Phorophyte specificity and environmental parameters versus stochasticity as determinants for species composition of corticolous crustose lichen communities in the Atlantic rain forest of northeastern Brazil

A transect of 47 mature trees was studied within an Atlantic rain-forest plot in northeastern Brazil to determinate effects of phorophyte specificity and environmental parameters vs. stochasticity on the structure of corticolous, crustose microlichen communities. A total of 150 lichen species was found, most being rare to extremely rare. Multivariate analysis of sample plots indicated subtle phorophyte preferences among certain lichen species, corresponding to differences in bark pH, degree of bark shedding, density and size of bark lenticels, and presence of milk sap. Individual and multiple regressions revealed correlations between lichen species richness; respectively, area cover and bark pH (negative); density and size of bark lenticels (negative); degree of bark shedding (negative); presence of milk sap (positive); and diffuse site factor (positive). No strongly delimited lichen communities were detected, but cluster analysis revealed three main groups and six subgroups with slightly different lichen species composition, each one with characteristic indicator species but with highly variable overall species composition. Beta diversity was high among samples and lacked spatial structure. However, beta diversity was significantly lower among samples belonging to the same tree species, independent of their spatial arrangement. It was concluded that community formation in tropical rain-forest understory lichens subtly correlates with two main environmental factor complexes—phorophyte bark characteristics and microclimate—but is to a large extent determined by the stochastic effects of species dispersal, especially of rare species.     

Temporal and spatial dynamics in a northern tallgrass prairie

It is well established that plants and soil properties are interdependent. What is less known is the degree to which the distribution of plant and soil properties, in both space and time, match one another. We assessed plant community and soil conditions in permanent sample plots in a tallgrass prairie community from 2002 to 2008. Redundancy analysis showed that the dominant grass species were associated with changes in elevation, soil pH, and gravimetric water content, but not nitrogen or phosphate. Indicator species analysis suggested the community is best described by four cluster types, with half of the plots changing community type over the 6-year sampling period. These cluster types were generally spatially aggregated, with semivariograms showing a range from 80 to 346 m. This degree of spatial structuring was observed in the elevation and soil water content data, but not in measures of soil inorganic N or P. This suggests that natural plant communities do not necessarily show a strong correspondence to all soil variables, especially those that vary rapidly in time and space. The dynamic nature of vegetation patch distribution, combined with their size, may contribute to the loss of species from small tallgrass prairie reserves.     

Eurosiberian meadows at their southern edge: patterns and phytogeography in the NW Tien Shan

Question: What are the community types, underlying gradients and phytogeographical affinities of montane meadows in the western Tien Shan? Location: Aksu‐Jabagly Nature Reserve, South Kazakhstan, Middle Asia. Methods: Species composition, structural and environmental variables were studied in 98 plots. Species composition was classified by cluster analysis and gradients explored using NMDS. Relationships between species richness, environmental and structural variables were investigated with regression analysis. Phytogeographic patterns were assessed by examining species distribution types. Results: Seven community types were distinguished by cluster analysis. Three axes of the NMDS explained 77% of the variation, showing different overlap of communities with environmental and structural properties. Species richness showed linear relationships with pH, altitude, heat load, soil skeletal content and structural variables. Middle Asian and Eurosiberian species constituted the majority of the species pool and cover. Conclusion: The studied communities represent a unique mixture of Middle Asian and Eurosiberian species that exhibit structural and environmental similarities to Eurosiberian meadows. The Tien Shan mountain meadows can thus be considered an endemic‐rich southern outlier of the broader Eurosiberian meadow formation. Shifts in land‐use patterns pose a potential threat that deserves more attention from conservationists.     

Environmental variables interact across spatial scales to structure trichopteran assemblages in Ouachita Mountain rivers

An important goal in aquatic ecology is to determine the interacting variables that regulate community structure; however, complex biotic and abiotic interactions coupled with the significance of scale have confounded the interpretation of community data. We evaluated stream and riparian habitat features in southeastern Oklahoma, USA at a range of spatial scales from local, in-stream variables to large-scale, regional characteristics to address the following questions: (1) How much variation in trichopteran community composition can be attributed to local, regional, and spatial variables? and (2) What environmental variables are most important in determining trichopteran community structure? We collected data on caddisfly community structure, local and regional environmental variables, and spatial location on the landscape from 25 sites in four rivers. We analyzed these data using canonical correspondence analysis (CCA) and variation partitioning. Our analysis explained approximately 60% of the variation in caddisfly community composition. We found that local and regional environmental variables were near equal in importance in governing caddisfly communities, with each accounting for approximately a quarter of the explained variation. Although pure spatial variables were less important, the amount of variation shared among spatial variables and local and regional variables was substantial, indicating that biogeographic history is also key to understanding caddisfly distributions. We also found a strong influence of human landuse (i.e., percent of land in agriculture, distance to roads) on caddisfly community composition. Our study indicated that communities are influenced by factors across scales, and that bioassessments should focus on not only local habitat conditions, but also incorporate larger-scale factors.     

Plant communities of New Brunswick in relation to environmental variation

Abstract. The objective of this study was to quantitatively describe vegetation-environment relationships at a regional scale within the Province of New Brunswick, Canada, using vegetation and environment data from 3947 provincial forestry sample plots. The major plant community types in the province were identified using cluster analysis. Relationships of these communities to climate, topography and soil variables were analyzed by Canonical Correspondence Analysis (CCA), using both a reduced data set consisting of cluster likelihood scores × sample plots and an unreduced species × sample plots data matrix. The vegetation types and major axes of environmental variation were mapped to examine the geographic distributions of these factors within the province. Eight communities were identified and described in terms of enhanced/reduced species (significantly higher or lower frequencies of occurrence in a specific community type relative to all plots) and common species (species in the community type with the highest frequencies of occurrence). The canonical axes explained 25 % of the variation in the vegetation cluster data. Vegetation composition was related to three major environmental gradients representing climate and elevation, soil moisture, and soil fertility. The geographic distributions of vegetation communities exhibited predictable but weak correspondence to the geographic distributions of individual environmental factors. Our findings emphasize the overriding importance of climate and topography and the secondary importance of soil factors in controlling vegetation pattern at the regional scale.     

Differential effects of goat browsing on herbaceous plant community in a two-phase mosaic

The impact of herbivores on herbaceous plant communities is usually attributed to direct consumption of plants. We hypothesized that goats affect herbaceous plants both directly (consumption by foraging) and indirectly, by changing environmental conditions through modification of woody plant structure. We assessed the effects of goats browsing on environmental conditions, landscape structure, and herbaceous plants to link the direct and indirect effects of goats on herbaceous communities. Our model system was the Mediterranean woodland in Mt. Carmel, Israel. This is a two-phase mosaic landscape, composed of herbaceous (open) and woody patches. We delineated 10 plots of 1000 m², goats were introduced to five plots and five plots remained without goats. We monitored plant species richness and composition in two adjacent patch types (woody and open) in each plot. For each patch type, in all plots, we collected data on environmental conditions. We analyzed landscape structure using landscape metrics derived from a high-resolution vegetation map. We found that goats modified the structure of woody plants and hence the landscape mosaic. This alteration was associated with changes in environmental conditions, with more light penetration and higher temperatures. The impact of goats on the herbaceous plant community depended on patch type. In open patches, goats affected the herbaceous community mostly by direct consumption, whereas in woody patches they affected the herbaceous community mainly by modification of abiotic conditions. Our results stress the importance of considering landscape and patch structure in analyzing the effect of herbivory on plant communities.     

Bole epiphytic lichens as potential indicators of environmental change in subtropical forest ecosystems in southwest China

Lichen epiphytes are applied as excellent environmental indicators worldwide. However, very little is known about epiphytic lichen communities and their response to forest dynamics in subtropical China. This paper proposes the applications of the cover, diversity, and functional traits of epiphytic lichens to assess environmental changes associated with succession in subtropical forests of southwest China. Bole lichens were sampled from 120 plots of eight representative forest types in the Ailao Mountains. Total cover, species richness, diversity and community structure of bole lichens differed significantly among forest types, and the highest cover and diversity occurred in the Populus bonatii secondary forest (PBSF). Sixty-one indicator species were associated with particular forest types and more than 50% occurred in the PBSF. Both cover and diversity of most lichen functional groups varied regularly during forest succession. Lichen pioneer species were not displaced by competitively superior species as succession proceeds and cyanolichens were more prevalent in secondary forests. The results also highlight the importance of habitat variables such as canopy openness, host diversity, forest age, tree size, the size of the largest tree, tree density, and basal area on the lichen community. Consequently, our findings support the notion that epiphytic lichens, in terms of cover, diversity, species composition and functional traits can be used as effective indicators for large-scale and long-term forest monitoring. More importantly, the narrowly lobed foliose group was the best candidate indicator of environmental conditions in this region. The combined application of lichen indicator species and functional groups seemed to be a more reliable and more powerful method for monitoring forest dynamics in subtropical montane ecosystems.     

乌鲁木齐南部山区森林生态系统树生地衣群落结构

为了探明乌鲁木齐南部山区树生地衣种类及其群落结构特征, 应用多元分析中的主成分分析及聚类分析方法, 对分布在乌鲁木齐南部山区森林生态系统中的树生地衣植物群落进行数量分类, 并对其群落结构的物种多样性、相似性和均匀度等群落参数进行了比较系统的研究。结果表明, 分布在乌鲁木齐南部山区的树生地衣共有39种, 隶属于5目13科26属。根据多元分析结果, 将该地区的树生地衣划分为3种类型: (1) 小茶渍(Lecanora hageni (Ach.) Ach.) + 蜈蚣衣(Physcia stellaris (L.) Nyl.) + 柳茶渍(L. saligna (Schrad.) Zahlbr.)群落; (2) 斑面蜈蚣衣(Physcia aipolia (Humb.) Furm.) + 对开蜈蚣衣(Ph. dimidiata (Arn.) Nyl.) + 喇叭石蕊(Cladonia pyxidata (L.) Hoffm.)群落; (3) 拟石黄衣(Xanthoria fallax (Hepp) Arnold.) + 丽石黄衣(X. elegans (Link.) Th. Fr.)群落。群落3的多样性指数最大, 为1.509, 其次为群落2, 其多样性指数为1.109, 群落1的多样性指数最低, 为1.088。同时, 研究发现海拔高度和树种是影响乌鲁木齐南部山区森林生态系统树生地衣结构的两个重要因素。     

Does phylogenetic distance aid in detecting environmental gradients related to species composition?

Questions: How should we evaluate the success of new distance measures combining community abundance and phylogenetic information? How do we interpret ordinations using these metrics? Methods: We generated synthetic data along a known environmental gradient with two hypothetical underlying phylogenetic structures: niche phylogenetically conserved or dispersed along a gradient. We also examined tree species composition associated with gradients in elevation and longitude in Oregon, USA. NMS ordinations of plots in species space from phylogenetic (PD) and Sørensen distance (SD) matrices allowed comparison of the use of PD in different scenarios. Results: PD caused plots to cluster based on the clades that they contained, reducing stress with the synthetic data but not with the real example. Phylogenetic distance highlighted clades related to gradients when these were associated. When phylogeny was not conserved along a gradient, that gradient was less strong. Regardless of phylogenetic conservation, NMS using SD consistently extracted the strongest gradients in species composition. Conclusions: The success of PD should be evaluated on how well it extracts gradients in species composition and allows community ecologists to determine which gradients are partially explained by phylogeny and not based on its ability to reduce ordination stress. PD ordinations can help community ecologists interpret niche conservation but may obscure gradients related to species composition when niches are not conserved along the gradient of interest at the scale of the study.     

Effects of forest management on epiphytic lichen diversity in Mediterranean forests

Question: What are the responses of epiphytic lichens to the intensity of management along a large environmental gradient in Mediterranean Quercus forests? Location: Central Spain. Methods: This study was carried out on 4590 trees located in 306 forest stands dominated by Quercus faginea or Quercus ilex ssp. ballota. The effect of forest management and other predictor variables on several species diversity indicators were studied. Variables modelled were total species richness, cyanolichen richness and community composition. A large number of predictor variables were included: forest fragmentation (patch size, stand variability), climate and topographic (altitude, slope, sun radiation, annual rainfall and mean annual temperature) and intensity of management. General linear models and constrained ordination techniques were used to model community traits and species composition, respectively. Results: Total richness and especially cyanolichens richness were significantly and negatively affected by the intensity of management. Lichen composition was influenced by management intensity, climatic and topographic variables and stand variability. Conclusions: In Mediterranean forests, human activities related to forestry, agricultural and livestock use cause impoverishment of lichen communities, including the local disappearance of the most demanding species. The conservation of unmanaged forests with a dense canopy is crucial for lichen diversity.     

The use of GIS techniques to quantify the hydrological regime of a karst wetland (Skealoghan turlough) in Ireland

Question: Can GIS and GPS technology be used to quantify the hydrological regime of different plant communities on turloughs (groundwater dependent calcareous wetlands)? Location: Skealoghan turlough, County Mayo, Ireland. Methods: Plant communities were mapped and digitised with GIS software and a digital elevation model of the site was constructed from differential GPS data. Together with records of water level fluctuations on the site from May 2001 to May 2004, these data were used to calculate hydrological variables for each plant community. Hierarchical cluster analysis was used to identify groups of plant communities with similar hydrological regimes. Results: 15 plant communities were mapped at Skea loghan, with the Cirsio‐Molinietum and Ranunculo‐Potentilletum anserinae being the dominant phytosociological associations. Skealoghan is subject to large temporal and spatial variation in its hydrological regime and fluctuations in water level are intrinsically linked to rainfall. The spatial variation in flooding can be linked to the vegetation zones. Conclusions: GIS and DGPS technology can be used to quantify the hydrological regime of different plant communities on turloughs. Since the hydrological regime is a major environmental factor controlling the vegetation composition of the site, the maintenance of natural flooding regimes is a vital component for the conservation and management of the diverse vegetation mosaic at Skealoghan turlough.     

Non-Destructive Lichen Biomass Estimation in Northwestern Alaska: A Comparison of Methods

Terrestrial lichen biomass is an important indicator of forage availability for caribou in northern regions, and can indicate vegetation shifts due to climate change, air pollution or changes in vascular plant community structure. Techniques for estimating lichen biomass have traditionally required destructive harvesting that is painstaking and impractical, so we developed models to estimate biomass from relatively simple cover and height measurements. We measured cover and height of forage lichens (including single-taxon and multi-taxa “community” samples, n = 144) at 73 sites on the Seward Peninsula of northwestern Alaska, and harvested lichen biomass from the same plots. We assessed biomass-to-volume relationships using zero-intercept regressions, and compared differences among two non-destructive cover estimation methods (ocular vs. point count), among four landcover types in two ecoregions, and among single-taxon vs. multi-taxa samples. Additionally, we explored the feasibility of using lichen height (instead of volume) as a predictor of stand-level biomass. Although lichen taxa exhibited unique biomass and bulk density responses that varied significantly by growth form, we found that single-taxon sampling consistently under-estimated true biomass and was constrained by the need for taxonomic experts. We also found that the point count method provided little to no improvement over ocular methods, despite increased effort. Estimated biomass of lichen-dominated communities (mean lichen cover: 84.9±1.4%) using multi-taxa, ocular methods differed only nominally among landcover types within ecoregions (range: 822 to 1418 g m⁻²). Height alone was a poor predictor of lichen biomass and should always be weighted by cover abundance. We conclude that the multi-taxa (whole-community) approach, when paired with ocular estimates, is the most reasonable and practical method for estimating lichen biomass at landscape scales in northwest Alaska.     

乌鲁木齐南部山区森林生态系统树生地衣群落结构

为了探明乌鲁木齐南部山区树生地衣种类及其群落结构特征,应用多元分析中的主成分分析及聚类分析方法,对分布在乌鲁木齐南部山区森林生态系统中的树生地衣植物群落进行数量分类,并对其群落结构的物种多样性、相似性和均匀度等群落参数进行了比较系统的研究。结果表明,分布在乌鲁木齐南部山区的树生地衣共有39种,隶属于5目13科26属。根据多元分析结果,将该地区的树生地衣划分为3种类型：（1）小茶渍（Lecanorahageni（Ach．）Ach．）＋蜈蚣衣（肋归ciastellaris（L．）Nyl．）＋柳茶渍（￡-。saligna（Schrad．）Zahlbr．）群落;（2）斑面蜈蚣衣（Physciaaipolia（Humb．）Furm．）＋对开蜈蚣衣（Ph．dimidiata（Arn．）Nyl．）＋喇叭石蕊（Cladoniapyxidata（L．）Hoffm．）群落：（3）拟石黄衣（Xanthoria fallax（Hepp）Arnold．）＋丽石黄衣（xelegans（Link．）Th．Fr．）群落。群落3的多样性指数最大,为1．509,其次为群落2,其多样性指数为1．109,群落1的多样性指数最低,为1．088。同时,研究发现海拔高度和树种是影响乌鲁木齐南部山区森林生态系统树生地衣结构的两个重要因素。     

Disentangling environmental and spatial processes of community assembly in tropical forests from local to regional scales

Understanding patterns and mechanisms of variation in the compositional structure of communities across spatial scales is one of the fundamental challenges in ecology and biogeography. In this study, we evaluated the effects of spatial extent (i.e. size of study region) on: 1) whether community composition can be better explained by environmental (i.e. niche‐based) or spatial (e.g. dispersal‐based) processes ; and 2) how climate and soils contribute to the influence of environment on plant community composition. We surveyed community composition across a network of 398 forest plots spanning a ～4000 m elevational gradient in the Madidi region in northwestern Bolivia. Using redundancy analyses and hierarchical variation partitioning, we disentangled the effects of environmental and spatial predictors on species composition, further decomposing the environmental effect between its climatic and soil components. We repeated analyses for 200 sub‐regions ranging in spatial extent from ～250 to ～17 500 km². Our analyses show a high degree of idiosyncrasy in results that come from different sub‐regions. Despite this variability, we were able to identify various important patterns in the structure of tropical plant communities in our study system. First, even though sub‐regions varied in size by nearly two orders of magnitude, the total amount of explained variation in community composition was scale independent; at all spatial scales, environment and space accounted for about 25% of the differences in community composition among plots. Second, the measured environmental effect was higher than the spatial effect on average and in the vast majority of sub‐regions. This was true regardless of the spatial extent of analysis. Finally, we found that both climatic and soil variables accounted for significant fractions of variation, but climate was always more important than soils.     

Are post-fire residual forest patches refugia for boreal bryophyte species? Implications for ecosystem based management and conservation

Residual patches of forest remaining after natural or anthropogenic disturbance may facilitate regeneration of fragmented forest. However, residual patch function remains unclear, especially after natural wildfire. We investigate the role of residual boreal forest patches as refugia for bryophytes and ask the question, do they house bryophyte communities similar to those encountered in undisturbed forests? Bryophytes were sampled in three habitat types in black spruce boreal forests illustrating a gradient of disturbance severity: undisturbed forests, residual patches and burned matrices. Temporal, disturbance severity, spatial and structural variables of habitats were also recorded. Bryophyte community composition differed among habitat types with residual patches characterized by higher species richness, the loss of forest specialists and the addition of disturbance-prone species. The bryophyte community found in residual patches is at the interface between the communities of undisturbed forests and burned matrices. As residual patches did not conserve all species, particularly forest specialists, they were not refugia. However, we identify temporal, spatial and structural characteristics that can maintain bryophyte communities most similar to undisturbed forests and enhance residual patch “refugia potential”. Residual patches enhance bryophyte diversity of the landscape housing species that cannot survive in the burned matrix. As conclusion we discuss the use of retention patches in harvested stands, together with the preservation of undisturbed stands that house singular bryophyte communities and especially sensitive forest specialists.     

陕西子午岭生态因素对植物群落的影响

为探讨生境对植被格局分布的影响,对黄土高原马栏林区60块样地进行植被学调查的基础上,采用17个环境指标刻画植物群落的空间位置、地形和土壤特征;利用双向指示种分析(TWINSPAN)划分了该区不同演替阶段的植物群落类型;利用前向选择法(forward selection)及Monte Carlo检验对不同演替阶段植物群落物种组成影响显著(p＜0.05)的环境因子进行筛选;利用去势典范对应分析(DCCA)排序方法分析不同演替阶段植物群落分布格局与环境的关系;利用偏典范对应分析(partial CCA)定量分离环境、空间及其交互作用对植被格局总体变异的影响.结果表明:(1)马栏林区的植物群落可划分为13个类型,分别属于4个不同的演替阶段;(2)对演替初期阶段群落影响显著的环境因子是土壤含盐量和碱解氮,对演替过渡阶段群落影响显著的环境因子是海拔和腐殖质厚度,对演替亚顶级阶段群落影响显著的因子是海拔、坡向、枯落物厚度、腐殖质厚度和pH值,而对演替顶级阶段群落分异影响显著的因子是海拔、坡向、pH值和速效磷;(3)不同演替阶段群落的生态学特性和分布规律与环境空间的生态梯度格局吻合较好;(4)随着演替的进行,环境因子单独对植物群落的影响越来越大,而样地位置单独作用和样地位置与环境因子的交互作用之和越来越小.     

Analysis of the vertical distribution of epiphytic lichens on Pinus nigra (Mount Olympos,Greece) along an altitudinal gradient

Epiphytic lichen vegetation was studied in 10 sites along an altitude gradient from 750 to 1510 m on NW-facing slopes of Mount Olympos, Greece to assess the main spatial heterogeneity of microhabitats affecting communities and species composition. Community structure along the gradient was studied by using multivariate techniques. The critical factor for spatial heterogeneity seems to be the height at which the lichen community develops on the tree trunks. Changes in the community structure of the epiphytic lichen vegetation were also detected along the altitudinal gradient and the altitude of 1200 m is considered to be an ecotone. A comparative study of epiphytic lichen communities on Mt. Olympos and in the Thessaloniki area revealed species indicators of air pollution.     

Congruence among vascular plants and butterflies in the evaluation of grassland restoration success

Using surrogate taxa in the monitoring of restoration success is strongly advocated but currently under debate. Are butterfly and vascular plant communities good surrogates for each other in monitoring the restoration of calcareous grassland grassland? The research was conducted in a small area in Tuscany (central Italy), which was the focus of a restoration project. We sampled vascular plants using 35 plots (1 m²) and butterflies using 20 transects (100 m in length) belonging to four treatment types: control scrubland, restored ex-arable, restored grassland and reference grassland. A mixed model nested ANOVA showed that reference grassland, 3 years after restoration, had the highest number of vascular plant species and the highest number of butterfly species. The different treatments were found to be distinct from a compositional point of view: pRDA showed that the “treatment” factor, independent of spatial variables, accounted for 22.1 and 21.9% of the total variance in the plant community and butterfly community, respectively (p < 0.01). The butterfly community was significantly correlated with the entire plant community data set and with the phanerophyte community (i.e. shrubs); larval host plants were significantly correlated with the composition of non-migratory butterflies. The results indicated that butterfly and vascular plant communities were congruent, suggesting the use of community composition of different taxa as a valuable tool for the evaluation of management success.     

天山森林生态系统树生地衣植物群落数量分类及其物种多样性的研究

地衣是由低等植物中的藻类与菌类中的真菌和兰细菌共生而成的一群特殊的植物。由于耐寒耐旱对生活中的养分要求不高,在养纷贫瘠、环境恶劣的高山寒漠、平原、戈壁和沙漠中地衣都能生长,因而广泛地分布和生长在不同的生态环境中。有关新疆地衣方面的研究报道集中在物种分类水平上,对于地衣群落结构方面的研究比较少。因此,我们应用多元分析中的主分量分析及聚类分析方法对分布在天山森林生态系统中树生地衣植物群落进行数量分类并对群落结构物种多样性、相似性和均匀度等群落参数进行了比较系统的研究。结果表明, 在西部天山不同森林生态系统中树生地衣群落的分布与海拔高度和树种有密切的关系, 不同海拔的不同类型的森林生态系统中分布着不同种类的树生地衣植物。 根据多元分析结果和生境的综合特征,该地区的树生地衣可划分为4种类型: 1) 茎口果粉衣+金黄茶衣群丛Chaenotheca stemonea+Candellaria aurella Association; 2)叉小孢衣+裸扁枝衣+粉唇蜈蚣衣群丛Bryoria furcellata+Evernia esorediosa+Physcia tribacoides Association; 3)亚广开梅衣+槽梅衣+疑小梅衣群丛Parmelia fertilis+Parmelia sulcata+Parmeliopsis ambigua Association; 4)睫毛黑蜈蚣衣+黑蜈蚣衣群丛Phaeophyscia ciliata+Phaeophyscia nigricans Association。其群落多样性指数以亚广开梅衣+槽梅衣+疑小梅衣群丛为最高 (1.920), 叉小孢衣+裸扁枝衣+粉唇蜈蚣衣群丛为最低 (1.562)。     

Spatial patterns of species and plant traits in response to 20 years of grazing exclusion in subalpine grassland communities

Question: Does long‐term grazing exclusion affect spatial patterns of canopy height, plant species and traits in subalpine grassland communities? Are spatial patterns of species and traits similarly affected by grazing exclusion? Are changes in spatial patterns of species associated with changes in species abundances? Location: Subalpine grasslands, Vercors and Oisans Mountains, Alps (France). Methods: Spatial sampling of vegetation and measurements of plant traits were carried out within nine pairs of grazed and ungrazed 10 m × 10‐m plots in three species‐rich communities with different productivities. We estimated within‐plot spatial patterns of canopy height, species and aggregated trait values by measuring the extent (or patch size) and intensity of spatial dependence with Moran's I. Abundance‐weighted averages for species patch size and intensity of spatial dependence were calculated across all species per plot and across species per life form. Such measures derived from analysis of spatial dependence were considered spatial traits. Results: Response of spatial patterns to grazing exclusion was only detected in patch size, whereas intensity of spatial dependence was not affected. Changes in spatial patterns were community‐dependent because spatial traits based on patch size of canopy height and species increased following grazing exclusion only in the less productive community. Unexpectedly, changes in spatial patterns of species did not support changes in spatial patterns of trait values. Abundances and patch sizes of several life forms were significantly affected by grazing exclusion. However, at the scale investigated, changes in abundance of life forms did not correspond to changes in their spatial patterns and vice versa. Conclusion: In species‐rich communities, grazing alters spatial spread of species (i.e. patch size) rather than intra‐specific aggregation (i.e. intensity of spatial dependence). Results revealed possible mechanisms of species spatial reorganisation that are independent of abundance variation. Therefore, it is important to consider changes in spatial patterns in addition to changes in mean values of vegetation features when assessing impacts of grazing management.