bluuebunny/crossref_metadata_2025 huggingface dataset:
Relative contributions of plant traits and soil microbial properties to mountain grassland ecosystem services
Authors: Grigulis Karl , Lavorel Sandra , Krainer Ute , Legay Nicolas , Baxendale Catherine , Dumont Maxime , Kastl Eva , Arnoldi Cindy , Bardgett Richard D. , Poly Franck , Pommier Thomas , Schloter Michael , Tappeiner Ulrike , Bahn Michael , Clément Jean‐Christophe
Published: May 2013

Plant functional diversity and soil microbial community composition are tightly coupled. Changes in these interactions may influence ecosystem functioning. Links between plant functional diversity, soil microbial communities and ecosystem functioning have been demonstrated in experiments using plant monocultures and mixtures, using broad plant and microbial functional groups, but have not been examined in diverse natural plant communities.

We quantified the relative effects of plant and microbial functional properties on key ecosystem functions. We measured plant functional diversity, soil microbial community composition and parameters associated with nitrogen (N) cycling and key nutrient cycling processes at three grassland sites in different parts of Europe. Because plant structure and function strongly influence soil microbial communities, we determined relationships between ecosystem properties, plant traits and soil community characteristics following a sequential approach in which plant traits were fitted first, followed by the additional effects of soil micro‐organisms.

We identified a continuum from standing green biomass and standing litter, linked mostly with plant traits, to potentialNmineralization and potential leaching of soil inorganicN, linked mostly with microbial properties. Plant and microbial functional parameters were equally important in explaining % organic matter content in soil. A parallel continuum ran from plant height, linked with above‐ground biomass, to plant quality effects captured by the leaf economics spectrum, which were linked with the recycling of carbon (C) andN.

More exploitative species (higher specific leaf area, leafNconcentrations and lower leaf dry matter content) and taller swards, along with soil microbial communities dominated by bacteria, with rapid microbial activities, were linked with greater fodder production, but poorCandNretention. Conversely, dominance by conservative species (with opposite traits) and soil microbial communities dominated by fungi, and bacteria with slow activities, were usually linked with low production, but greater soilCstorage andNretention.

Synthesis– Grassland production,Csequestration and soilNretention are jointly related to plant and microbial functional traits. Managing grasslands for selected, or multiple, ecosystem services will thus require a consideration of the joint effects of plant and soil communities. Further understanding of the mechanisms that link plant and microbial functional traits is essential to achieve this.
Using functional traits to quantify the value of plant communities to invertebrate ecosystem service providers in arable landscapes
Authors: Storkey Jonathan , Brooks David , Haughton Alison , Hawes Cathy , Smith Barbara M. , Holland John M.
Published: May 2013

The loss of farmland biodiversity threatens the sustainability of ecosystem services delivered within agricultural landscapes. The functional trait approach has been successfully used in grassland systems to quantify trade‐offs and synergies between services delivered directly by plant communities. Many of the services delivered by arable landscapes, however, depend on invertebrate consumers, and the application of the trait‐based approach to these systems depends on quantifying functional relationships between trophic levels.

Two data sets of plant and invertebrate communities from a range of annual crops and uncropped land habitats were analysed. The community‐weighted means of plant functional traits were calculated for the vegetation samples and used as the explanatory variables in a multivariate analysis of plant species composition across habitats. The constrained axes scores were used in statistical models to explain the variance in associated total invertebrate abundance, phytophagous invertebrates and invertebrate numbers weighted by importance in the diet of farmland bird chicks.

The multivariate analysis discriminated between plant communities characterized by ruderal traits (high specific leaf area and early flowering) and those with more competitive traits. More ruderal communities also supported proportionally more invertebrates. The suite of traits included in the analysis explained a greater proportion of the variance in invertebrate abundance between uncropped habitats, as opposed to between annual crops.

The overlap between the plant traits that respond to disturbance (functional response traits) and those that affect the abundance of phytophagous invertebrates (functional effect traits) and the diet of farmland birds demonstrates the potential for using common functional metrics to integrate the assessment of an ecosystem service across different habitats particularly on uncropped land where intensity of disturbance is the main environmental driver.

Synthesis. The quantification of functional linkages between arable plants and the abundance of their associated invertebrate consumer communities is the first step in extending the trait‐based approach to quantify trade‐offs and synergies between ecosystem services developed in grassland systems to landscapes dominated by arable crops. However, applying the functional approach to in‐crop weed communities and other service providers such as pollinators will require the incorporation of additional response and effect traits.
Imperfect detection is the rule rather than the exception in plant distribution studies
Authors: Chen Guoke , Kéry Marc , Plattner Matthias , Ma Keping , Gardner Beth
Published: May 2013

Imperfect detection can seriously bias conventional estimators of species distributions and species richness. Plant traits, survey‐specific conditions and site‐specific characteristics may influence plant detection probability. However, the generality of the problems induced by imperfect detection in plants and the magnitude of this challenge for plant distribution studies are currently unknown.

We address this question based on data from theSwissBiodiversityMonitoring, in which vascular plants are surveyed twice in the same year along a 2.5‐km transect in 451 1‐km2quadrats. Overall, 1700 species were recorded. We chose a random sample of 100 species from the 1700 species to determine general detection levels. To examine the relationship of covariates on detection, we chose a stratified random sample of 100 species from 886 species that were detected in at least 18 locations, with 25 each from four life‐forms (LF): grass, forb, shrub and tree. Using aBayesian multispecies site‐occupancy model, we estimated occurrence and detection probability of these species and their relation to covariates.

Based on the random sample of 100 species, detection probability during the first survey ranged 0.03–0.99 (median 0.74) and during the second survey, 0.03–0.99 (median 0.82). Based on the stratified random sample of 100 species, detection probability during the first survey ranged 0.02–0.99 (median 0.87) and during the second survey, 0.01–1 (median 0.89). Detection probability differed slightly among the fourLFs. In 60 species, survey season or elevation had significant effects on detection. We illustrated detection probability maps forSwitzerland based on the modelled relationships with environmental covariates.

Synthesis. Our findings suggest that even in a standardized monitoring program, imperfect detection of plants may be common. With the absence of a correction for detection errors, maps in plant distribution studies will be confounded with spatial patterns in detection probability. We presume that these problems will be much more widespread in the data sets that are used for conventional plant species distribution modelling. Imperfect detection should be estimated, even in distribution studies of plants and other sessile organisms, to better control detection errors that may compromise the results of species distribution studies.
An experimental framework to identify community functional components driving ecosystem processes and services delivery
Authors: Dias André T. C. , Berg Matty P. , de Bello Francesco , Van Oosten Arend Raoul , Bílá Karolína , Moretti Marco
Published: May 2013

There is a growing consensus that the distribution of species trait values in a community can greatly determine ecosystem processes and services delivery. Two distinct components of community trait composition are hypothesized to chiefly affect ecosystem processes: (i) the average trait value of the species, quantified by community‐weighted mean trait values (CWM; related to the mass ratio hypothesis) and (ii) the degree to which trait values differ between species in a community, quantified by different indices of functional diversity (FD; related to non‐additive community effects). The uncertainty on the relative effect of these two components is stimulating an increasing number of empirical studies testing their effects on ecosystem processes and services delivery.

We suggest, however, that the interdependence between CWM and FD poses a challenge on disentangling their relative importance. We present a framework that allows designing experiments to decouple and assess the effects of these two community functional components on ecosystem processes and services. To illustrate the framework, we focused on leaf litter decomposition, as this is an essential process related to important ecosystem services. Using simulations, we applied the framework for plant leaf litter traits (litter nitrogen and phenolic content) that are related to litter decomposition.

CWM and FD generally showed a hump‐shaped relationship (i.e. at more extreme CWM values, communities can have only low FD values). Within this relationship, we showed that it is possible to select quasi‐orthogonal combinations of CWM and FD that can be treated statistically. Within these orthogonal CWM and FD combinations, it is also possible to select species assemblages controlling for other community parameters, such as total biomass, total density and species richness.

Synthesis. The framework provides a novel approach for designing experiments to decouple the effects of CWM and FD of communities on ecosystem processes, which otherwise cannot be easily disentangled. To apply the framework and design proper experimental layouts, it is essential to have a priori knowledge of the key traits by which species affect ecosystem processes and service delivery.
Identification of 100 fundamental ecological questions
Authors: Sutherland William J. , Freckleton Robert P. , Godfray H. Charles J. , Beissinger Steven R. , Benton Tim , Cameron Duncan D. , Carmel Yohay , Coomes David A. , Coulson Tim , Emmerson Mark C. , Hails Rosemary S. , Hays Graeme C. , Hodgson Dave J. , Hutchings Michael J. , Johnson David , Jones Julia P. G. , Keeling Matt J. , Kokko Hanna , Kunin William E. , Lambin Xavier , Lewis Owen T. , Malhi Yadvinder , Mieszkowska Nova , Milner‐Gulland E. J. , Norris Ken , Phillimore Albert B. , Purves Drew W. , Reid Jane M. , Reuman Daniel C. , Thompson Ken , Travis Justin M. J. , Turnbull Lindsay A. , Wardle David A. , Wiegand Thorsten
Published: May 2013

Fundamental ecological research is both intrinsically interesting and provides the basic knowledge required to answer applied questions of importance to the management of the natural world. The 100th anniversary of the British Ecological Society in 2013 is an opportune moment to reflect on the current status of ecology as a science and look forward to high‐light priorities for future work.

To do this, we identified 100 important questions of fundamental importance in pure ecology. We elicited questions from ecologists working across a wide range of systems and disciplines. The 754 questions submitted (listed in the online appendix) from 388 participants were narrowed down to the final 100 through a process of discussion, rewording and repeated rounds of voting. This was done during a two‐day workshop and thereafter.

The questions reflect many of the important current conceptual and technical pre‐occupations of ecology. For example, many questions concerned the dynamics of environmental change and complex ecosystem interactions, as well as the interaction between ecology and evolution.

The questions reveal a dynamic science with novel subfields emerging. For example, a group of questions was dedicated to disease and micro‐organisms and another on human impacts and global change reflecting the emergence of new subdisciplines that would not have been foreseen a few decades ago.

The list also contained a number of questions that have perplexed ecologists for decades and are still seen as crucial to answer, such as the link between population dynamics and life‐history evolution.

Synthesis. These 100 questions identified reflect the state of ecology today. Using them as an agenda for further research would lead to a substantial enhancement in understanding of the discipline, with practical relevance for the conservation of biodiversity and ecosystem function.
Costs and benefits of relative bark thickness in relation to fire damage: a savanna/forest contrast
Authors: Lawes Michael J. , Midgley Jeremy J. , Clarke Peter J.
Published: May 2013

In fire‐prone ecosystems, bark protects the stem bud bank from fire. Absolute bark thickness is a good indicator of this protective function, but it depends on stem size as well as inherent differences between species. Relative bark thickness (i.e. relative to stem diameter) takes the latter into account. We argue that relative bark thickness is an important functional trait offering insights to the evolution of species persistence in fire‐prone habitats.

During growth ontogeny different species can acquire absolutely thick bark through having: (i) relatively thick bark (i.e. an early commitment to thick bark) or (ii) relatively thin bark but fast stem diameter growth rates. We test the hypothesis that the most effective way of protecting tree stems from frequent fire is by having relatively thick‐barked small stems. We predict that species with higher relative bark thickness are more common in fire‐prone habitats. In habitats with long fire‐free intervals such as rainforest, delayed investment in bark thickness results in thin bark.

We examined the relative bark thickness of woody congeners from Australian non‐fire‐prone forest and fire‐prone savanna and in other tree‐dominated systems world‐wide. We determined the relative cost of acquiring absolute bark thickness of 0.5 cm for different rates of bark allocation. The insulating benefits of bark were considered a linear function of bark thickness.

Synthesis. We suggest that relatively thick bark minimizes the costs of acquiring absolutely thick bark, and it confers greater protection to smaller stems. The cost of acquiring thick bark prevents small trees from merely accumulating bark as a consequence of fast height or stem diameter growth. Accordingly, our field survey indicated that forest species had relatively thin bark and acquired thick bark only as a consequence of very large size, while fire‐prone savanna species had relatively thick‐barked small stems. Based on this, relative bark thickness appears to be a good predictor of local fire regimes and is a useful plant functional trait.
Herbivore‐induced plant volatiles provide associational resistance against an ovipositing herbivore
Authors: Zakir Ali , Sadek Medhat M. , Bengtsson Marie , Hansson Bill S. , Witzgall Peter , Anderson Peter
Published: May 2013

Plants produce herbivore‐induced plant volatiles (HIPVs) in response to damage by herbivores. AlthoughHIPVs are known to enhance plant resistance by affecting herbivore host plant preferences and by attracting natural enemies, little is known about the role ofHIPVs on the resistance of neighbouring plants and the mechanism behind this associational resistance.

This study examined the effect ofHIPVs from herbivore‐damaged host plants (alfalfa (Medicago sativa), clover (Trifolium alexandrinum) and cotton (Gossypium hirsutum)) on oviposition byEgyptian cotton leafworm (Spodoptera littoralis) (Lepidoptera:Noctuidae) on neighbouring, undamaged host plants.

There was a significant reduction in oviposition byS. littoralison undamaged plants adjacent to herbivore‐damaged cotton plants under both field and laboratory conditions. The results showed that the associational resistance byHIPVs depends on direct effects on oviposition behaviour inS. littoralis. There were also indications that other mechanisms may be involved.

Associational resistance viaHIPVs was not observed for all plant species tested. Emission ofHIPVs from damaged cotton increased the resistance of undamaged cotton and alfalfa plants to oviposition byS. littoralis, butHIPVs from damaged alfalfa and clover neighbours did not provide resistance to undamaged cotton plants.

Synthesis. Our results suggest that the presence ofHIPV‐emitting plant neighbours can reduce herbivory on undamaged plants and enhance plant resistance by affecting oviposition behaviour in insect herbivores.
Soil heterogeneity generated by plant–soil feedbacks has implications for species recruitment and coexistence
Authors: Brandt Angela J. , de Kroon Hans , Reynolds Heather L. , Burns Jean H.
Published: May 2013

Most studies of soil heterogeneity have focused on underlying abiotic factors such as soil nutrients. However, increasing recognition of plant–soil feedback (PSF) effects on plant growth, combined with the observation that PSFs operate at small spatial scales, suggests that heterogeneity due to PSF could affect plant population and community dynamics. The consequences of PSF‐generated heterogeneity for coexistence depend on heterogeneity's effects on vital rates and how those vital rates influence population‐level recruitment dynamics.

We measured vital rates and recruitment dynamics of three congeneric pairs of introduced perennial plants grown as monocultures in experimental PSF‐generated soil environments. Field soils collected from conspecifics and congeners were alternated in patches or mixed together to produce heterogeneous and homogeneous soils, respectively.

We quantified the effects of PSF‐generated heterogeneity on germination and establishment and determined how these vital rates affected recruitment. We calculated net pairwise interaction coefficients to predict whether PSFs could mediate coexistence between congeners.

Soil heterogeneity altered the relationship of vital rates to recruitment dynamics for some species. For example, Solanum dulcamara recruited later into heterogeneous than homogeneous soils, and germination was a stronger predictor of the timing of recruitment in heterogeneous soil, while mortality was a stronger predictor in homogeneous soil. Contrasts between soils of different origin suggest that mixing soils had non‐additive effects on vital rates (e.g. Rumex crispus mortality was higher in homogeneous than in conspecific or congener soil). Interaction coefficients predicted that PSFs in heterogeneous soils might mediate stable coexistence only of Rumex congeners.

Synthesis. Heterogeneity generated by PSFs had species‐specific effects on vital rates, with consequences for recruitment dynamics. Mixing soils of different origin often resulted in non‐additive effects, which may indicate an interaction between soil abiotic and/or biotic properties and could predict non‐additive responses to soil disturbance. Finally, quantifying the reciprocal effects of PSFs on congeners suggests that PSF‐generated heterogeneity may promote coexistence of certain species, which was not evident from individual PSF responses. Future studies should determine whether such mechanisms might operate for more distantly related species.
Above‐ and below‐ground herbivory effects on below‐ground plant–fungus interactions and plant–soil feedback responses
Authors: Martijn Bezemer T. , van der Putten Wim H. , Martens Henk , van de Voorde Tess F. J. , Mulder Patrick P. J. , Kostenko Olga
Published: May 2013

Feeding by insect herbivores can affect plant growth and the concentration of defense compounds in plant tissues. Since plants provide resources for soil organisms, herbivory can also influence the composition of the soil community via its effects on the plant. Soil organisms, in turn, are important for plant growth. We tested whether insect herbivores, via their effects on the soil microbial community, can influence plant‐soil feedbacks.

We first examined the effects of above‐ground (AG) and below‐ground (B) insect herbivory on the composition of pyrrolizidine alkaloids (PAs) in roots and on soil fungi in roots and rhizosphere soil of ragwort (Jacobaea vulgaris). The composition of fungal communities in roots and rhizosphere soil was affected by both AG and BG herbivory, but fungal composition also differed considerably between roots and rhizosphere soil. The composition of PAs in roots was affected only by BG herbivory.

Thirteen different fungal species were detected in roots and rhizosphere soil. The presence of the potentially pathogenic fungus Fusarium oxysporum decreased and that of Phoma exigua increased in presence of BG herbivory, but only in soil samples.

We then grew new plants in the soils conditioned by plants exposed to the herbivore treatments and in unconditioned soil. A subset of the new plants was exposed to foliar insect herbivory. Plant‐soil feedback was strongly negative, but the feedback effect was least negative in soil conditioned by plants that had been exposed to BG herbivory. There was a negative direct effect of foliar herbivory on plant biomass during the feedback phase, but this effect was far less strong when the soil was conditioned by plants exposed to AG herbivory. AG herbivory during the conditioning phase also caused a soil feedback effect on the PA concentration in the foliage of ragwort.

Synthesis. Our results illustrate how insect herbivory can affect interactions between plants and soil organisms, and via these effects how herbivory can alter the performance of late‐growing plants. Plant‐soil feedback is emerging as an important theme in ecology and these results highlight that plant‐soil feedback should be considered from a multitrophic AG and BG perspective.
Biotic plant–soil feedbacks across temporal scales
Authors: Kardol Paul , De Deyn Gerlinde B. , Laliberté Etienne , Mariotte Pierre , Hawkes Christine V.
Published: May 2013

Plant effects on soil biota can result in feedbacks affecting plant performance, with consequences for plant community and ecosystem dynamics on short and long time‐scales. In addition, the strength and direction of plant–soil feedbacks depend on temporal shifts in abiotic environmental conditions.

We synthesize current knowledge on temporal aspects of plant–soil feedbacks and present new ideas to better understand and predict the effects of plant–soil feedbacks on community and ecosystem properties across temporal scales.

Explaining short‐term temporal feedback dynamics requires us to better understand mechanistic linkages between plants, soil organisms and locally available resources. On the other hand, we need to refine our understanding of the context‐dependency of plant–soil feedbacks, as the strength and direction of feedback interactions are influenced by ‘external’ temporal ecosystem dynamics, such as variation in soil resource availability after disturbance or during succession.

Synthesis. Based on our synthesis of temporal aspects of plant–soil feedbacks, we suggest three main avenues for future research: (i) how plant–soil feedbacks changes with ontogeny, (ii) how plant and soil organism traits drive temporal variation in plant–soil feedbacks and (iii) how environmental changes across temporal scales alter the strength and direction of plant–soil feedbacks.
Multi‐millennial fire frequency and tree abundance differ between xeric and mesic boreal forests in centralCanada
Authors: Senici Dominic , Lucas Aurore , Chen Han Y. H. , Bergeron Yves , Larouche Alayn , Brossier Benoit , Blarquez Olivier , Ali Adam A.
Published: May 2013

Macroscopic sedimentary charcoal and plant macroremains from two lakes, 50 km apart, in north‐westernOntario,Canada, were analysed to investigate fire frequency and tree abundance in the central boreal forest. These records were used to examine the controls over the long‐term fire regime, and vegetative dynamics associated with fire return intervals (FRIs).

There were 52 fire events atLakeBen (surrounded by a xeric landscape) between 10 174 calibrated years before present (cal. yearbp) and the present with an averageFRIof 186 years with values oscillating between 40 and 820 years. Forty‐three fire events were recorded atLakeSmall (surrounded by a mesic landscape) between 9972 cal. yearbpand the present with an averageFRIof 229 years and a range of 60–660 years.FRIs atLakeSmall decreased significantly afterc. 4500 cal. yearbp, whereas atLakeBenFRIs remained similar throughout theHolocene. DifferentFRIdistributions and independence in the occurrence of fire events were detected between 10 000 and 4500 cal. yearbpfor the two sites. Between 4500 cal. yearbpand the present, similarFRIs were observed, but fires continued to occur independently.

LongerFRIs resulted in declining abundance ofLarix laricinain both landscapes. LongerFRIs resulted in a decline in the abundance ofPicea marianain the xeric landscape, but a marginal increase in the mesic landscape. Abundances ofPinus banksiana,Pinus strobusandBetula papyriferawere unrelated toFRI, underlying that these species maintain their local abundance irrespective of fire frequency.

Synthesis. Our results show contrasting fire regime dynamics between a xeric and mesic landscape in central boreal forests,Canada. These results highlight the influence of local factors as important drivers of fire frequency at centennial to millennial scales. Local site factors, especially soil moisture, need to be incorporated into predictive models of vegetation response to climate change.
Chasing a moving target: projecting climate change‐induced shifts in non‐equilibrial tree species distributions
Authors: García‐Valdés Raúl , Zavala Miguel A. , Araújo Miguel B. , Purves Drew W.
Published: May 2013

The geographic distributions of plant species show marked correlations with the current climate, suggesting that they are likely to shift if climate changes. However, before projecting any such shifts, it is important to establish whether distributions are at equilibrium with the current climate. If they are not, distributional shifts could occur even without climate change, making it difficult to tease apart climate‐induced shifts from shifts occurring naturally without climate change.

We forecast the geographical distributions of the 10 most common trees occurring in the Iberian Peninsula using a new method that relaxes the species–climate equilibrium assumption implicit in most species distributions models. For each species, we developed a spatially explicit patch occupancy model (SPOM) with climate‐dependent extinction rates and with colonization rates that depend on both climate and local seed dispersal. Bayesian methods were used to estimate the colonization, extinction and seed dispersal functions against observed colonization and extinction events recorded in repeat surveys of 46 596 forest plots in the Spanish Forest Inventories (1986–96 and 1997–2007). We then simulated distributional changes between the years 2000–2100.

Without climate change, 9 of the 10 species substantially increased in regional frequency. These increases occurred primarily within current ranges, although some species also expanded across their range edges. With climate change, one temperate conifer species and two sub‐Mediterranean species would reduce their frequency of occurrence across the studied region, whereas temperate broad‐leaved species were unaffected and Mediterranean species were either unaffected or increased their frequency of occurrence.

Synthesis. The analysis suggests that these species are substantially out of equilibrium, such that abundances and ranges would increase without climate change. Climate change may increase, decrease, stabilize or shift distributions, in a way that can only be understood by comparing predictions against baseline scenarios that account for these non‐equilibrium range dynamics.
Patterns and drivers of β‐diversity and similarity of Lobaria pulmonaria communities in Italian forests
Authors: Nascimbene Juri , Benesperi Renato , Brunialti Giorgio , Catalano Immacolata , Vedove Marilena D. , Grillo Maria , Isocrono Deborah , Matteucci Enrica , Potenza Giovanna , Puntillo Domenico , Puntillo Michele , Ravera Sonia , Rizzi Guido , Giordani Paolo
Published: May 2013

We attempted to elucidate the roles of β‐diversity components and similarity in shaping Lobaria pulmonaria lichen communities in Italian forests to provide scientific tools for improving their long‐term conservation.

A total of 20 sites were selected by stratified random sampling, including five chestnut forests, seven beech–silver fir forests and eight oak forests distributed across 10 administrative regions of Italy. Site selection was based on a national data base including all the available records of L. pulmonaria in Italy. In each forest, four plots were randomly placed, and in each plot, 5–6 trees were randomly selected for lichen sampling. For each forest and plot, meaningful predictors of lichen patterns were quantified. In particular, factors indicative of both geographic conditions and forests structure were considered. The SDR simplex approach was used to estimate the relative importance of similarity (S), relative species replacement (R) and relative richness difference (D) to β‐diversity and similarity, while a hierarchical partitioning (HP) method was used to evaluate the relative importance of environmental predictors in explaining their patterns.

A total of 201 lichens and three nonlichenized fungi were found, including 51 species of conservation concern. The components of β‐diversity and similarity contributed to shaping L. pulmonaria communities at both forest and plot scales across Italy, resulting in nearly random compositions, that is, the species set on each tree was a random sample from the available species pool. Species replacement and similarity were generally associated with forest structure predictors, while richness difference was mainly associated with geographic predictors. The implication of this is that the long‐term conservation of L. pulmonaria communities could be promoted by maintaining scattered nodes and appropriate habitat traits, especially in large forested landscapes where species turnover is higher.

Synthesis. In this work, we used a new approach for analysing a countrywide data set improving the ecological understanding of the dynamics regulating epiphytic communities. In particular, this study improves the understanding of the contribution of different components of diversity across two spatial scales and evaluates the relative importance of environmental predictors in explaining variation of each diversity component.
The ancient forests of La Gomera, Canary Islands, and their sensitivity to environmental change
Authors: Nogué Sandra , de Nascimento Lea , Fernández‐Palacios José María , Whittaker Robert J. , Willis Kathy J.
Published: May 2013

Garajonay National Park in La Gomera (Canary Islands) contains one of the largest remnant areas of a forest formation once widespread throughout Europe and North Africa. Here, we aim to address the long‐term dynamics (the last 9600 cal. years) of the monteverde forest (laurel forest and Morella‐Erica heath) located close to the summit of the National Park (1487 m a.s.l.) and determine past environmental and human impacts.

We used palaeoecological (fossil pollen, microscopic and macroscopic charcoal) and multivariate ecological techniques to identify compositional change in the monteverde forest in relation to potential climatic and human influences, based on the analysis of a core site at 1250‐m elevation.

The regional mid‐Holocene change towards drier conditions was matched in this system by a fairly rapid shift in representation of key forest elements, with declines in Canarian palm tree (Phoenix canariensis), Canarian willow (Salix canariensis) and certain laurel forest taxa and an increase in representation of the Morella–Erica woody heath.

Charcoal data suggest that humans arrived on the island between about 3000 and 1800 years ago, a period of minimal vegetation change. Levels of burning over the last 800 years are among the lowest of the entire 9600 years.

Synthesis. A rapid climatic‐induced shift of forest taxa occurred 5500 years ago, with a decrease in hygrophilous species in the pollen record. In contrast, we found no evidence of a significant response to human colonization. These findings support the idea that Garajonay National Park is protecting a truly ancient relict, comprising a largely natural rather than cultural legacy.
An improved model to predict the effects of changing biodiversity levels on ecosystem function
Authors: Connolly John , Bell Thomas , Bolger Thomas , Brophy Caroline , Carnus Timothee , Finn John A. , Kirwan Laura , Isbell Forest , Levine Jonathan , Lüscher Andreas , Picasso Valentin , Roscher Christiane , Sebastia Maria Teresa , Suter Matthias , Weigelt Alexandra
Published: May 2013

The development of models of the relationship between biodiversity and ecosystem function (BEF) has advanced rapidly over the last 20 years, incorporating insights gained through extensive experimental work. We proposeGeneralisedDiversity‐Interactions models that include many of the features of existing models and have several novel features.GeneralisedDiversity‐Interactions models characterise the contribution of two species to ecosystem function as being proportional to the product of their relative abundances raised to the power of a coefficient θ.

A value of θ < 1 corresponds to a stronger than expected contribution of species' pairs to ecosystem functioning, particularly at low relative abundance of species.

Varying the value of θ has profound consequences for community‐level properties ofBEFrelationships, including: (i) saturation properties of theBEFrelationship; (ii) the stability of ecosystem function across communities; (iii) the likelihood of transgressive overyielding.

For low values of θ, loss of species can have a much greater impact on ecosystem functioning than loss of community evenness.

GeneralisedDiversity‐Interactions models serve to unify the modelling ofBEFrelationships as they include several other current models as special cases.

GeneralisedDiversity‐Interactions models were applied to seven data sets and three functions: total biomass (five grassland experiments), community respiration (one bacterial experiment) and nitrate leaching (one earthworm experiment). They described all the nonrandom structure in the data in six experiments, and most of it in the seventh experiment and so fit as well or better than competingBEFmodels for these data. They were significantly better than Diversity‐Interactions models in five experiments.

Synthesis. We show thatGeneralizedDiversity‐Interactions models quantitatively integrate several methods that separately address effects of species richness, evenness and composition on ecosystem function. They describe empirical data at least as well as alternative models and improve the ability to quantitatively test among several theoretical and practical hypotheses about the effects of biodiversity levels on ecosystem function. They improve our understanding of important aspects of the relationship between biodiversity (evenness and richness) and ecosystem function (BEF), which include saturation, effects of species loss, the stability of ecosystem function and the incidence of transgressive overyielding.
Strong congruence in tree and fern community turnover in response to soils and climate in central Panama
Authors: Jones Mirkka M. , Ferrier Simon , Condit Richard , Manion Glenn , Aguilar Salomon , Pérez Rolando
Published: May 2013

Plant species turnover in central Panamanian forests has been principally attributed to the effects of dispersal limitation and a strong Caribbean to Pacific gradient in rainfall seasonality. Despite marked geological heterogeneity, the role of soil variation has not been rigorously examined.

We modelled the compositional turnover of trees and ferns in the Panama Canal watershed as a function of soil chemistry, climate and geographical separation, using generalized dissimilarity models (GDMs).

Predictability in both plant groups was strong, with 74% of turnover explained in trees and 49% in ferns. Major trends in the two plant groups were strikingly similar. The independent effects of soils, and of climate for trees, were sizeable, but those of geographical distance were minor. In both plant groups, distance and climatic effects on species turnover covaried strongly.

Including floristic dissimilarity of the other taxon as a predictor increased explained deviance to 81% in trees and 59% in ferns. Controlling for differences in plant density among plots reduced deviance explained by climate and distance, while soil effects remained strong. Limiting the analyses to soils of volcanic origin increased deviance explained by climate, soils and distance, but their effects covaried strongly. Independent soil effects on tree turnover were reduced, but their effects on fern turnover remained pronounced.

Dry season length was the most important climatic predictor for both taxa, and P and pH were the most important soil predictors. Particularly, rapid species turnover was associated with the driest end of the seasonality gradient, linked to declining individual densities and species richness, and with the low end of the phosphorus gradient.

Synthesis. While changes in rainfall and seasonality undoubtedly limit plant distributions in this region, soil effects are at least as important, and interactions between the two are sizeable. This is likely to hold elsewhere in the Caribbean region, where mosaics of marine and volcanic soils combined with pronounced rainfall gradients are common. Strong congruence between our focal taxa suggests that our results can be extrapolated to other plant groups, particularly as trees and ferns are distantly related and represent different life‐forms.
Leaf adaptations of evergreen and deciduous trees of semi‐arid and humid savannas on three continents
Authors: Tomlinson Kyle W. , Poorter Lourens , Sterck Frank J. , Borghetti Fabian , Ward David , de Bie Steven , van Langevelde Frank
Published: May 2013

Drought stress selects for a suite of plant traits at root, stem and leaf level. Two strategies are proposed for trees growing in seasonally water‐stressed environments: drought tolerance and drought avoidance. These are respectively associated with evergreen phenology, where plants retain their leaves throughout the year, and deciduous phenology, where plants drop their leaves during dry seasons. Evergreen species are thought to have leaf traits supporting lower photosynthesis and transpiration rates, in order to conserve water during dry periods.

We evaluated 18 morphological, chemical and physiological leaf traits of 51 abundant savanna tree species that differed in leaf habit (deciduous and evergreen), selected from two climate types (semi‐arid and humid) in three continents (Australia, Africa and South America) (annual rainfall range: 500–1550 mm), and grown in a common garden experiment. We hypothesised that evergreen species have more conservative water use and differ more across climate types than deciduous species because evergreen species are forced to endure extended water deficits during dry seasons.

Trait shifts between semi‐arid and humid savannas did not differ between evergreen and deciduous species.

Evergreen species had similar assimilation rates but lower photosynthetic water‐use efficiency (PWUE) than deciduous species, possibly to extend their leaf lifespans by protecting their photosynthetic machinery from overheating through evaporative cooling.

Species of humid and semi‐arid environments did not differ with respect to assimilation rate or PWUE, but semi‐arid species did have smaller leaf sizes and greater leaf potassium and phosphorus concentrations. These traits may enable semi‐arid species to maximize growth during episodes of favourable moisture availability.

Species from the three continents differed in their leaf traits. These probably reflect the greater proportion of evergreen species in Australia as compared to the other continents and generally infertile soils in the South American sampling sites compared to the wider fertility range in the African sites.

Synthesis: Water stress in savannas does not select for more conservative water use, but may select for rapid adjustment to prevailing water conditions and for heat avoidance mechanisms.
Let the best one stay: screening of ant defenders by Acacia host plants functions independently of partner choice or host sanctions
Authors: Heil Martin
Published: May 2013

Multiple plant species are engaged in defensive mutualisms with members of the third trophic level. However, mutualisms are prone to exploitation by low‐quality symbionts that do not provide the adequate service to their host. Can mutualisms proceed only when hosts identify their symbionts in advance or continuously monitor their activity, or are there other mechanisms to avoid the invasion of mutualisms by exploiters?

High‐reward species amongst Mesoamerican Acacia myrmecophytes are dominantly colonized by defending mutualistic ants, whereas about 50% of the low‐reward hosts are inhabited by non‐defending exploiters. I followed the development of recently founded ant colonies on a high‐reward and a low‐reward Acacia host species over 7 months, to investigate whether reward production correlates with a preferred maintenance of defending ants on the respective hosts.

Ant diversity decreased sooner on high‐reward than on low‐reward hosts, and mutualistic ants were more likely to finally dominate the high‐reward hosts. I observed an increased frequency of mutualists replacing parasites at high initial rates of reward production. Apparently, higher nectar provisioning by the host plants shifted the competitive balance between mutualistic and parasitic ants. Independently of the causal reason for the different secretion rates, producing more nectar thereby favours the maintenance of defending mutualists on high‐reward hosts.

Synthesis. The aggressiveness that enables ants to outcompete other ants also underlies their defensive effect against herbivores. I conclude that hosts can preferably associate with high‐quality mutualists without measuring their effectiveness. Mutualisms remain stable when partner screening is based on traits that are relevant for the mutualistic interaction, with no need for the host to have information on the quality or identity of the symbiont.
Latitudinal gradients as natural laboratories to infer species' responses to temperature
Authors: De Frenne Pieter , Graae Bente J. , Rodríguez‐Sánchez Francisco , Kolb Annette , Chabrerie Olivier , Decocq Guillaume , De Kort Hanne , De Schrijver An , Diekmann Martin , Eriksson Ove , Gruwez Robert , Hermy Martin , Lenoir Jonathan , Plue Jan , Coomes David A. , Verheyen Kris
Published: May 2013

Macroclimatic variation along latitudinal gradients provides an excellent natural laboratory to investigate the role of temperature and the potential impacts of climate warming on terrestrial organisms.

Here, we review the use of latitudinal gradients for ecological climate change research, in comparison with altitudinal gradients and experimental warming, and illustrate their use and caveats with a meta‐analysis of latitudinal intraspecific variation in important life‐history traits of vascular plants.

We first provide an overview of latitudinal patterns in temperature and other abiotic and biotic environmental variables in terrestrial ecosystems. We then assess the latitudinal intraspecific variation present in five key life‐history traits [plant height, specific leaf area (SLA), foliar nitrogen:phosphorus (N:P) stoichiometry, seed mass and root:shoot (R:S) ratio] in natural populations or common garden experiments across a total of 98 plant species.

Intraspecific leaf N:P ratio and seed mass significantly decreased with latitude in natural populations. Conversely, the plant height decreased and SLA increased significantly with latitude of population origin in common garden experiments. However, less than a third of the investigated latitudinal transect studies also formally disentangled the effects of temperature from other environmental drivers which potentially hampers the translation from latitudinal effects into a temperature signal.

Synthesis. Latitudinal gradients provide a methodological set‐up to overcome the drawbacks of other observational and experimental warming methods. Our synthesis indicates that many life‐history traits of plants vary with latitude but the translation of latitudinal clines into responses to temperature is a crucial step. Therefore, especially adaptive differentiation of populations and confounding environmental factors other than temperature need to be considered. More generally, integrated approaches of observational studies along temperature gradients, experimental methods and common garden experiments increasingly emerge as the way forward to further our understanding of species and community responses to climate warming.
The impact of secondary compounds and functional characteristics on lichen palatability and decomposition
Authors: Asplund Johan , Wardle David A.
Published: May 2013

There has been much recent interest in understanding how functional traits of vascular plant species drive ecological processes such as herbivory and litter decomposition. In plants, these two processes are often driven by the same or similar suites of traits and therefore correlate across species. However, few studies have considered how traits of plant‐like life forms such as lichens determine species differences in their effects on ecological processes. This is despite the significant contribution of lichens to carbon and nutrient cycling in many environments.

We collected 28 lichen species that differed in their growth form, substrate type and capacity to fix N, and determined key traits for each species. For each species, we performed a feeding bioassay using the generalist snail Cepaea hortensis and carried out a laboratory bioassay to assess decomposability. We did these tests both with intact lichen material containing natural concentrations of carbon‐based secondary compounds (CBSCs), and material that had been acetone rinsed to reduce concentrations of CBSCs, to evaluate the effect of CBSC on palatability and decomposability.

We found that reducing CBSC concentrations greatly increased palatability for 17 species, and decomposability of 10 species. However, decomposability was correlated with several lichen traits while palatability was not, regardless of whether or not CBSCs were removed, and we therefore found no relationship between decomposability and palatability across species. Decomposability and palatability both varied, but in contrasting directions, among N‐fixing vs. non‐fixing lichens, lichens with different growth forms and those from contrasting substrate types. As such, N‐fixing lichens had higher decomposition rates but lower consumption rates than non‐fixing lichens, while foliose species had higher decomposition rates but lower consumption rates than fruticose species.

Synthesis: We have shown that lichen CBSCs regulate key processes such as lichenivory and decomposition, that lichen decomposability but not palatability are related to traits, and that these two processes are unrelated across species. These results highlight the potential role of lichen species differences in influencing ecosystem processes relating to decomposition and nutrient cycling and the role that grazers may play in driving this.