon: nitrogen: phosphorus ratios, they exhibit a higher degree of 'stoichiometric homeostasis' than previously appreciated. Thus, terrestrial carbon: nitrogen: phosphorus stoichiometry will reflect the effects of adjustment to local growth conditions as well as species' replacements. Plant stoichiometry exhibits size scaling, as foliar nutrient concentration decreases with increasing plant size, especially for phosphorus. Thus, small plants have lower nitrogen: phosphorus ratios. Furthermore, foliar nutrient concentration is reflected in other tissues (root, reproductive, support), permitting the development of empirical models of production that scale from tissue to whole-plant levels. Plant stoichiometry exhibits large-scale macroecological patterns, including stronger latitudinal trends and environmental correlations for phosphorus concentration (relative to nitrogen) and a positive correlation between nutrient concentrations and geographic range size. Given this emerging knowledge of how plant nutrients respond to environmental variables and are connected to size, the effects of global change factors (such as carbon dioxide, temperature, nitrogen deposition) can be better understood. © The Authors (2010). Journal compilation © New Phytologist Trust (2010).
Savage, V. M., Bentley, L. P., Enquist, B. J., Sperry, J. S., Smith, D. D., Reich, P. B., & Allmen, E. V. (2010). Hydraulic trade-offs and space filling enable better predictions of vascular structure and function in plants. Proceedings of the National Academy of Sciences of the United States of America , 107(52), 22722-22727.
PMID: 21149696;PMCID: PMC3012458;Abstract: Plant vascular networks are central to botanical form, function, and diversity. Here, we develop a theory for plant network scaling that is based on optimal space filling by the vascular system along with trade-offs between hydraulic safety and efficiency. Including these evolutionary drivers leads to predictions for sap flow, the taper of the radii of xylem conduits from trunk to terminal twig, and how the frequency of xylem conduits varies with conduit radius. To test our predictions, we use comprehensive empirical measurements of maple, oak, and pine trees and complementary literature data that we obtained for a wide range of tree species. This robust intra- and interspecific assessment of our botanical network model indicates that the central tendency of observed scaling properties supports our predictions much better than the West, Brown, and Enquist (WBE) or pipe models. Consequently, our model is a more accurate description of vascular architecture than what is given by existing network models and should be used as a baseline to understand and to predict the scaling of individual plants to whole forests. In addition, our model is flexible enough to allow the quantification of species variation around rules for network design. These results suggest that the evolutionary drivers that we propose have been fundamental in determining how physiological processes scale within and across plant species.
Conlisk, E., Conlisk, J., Enquist, B., Thompson, J., & Harte, J. (2009). Improved abundance prediction from presence-absence data. GLOBAL ECOLOGY AND BIOGEOGRAPHY , 18(1), 1-10.
Enquist, B. J., West, G. B., & Brown, J. H. (2009). Extensions and evaluations of a general quantitative theory of forest structure and dynamics. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA , 106(17), 7046-7051.
Enquist, B. J., West, G. B., & Brown, J. H. (2009). Extensions and evaluations of a general quantitative theory of forest structure and dynamics. Proceedings of the National Academy of Sciences of the United States of America , 106(17), 7046-51.
Here, we present the second part of a quantitative theory for the structure and dynamics of forests under demographic and resource steady state. The theory is based on individual-level allometric scaling relations for how trees use resources, fill space, and grow. These scale up to determine emergent properties of diverse forests, including size-frequency distributions, spacing relations, canopy configurations, mortality rates, population dynamics, successional dynamics, and resource flux rates. The theory uniquely makes quantitative predictions for both stand-level scaling exponents and normalizations. We evaluate these predictions by compiling and analyzing macroecological datasets from several tropical forests. The close match between theoretical predictions and data suggests that forests are organized by a set of very general scaling rules. Our mechanistic theory is based on allometric scaling relations, is complementary to "demographic theory," but is fundamentally different in approach. It provides a quantitative baseline for understanding deviations from predictions due to other factors, including disturbance, variation in branching architecture, asymmetric competition, resource limitation, and other sources of mortality, which are not included in the deliberately simplified theory. The theory should apply to a wide range of forests despite large differences in abiotic environment, species diversity, and taxonomic and functional composition.
McCarthy, M. C., Enquist, B. J., & Kerkhoff, A. J. (2009). Organ partitioning and distribution across the seed plants: Assessing the relative importance of phylogeny and function. INTERNATIONAL JOURNAL OF PLANT SCIENCES , 168(5), 751-761.
Morlon, H., White, E. P., Etienne, R. S., Green, J. L., Ostling, A., Alonso, D., Enquist, B. J., He, F., Hurlbert, A., Magurran, A. E., Maurer, B. A., McGill, B. J., Olff, H., Storch, D., & Zillio, T. (2009). Taking species abundance distributions beyond individuals. ECOLOGY LETTERS , 12(6), 488-501.
The species abundance distribution (SAD) is one of the few universal patterns in ecology. Research on this fundamental distribution has primarily focused on the study of numerical counts, irrespective of the traits of individuals. Here we show that considering a set of Generalized Species Abundance Distributions (GSADs) encompassing several abundance measures, such as numerical abundance, biomass and resource use, can provide novel insights into the structure of ecological communities and the forces that organize them. We use a taxonomically diverse combination of macroecological data sets to investigate the similarities and differences between GSADs. We then use probability theory to explore, under parsimonious assumptions, theoretical linkages among them. Our study suggests that examining different GSADs simultaneously in natural systems may help with assessing determinants of community structure. Broadening SADs to encompass multiple abundance measures opens novel perspectives in biodiversity research and warrants future empirical and theoretical developments.
Price, C. A., & Enquist, B. J. (2009). Comment on Coomes et al. 'Scaling of xylem vessels and veins within the leaves of oak species'. Biology letters , 5(3), 380; author reply 381-2.
West, G. B., Enquist, B. J., & Brown, J. H. (2009). A general quantitative theory of forest structure and dynamics. Proceedings of the National Academy of Sciences of the United States of America , 106(17), 7040-5.
We present the first part of a quantitative theory for the structure and dynamics of forests at demographic and resource steady state. The theory uses allometric scaling relations, based on metabolism and biomechanics, to quantify how trees use resources, fill space, and grow. These individual-level traits and properties scale up to predict emergent properties of forest stands, including size-frequency distributions, spacing relations, resource flux rates, and canopy configurations. Two insights emerge from this analysis: (i) The size structure and spatial arrangement of trees in the entire forest are emergent manifestations of the way that functionally invariant xylem elements are bundled together to conduct water and nutrients up from the trunks, through the branches, to the leaves of individual trees. (ii) Geometric and dynamic properties of trees in a forest and branches in trees scale identically, so that the entire forest can be described mathematically and behaves structurally and functionally like a scaled version of the branching networks in the largest tree. This quantitative framework uses a small number of parameters to predict numerous structural and dynamical properties of idealized forests.
Bryant, J. A., Lamanna, C., Morlon, H., Kerkhoff, A. J., Enquist, B. J., & Green, J. L. (2008). Colloquium paper: microbes on mountainsides: contrasting elevational patterns of bacterial and plant diversity. Proceedings of the National Academy of Sciences of the United States of America , 105 Suppl 1, 11505-11.
The study of elevational diversity gradients dates back to the foundation of biogeography. Although elevational patterns of plant and animal diversity have been studied for centuries, such patterns have not been reported for microorganisms and remain poorly understood. Here, in an effort to assess the generality of elevational diversity patterns, we examined soil bacterial and plant diversity along an elevation gradient. To gain insight into the forces that structure these patterns, we adopted a multifaceted approach to incorporate information about the structure, diversity, and spatial turnover of montane communities in a phylogenetic context. We found that observed patterns of plant and bacterial diversity were fundamentally different. While bacterial taxon richness and phylogenetic diversity decreased monotonically from the lowest to highest elevations, plants followed a unimodal pattern, with a peak in richness and phylogenetic diversity at mid-elevations. At all elevations bacterial communities had a tendency to be phylogenetically clustered, containing closely related taxa. In contrast, plant communities did not exhibit a uniform phylogenetic structure across the gradient: they became more overdispersed with increasing elevation, containing distantly related taxa. Finally, a metric of phylogenetic beta-diversity showed that bacterial lineages were not randomly distributed, but rather exhibited significant spatial structure across the gradient, whereas plant lineages did not exhibit a significant phylogenetic signal. Quantifying the influence of sample scale in intertaxonomic comparisons remains a challenge. Nevertheless, our findings suggest that the forces structuring microorganism and macroorganism communities along elevational gradients differ.
Poore, R. E., Lamanna, C. A., Ebersole, J. J., & Enquist, B. J. (2008). CONTROLS ON RADIAL GROWTH OF MOUNTAIN BIG SAGEBRUSH AND IMPLICATIONS FOR CLIMATE CHANGE. WESTERN NORTH AMERICAN NATURALIST , 69(4), 556-562.
Swenson, N. G., Enquist, B. J., Thompson, J., & Zimmerman, J. K. (2008). The influence of spatial and size scale on phylogenetic relatedness in tropical forest communities. ECOLOGY , 88(7), 1770-1780.
Weiser, M. D., Enquist, B. J., Boyle, B., Killeen, T. J., Jorgensen, P. M., Fonseca, G., Jennings, M. D., Kerkhoff, A. J., Lacher, T. E., Monteagudo, A., Vargas, M. P., Phillips, O. L., Swenson, N. G., & Martinez, R. V. (2008). Latitudinal patterns of range size and species richness of New World woody plants. GLOBAL ECOLOGY AND BIOGEOGRAPHY , 16(5), 679-688.
Bryant, J. A., Lamanna, C., Morlon, H., Kerkhoff, A. J., Enquist, B. J., & Green, J. L. (2007). Microbes on mountainsides: Contrasting elevational patterns of bacterial and plant diversity. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA , 105, 11505-11511.
Cable, J. M., Enquist, B. J., & Moses, M. E. (2007). The Allometry of Host- Pathogen Interactions. PLOS ONE , 2(11).
Conlisk, E., Bloxham, M., Conlisk, J., Enquist, B., & Harte, J. (2007). A new class of models of spatial distribution. ECOLOGICAL MONOGRAPHS , 77(2), 269-284.
Enquist, B. J., & Stark, S. C. (2007). Follow Thompson's map to turn biology from a science into a Science. NATURE , 446(7136), 611-611.
Enquist, B. J., & Stark, S. C. (2007). Follow Thompson's map to turn biology from a science into a Science. Nature , 446(7136), 611.
Enquist, B. J., Allen, A. P., Brown, J. H., Gillooly, J. F., Kerkhoff, A. J., Niklas, K. J., Price, C. A., & West, G. B. (2007). Biological scaling: does the exception prove the rule?. Nature , 445(7127), E9-10; discussion E10-1.
Reich et al. report that the whole-plant respiration rate, R, in seedlings scales linearly with plant mass, M, so that R=C(R)M(theta) when theta approximately 1, in which c(R) is the scaling normalization and theta is the scaling exponent. They also state that because nitrogen concentration (N) is correlated with c(R), variation in N is a better predictor of R than M would be. Reich et al. and Hedin incorrectly claim that these "universal" findings question the central tenet of metabolic scaling theory, which they interpret as predicting theta = (3/4), irrespective of the size of the plant. Here we show that these conclusions misrepresent metabolic scaling theory and that their results are actually consistent with this theory.
Enquist, B. J., Kerkhoff, A. J., Stark, S. C., Swenson, N. G., McCarthy, M. C., & Price, C. A. (2007). A general integrative model for scaling plant growth, carbon flux, and functional trait spectra. NATURE , 449(7159), 218-222.
Enquist, B. J., Kerkhoff, A. J., Stark, S. C., Swenson, N. G., McCarthy, M. C., & Price, C. A. (2007). A general integrative model for scaling plant growth, carbon flux, and functional trait spectra. Nature , 449(7159), 218-22.
Marquet, P. A., Allen, A. P., Brown, J. H., Dunne, J. A., Enquist, B. J., Gillooly, J. F., Gowaty, P. A., Green, J. L., Harte, J., Hubbell, S. P., O'Dwyer, J., Okie, J. G., Ostling, A., Ritchie, M., Storch, D., & West, G. B. (2007). On Theory in Ecology. BIOSCIENCE , 64(8), 701-710.
McGill, B. J., Etienne, R. S., Gray, J. S., Alonso, D., Anderson, M. J., Benecha, H. K., Dornelas, M., Enquist, B. J., Green, J. L., He, F., Hurlbert, A. H., Magurran, A. E., Marquet, P. A., Maurer, B. A., Ostling, A., Soykan, C. U., Ugland, K. I., & White, E. P. (2007). Species abundance distributions: moving beyond single prediction theories to integration within an ecological framework. ECOLOGY LETTERS , 10(10), 995-1015.
Species abundance distributions (SADs) follow one of ecology's oldest and most universal laws--every community shows a hollow curve or hyperbolic shape on a histogram with many rare species and just a few common species. Here, we review theoretical, empirical and statistical developments in the study of SADs. Several key points emerge. (i) Literally dozens of models have been proposed to explain the hollow curve. Unfortunately, very few models are ever rejected, primarily because few theories make any predictions beyond the hollow-curve SAD itself. (ii) Interesting work has been performed both empirically and theoretically, which goes beyond the hollow-curve prediction to provide a rich variety of information about how SADs behave. These include the study of SADs along environmental gradients and theories that integrate SADs with other biodiversity patterns. Central to this body of work is an effort to move beyond treating the SAD in isolation and to integrate the SAD into its ecological context to enable making many predictions. (iii) Moving forward will entail understanding how sampling and scale affect SADs and developing statistical tools for describing and comparing SADs. We are optimistic that SADs can provide significant insights into basic and applied ecological science.
Price, C. A., & Enquist, B. J. (2007). Scaling mass and morphology in leaves: An extension of the WBE model. ECOLOGY , 88(5), 1132-1141.
Price, C. A., & Enquist, B. J. (2007). Scaling mass and morphology in leaves: an extension of the WBE model. Ecology , 88(5), 1132-41.
Recent advances in metabolic scaling theory have highlighted the importance of exchange surfaces and vascular network geometry in understanding the integration and scaling of whole-plant form and function. Additional work on leaf form and function has also highlighted general scaling relationships for many leaf traits. However, it is unclear if a common theoretical framework can reveal the general rules underlying much of the variation observed in scaling relationships at the whole-plant and leaf level. Here we present an extension of the general model introduced by G. B. West, J. H. Brown, and B. J. Enquist that has previously been applied to scaling phenomena for whole plants to predict scaling relationships in leaves. Specifically, the model shows how the exponents that describe the scaling of leaf surface area, length, and petiole diameter should change with increasing leaf mass (or with one another) and with variation in leaf dimensionality. The predictions of the model are tested and found to be in general agreement with a large data set of leaves collected from both temperate and arid sites. Our results demonstrate that a general model based on the scaling properties of biological distribution networks can also be successfully applied to understand the diversity of leaf form and function.
Price, C. A., Enquist, B. J., & Savage, V. M. (2007). A general model for allometric covariation in botanical form and function. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA , 104(32), 13204-13209.
Price, C. A., Enquist, B. J., & Savage, V. M. (2007). A general model for allometric covariation in botanical form and function. Proceedings of the National Academy of Sciences of the United States of America , 104(32), 13204-9.
The West, Brown, and Enquist (WBE) theory for the origin of allometric scaling laws is centered on the idea that the geometry of the vascular network governs how a suite of organismal traits covary with each other and, ultimately, how they scale with organism size. This core assumption has been combined with other secondary assumptions based on physiological constraints, such as minimizing the scaling of transport and biomechanical costs while maximally filling a volume. Together, these assumptions give predictions for specific "quarter-power" scaling exponents in biology. Here we provide a strong test of the core assumption of WBE by examining how well it holds when the secondary assumptions have been relaxed. Our relaxed version of WBE predicts that allometric exponents are highly constrained and covary according to specific quantitative functions. To test this core prediction, we assembled several botanical data sets with measures of the allometry of morphological traits. A wide variety of plant taxa appear to obey the predictions of the model. Our results (i) underscore the importance of network geometry in governing the variability and central tendency of biological exponents, (ii) support the hypothesis that selection has primarily acted to minimize the scaling of hydrodynamic resistance, and (iii) suggest that additional selection pressures for alternative branching geometries govern much of the observed covariation in biological scaling exponents. Understanding how selection shapes hierarchical branching networks provides a general framework for understanding the origin and covariation of many allometric traits within a complex integrated phenotype.
Savage, V. M., Enquist, B. J., & West, G. B. (2007). Comment on 'A critical understanding of the fractal model of metabolic scaling'. JOURNAL OF EXPERIMENTAL BIOLOGY , 210(21), 3873-3874.
Swenson, N. G., & Enquist, B. J. (2007). Ecological and evolutionary determinants of a key plant functional trait: Wood density and its community-wide variation across latitude and elevation. AMERICAN JOURNAL OF BOTANY , 94(3), 451-459.
Swenson, N. G., & Enquist, B. J. (2007). Opposing assembly mechanisms in a Neotropical dry forest: implications for phylogenetic and functional community ecology. ECOLOGY , 90(8), 2161-2170.
Swenson, N. G., & Enquist, B. J. (2007). The relationship between stem and branch wood specific gravity and the ability of each measure to predict leaf area. AMERICAN JOURNAL OF BOTANY , 95(4), 516-519.
White, E. P., Enquist, B. J., & Green, J. L. (2007). On estimating the exponent of power-law frequency distributions. ECOLOGY , 89(4), 905-912.
White, E. P., Ernest, S. K., Kerkhoff, A. J., & Enquist, B. J. (2007). Relationships between body size and abundance in ecology. Trends in ecology & evolution , 22(6), 323-30.
Body size is perhaps the most fundamental property of an organism and is related to many biological traits, including abundance. The relationship between abundance and body size has been extensively studied in an attempt to quantify the form of the relationship and to understand the processes that generate it. However, progress has been impeded by the under appreciated fact that there are four distinct, but interrelated, relationships between size and abundance that are often confused in the literature. Here, we review and distinguish between these four patterns, and discuss the linkages between them. We argue that a synthetic understanding of size-abundance relationships will result from more detailed analyses of individual patterns and from careful consideration of how and why the patterns are related.
White, E. P., Ernest, S., Kerkhoff, A. J., & Enquist, B. J. (2007). Relationships between body size and abundance in ecology. TRENDS IN ECOLOGY & EVOLUTION , 22(6), 323-330.
Kerkhoff, A. J., & Enquist, B. J. (2006). Ecosystem allometry: the scaling of nutrient stocks and primary productivity across plant communities. Ecology letters , 9(4), 419-27.
A principal challenge in ecology is to integrate physiological function (e.g. photosynthesis) across a collection of individuals (e.g. plants of different species) to understand the functioning of the entire ensemble (e.g. primary productivity). The control that organism size exerts over physiological and ecological function suggests that allometry could be a powerful tool for scaling ecological processes across levels of organization. Here we use individual plant allometries to predict how nutrient content and productivity scale with total plant biomass (phytomass) in whole plant communities. As predicted by our model, net primary productivity as well as whole community nitrogen and phosphorus content all scale allometrically with phytomass across diverse plant communities, from tropical forest to arctic tundra. Importantly, productivity data deviate quantitatively from the theoretically derived prediction, and nutrient productivity (production per unit nutrient) of terrestrial plant communities decreases systematically with increasing total phytomass. These results are consistent with the existence of pronounced competitive size hierarchies. The previously undocumented generality of these 'ecosystem allometries' and their basis in the structure and function of individual plants will likely provide a useful quantitative framework for research linking plant traits to ecosystem processes.
Kerkhoff, A. J., Fagan, W. F., Elser, J. J., & Enquist, B. J. (2006). Phylogenetic and growth form variation in the scaling of nitrogen and phosphorus in the seed plants. AMERICAN NATURALIST , 168(4), E103-E122.
Kerkhoff, A. J., Fagan, W. F., Elser, J. J., & Enquist, B. J. (2006). Phylogenetic and growth form variation in the scaling of nitrogen and phosphorus in the seed plants. The American naturalist , 168(4), E103-22.
Plant biomass and nutrient allocation explicitly links the evolved strategies of plant species to the material and energy cycles of ecosystems. Allocation of nitrogen (N) and phosphorus (P) is of particular interest because N and P play pivotal roles in many aspects of plant biology, and their availability frequently limits plant growth. Here we present a comparative scaling analysis of a global data compilation detailing the N and P contents of leaves, stems, roots, and reproductive structures of 1,287 species in 152 seed plant families. We find that P and N contents (as well as N : P) are generally highly correlated both within and across organs and that differences exist between woody and herbaceous taxa. Between plant organs, the quantitative form of the scaling relationship changes systematically, depending on whether the organs considered are primarily structural (i.e., stems, roots) or metabolically active (i.e., leaves, reproductive structures). While we find significant phylogenetic signals in the data, similar scaling relationships occur in independently evolving plant lineages, which implies that both the contingencies of evolutionary history and some degree of environmental convergence have led to a common set of rules that constrain the partitioning of nutrients among plant organs.
McGill, B. J., Enquist, B. J., Weiher, E., & Westoby, M. (2006). Rebuilding community ecology from functional traits. Trends in ecology & evolution , 21(4), 178-85.
There is considerable debate about whether community ecology will ever produce general principles. We suggest here that this can be achieved but that community ecology has lost its way by focusing on pairwise species interactions independent of the environment. We assert that community ecology should return to an emphasis on four themes that are tied together by a two-step process: how the fundamental niche is governed by functional traits within the context of abiotic environmental gradients; and how the interaction between traits and fundamental niches maps onto the realized niche in the context of a biotic interaction milieu. We suggest this approach can create a more quantitative and predictive science that can more readily address issues of global change.
McGill, B. J., Enquist, B. J., Weiher, E., & Westoby, M. (2006). Response to Kearney and Porter: Both functional and community ecologists need to do more for each other. TRENDS IN ECOLOGY & EVOLUTION , 21(9), 482-483.
Smith, F. A., Brown, J. H., Haskell, J. P., Lyons, S. K., Alroy, J., Charnov, E. L., Dayan, T., Enquist, B. J., Ernest, S. K., Hadly, E. A., Jones, K. E., Kaufman, D. M., Marquet, P. A., Maurer, B. A., Niklas, K. J., Porter, W. P., Tiffney, B., & Willig, M. R. (2004). Similarity of mammalian body size across the taxonomic hierarchy and across space and time. The American naturalist , 163(5), 672-91.
Although it is commonly assumed that closely related animals are similar in body size, the degree of similarity has not been examined across the taxonomic hierarchy. Moreover, little is known about the variation or consistency of body size patterns across geographic space or evolutionary time. Here, we draw from a data set of terrestrial, nonvolant mammals to quantify and compare patterns across the body size spectrum, the taxonomic hierarchy, continental space, and evolutionary time. We employ a variety of statistical techniques including "sib-sib" regression, phylogenetic autocorrelation, and nested ANOVA. We find an extremely high resemblance (heritability) of size among congeneric species for mammals over approximately 18 g; the result is consistent across the size spectrum. However, there is no significant relationship among the body sizes of congeneric species for mammals under approximately 18 g. We suspect that life-history and ecological parameters are so tightly constrained by allometry at diminutive size that animals can only adapt to novel ecological conditions by modifying body size. The overall distributions of size for each continental fauna and for the most diverse orders are quantitatively similar for North America, South America, and Africa, despite virtually no overlap in species composition. Differences in ordinal composition appear to account for quantitative differences between continents. For most mammalian orders, body size is highly conserved, although there is extensive overlap at all levels of the taxonomic hierarchy. The body size distribution for terrestrial mammals apparently was established early in the Tertiary, and it has remained remarkably constant over the past 50 Ma and across the major continents. Lineages have diversified in size to exploit environmental opportunities but only within limits set by allometric, ecological, and evolutionary constraints.
Enquist, B. J., Economo, E. P., Huxman, T. E., Allen, A. P., Ignace, D. D., & Gillooly, J. F. (2003). Scaling metabolism from organisms to ecosystems. Nature , 423(6940), 639-42.
Understanding energy and material fluxes through ecosystems is central to many questions in global change biology and ecology. Ecosystem respiration is a critical component of the carbon cycle and might be important in regulating biosphere response to global climate change. Here we derive a general model of ecosystem respiration based on the kinetics of metabolic reactions and the scaling of resource use by individual organisms. The model predicts that fluxes of CO2 and energy are invariant of ecosystem biomass, but are strongly influenced by temperature, variation in cellular metabolism and rates of supply of limiting resources (water and/or nutrients). Variation in ecosystem respiration within sites, as calculated from a network of CO2 flux towers, provides robust support for the model's predictions. However, data indicate that variation in annual flux between sites is not strongly dependent on average site temperature or latitude. This presents an interesting paradox with regard to the expected temperature dependence. Nevertheless, our model provides a basis for quantitatively understanding energy and material flux between the atmosphere and biosphere.
West, G. B., Savage, V. M., Gillooly, J., Enquist, B. J., Woodruff, W. H., & Brown, J. H. (2003). Physiology: Why does metabolic rate scale with body size?. Nature , 421(6924), 713; discussion 714.
Enquist, B. J. (2002). Universal scaling in tree and vascular plant allometry: toward a general quantitative theory linking plant form and function from cells to ecosystems. Tree physiology , 22(15-16), 1045-64.
A general theory of allometric scaling that predicts how the proportions of vascular plants and the characteristics of plant communities change or scale with plant size is outlined. The theory rests, in part, on the assumptions of (1) minimal energy dissipation in the transport of fluid through space-filling, fractal-like, branching vascular networks; and (2) the absence of scaling with plant size in the anatomical and physiological attributes of leaves and xylem. The theory shows how the scaling of metabolism with plant size is central to the scaling of whole-plant form and function. It is shown how allometric constraints influence plant populations and, potentially, processes in plant evolution. Rapidly accumulating evidence in support of the general allometric model is reviewed and new evidence is presented. Current work supports the notion that scaling of how plants utilize space and resources is central to the development of a general synthetic and quantitative theory of plant form, function, ecology and diversity.
Enquist, B. J., & Niklas, K. J. (2002). Global allocation rules for patterns of biomass partitioning in seed plants. Science (New York, N.Y.) , 295(5559), 1517-20.
Enquist, B. J., Haskell, J. P., & Tiffney, B. H. (2002). General patterns of taxonomic and biomass partitioning in extant and fossil plant communities. Nature , 419(6907), 610-3.
A central goal of evolutionary ecology is to identify the general features maintaining the diversity of species assemblages. Understanding the taxonomic and ecological characteristics of ecological communities provides a means to develop and test theories about the processes that regulate species coexistence and diversity. Here, using data from woody plant communities from different biogeographic regions, continents and geologic time periods, we show that the number of higher taxa is a general power-function of species richness that is significantly different from randomized assemblages. In general, we find that local communities are characterized by fewer higher taxa than would be expected by chance. The degree of taxonomic diversity is influenced by modes of dispersal and potential biotic interactions. Further, changes in local diversity are accompanied by regular changes in the partitioning of community biomass between taxa that are also described by a power function. Our results indicate that local and regional processes have consistently regulated community diversity and biomass partitioning for millions of years.
Boyle, B., Meyer, H. W., Enquist, B., Salas, S., Meyer, H., & Smith, D. (2012, 2008). Higher taxa as paleoecological and paleoclimatic indicators: A search for the modern analog of the Florissant fossil flora. In PALEONTOLOGY OF THE UPPER EOCENE FLORISSANT FORMATION, COLORADO , 435, 33-51.
Ernst, K. C., Enquist, B. J., Ferguson, D. B., Merideth, R., Park, D. T., Dang, T., Nuñez-Regueiro, M. M., Baldwin, E., Soto, J. R., Breshears, D. D., Swann, A. L., Lien, A., Huang, T., Feng, X., & Lopez Hoffman, L. (2018, June). Crops in a Changing World: Hidden Forest-Agriculture Teleconnections . 5th European Congress of Conservation Biology. Jyväskylä, Finland: European Congress of Conservation Biology.
Frank, D. C., Friend, A., Girardin, M., Mahecha, M., Bodesheim, P., Klesse, S., Bjorklund, J., Seftigen, K., Enquist, B. J., Record, S., Charney, N., Evans, M. E., Trouet, V. M., Zhang, Z., Poulter, B., Bouriaud, O., & Babst, F. (2017, April). When tree rings go global: challenges and opportunities for retro- and prospective insights . European Geosciences Union General Assembly. Vienna, Austria: European Geosciences Union.
Evans, M. E., Merow, C., Record, S., McMahon, S. M., & Enquist, B. J. (2016. Towards Process-based Range Modeling of Many Species(pp 860-871).
Understanding and forecasting species' geographic distributions in the face of global change is a central priority in biodiversity science. The existing view is that one must choose between correlative models for many species versus process-based models for few species. We suggest that opportunities exist to produce process-based range models for many species, by using hierarchical and inverse modeling to borrow strength across species, fill data gaps, fuse diverse data sets, and model across biological and spatial scales. We review the statistical ecology and population and range modeling literature, illustrating these modeling strategies in action. A variety of large, coordinated ecological datasets that can feed into these modeling solutions already exist, and we highlight organisms that seem ripe for the challenge.
Enquist, B. J., Tiffney, B. H., & Niklas, K. J. (2014. Metabolic scaling and the evolutionary dynamics of plant size, form, and diversity: Toward a synthesis of ecology, evolution, and paleontology(pp 729-749).
Goff, S. A., Vaughn, M., McKay, S., Lyons, E., Stapleton, A. E., Gessler, D., Matasci, N., Wang, L., Hanlon, M., Lenards, A., Muir, A., Merchant, N., Lowry, S., Mock, S., Helmke, M., Kubach, A., Narro, M., Hopkins, N., Micklos, D., , Hilgert, U., et al. (2011. The iPlant collaborative: cyberinfrastructure for plant biology.
Enquist, B. J., Kerkhoff, A. J., Huxman, T. E., & Economo, E. P. (2009. Adaptive differences in plant physiology and ecosystem paradoxes: insights from metabolic scaling theory(pp 591-609).
Violle, C., Enquist, B. J., McGill, B. J., Jiang, L., Albert, C. H., Hulshof, C., Jung, V., & Messier, J. (2007. The return of the variance: intraspecific variability in community ecology(pp 244-252).
Kerkhoff, A. J., & Enquist, B. J. (2012, APR 7). Multiplicative by nature: Why logarithmic transformation is necessary in allometry. JOURNAL OF THEORETICAL BIOLOGY.
Enquist, B. J., Allen, A. P., Brown, J. H., Gillooly, J. F., Kerkhoff, A. J., Niklas, K. J., Price, C. A., & West, G. B. (2011, FEB 1). Does the exception prove the rule?. NATURE.

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