Uncoupled changes in tree cover and field layer vegetation at two Pyrenean treeline ecotones over 11 years

Background: The alpine treeline ecotone is regarded as a sensor of the effects of global change on alpine plant communities. However, little is known about how treeline dynamics influence the diversity and composition of alpine plant communities. Such information is necessary to forecast how ascending montane forests may affect the composition of alpine flora.

Aims: We analysed the temporal variations in tree cover, plant diversity and composition, and the effect of tree cover dynamics on field layer vegetation over a period of 11 years, at two alpine treeline ecotones in the central Pyrenees, Spain.

Methods: Tree and field layer vegetation was sampled in permanent transects in 1998 and 2009, using the point-intercept method. Temporal changes in tree cover, plant species richness and abundance were characterised along the ecotone by using a randomisation approach, rarefaction curves, and a non-parametric multivariate test, respectively.

Results: Tree cover increased significantly at one of the sites, whereas plant species richness only increased at the other site where tree cover had not changed. Vegetation composition changed significantly at both sites, but it was not spatially coupled with changes in tree cover along the ecotone.

Conclusions: A change of tree cover does not necessarily trigger changes in the ground flora at the treeline over relatively short periods (decade scale). The results challenge our ability to infer short-term biodiversity impacts from upslope advance of forests. Integrated tree and field layer monitoring approaches are necessary to produce a better understanding of the impact of ongoing global change on treeline ecotones.     

Vegetation patterns at the alpine treeline ecotone: the influence of tree cover on abrupt change in species composition of alpine communities

Aims: The upper elevation limit of forest vegetation in mountain ranges (the alpine treeline ecotone) is expected to be highly sensitive to global change. Treeline shifts and/or ecotone afforestation could cause fragmentation and loss of alpine habitat, and are expected to trigger considerable alterations in alpine vegetation. We performed an analysis of vegetation structure at the treeline ecotone to evaluate whether distribution of the tree population determines the spatial pattern of vegetation (species composition and diversity) across the transition from subalpine forest to alpine vegetation. Location: Iberian eastern range of the Pyrenees. Methods: We studied 12 alpine Pinus uncinata treeline ecotones. Rectangular plots ranging from 940 to 1900 m² were placed along the forest‐alpine vegetation transition, from closed forest to the treeless alpine area. To determine community structure and species distribution in the treeline ecotone, species variation along the forest‐alpine vegetation transition was sampled using relevés of 0.5 m² set every 2 m along the length of each plot. Fuzzy C‐means clustering was performed to assess the transitional status of the relevés in terms of species composition. The relation of P. uncinata canopy cover to spatial pattern of vegetation was evaluated using continuous wavelet transform analysis. Results: Vegetation analyses revealed a large degree of uniformity of the subalpine forest between all treeline ecotone areas studied. In contrast, the vegetation mosaic found upslope displayed great variation between sites and was characterized by abrupt changes in plant community across the treeline ecotone. Plant richness and diversity significantly increased across the ecotone, but tree cover and diversity boundaries were not spatially coincident. Conclusions: Our results revealed that no intermediate communities, in terms of species composition, are present in the treeline ecotone. Ecotone vegetation reflected both bedrock type and fine‐scale heterogeneity at ground level, thereby reinforcing the importance of microenvironmental conditions for alpine community composition. Tree cover did not appear to be the principal driver of alpine community changes across the treeline ecotone. Microenvironmental heterogeneity, together with effects of past climatic and land‐use changes on ecotone vegetation, may weaken the expected correlation between species distribution and vegetation structure.     

Functional diversity and composition of bryophyte water-related traits in Azorean native vegetation

Background: Functional trait-based approaches link species diversity patterns to ecosystem functioning. In the context of global change, understanding these links is vital for developing holistic biodiversity management strategies. Bryophytes, important ecosystem components owing to their biogeochemical functions, have not been the focus of many functional studies.

Aims: This is the first assessment of bryophyte functional diversity in the Azores archipelago, aiming to uncover multivariate trait richness and composition patterns along the elevational gradient on Terceira Island.

Methods: Based on five water acquisition and retention traits of leafy liverworts and mosses, we calculated functional diversity metrics within and among six bryophyte communities sampled along a 1021-m elevational transect.

Results: Trait composition differed significantly between coastal and mountain communities. Mosses presented inrolled leaves and ornamented leaf cells at low elevation but not at high elevation. These patterns were associated with an uphill shift from drier and warmer conditions to a moister and cooler environment.

Conclusions: Future climatic changes might affect bryophyte functional diversity patterns in Terceira Island, particularly for mosses. These results can be directly compared with those obtained for other archipelagos where the same protocol has been applied, allowing a joint assessment of insular vegetation functional diversity patterns.     

Recurrent landslides affect the functional beta diversity of a megadiverse tropical forest

Background: Natural disturbance is an important factor that contributes to structuring plant communities. In tropical mountain areas, landslides are frequent and could enhance the diversity in mountain forests. However, the spatial scale in which landslide affect diversity is not known.

Aims: To investigate whether landslides affect taxonomic and functional diversity at different spatial scales. We tested if: (1) taxonomic and functional α-diversity were lower in areas with landslide history; (2) the taxonomic β-diversity was high while the functional β-diversity was low in landslide-affected areas; and (3) plants in areas with landslide history would have, on average, smaller and thicker leaves, with greater pubescence, lower specific leaf area and higher dry matter content.

Methods: At five sites in the Atlantic Forest, we sampled five 5 m × 5 m plots in areas with recent landslide history (from 2 to 39 years) and in adjacent control areas. We identified all juvenile trees (30–100 cm in height) and measured their leaf traits.

Results: Taxonomic α-diversity and functional β-diversity and the occurrence of leaves with trichomes were greater in areas affected by landslide.

Conclusion: The habitat heterogeneity in areas subject to recurrent landslides influenced the functional dispersion and the structuring of plant communities.     

The forest–alpine ecotone: a multi-scale approach to spatial and temporal dynamics of treeline change at Niwot Ridge

Background: Current understanding of treeline or forest-alpine ecotone (FAE) dynamics does not fully explain past and present FAE patterns and their underlying processes, nor allow prediction of their response to climate change.

Aims: We address the overarching hypothesis that the FAE is a mosaic of distinct landscape units of vegetation and landforms that result in differential responses to climate change. We focus on climate-related, landscape and vegetation characteristics, but also consider the effect of landscape heterogeneity on biogeochemistry and overall resilience of the FAE to climate change.

Results: There are three distinct FAE land units at Niwot Ridge, generated by different interactions of climate with vegetation, landforms and topography. Within these FAEs, a process of self-organisation takes place from organism to patch to landscape scales, and is modulated by positive and negative feedback loops along an elevation gradient. The underlying controls cannot be attributed solely to temperature, but to a combination of interactions along a physical/biotic gradient.

Conclusions: FAE dynamics result from interactions among mechanisms and processes at the microsite, patch and landscape scales: (1) tree persistence; (2) forest patch establishment; (3) drivers of patch forest configurations and (4) resilience, increasing along a gradient of biotic control.     

Phylogenetic diversity,structure and diversification patterns of endemic plants along the elevational gradient in the Eastern Himalaya

ABSTRACT

Background: Several studies have documented the variation in species diversity patterns along elevational gradients in the Himalaya, but few have reported the evolutionary and biogeographic processes behind these patterns.

Aims: To understand whether evolutionary history and phylogeny have any role in structuring plant species communities along an elevational gradient in the Sikkim Himalaya.

Methods: We used data on endemic plant species occurrence from primary and secondary sources to construct family-level phylogenetic supertrees for different growth forms with the help of Phylomatic tool of Phylocom. These phylogenetic supertrees were used as a base for testing phylogenetic diversity (PD), niche conservatism, diversification time patterns and phylogenetic structure of various plant growth forms along an elevational gradient.

Results: PD was the highest at mid-elevations for all growth forms and PD had a significant positive correlation with endemic species richness. Species at mid-elevations were dominated by the ancestral/primitive taxa. There was phylogenetic clustering at higher elevations and phylogenetic overdispersion at lower and mid-elevations for the majority of the growth forms.

Conclusions: Time-for-speciation effect and niche conservatism along elevation (retention of niche-related ancestral elevational distribution over evolutionary time scale by species) together determine plant species diversity patterns in the Himalaya.     

Spatial distribution of functional traits of bryophytes along environmental gradients in an Atlantic Forest remnant in north-eastern Brazil

ABSTRACT

Background: Functional trait-based approaches have been used to identify patterns of plant species diversity and composition related to environmental variability/changes. Bryophytes are rapidly affected by perturbations and thus their traits and distribution are expected to show well-defined relationships with environmental variability.

Aim: To quantify the impacts of fragmentation on the diversity and structure of epiphytic bryophytes to vertical and horizontal environmental gradients in an Atlantic Forest remnant.

Methods: Six functional traits related to water relations and light tolerance were recorded and one of them, the leaf lobule area in liverworts, was selected for morphometric measurements along the gradients analysed. Functional diversity and composition metrics of bryophytes along gradients were compared.

Results: Functional diversity changed little along the vertical and horizontal gradients. Conversely, the functional composition of traits changed markedly. Traits related to water storage, such as the presence and area of lobules, and to protection against excess light incidence, such as dark pigments, were more numerous in the canopy and at the fragment edge.

Conclusions: Functional composition is more correlated with the vertical and horizontal gradients than functional diversity. The lobule of liverworts stood out as the most relevant trait to explain the adaptive strategies of bryophytes.     

长白山林线过渡带树岛土壤微生物群落结构和生态功能

林线过渡带是指从郁闭森林上限到树种分布上限之间的区域,过渡带内生物多样性丰富,生态系统结构、功能和生态过程在很小的海拔梯度内发生剧烈变化,因此对全球气候变化和人类活动极为敏感。树岛是在林线过渡带内出现的斑块状或条带形不连续分布的树木集群,树岛内生存的树木通常能达到与较低海拔郁闭森林同样的高度和胸径,因此揭示树岛这一特殊生境的生态特征及其形成机制,对于预测未来气候变化下林线动态具有重要意义。以长白山岳桦林线过渡带一大型树岛作为研究对象,测定了土壤理化性质和土壤酶活性,采用宏基因组测序技术分析了微生物群落结构组成和功能基因丰度,通过与同海拔的开阔区生境进行对比,揭示了树岛这一特殊生境的土壤微生物群落结构特征和潜在生态功能,从土壤养分和土壤微生物学角度,阐明树岛形成的可能驱动机制。结果表明,树岛土壤的含水量、总碳、总氮和微生物生物量显著高于同海拔开阔区（P<0.05）,与微生物r-策略相关的生理生化和遗传学指标,包括纤维素酶活性、放线菌相对丰度、与转录、防御、控制细胞周期相关的基因丰度、小分子碳降解基因丰度,均高于开阔区（P<0.05）。相反的,与微生物K-策略相关的指标,包括酸杆菌相对丰度、大分子碳降解基因相对丰度低于开阔区。揭示了树岛土壤微生物学特征,并从土壤微生物组学角度探讨了树岛形成的潜在机制,认为树岛内土壤养分增加并导致微生物群落r-策略倾向,这种变化反过来也可能促进树岛进一步扩大,进而影响林线动态。     

Genetic and phenotypic variation,dispersal limitation and reproductive success in the invasive herb Eschscholzia californica along an elevation gradient in central Chile

Background: Reductions of genetic diversity and phenotypic changes in invasive plants are often observed to occur at high elevations. Genetic/phenotypic changes of invasive plants along elevation help to understand mechanisms of the presumed resistance of mountain ecosystems to invasion.

Aims: To assess genetic variability and phenotypic plasticity along an elevation gradient of Eschscholzia californica in the Andes, central Chile.

Methods: Eleven microsatellites were used to describe the genetic structure and the allelic diversity individuals, distributed at three elevations and two sites. We assessed the number of flowers per plant, floral biomass, leaf area, number of leaves, vegetative biomass and plant height of plants at each elevation.

Results: Genetic diversity as genetic structure did not decrease with elevations. Plant height and flower numbers decreased while leaf number and vegetative biomass increased with elevation. The ratio of the number of flowers to vegetative biomass, decreased significantly with elevation.

Conclusions: Strong genetic differences among elevations and similar genetic diversity along elevation do not suggest dispersal limitation to higher elevation. Reduction of reproductive and vegetative traits concomitantly with an increase of the reproductive cost suggests reproductive stress with increasing elevation, reducing the invasiveness of this species to higher elevation.     

Trait dynamics of Mediterranean xerophytic shrub communities growing on stabilised inland dunes respond to nutrient and aridity gradients

Background: Understanding the processes that determine community assembly and their dynamics is a central issue in ecology. The analysis of functional diversity can improve our understanding of these dynamics by identifying community assembly processes.

Aims: We studied the effect of environment–community covariations on both functional diversity and functional structure of xerophytic shrub communities for inferring the community assembly processes shaping this vegetation type.

Methods: Functional diversity was quantified using (1) community-weighted mean of the studied traits, (2) functional groups, defined using Ward’s hierarchical agglomerative clustering method and (3) Rao’s quadratic entropy. Relationships between functional diversity and environmental gradients were identified by Spearman correlations and modelled using generalised additive models.

Results: Variations in community composition and functional diversity correlated with soil nutrient availability and aridity. Increasing nutrient availability resulted in both greater average plant height and higher abundance of plants with green photosynthetic organ colour, whereas the abundance of nanophanerophytes increases with aridity.

Conclusions: The species composition and trait structure of the studied Mediterranean xerophytic shrub communities varies along nutrient and aridity gradients. This supports the importance of environmental filters for the local assembly and dynamics of these inland dune communities.     

The effect of elevation and habitat cover on nest box occupancy and diet composition of Boreal Owls Aegolius funereus

Capsule: Diet composition of Boreal Owls Aegolius funereus was not affected by habitat cover, but it changed along the elevational gradient.

Aims: To assess the effect of elevation and habitat cover on nest box occupancy and diet composition of a central European population of Boreal Owls.

Methods: A Boreal Owl population was studied in the ?umava Mountains, Czech Republic, at elevations from 500 to 1300?m above sea level (asl), during 1984–2005.

Results: Boreal Owls occupied more frequently nest boxes above 600?m asl, but they did not clearly prefer any elevational band. Habitat cover did not affect the number of nesting attempts. There was also no relationship between habitat cover and diet composition. However, diet composition significantly changed along the elevational gradient. In particular, the proportion of alternative prey of Boreal Owls, i.e. birds and shrews Sorex sp., rose with increasing elevation. The proportion of voles Myodes and mice Apodemus in the diet decreased with increasing elevation. Among bird prey, the proportion of finches Fringillidae positively correlated with elevation.

Conclusions: Central European Boreal Owls did not show a clear preference for any habitat cover or elevational band, but the quality of the owls’ diet significantly decreased with increasing elevation.     

Factors that shape the elevational patterns of plant diversity in the Yatsugatake Mountains,Japan

Elevation is involved in determining plant diversity in montane ecosystems. This study examined whether the distribution of plants in the Yatsugatake Mountains, central Japan, substantiated hypotheses associated with an elevational diversity gradient. Species richness of trees, shrubs, herbs, ferns, and bryophytes was investigated in study plots established at 200‐m elevational intervals from 1,800 to 2,800 m. The changes in plant diversity (alpha and beta diversities, plant functional types, and elevational ranges) with elevation were analyzed in relation to climatic factors and elevational diversity gradient hypotheses, that is, mass effect, mid‐domain effect, and Rapoport''s elevational rule. In addition, the elevational patterns of dominance of plant functional types were also analyzed. A comparison of alpha and beta diversities revealed that different plant groups responded variably to elevation; the alpha diversity of trees and ferns decreased, that of herbs increased, whereas the alpha diversity of shrubs and bryophytes showed a U‐shaped relationship and a hump‐shaped pattern. The beta diversity of shrubs, herbs, and bryophytes increased above the subalpine–alpine ecotone. In accordance with these changes, the dominance of evergreen shrubs and graminoids increased above this ecotone, whereas that of evergreen trees and liverworts decreased. None of the plant groups showed a wide elevational range at higher elevations. These elevational patterns of plant groups were explained by climatic factors, and not by elevational diversity gradient hypotheses. Of note, the changes in the dominance of plant groups with elevation can be attributed to plant–plant interactions via competition for light and the changes in physical habitat. These interactions could alter the elevational diversity gradient shaped by climatic factors.     

Soil bacterial diversity patterns and drivers along an elevational gradient on Shennongjia Mountain,China

Understanding biological diversity elevational pattern and the driver factors are indispensable to develop the ecological theories. Elevational gradient may minimize the impact of environmental factors and is the ideal places to study soil microbial elevational patterns. In this study, we selected four typical vegetation types from 1000 to 2800 m above the sea level on the northern slope of Shennongjia Mountain in central China, and analysed the soil bacterial community composition, elevational patterns and the relationship between soil bacterial diversity and environmental factors by using the 16S rRNA Illumina sequencing and multivariate statistical analysis. The results revealed that the dominant bacterial phyla were Acidobacteria, Actinobacteria, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria and Verrucomicrobia, which accounted for over 75% of the bacterial sequences obtained from tested samples, and the soil bacterial operational taxonomic unit (OTU) richness was a significant monotonous decreasing (P < 0.01) trend with the elevational increasing. The similarity of soil bacterial population composition decreased significantly (P < 0.01) with elevational distance increased as measured by the Jaccard and Bray–Curtis index. Canonical correspondence analysis and Mantel test analysis indicated that plant diversity and soil pH were significantly correlated (P < 0.01) with the soil bacterial community. Therefore, the soil bacterial diversity on Shennongjia Mountain had a significant and different elevational pattern, and plant diversity and soil pH may be the key factors in shaping the soil bacterial spatial pattern.     

Contrasting patterns of intraspecific trait variability in native and non-native plant species along an elevational gradient on Tenerife,Canary Islands

Background and AimsNon-native plant species are not restricted to lowlands, but increasingly are invading high elevations. While for both native and non-native species we expected variability of plant functional traits due to the changing environmental conditions along elevational gradients, we additionally assumed that non-native species are characterized by a more acquisitive growth strategy, as traits reflecting such a strategy have been found to correlate with invasion success. Furthermore, the typical lowland introduction of non-native species coming from multiple origins should lead to higher trait variability within populations of non-native species specifically at low elevations, and they might therefore occupy a larger total trait space.MethodsAlong an elevational gradient ranging from 55 to 1925 m a.s.l. on Tenerife, we collected leaves from eight replicate individuals in eight evenly distributed populations of five native and six non-native forb species. In each population, we measured ten eco-morphological and leaf biochemical traits and calculated trait variability within each population and the total trait space occupied by native and non-native species.Key ResultsWe found both positive (e.g. leaf dry matter content) and negative (e.g. leaf N) correlations with elevation for native species, but only few responses for non-native species. For non-native species, within-population variability of leaf dry matter content and specific leaf area decreased with elevation, but increased for native species. The total trait space occupied by all non-native species was smaller than and a subset of that of native species.ConclusionsWe found little evidence that intraspecific trait variability is associated with the success of non-native species to spread towards higher elevations. Instead, for non-native species, our results indicate that intermediate trait values that meet the requirements of various conditions are favourable across the changing environmental conditions along elevational gradients. As a consequence, this might prevent non-native species from overcoming abruptly changing environmental conditions, such as when crossing the treeline.     

Trait variation and functional diversity maintenance of understory herbaceous species coexisting along an elevational gradient in Yulong Mountain,Southwest China

Characterizing trait variation across different ecological scales in plant communities has been viewed as a way to gain insights into the mechanisms driving species coexistence. However, little is known about how changes in intraspecific and interspecific traits across sites influence species richness and community assembly, especially in understory herbaceous communities. Here we partitioned the variance of four functional traits (maximum height, leaf thickness, leaf area and specific leaf area) across four nested biological scales: individual, species, plot, and elevation to quantify the scale-dependent distributions of understory herbaceous trait variance. We also integrated the comparison of the trait variance ratios to null models to investigate the effects of different ecological processes on community assembly and functional diversity along a 1200-m elevational gradient in Yulong Mountain. We found interspecific trait variation was the main trait variation component for leaf traits, although intraspecific trait variation ranged from 10% to 28% of total variation. In particular, maximum height exhibited high plasticity, and intraspecific variation accounted for 44% of the total variation. Despite the fact that species composition varied across elevation and species richness decreased dramatically along the elevational gradient, there was little variance at our largest (elevation) scale in leaf traits and functional diversity remained constant along the elevational gradient, indicating that traits responded to smaller scale influences. External filtering was only observed at high elevations. However, strong internal filtering was detected along the entire elevational gradient in understory herbaceous communities, possibly due to competition. Our results provide evidence that species coexistence in understory herbaceous communities might be structured by differential niche-assembled processes. This approach--integrating different biological scales of trait variation--may provide a better understanding of the mechanisms involved in the structure of communities.     

Direct and indirect facilitation affect community productivity through changes in functional diversity in an alpine system

Background and AimsFacilitation is an important ecological process for plant community structure and functional composition. Although direct facilitation has accrued most of the evidence so far, indirect facilitation is ubiquitous in nature and it has an enormous potential to explain community structuring. In this study, we assess the effect of direct and indirect facilitation on community productivity via taxonomic and functional diversity.MethodsIn an alpine community on the Tibetan Plateau, we manipulated the presence of the shrub Dasiphora fruticosa and graminoids in a fenced meadow and a grazed meadow to quantify the effects of direct and indirect facilitation. We measured four plant traits: height, lateral spread, specific leaf area (SLA) and leaf dry matter content (LDMC) of forbs; calculated two metrics of functional diversity [range of trait and community-weighted mean (CWM) of trait]; and assessed the responses of functional diversity to shrub facilitation. We used structural equation modelling to explore how shrubs directly and indirectly drove community productivity via taxonomic diversity and functional diversity.Key ResultsWe found stronger effects from herbivore-mediated indirect facilitation than direct facilitation on productivity and taxonomic diversity, regardless of the presence of graminoids. For functional diversity, the range and CWM of height and SLA, rather than lateral spread and LDMC, generally increased due to direct and indirect facilitation. Moreover, we found that the range of traits played a primary role over taxonomic diversity and CWM of traits in terms of shrub effects on community productivity.ConclusionsOur study reveals that the mechanism of shrub direct and indirect facilitation of community productivity in this alpine community is expanding the realized niche (i.e. expanding range of traits). Our findings indicate that facilitators might increase trait dispersion in the local community, which could alleviate the effect of environmental filters on trait values in harsh environments, thereby contributing to ecosystem functioning.     

Nitrogen status of conifer needles at the alpine treeline

Background and Aims: High elevation treelines occur worldwide at similar mean growing season temperatures. Does this result from direct impact of low temperature on growth or carbon metabolism, or does nutrient limitation, induced by low soil temperature, play a role? Similar treeline elevations at contrasting soil fertility argue against the latter, but the actual nutritional status of treeline trees (here addressed as foliage nitrogen concentration) has never been assessed systematically. Although needle nitrogen (N) concentration does not necessarily indicate growth limitation by N, the relative abundance of N would indicate obvious depletions at the treeline.

Methods: A central problem with any foliage nutrient assay is that the units for describing the element concentration are dependent on elevation themselves. Here we separate changes in N per unit tissue from changes in reference units.

Results: Needles of Pinus cembra and Picea abies in the Alps do not show elevational differences in N concentration per dry weight, water content, area or volume, thus, there is no N depletion near the elevational tree limit. Hence, nutrient supply is either unaltered, or growth is adjusted so that nutrient depletion in needle tissue does not occur.

Conclusions: Chronic N shortage at needle level is not an explanation for low tree vigour at the treeline.     

Spatial patterns of plant richness across treeline ecotones in the Pyrenees reveal different locations for richness and tree cover boundaries

Aim  To forecast the responses of alpine flora to the expected upward shift of treeline ecotones due to climatic warming, we investigated species richness patterns of vascular plants at small spatial scales across elevational transects.
Location  Richness patterns were assessed at local scales along the elevational gradient in two undisturbed treeline ecotones and one disturbed treeline ecotone in the Spanish Pyrenees.
Methods  We placed a rectangular plot (0.3–0.4 ha) in each treeline ecotone. We estimated and described the spatial patterns of plant richness using the point method and Moran's I correlograms. We delineated boundaries based on plant richness and tree cover using moving split windows and wavelet analysis. Then, to determine if floristic and tree cover boundaries were spatially related, overlap statistics were used.
Results  Plant richness increased above the forest limit and was negatively related to tree cover in the undisturbed sites. The mean size of richness patches in one of these sites was 10–15 m. Moving split windows and wavelets detected the sharpest changes in plant richness above the forest limit at both undisturbed sites. Most tree cover and plant richness boundaries were not spatially related.
Main conclusions  The upslope decrease of tree cover may explain the increase of plant richness across alpine treeline ecotones. However, the detection of abrupt richness boundaries well above the forest limit indicates the importance of local environmental heterogeneity to explain the patterns of plant richness at smaller scales. We found highly diverse microsites dominated by alpine species above the forest limit, which should be monitored to describe their response to the predicted upward shift of forests.     

甘南高寒草甸坡向梯度对植物群落功能多样性的影响

植物群落功能多样性对于维持生态系统功能具有十分重要的意义。该研究以青藏高原高寒草甸植物群落为研究对象,运用R软件程序包(FD、Vegan)与单因素方差分析法,分析高寒草甸不同坡向植物群落功能多样性的变化及其与环境因子的关系,以揭示微生境梯度上植物对环境的适应策略以及群落种间功能特征及生态系统内部结构和功能的变化机制。结果显示：(1)青藏高原高寒草甸的北坡和西北坡的物种丰富度、植物株高、比叶面积、叶片有机碳、叶片氮以及叶片磷显著高于其他坡向,且坡向间差异显著(P<0.05)。(2)在北坡到南坡的变化中,功能丰富度差异比较明显(P<0.05),株高、比叶面积、叶片有机碳、叶片氮及叶片磷等功能丰富度均呈递减趋势。(3)北坡的株高功能均匀度、西北坡比叶面积、叶片有机碳、叶片氮及叶片磷等功能均匀度均显著高于南坡,且多元性状功能均匀度在坡向间差异显著(P<0.05)。(4)北坡的比叶面积、叶片氮功能离散度及西北坡的株高、叶片有机碳、叶片磷等功能离散度均高于南坡,且坡向间差异显著(P<0.05)。(5)植物群落功能多样性与土壤含水量、土壤有机碳、土壤全氮、土壤全磷呈显著正相关关系(P<0.05),与坡度、土壤pH、土温、照度呈显著负相关关系(P<0.05)。     

Transactions of the Botanical Society of Edinburgh

Background: Due to the dry continental climate, the mountains of eastern Ladakh are unglaciated up to 6200–6400 m, with relatively large areas of developed soils between 5600 and 6000 m covered by sparse subnival vegetation. However, there are no studies on the composition of plant assemblages from such extreme elevations, their microclimates, vertical distributions and adaptive strategies.

Aims: The subnival vegetation was described and the relationship between microclimate, species distribution and species functional traits was analysed.

Methods: In total, 481 vegetation samples from 91 permanent plots, a floristic database of Ladakh and extensive microclimate measurements were used. Measurements of 15 functional traits were made and their relationship with species distribution between 4600 and 6150 m was tested.

Results: The subnival zone was characterised by extreme diurnal temperature fluctuations, a short growing season (between 88 and 153 days) and low soil temperature during the growing season (between 2.9 °C and 5.9 °C). It hosted 67 species, mainly hemicryptophytes, and ranged from ca. 5600 m to the highest known occurrence of vascular plants in the region (6150 m). The most common plant families were Brassicaceae, Asteraceae, Poaceae, Fabaceae and Cyperaceae. Subnival specialists with narrow elevational ranges represented 42% of the flora; these species were shorter, had relatively higher water content and water-use efficiency and contained more nutrients and soluble carbohydrates than species with a wider elevational range.

Conclusions: The subnival vegetation of eastern Ladakh is dominated by generalist species with wide vertical ranges and not by high-elevation specialists. These findings, in view of the vast unglaciated areas available for range extension, suggest a relatively high resilience of the subnival flora to climate change in this region.