bluuebunny/crossref_metadata_2025 huggingface dataset:
Light as an environmental filter in fen vegetation
Authors: Kotowski Wiktor , van Diggelen Rudy
Published: February 2009

Questions: 1. To what extent does light availability differ among fen plant communities? 2. To what extent does light coincide with productivity and moisture gradients? 3. Does light act as an important environmental filter in natural and transformed riparian landscapes?

Location: Current data from the Biebrza Valley, NE Poland; literature data from the Třeboň area, Czech Republic and four sites in the western and southern Netherlands.

Methods: Relative light intensity (RLI) was measured in vertical profiles, next to vegetation relevés accompanied by measurements of above‐ground biomass, summer groundwater level, N and P content in vegetation, pH and soil redox potential. Data derived from literature included profiles of RLI, biomass and vegetation records. Relationships between RLI and biomass and between species distribution, RLI and other variables were examined by regression analysis and CCA. Four traits were analysed: ability to spread clonally, seed weight, maximum height of adults and time of commencement of flowering.

Results: RLI at ground level varied from < 1% in reed beds and tall herb meadows to > 60% in sedge‐moss communities and litter meadows. RLI was largely determined by the standing crop and explained a large part of variation in species occurrence. The combinations of analysed functional traits were constrained by the communities’ light profiles.

Conclusion: Light availability is related more closely to site fertility than to hydrological regime. This confirms that hydrological regime and productivity should be analysed separately with regard to their effect on species distribution in wetlands. Limited light availability seems the major environmental control of the distribution of low growing and late flowering species.
Probability distributions, vulnerability and sensitivity in Fagus crenata forests following predicted climate changes in Japan
Authors: Matsui Tetsuya , Yagihashi Tsutomu , Nakaya Tomoki , Taoda Hirosi , Yoshinaga Shuichiro , Daimaru Hiromu , Tanaka Nobuyuki
Published: February 2009

Question: How much is the probability distribution of Fagus crenata forests predicted to change under a climate change scenario by the 2090s, and what are the potential impacts on these forests? What are the main factors inducing such changes?

Location: The major islands of Japan.

Methods: A predictive distribution model was developed with four climatic factors (summer precipitation, PRS; winter precipitation, PRW; minimum temperature of the coldest month, TMC; and warmth index, WI) and five non‐climatic factors (topography, surface geology, soil, slope aspect and inclination). A climate change scenario was applied to the model.

Results: Areas with high probability (> 0.5) were predicted to decrease by 91%, retreating from the southwest, shrinking in central regions, and expanding northeastwards beyond their current northern limits. A vulnerability index (the reciprocal of the predicted probability) suggests that Kyushu, Shikoku, the Pacific Ocean side of Honshu and southwest Hokkaido will have high numbers of many vulnerable F. crenata forests. The forests with high negative sensitivity indices (the difference between simulated probabilities of occurrence under current and predicted climates) mainly occur in southwest Hokkaido and the Sea of Japan side of northern Honshu.

Conclusion: F. crenata forest distributions may retreat from some islands due to a high WI. The predicted northeastward shift in northern Hokkaido is associated with increased TMC and PRS. High vulnerability and negative sensitivity of the forests in southern Hokkaido are due to increased WI.
Cover‐weighted averaging of indicator values in vegetation analyses
Authors: Käfer Jos , Witte Jan‐Philip M.
Published: February 2009

Question: How should species cover be weighted when calculating average indicator values of vegetation relevés?

Location: The Netherlands.

Method: Various weighting methods were statistically investigated with 188 relevés from The Netherlands for which accurate groundwater levels were available. For each method the correlation between average Ellenberg indicator value for moisture and mean spring groundwater level was calculated. A permutation test on correlation coefficients revealed whether differences between methods were significant or not.

Results: Optimization of a general weighting function did not produce a significantly higher correlation than disregarding cover and calculating the average as the arithmetical mean of indicator values. Giving a higher weight to species at both ends of the indicator scale and using indifferent species as indicators of mediocre conditions did improve the correlation significantly. Weighting species proportionate to their cover yielded a significantly lower correlation than the correlation obtained with the method that disregards cover. A significantly lower correlation was also established when taking into account the fact that cover is related to the growth strategy of species.
More efficient estimation of plant biomass
Authors: Bråthen Kari Anne , Hagberg Oskar
Published: February 2009

Question: The optimal use of the point intercept method (PIM) for efficient estimation of plant biomass has not been addressed although PIM is a commonly used method in vegetation analysis. In this study we compare results achieved using PIM at a range of efforts, we assess a method for calculating these results that are new with PIM and we provide a formula for planning the optimal use of PIM.

Location: Northern Norway.

Methods: We collected intercept data at a range of efforts, i.e. from one to 100 pins per 0.25 m2 plots, on three plant growth forms in a mountain meadow. After collection of intercept data we clipped and weighed the plant biomass. The relationship between intercept frequency and weighed biomass (b) was estimated using both a weighted linear regression model (WLR) and an ordinary linear regression model (OLR). The accuracy of the estimate of biomass achieved by PIM at different efforts was assessed by running computer simulations at different pin densities.

Results: The relationship between intercept frequency and weighed biomass (b) was far better estimated using WLR compared to the normally used OLR. Efforts above 10 pins per 0.25 m2 plot had a negligible effect on the accuracy of the estimate of biomass achieved by PIM whereas the number of plots had a strong effect. Moreover, for a given level of accuracy, the required number of plots varied depending on plant growth form. We achieved similar results to that of the computer simulations when applying our WLR based formula.

Conclusion: This study shows that PIM can be applied more efficiently than was done in previous studies for the purpose of plant biomass estimation, where several plots should be analysed but at considerably less effort per plot. Moreover, WLR rather than OLR should be applied when estimating biomass from intercept frequency. The formula we have deduced is a useful tool for planning plant biomass analysis with PIM.
Plant species and community responses to sand burial on the machair of the Outer Hebrides, Scotland
Authors: Owen Nia W. , Kent Martin , Dale M. Pamela
Published: February 2009

Question: Is there a critical depth of burial by sand beyond which species and communities fail to recover, and does repeated incremental burial have a greater impact than a single large deposition?

Location: The machair on the calcareous sand dunes on South Uist, in the Outer Hebrides of Scotland, UK.

Methods: Eight turves were collected from each of four machair sub‐community types. After acclimatization in an unheated polythene tunnel, they were buried with sterilized machair shell sand, either by one single burial to 5 cm or by five applications of 1 cm of sand at approximately seven‐week intervals. Species response was recorded on five occasions.

Results: Within machair sub‐communities, burial by sand reduced the abundance (local rooted frequency) of plants more than it reduced species richness. Intermittent burial was more damaging than a single burial event. Those species with the highest pre‐burial frequencies tended to dominate recovery in the sub‐community as a whole. Species occurring across all four sub‐community types exhibited varying responses to community burial between the differing types. Samples from slack sub‐communities had distinctly different response characteristics from those of foredunes and unploughed and three‐year fallow dune grassland.

Conclusions: The perennial life‐form of many machair species has been evolutionarily selected for and dominates throughout the machair habitat. Account needs to be taken of competitive interaction between species in relation to burial response. The results of the investigation show that the hypotheses of Gilbertson et al. and Kent et al. on ‘machair stratification’ require refinement in that frequency of shallow burial can be as important as overall burial depth.
Refining vegetation simulation models: From plant functional types to bioclimatic affinity groups of plants
Authors: Laurent J.‐M. , Bar‐Hen A. , François L. , Ghislain M. , Cheddadi R.
Published: February 2009

Question:How to refine simulations based on a global vegetation model in order to apply it to regional scale?

Location:Europe from 35° N to 71° N and 25° W to 70° E.

Methods:Geographical ranges of European plants were georeferenced and used with monthly mean climatic data (diurnal temperature ranges, ground frost frequencies, precipitation, relative humidity, rain frequencies, amount of sunshine hours and temperature) and growing degree days to infer climatic boundaries for 320 taxa. We performed a discriminant analysis to define their potential geographic ranges. Hierarchical clustering was computed on potential ranges.

Results:Clustering provided 25 Bioclimatic Affinity Groups (BAG) of plants consisting of 13 tree, seven shrub and five herb groups. These B AGs are characterized by different geographical ranges and climatic tolerances and requirements.

Conclusion:The use of monthly data instead of annual values improved the prediction of potential distribution ranges and highlighted the importance of climate seasonality for defining the plant groups with accuracy. The B AGs are detailed enough to provide finer reconstructions and simulations of the vegetation at the regional scale.
Effect of error in the DEM on environmental variables for predictive vegetation modelling
Authors: Van Niel Kimberly P. , Laffan Shawn W. , Lees Brian G.
Published: February 2009

Question: Predictive vegetation modelling relies on the use of environmental variables, which are usually derived from abase data set with some level of error, and this error is propagated to any subsequently derived environmental variables. The question for this study is: What is the level of error and uncertainty in environmental variables based on the error propagated from a Digital Elevation Model (DEM) and how does it vary for both direct and indirect variables?

Location: Kioloa region, New South Wales, Australia

Methods: The level of error in a DEM is assessed and used to develop an error model for analysing error propagation to derived environmental variables. We tested both indirect (elevation, slope, aspect, topographic position) and direct (average air temperature, net solar radiation, and topographic wetness index) variables for their robustness to propagated error from the DEM.

Results: It is shown that the direct environmental variable net solar radiation is less affected by error in the DEM than the indirect variables aspect and slope, but that regional conditions such as slope steepness and cloudiness can influence this outcome. However, the indirect environmental variable topographic position was less affected by error in the DEM than topographic wetness index. Interestingly, the results disagreed with the current assumption that indirect variables are necessarily less sensitive to propagated error because they are less derived.

Conclusions: The results indicate that variables exhibit both systematic bias and instability under uncertainty. There is a clear need to consider the sensitivity of variables to error in their base data sets in addition to the question of whether to use direct or indirect variables.
Slow recovery in desert perennial vegetation following prolonged human disturbance
Authors: Guo Qinfeng
Published: February 2009

Questions: How long may it take for desert perennial vegetation to recover from prolonged human disturbance and how do different plant community variables (i.e. diversity, density and cover) change during the recovery process?

Location: Sonoran Desert, Arizona, USA.

Methods: Since protection from grazing from 1907 onwards, plant diversity, density and cover of perennial species were monitored intermittently on ten 10 m × 10 m permanent plots on Tumamoc Hill, Tucson, Arizona, USA.

Results: The study shows an exceptionally slow recovery of perennial vegetation from prolonged heavy grazing and other human impacts. Since protection, overall species richness and habitat heterogeneity at the study site continued to increase until the 1960s when diversity, density and cover had been stabilized. During the same period, overall plant density and cover also increased. Species turnover increased gradually with time but no significant relation between any of the three community variables and precipitation or Palmer Drought Severity Index (PDSI) was detected.

Conclusions: It took more than 50 yr for the perennial vegetation to recover from prolonged human disturbance. The increases in plant species richness, density, and cover of the perennial vegetation were mostly due to the increase of herbaceous species, especially palatable species. The lack of a clear relationship between environment (e.g. precipitation) and community variables suggests that site history and plant life history must be taken into account in examining the nature of vegetation recovery processes after disturbance.
Vascular plant compositional gradients within and between Iowa fens
Authors: Nekola Jeffery C.
Published: February 2009

Question: What is the nature and relative importance of compositional gradients within‐ and between fens?

Location: Iowa, USA.

Methods: 506 0.5 m × 0.5 m quadrats were sampled from 31 fens across a 550 km extent. Presence/absence of all vascular plant taxa, plus the non‐vascular genera Sphagnum and Chara, and values for 24 environmental variables were noted. Global Non‐Metric Multidimensional Scaling and Monte Carlo tests were used to describe compositional variation and identify significant environmental co‐variables. Model‐based cluster analysis was used to identify the optimal number of groups supported by the data, while k‐means clustering was used to assign each quadrat to a group. The number of occurrences (and frequency) of each species within each group was calculated. Two‐dimensional 95% Gaussian confidence intervals, ANOVA, correlation coefficient homogeneity tests, log‐linear modelling, and Fisher's exact tests were used to document patterns of compositional change.

Results: Two stable axes of variation were identified: the first being most closely correlated with soil pH, Mg, Ca, P, S, vegetation height, surface and −10 cm soil temperature, site area, perimeter, perimeter/area ratio, growing season, and air temperature, with the second being most correlated to soil moisture, N, disturbance level, % organic matter, hummock height, N‐S coordinate, and precipitation. Individual sites harboured between 20–47% of total compositional variation, with 28% of Axis 1 and 55% of Axis 2 scores being contained within‐sites. Five compositional regions were identified that differed in the proportion of calciphile and hydrophile species. Compositional groups differed significantly between geologic types.

Conclusions: While the principal axis of variation (corresponding to the rich‐poor fen gradient) is present largely between sites, the second axis (corresponding to water level) is largely repeated within sites. Documentation and protection of vegetation patterns and species diversity within Iowa fens will thus require consideration of multiple sites across the landscape.
Competitive exclusion and the No‐Interaction model operate simultaneously in microcosm plant communities
Authors: Chiarucci Alessandro , Alongi Carmela , Wilson J. Bastow
Published: February 2009

Question: Is the relation between productivity and species richness due to an increase in plant size and hence a reduced plant density?

Location: Glasshouse experiment.

Methods: Productivity was manipulated with fertilizer and irrigation in a microcosm experiment. The ‘sampling effect’ was removed using rarefaction to a common density of individual plants per pot.

Results: Fertility increased community biomass towards an asymptotic maximum, and reduced the light passing through plant canopies towards an asymptotic minimum. As biomass increased, so did species richness. However, this did not seem to be a direct effect of productivity on species richness, but rather one mediated by plant density, since: (1) the richness/ density relation was stronger than the richness/biomass one; (2) adding biomass to the richness/density regression did not increase its predictivity; (3) the richness/biomass relation was removed by rarefaction to 200 individuals per pot. It is therefore concluded that the richness/biomass relation observed was due to the sampling effect. Rarefaction to a small number of plants gave a quite different trend: lower richness at high biomass. This seems to be due to an increased number of subordinate species at high community biomass, and a more uneven distribution of abundance.

Conclusion: The Competitive Exclusion and No‐Interaction hypotheses have been seen as alternatives. We suggest that they can operate simultaneously.
A spatio‐temporal framework for efficient inventories of natural resources: A case study with submersed macrophytes
Authors: Schmieder K. , Lehmann A.
Published: February 2009

Questions: Does a reduced nutrient load in open water increase species richness and the importance of regional and local site characteristics for species abundance and spatial distribution? Can we build lake‐specific models of macrophyte abundance and distribution based on site characteristics in order to prepare a cost‐efficient framework for future surveys?

Location: Lake Constance, 47°39′N, 9°18′E.

Methods: Generalized additive models (GAMs) were used to predict the potential distributions of eight species and overall species richness. Submersed macrophyte distribution in 1993 was compared with corresponding data from 1978, when eutrophication was at its maximum.

Results: Spatial predictions for eight species and overall species richness were relatively accurate and independent of water chemistry. Depth was confirmed as a main predictor of species distribution, while effective fetch distance was retained in many models. Mineralogical variables of sediment composition represent allogenic and autogenic sediment sources and their east‐west gradient in Lake Constance corresponded to east‐west gradients of species distribution and richness. GAMs appeared more efficient than generalized linear models (GLMs) for modelling species responses to environmental gradients.

Conclusions: Reduced trophic status increases species richness and the importance of regional and local site characteristics for species abundance and distribution. Our models represent a spatio‐temporal framework for future lake monitoring purposes and allow the development of effective monitoring; this could be generalized for many ecosystem types and would be particularly efficient for large lakes such as Lake Constance.
Advances in spatial, individual‐based modelling of forest dynamics
Authors: Busing Richard T. , Mailly Daniel
Published: February 2009

Many individual‐based models of forest dynamics lack spatial complexity. Although, in certain cases, spatially simple models may not be substantially inferior to spatially complex models, advances in vegetation science indicate potential weaknesses, particularly the lack of consideration of propagule availability in horizontal space, and varying patch (or canopy gap) dimensions. Models with vertical and horizontal spatial complexity can address these issues, but, thus far, evidence that they outperform patch (or gap) models is limited. Comparison of projections from models that differ only in their spatial complexity is needed to address the effects of propagule availability in space, spatial pattern of canopy tree mortality, and spatial resolution.
Patterns of functional clonal traits and clonal growth modes in contrasting grasslands in the central Apennines, Italy
Authors: Halassy Melinda , Campetella Giandiego , Canullo Roberto , Mucina Ladislav
Published: February 2009

Abstract. Aim: Patterns of plant functional traits related to clonality (clonal growth modes; CGM) in plant communities were studied and hypotheses on the importance of the selected traits in plant communities supported by soils differing in moisture and nutrient status were tested.

Material and Methods: Selected plant functional traits, such as the position of the mother‐daughter plants connections, length of spacers, frequency of multiplication, persistency of ramets connections, presence of storage organs and bud protection were studied in two contrasting plant communities (xeric and mesic abandoned pastures) typical of central Apennines, Italy.

Results and Discussion: Clonality was shown to be of great importance in both mesic and xeric grasslands. The major differences between the two communities were due to the dominant CGMs: turf graminoids (having effective protection of growth meristems in dense tussocks) dominated xeric grasslands, while rhizomatous graminoids (typical of competitive resource‐rich environments) dominated mesic grasslands. Below‐ground CGOs (clonal growth organs), shorter spacers, higher multiplication potential, permanent ramet connection, large bud bank and increased importance of bud protection were found to be of importance in water stressed xeric grassland. Contrary to our expectations, the mesic (less stressed) grasslands have the higher number of clonal plants possessing storage organs.
Effects of grazing on patch structure in a semi‐arid two‐phase vegetation mosaic
Authors: Cipriotti Pablo A. , Aguiar Martin R.
Published: February 2009

Abstract. Question: What are the grazing effects in the spatial organization and the internal structure of high and low cover patches from a two‐phase vegetation mosaic?

Location: Patagonian steppe, Argentina.

Methods: We mapped vegetation under three different grazing conditions: ungrazed, lightly grazed and heavily grazed. We analysed the spatial patterns of the dominant life forms. Also, in each patch type, we determined density, species composition, richness, diversity, size structure and dead biomass of grasses under different grazing conditions.

Results: The vegetation was spatially organized in a two‐phase mosaic. High cover patches resulted from the association of grasses and shrubs and low cover patches were represented by scattered tussock grasses on bare ground. This spatial organization was not affected by grazing, but heavy grazing changed the grass species involved in high cover patches and reduced the density and cover of grasses in both patch types. Species richness and diversity in high cover patches decreased under grazing conditions, whereas in low cover patches it remained unchanged. Also, the decrease of palatable grasses was steeper in high cover patches than in low cover patches under grazing conditions.

Conclusions: We suggest that although grazing promotes or inhibits particular species, it does not modify the mosaic structure of Patagonian steppe. The fact that the mosaic remained unchanged after 100 years of grazing suggests that grazing does not compromize population processes involved in maintaining patch structure, including seed dispersal, establishment or biotic interactions among life forms.
Effects of vegetation canopy and climate on seedling establishment in Mediterranean shrubland
Authors: Lloret Francisco , Peñuelas Josep , Estiarte Marc
Published: February 2009

Abstract. Question: Does the influence of plant canopy on seedling establishment interact with climate conditions, and particularly, do intensified drought conditions, enhance a positive effect of the vegetation canopy on seedlings in Mediterranean‐type ecosystems.

Location: Mediterranean shrubland near Barcelona, Spain at 210 m a.s.l.

Methods: Over the course of four years we recorded seedling emergence and survival in open areas and below vegetation under control, drier and warmer experimental climatic conditions.

Results: Seedling emergence is more sensitive to climate conditions than later stages of growth. When considering the whole set of species, the total number of established seedlings at the end of the experiment was lower in the drought and warming stands than in control ones, and vegetation canopy increased the number of these seedlings in the drought stands. Drought reduced seedling emergence but not warming, while the interaction between climate treatments and vegetation canopy was not significant. Seedling survival was lower in the warming treatment than in the control. Under drought conditions, vegetation canopy increased seedling emergence of the dominant Globularia alypum. In control stands, vegetation canopy reduced their survival. Vegetation canopy increased the survival of the dominant Erica multiflora in warming stands, and it reduced the survival of G alypum in drought stands. No significant effects of drought and warming were observed in the seed rain of these two species.

Conclusions: The balance of the facilitation‐competition interactions between vegetation canopy and seedling establishment in Mediterranean‐type ecosystems determined by water availability, and drought conditions enhance the positive effect of vegetation canopy. This interaction is species‐specific and shows important between‐year variability.
Can differential responses to nutrients explain the success of environmental weeds?
Authors: Hastwell Graeme T. , Panetta F. Dane
Published: February 2009

Abstract. Question: The use of plant traits to predict weed impact is a long‐standing goal in weed ecology. In particular, trait plasticity, i.e. the variability of a trait response to environmental change, is widely considered to contribute to weed success. However, the generality of the role of trait plasticity in determining weed impacts has never been systematically tested.

Methods and location: We tested the hypothesis that high‐impact environmental weeds have greater plasticity in growth responses to nutrient availability than low‐impact species. In a glasshouse experiment, we supplied a complete nutrient solution at five different concentrations to seedlings of 24 species of high‐ and low‐impact environmental weeds from south east Queensland, Australia.

Results: Almost all species showed plasticity in biomass accumulation in response to the nutrient treatments, but plasticity in biomass accumulation did not differ between related high‐ and low‐impact species. There was no evidence of nutrient‐related plasticity in root: shoot allocation. Seedling survival was greater at higher nutrient concentrations, and also differed greatly between families. Survival among low‐impact species was marginally (p= 0.0610) lower than among high‐impact species.

Conclusion: We conclude that the impact of environmental weeds in south east Queensland cannot be predicted from nutrient‐related plasticity in seedling growth. The effects of nutrients on seedling survival warrant further research.
Refuge effects of a cactus in grazed short‐grass steppe
Authors: Rebollo Salvador , Milchunas Daniel G. , Noy‐Meir Imanuel
Published: February 2009

Abstract. Question: Which factors influence the effectiveness of biotic refuges for harbouring grazing‐sensitive species in pastures with a long history of grazing by large herbivores? Previous research showed that spiny clumps of the cactus Opuntia polyacantha provided refuges from cattle grazing for plants and for inflorescence production on short‐grass steppe. In this paper, seven factors that may have a potential positive influence on the refuge effects of cactus at a landscape scale were assessed.

Location: Short‐grass steppe of the Great Plains of North America.

Methods: The study was conducted in eight long‐term grazed pastures and their respective ungrazed controls that were established 60 years ago.

Results: Heavy grazing intensities were necessary for some positive effects of cactus to manifest, and some refuge effects changed to negative effects under lower grazing pressure. Refuge effects increased with plant community productivity due to greater abundances of grazing‐sensitive species, and greater grazing intensities in the more productive areas. Cover of cactus cladodes (spine‐covered pads) inside clumps appeared to be the main limiting factor for refuge effects, probably by limiting available space for grazing‐sensitive species in the clumps. Other factors such as size and density of cactus clumps, and the presence of large refuges in the proximity of clumps had minor influence on the effectiveness of cactus refuges.

Conclusions: The effects of biotic refuges largely varied with ecological conditions and structural characteristics of the refuge. Refuge effects were mainly influenced by grazing intensity, plant community productivity, and structural characteristics of the biotic refuges. A conceptual model of factors influencing refuge effects at a local landscape scale in plant communities grazed by large herbivores is presented.
A technique for identifying the roots of different species in mixed samples using nuclear ribosomal DNA
Authors: Moore L.A. , Field C.B.
Published: February 2009

Abstract. Question: Is it possible to determine the species composition of root samples containing multiple species, without first disentangling individual roots?

Methods: The internal transcribed spacer (ITS) region of nuclear ribosomal DNA was amplified and sequenced from four California annual grassland species (two Poaceae and two Asteraceae). Restriction enzymes that cut the ITS region of each species into uniquely sized fragments were identified based on DNA sequence variation of the ITS regions. Mixed root samples were analysed to test the ability of the method to identify the presence or absence of each species in multi‐species samples.

Results: The technique successfully identified species present in multi‐species samples. ITS regions were shorter in Poaceae than in Asteraceae, so size differences alone were sufficient to distinguish these taxonomic groups. At the species level, digestion of ITS regions with the appropriate restriction enzymes yielded at least one uniquely sized fragment for each species.

Conclusions: This method is the first to identify the species composition of mixed root samples. It should be applicable to most plant species because the ITS region is flanked by universal primers and most species have unique ITS sequences. The ability to determine species‐specific rooting distributions has broad applications in vegetation science.
Plant traits and functional types in response to reduced disturbance in a semi‐natural grassland
Authors: Louault F. , Pillar V.D. , Aufrère J. , Garnier E. , Soussana J.‐F.
Published: February 2009

Abstract. Question: How do functional types respond to contrasting levels of herbage use in temperate and fertile grasslands?

Location: Central France (3°1’E, 45°43’N), 870 m a.s.l.

Methods: Community structure and the traits of dominant plant species were evaluated after 12 years of contrasted grazing and mowing regimes in a grazing trial, comparing three levels of herbage use (high, medium and low).

Results and Conclusions: Of 22 measured traits (including leaf traits, shoot morphology and composition, phenology), seven were significantly affected by the herbage use treatment. A decline in herbage use reduced individual leaf mass, specific leaf area and shoot digestibility, but increased leaf C and dry matter contents. Plants were taller, produced larger seeds and flowered later under low than high herbage use. Nine plant functional response types were identified by multivariate optimization analysis; they were based on four optimal traits: leaf dry matter content, individual leaf area, mature plant height and time of flowering. In the high‐use plots, two short and early flowering types were co‐dominant, one competitive, grazing‐tolerant and moderately grazing‐avoiding, and one grazing‐avoiding but not ‐tolerant. Low‐use plots were dominated by one type, neither hardly grazing‐avoiding nor grazing‐tolerant, but strongly competitive for light.
Distance decay in an old‐growth neotropical forest
Authors: Palmer Michael W.
Published: February 2009

Abstract. Questions: Does distance decay exist in an old‐growth neotropical forest? Is this distance decay stronger than expected due to environmental heterogeneity alone? At what spatial scales are distance decay manifested?

Location: La Selva Biological Station, Costa Rica, Central America.

Methods: An index of distance decay is applied appropriate for small quadrats (the probability of encountering a conspecific tree) to a grid of 1170 0.01‐ha plots. A null model is provided that accounts for environmental heterogeneity.

Results: Significant, but weak, distance decay is found. After correcting for known patterns of environmental heterogeneity, the distance decay almost disappears, except for fine spatial scales.

Conclusions: These results are inconsistent with models that predict distance decay at all spatial scales. However, biological processes leading to distance decay may be more relevant and detectable at scales broader than this study. Research utilizing objectively‐located samples over much broader scales is necessary to evaluate the generality and magnitude of distance decay.
Plant traits: Their role in the regeneration of alpine plant communities in sub‐arctic Finland
Authors: Welling Pirjo , Tolvanen Anne , Laine Kari
Published: February 2009

Abstract. Question: How do the relative frequencies of plant traits (clonality, growth form, seed weight, diaspore morphology) vary during the life cycle and how does this affect regeneration?

Location: Alpine meadow and heath communities at Kilpisjärvi, sub‐Arctic Finland.

Methods: Control plots and three treatments were used to measure relative species abundances for five life cycle stages: standing vegetation, seed rain, seed bank and seedlings emerging in gaps and in closed vegetation.

Results: The relative frequencies of plant traits varied between the life cycle stages. The meadows were dominated by weakly clonal herbs, small or intermediate seeds and unappendaged diaspores, while the heaths were dominated by clonal dwarf shrubs, small seeds and fleshy fruits. In the meadows, species with small seeds dominated during the seed rain and in the seedling stage in gaps, while species with intermediate seeds dominated the seed bank and the seedling stage in closed vegetation. Species with unappendaged diaspores dominated throughout the life cycle. In the heaths, seed bank and seedling stage were practically absent.

Conclusions: The observed differences in plant trait spectra between life cycle stages indicate that important environmental factors differ among the stages. Small seeds are advantageous for dispersal, whereas intermediate seeds have a greater probability of germinating and establishing in closed vegetation. Appendages facilitate dispersal, whereas unappendaged diaspores favour seed burial. Although the plant growth form spectrum largely reflects environmental constraints during the regeneration cycle, information on seed weight and diaspore morphology improves our knowledge of the relative importance of morphological adaptations of sexual structures in different stages during the life cycle.
Canopy vs. soil effects of shrubs facilitating tree seedlings in Mediterranean montane ecosystems
Authors: Gómez‐Aparicio Lorena , Gómez Jose M. , Zamora Regino , Boettinger Janis L.
Published: February 2009

Abstract. Question: Is the facilitative effect of nurse shrubs on early recruitment of trees mediated by a ‘canopy effect’(microclimate amelioration and protection from herbivores), a ‘soil effect’(modification of soil properties), or both?

Location: Two successional montane shrublands at the Sierra Nevada Protected Area, SE Spain.

Method: Seedlings of Quercus and Pinus species were planted in four experimental treatments: (1) under shrubs; (2) in open interspaces without vegetation; (3) under shrubs where the canopies were removed; (4) in open interspaces but covering seedlings with branches, mimicking a shrub canopy.

Results: Both effects benefited seedling performance. However, microclimatic amelioration due to canopy shading had the strongest effect, which was particularly pronounced in the drier site. Below‐ground, shrubs did not modify soil physical characteristics, organic matter, total N and P, or water content, but significantly increased available K, which has been shown to improve seedling water‐use efficiency under drought conditions.

Conclusions: We propose that in Mediterranean montane ecosystems, characterised by a severe summer drought, pioneer shrubs represent a major safe site for tree early recruitment during secondary succession, improving seedling survival during summer by the modification of both the above‐and below‐ground environment.
Plot shape effects on plant species diversity measurements
Authors: Keeley Jon E. , Fotheringham C.J.
Published: February 2009

Abstract.Question:Do rectangular sample plots record more plant species than square plots as suggested by both empirical and theoretical studies?

Location:Grasslands, shrublands and forests in the Mediterranean‐climate region of California, USA.

Methods:We compared three 0.1‐ha sampling designs that differed in the shape and dispersion of 1‐m2and 100‐m2nested subplots. We duplicated an earlier study that compared the Whittaker sample design, which had square clustered subplots, with the modified Whittaker design, which had dispersed rectangular subplots. To sort out effects of dispersion from shape we used a third design that overlaid square subplots on the modified Whittaker design. Also, using data from published studies we extracted species richness values for 400‐m2subplots that were either square or 1:4 rectangles partially overlaid on each other from desert scrub in high and low rainfall years, chaparral, sage scrub, oak savanna and coniferous forests with and without fire.

Results:We found that earlier empirical reports of more than 30% greater richness with rectangles were due to the confusion of shape effects with spatial effects, coupled with the use of cumulative number of species as the metric for comparison. Average species richness was not significantly different between square and 1:4 rectangular sample plots at either 1‐ or 100‐m2. Pairwise comparisons showed no significant difference between square and rectangular samples in all but one vegetation type, and that one exhibited significantly greater richness with squares. Our three intensive study sites appear to exhibit some level of self‐similarity at the scale of 400 m2, but, contrary to theoretical expectations, we could not detect plot shape effects on species richness at this scale.

Conclusions:At the 0.1‐ha scale or lower there is no evidence that plot shape has predictable effects on number of species recorded from sample plots. We hypothesize that for the mediterranean‐climate vegetation types studied here, the primary reason that 1:4 rectangles do not sample greater species richness than squares is because species turnover varies along complex environmental gradients that are both parallel and perpendicular to the long axis of rectangular plots. Reports in the literature of much greater species richness recorded for highly elongated rectangular strips than for squares of the same area are not likely to be fair comparisons because of the dramatically different periphery/area ratio, which includes a much greater proportion of species that are using both above and below‐ground niche space outside the sample area.
EcoPlant: A forest site database linking floristic data with soil and climate variables
Authors: Gégout Jean‐Claude , Coudun Christophe , Bailly Gilles , Jabiol Bernard
Published: February 2009

Abstract. A new database is described, named EcoPlant, that currently holds data from 6432 phytosociological relevés of French forests. The aim of the database is to investigate and model the distribution of forest plant species, and their response to ecological factors, i.e. their ecological niche. Unlike other similar databases, a full environmental description is stored with the floristic data of each site. The climatic data at the site are included, and access to direct climatic variables is possible through geographic information system (GIS) modelling. Precise data on the soil are also stored for each site (soil profile and horizon descriptions, physical and chemical analyses of soil samples). The database is designed to enable linkages to existing soil, floristic or plant‐trait databases.
The Circumpolar Arctic vegetation map
Authors: Walker Donald A. , Raynolds Martha K. , Daniëls Fred J.A. , Einarsson Eythor , Elvebakk Arve , Gould William A. , Katenin Adrian E. , Kholod Sergei S. , Markon Carl J. , Melnikov Evgeny S. , Moskalenko Natalia G. , Talbot Stephen S. , Yurtsev Boris A.(†) , The other members of the CAVM Team
Published: February 2009

Abstract. Question: What are the major vegetation units in the Arctic, what is their composition, and how are they distributed among major bioclimate subzones and countries?

Location: The Arctic tundra region, north of the tree line.

Methods: A photo‐interpretive approach was used to delineate the vegetation onto an Advanced Very High Resolution Radiometer (AVHRR) base image. Mapping experts within nine Arctic regions prepared draft maps using geographic information technology (ArcInfo) of their portion of the Arctic, and these were later synthesized to make the final map. Area analysis of the map was done according to bioclimate subzones, and country. The integrated mapping procedures resulted in other maps of vegetation, topography, soils, landscapes, lake cover, substrate pH, and above‐ground biomass.

Results: The final map was published at 1:7 500 000 scale map. Within the Arctic (total area = 7.11 × 106 km2), about 5.05 × 106 km2 is vegetated. The remainder is ice covered. The map legend generally portrays the zonal vegetation within each map polygon. About 26% of the vegetated area is erect shrublands, 18% peaty graminoid tundras, 13% mountain complexes, 12% barrens, 11% mineral graminoid tundras, 11% prostrate‐shrub tundras, and 7% wetlands. Canada has by far the most terrain in the High Arctic mostly associated with abundant barren types and prostrate dwarf‐shrub tundra, whereas Russia has the largest area in the Low Arctic, predominantly low‐shrub tundra.

Conclusions: The CAVM is the first vegetation map of an entire global biome at a comparable resolution. The consistent treatment of the vegetation across the circumpolar Arctic, abundant ancillary material, and digital database should promote the application to numerous land‐use, and climate‐change applications and will make updating the map relatively easy.
Distribution patterns of plant communities on Santiago Island, Cape Verde
Authors: Duarte M.C. , Rego F. , Moreira I.
Published: February 2009

Abstract. Question: What is the composition, ecology and distribution of the main plant communities on Santiago Island?

Location: Santiago Island (Cape Verde archipelago).

Methods: 308 plots were established using a stratified sampling system according to habitat type; random sampling was employed in each habitat type. Floristic and ecological (topographic, edaphic, climatic and land use) data were collected and analysed using classification and ordination methods and regression analysis.

Results: The classification results led to the recognition often plant communities. Ordination pointed to the importance of altitudinal gradient, slope angle and soil moisture in vegetation variation, as well as some categories of land use, land form or soil type. Regression analysis of sample distributions in ordination space and altitude, according to the two main types of slope aspect — leeward vs. windward — produced altitude differences of ca. 100 m. Variation in rainfall proved more effective at lower altitudes, resulting in the differentiation of more vegetation belts. Slope angle proved to be more important for vegetation differentiation when values exceeded 40°, particularly at medium and higher altitudes. Plant communities are mainly dominated by herbaceous annual species, many of which are exotic.

Conclusions

: Two main phyto‐ecological zones can be distinguished: a xerophilous zone (up to 300/400 m) and a mesophilous zone (above 300/400 m). The zonal communities (four mesophilous and three xerophilous) were distributed in altitudinal belts (mainly reflected in a precipitation gradient); different altitudinal ranges were estimated for these communities according to aspect. The two hygrophilous and one psammophilous communities presented an azonal distribution.
Effects of microsite conditions on seedling establishment on the foreland of Coleman Glacier, Washington
Authors: Jones Chad C. , del Moral Roger
Published: February 2009

Abstract. Questions: How do physical microsite conditions of microsites affect germination and seedling survival in different successional stages? Do different species germinate in similar microsites in a given successional stage?

Location: Coleman Glacier foreland, Mount Baker, Washington State, USA.

Methods: Two methods were used to characterize safe sites. 1. Grids of 300 10 cm × 10 cm plots were located in four different age classes on the foreland. 2.105 pairs of plots, with and without seedlings of Abies amabilis, were located in each age class. For each plot we identified all seedlings and all individuals < 1 m tall. Microsite characteristics such as topography and presence of rocks or woody debris were noted for each plot. Microsite characteristics were compared between plots with and without each species. In addition we examined the effect of distance from seed sources on the presence of Alnus viridis seeds and seedlings in a newly disturbed area.

Results: In early successional sites, seedlings of several species were positively associated with depressions and presence of rocks, and negatively associated with ridges. Patterns were generally consistent among species. In later succession, seedlings were not significantly associated with any microsite characteristics. For Alnus viridis, seed density decreased with distance from seed sources but seedling density did not.

Conclusions: Because of harsh conditions in early succession, physical microsites are important, and most species have similar microsite requirements. In later succession, physical microsites characteristics are not as important and are more variable. Microsites appear to be more important than seed rain in controlling the distribution of Alnus viridis in early succession.