Effect of climate and altitude on plant community composition and richness in Brazilian inselbergs

Plant communities are shaped by multiple factors along environmental gradients;however,studies are limited on how environmental filtering drives community composition and species richness on tropical inselbergs.We evaluate the influence of altitude and climatic variables related to temperature and precipitation on plant community composition and species richness on Brazilian inselbergs.We assume as a premise that both climate and altitude would induce changes on plant community composition and species richness at the local level.We used plant inventory data from 370 sampling units across four inselberg sites in the Atlantic Forest of Espírito Santo State,south-eastern Brazil.We tested the univariate and multivariate effects of altitude and climate variables on community composition and species richness with multiple models.Differences in species richness between inselbergs were evaluated using sample-based data to estimate rarefaction and extrapolation curves.In addition,differences in species composition and taxonomic beta diversity were examined via novel frequency-based metrics.A contrasting climate pattern was observed between the inselberg sites,with south sites being wet compared to the dry conditions found in northern sites.Species richness by rarefaction showed a similar pattern within regional sites;however,there were marked differences between regions.Species richness and beta diversity showed significant differences among sites,with higher values in southern sites than in northern sites.In a multi-model comparison between inselberg sites,altitude significantly influenced community composition and species richness and explained more variance than climate models.This finding suggested that climate could act to some extent on these tropical inselbergs;however,altitude was a better predictor of plant community composition and species richness at the local level.     

Shrub Communities and Environmental Variables Responsible for Species Distribution Patterns in an Alpine Zone of the Qilian Mountains,Northwest China

Understanding the factors that drive variation in species distribution is a central theme of ecological research. Although several studies focused on alpine vegetation, few efforts have been made to identify the environmental factors that are responsible for the variations in species composition and richness of alpine shrublands using numericalmethods. In the present study, we investigated vegetation and associated environmental variables from 45 sample plots in the middle Qilian Mountains of the northwestern China to classify different community types and to elucidate the speciesenvironment relationships. We also estimated the relative contributions of topography and site conditions to spatial distribution patterns of the shrub communities using the variation partitioning. The results showed that four shrub community types were identified and striking differences in floristic composition were found among them. Species composition greatly depended on elevation, slope,shrub cover, soil p H and organic carbon. The important determinants of species richness were soil bulk density and slope. No significant differences in species richness were detected among the community types. Topography and site conditions had almost equal effects on compositional variation. Nonetheless,a large amount of the variation in species composition remained unexplained.     

Higher species diversity occurs in more fertile habitats without fertilizer disturbance in an alpine natural grassland community

Are there some relationships among species diversity and soil chemical properties of high altitude natural grasslands？ Plant community composition and chemical properties of soil samples were compared to investigate the relationship between soil and species diversity, and the richness in Tibetan alpine grasslands. Results showed that species diversity was significantly positively related to soil organic matter （SOM）, total nitrogen （TN）, available nitrogen （AN）, total phosphorus （TP）, available phosphorus （AP）, and available potassium （AK） in the high alpine grasslands. Margalefs species richness index was also significantly positively related to SOM, TN, AN, and TP. Most soil chemical properties showed significantly positive correlation with species diversity and Margalef＇s richness index. Our results suggested that higher plant species richness index and diversity occurred in more fertile soil habitats in high altitude natural grassland community. In practice, fertilization management for the restoration of degraded grassland should be conducted with reference to the nutrient levels ofnatural grassland without the additional artificial fertilizer and with higher species-diversity and richness index.     

Alpine Ecosystems of Northwest Yunnan, China： an Initial Assessment for Conservation

Implementing conservation actions on-the-ground is not a straightforward process,especially when faced with high scientific uncertainty due to limited available information. This is especially acute in regions of the world that harbor many unique species that have not been well studied,such as the alpine zone of the Hengduan Mountains of Northwest Yunnan (NWY),a global biodiversity hotspot and site of The Nature Conservancy’s Yunnan Great Rivers Project. We conducted a quantitative,but rapid regional-level assessment of the alpine flora across NWY to provide a broad-based understanding of local and regional patterns of the alpine flora,the first large-scale analysis of alpine biodiversity patterns in this region. Multivariate analyses were used to classify the major plant community types and link community patterns to habitat variables. Our analysis indicated that most species had small distributions and/or small population sizes. Strong patterns emerged with higher diversity in the more northern mountains,but beta diversity was high,averaging only 10% among sites. The ordinations indicated that elevation and geographic location were the dominant environ-mental gradients underlying the differences in the species composition among communities. The high beta diversity across the alpine of these mountains implies that conservation strategies ultimately will require the protection of large numbers of species over a large geographical area. However,prioritiza-tion should be given to areas where potential payoffs are greatest. Sites with high species richness also have a greater number of endemic species,and,by focusing efforts on these sites,conservation investments would be maximized by protecting the greatest number of unique species.     

Species composition and diversity of woody communities along an elevational gradient in tropical Dwarf Cloud Forest

Elucidating woody community diversity and structure change along environmental gradients is still a central issue of tropical forest ecology. We have evaluated changes in alpha and beta diversity, community composition and structure of woody communities along an elevational gradient in Dwarf Cloud Forests, Southeast Brazil. We selected five areas along an elevational gradient(1,300-1,600 m asl), and randomly allocated 10 plots(10 m × 20 m) in each area in the Ibitipoca State Park(ISP), Serra da Mantiqueira, southeastern Brazil. All woody species(diameter at breast height ≥ 5.0 cm) were collected for taxonomic identification. Thus, we analysed the woody communities based on a phytosociological approach. Overall, 147 species and 37 families were recorded, distributed in 2,303 individuals. No differences in the species richness pattern were observed between areas using the rarefaction and extrapolation curves. Significant differences in species composition and structure between areas were observed. The high beta diversity observed, corroborated by the Jaccard coefficient, increases with decreasing altitude. Our results showed that woody communities in the studied Dwarf Cloud Forests have a higher diversity and structural variability along elevational gradient.     

Ecological consequences of land use change: Forest structure and regeneration across the forest-grassland ecotone in mountain pastures in Nepal

The ecotone, the spatial transition zone between two vegetation communities, is claimed to have more species than the adjoining communities. However, empirical studies do not always confirm higher richness at the ecotone. The ecotone position and structure are dynamic over time and space and it is driven by the changes in climate, land use or their interaction. In this context, we assessed the forest- grassland ecotone of temperate mountains in central Nepal by i） comparing species composition and richness across the ecotone, ii） analyzing if the forestgrassland ecotone is shifting towards the grassland center by colonizing them with trees, and iii） discussing the consequence of changed disturbance regime in the dynamics of this ecotone and the surrounding grasslands. We analyzed vegetation data sampled from belt transects laid across the forest- grassland ecotone in semi-natural grassland patches. Vegetation data consisting of species richness and composition, and size structure and regeneration of the two most dominant tree species, namely Rhododendron arboreum and Abies spectabilis, from the transects, were used to analyze the trend of the forest-grassland ecotone. Forest and grasslands were different in terms of floristic composition and diversity. Vascular plant speciesrichness linearly increased while moving from forest interior to grassland center. Spatial pattern of tree size structure and regeneration infers that forest boundary is advancing towards the grasslands at the expense of the grassland area, and tree establishment in the grasslands is part of a suceessional process. Temporally, tree establishment in grasslands started following the gradual decline in disturbance. We argue that local processes in terms of changed land use may best explain the phenomenon of ecotone shift and consequent forest expansion in these grasslands. We underpin the need for further research on the mechanism, rate and spatial extent of ecotone shift by using advaneed tools to understand the process indepth.     

How do altitude and soil properties influence the taxonomic and phylogenetic structure and diversity of Brazilian páramo vegetation?

Altitude and environmental variables such as edaphic properties are considered determinants of species distribution and community composition in mountain ecosystems.Here,we aimed to outline the effects of distinct mountain peaks,altitude and soil properties on community composition,species density,phylogenetic structure and diversity of angiosperm páramo communities from the Serra do Brigadeiro State Park,Minas Gerais,southeastern Brazil.For that,we identified all angiosperm species found in 300 plots(1 m×1 m)from three mountain peaks,measured soil depth and analyzed soil fertility and texture in each plot.To reduce the number of soil variables and species composition,we computed principal coordinates based on soil properties and principal coordinates based on species-plot matrix for each plot.Furthermore,we computed the standard effect sizes of the mean phylogenetic pairwise distance and the mean nearest phylogenetic taxon distance for each plot to investigate differences in the degree of relatedness among coexisting species.We compared differences in response variables between peaks and modelled them in function of altitude and principle components of soil properties using mixed effect models.Species density and phylogenetic diversity differed between peaks,but,contrary to the previous findings,no relationships between species richness or phylogenetic diversity and altitude or soil properties were found,indicating that further investigations are necessary to understand the altitude-biodiversity relationship in Brazilian páramo vegetation.Community composition differed between peaks and depended on altitude,soil properties and interactions between them,indicating that upward shifting of bioclimatic conditions due to climate changes may alter communities of this ecosystem.Phylogenetic structure differed between peaks and was influenced by altitude and soil properties.As phylogenetic clustering increased with altitude,eventual upward movements of species in Brazilian páramo vegetation due to climate change may alter community composition and the degree of relatedness among coexisting species,increasing the risk of species from higher altitudes to disappear.Therefore,conservation priorities arise for higher landscape portions,where these high altitude species may find refuges.     

Fauna and standing crop of freshwater mussels in Poyang Lake, China

Freshwater mussels are a major component of the zoobenthos and they therefore play an important role in freshwater ecosystems. The community composition and the standing crop of freshwater mussels in Poyang Lake, the largest freshwater lake in China and one of two lakes connected to the Changjiang (Yangtze) River, were investigated from February 2008 to May 2009. Mussels were sampled in hydrologically and geographically distinct sampling areas. A total of 42 species and 13 genera were identified, of which 32 species were endemic to China. Two species, Unio douglasiae and Lamprotula caveata, dominated all sampling areas. The number of genera and species, and the number of species within each genus, differed significantly among sampling areas. Freshwater mussels were very abundant, with an overall density of 0.28 ± 0.22 ind./m2 and biomass of 4.08 ± 3.96 g/m2. Significant variation observed among sampling areas and among genera was probably due to the variety of habitats among the areas sampled and to the adaptability of different freshwater mussels to environments. This study suggests that Poyang Lake and other freshwater lakes in the region are important sites of freshwater mussel biodiversity and conservation.     

Seasonal and spatial variations of macro-and megabenthic community characteristics in two sections of the East China Sea

In spring and summer 2011,the macro-and megabenthic fauna in two sections of the East China Sea were investigated using an Agassiz net trawl to detect the seasonal and spatial variations of benthic community characteristics and the relation to environmental variables.The total number of species increased slightly from spring(131 species)to summer(133)whereas the percentage of Mollusca decreased signifi cantly.The index of relative importance(IRI)indicated that the top fi ve important species changed completely from spring to summer.Species number,abundance and biomass in summer were signifi cantly higher than in spring,but no signifi cant dif ference was observed among areas(coastal,transitional and oceanic areas,divided basically from inshore to of fshore).Species richness(d),diversity(H′)and evenness(J′)showed no signifi cant seasonal or spatial variations.Cluster analysis and n MDS ordination identifi ed three benthic communities from inshore to of fshore,corresponding to the three areas.Analysis of Similarity(ANOSIM)indicated the overall signifi cant dif ference in community structure between seasons and among areas.K-dominance curves revealed the high intrinsic diversity in the off shore area.Canonical correspondence analysis showed that the coastal community was positively correlated to total nitrogen and total organic carbon in spring,but negatively in summer;oceanic community was positively correlated to total nitrogen and total organic carbon in both seasons.Species such as Coelorhynchus multispinulosus,Neobythites sivicola,Lepidotrigla alata,Solenocera melantho,Parapenaeus fi ssuroides,Oratosquilla gonypetes and Spiropagurus spiriger occurred exclusively in the of fshore oceanic area and their presence may refl ect the infl uence of the off shore Kuroshio Current.     

Comparative Assessment of Tundra Vegetation Changes Between North and Southwest Slopes of Changbai Mountains,China, in Response to Global Warming

Vegetation in high altitude areas normally exhibits the strongest response to global warming. We investigated the tundra vegetation on the Changbai Mountains and revealed the similarities and differences between the north and the southwest slopes of the Changbai Mountains in response to global warming. Our results were as follows: 1) The average temperatures in the growing season have increased from 1981 to 2015, the climate tendency rate was 0.38℃/10 yr, and there was no obvious change in precipitation observed. 2) The tundra vegetation of the Changbai Mountains has changed significantly over the last 30 years. Specifically, herbaceous plants have invaded into the tundra zone, and the proportion of herbaceous plants was larger than that of shrubs. Shrub tundra was transforming into shrub-grass tundra. 3) The tundra vegetation in the north and southwest slopes of the Changbai Mountains responded differently to global warming. The southwest slope showed a significantly higher degree of invasion from herbaceous plants and exhibited greater vegetation change than the north slope. 4) The species diversity of plant communities on the tundra zone of the north slope changed unimodally with altitude, while that on the tundra zone of the southwest slope decreased monotonously with altitude. Differences in the degree of invasion from herbaceous plants resulted in differences in species diversity patterns between the north and southwest slopes. Differences in local microclimate, plant community successional stage and soil fertility resulted in differential responses of tundra vegetation to global warming.     

Distribution patterns of medicinal plants along an elevational gradient in central Himalaya, Nepal

This study aimed to compare the distribution patterns and trends of plant parts used among different groups of medicinal plants, geographical regions,and between medicinal plants and all vascular plants.We used the published sources for elevation records of 2,331 medicinal plant species to interpolate presence between minimum and maximum elevations and estimated medicinal plant richness for each 100-m elevational band. Monte Carlo simulations were used to test whether differences in elevational distribution between different groups of medicinal plants were significant. Total number of medicinal plants as well as different groups showed unimodal relationship with elevation. The elevational distributions of medicinal plants significantly differ between regions and between medicinal plant groups.When comparing the richness of all medicinal plants to all vascular plants,Monte Carlo simulations indicated that the numbers of medicinal plants are higher than expected at low elevations.The highest richness of medicinal plants at low elevation could be possibly due to favorable environmental factors such as high temperature, rainfall,sunlight or due to higher density of human population and thus higher pressure on use of any plants in lower elevations.     

Environmental Factors that Affect Primary Plant Succession Trajectories on Lahars(Popocatépetl Volcano,Mexico)

The earliest stages of plant succession on severely disturbed sites usually follow highly unpredictable trajectories. However, in the Popocatépetl volcano area(50 km SE of Mexico City),the development of physiognomically distinct primary plant communities suggests the occurrence of various successional trajectories only 10 years after the onset of colonization of a temperate forest on lahars. To characterize plant communities and determine the environmental factors that drive the differences observed between plant communities and their successional trajectories, we monitored 64 circular sample plots(3.14 m2) from 2002 to 2011. We examined the plant communities' composition and structure in terms of their species richness and abundance, plant cover, and maximum stem height,and recorded 13 environmental factors related to the volcanic deposit characteristics, microclimate, soil,flow dynamics and gravitational processes. A cluster analysis of the species abundance data showed that,by 2011, six plant community types(CT's) had established, including grasslands, and open, dense and very dense shrub lands. As these communities developed over the same period of time and within the same overall ecosystem, then these plant community types were interpreted as different stages of the same successional trajectory. Two sequential main stages that drive regeneration were identified from this successional trajectory: a) the first four years are characterized by a steady increase in species richness and physiognomic development(plant size and coverage), mostly dominated by Baccharis conferta, Eupatorium glabratum and Senecio barbajohannis; b) from the sixth year onwards, a continued increase in the abundance of those same species led to the development of the dense shrubland communities.Differences in the availability of soil resources and disturbances linked to recent lahar flows were the main factors accounting for such differences.     

Assessing mariculture water quality with the structural and functional characteristics of a ciliate community

Ciliated protozoa play important roles in micro-ecosystems, especially in marine biotopes. However, few studies have been carried out on the periphytic, or aufwuch, forms in mariculture waters so far. In this study, we sampled periphytic ciliate communities in two closed mariculture ponds (ponds CP1 and CP2) and a natural seawater reservoir (pond RP) using a glass slide method to evaluate their colonizing processes and general ecological features, as well as their application as water quality indicators. We analyzed species compositions, structural parameters (species number, richness, diversity, evenness, abundance and dBP) and functional parameters (G, Seq and T90%). Pond RP was characterized by higher levels of structural parameters (except for abundance and dBP) and more equal proportion of the major taxonomic groups. The values of Seq were significantly higher in pond RP and similar in both pond CP1 and CP2. It was also demonstrated that environmental factors, including NO2-H, NO3-H, NH3-H, soluble reactive phosphate, temperature and pH, were the first principal factors affecting the communities. Among them, temperature and chemical factors were all significantly and negatively correlated with species number (P<0.01), richness (P<0.01), diversity (P<0.01), and positive correlated with abundance (P<0.01). Opposite correlations between pH and structural parameters were observed. This study showed that there were significant differences in species composition, structural parameters and functional parameters of the periphytic ciliate communities among the ponds, which were in agreement with the water quality. Results of this study confirmed the periphytic ciliate communities to be useful bioindicators of water quality in intensive mariculture waters.     

Effects of land-use types on soil organic carbon stocks: a case study across an altitudinal gradient within a farm-pastoral area on the eastern Qinghai-Tibetan Plateau,China

A crucial region for China's ‘Grain-forGreen Policy' is located within a traditional farmpastoral area, between 2000 to 3000 m above sea level, on the eastern Qinghai-Tibetan Plateau.However, the responses of soil organic carbon(SOC) to different land-use patterns in this region are unclear. Here, we determined the SOC(0–20 cm) content of grasslands and forests that are being converted from farmlands, as well as in abandoned arable land and arable land in this region. The factors influencing the reclaimed lands were analyzed along altitudes from 2030 to 3132 m. Our results showed that SOC content was higher for grassland and abandoned arable land than forest and arable land. The SOC content increased with the increase in altitude for total land-use patterns. Further, the grassland and abandoned arable land had higher SOC content than the forest with almost parallel trends along the increase in altitude. However, the proportion of regulated factors of altitude and species richness varied among forest, grassland, and abandoned arable land. Our results indicated that the land-use pattern of returning farmland to grassland and abandoned arable land was more effective in terms of the SOC storage in the superficial layer in this altitude range in the Qinghai-Tibetan Plateau, thereby being beneficial to optimizing land management in this region.     

Mountain pastures and grasslands in the SW Tien Shan, Kyrgyzstan �� Floristic patterns, environmental gradients, phytogeography, and grazing impact

Vast grasslands are found in the walnut-fruit forest region of southern Kyrgyzstan,Middle Asia.Located above the worldwide unique walnutfruit forests and used for grazing,they play a pivotal role in the mixed mountain agriculture of local farmers.Accordingly,these pastures are subject to an increasing utilization pressure reflecting the changing political and social conditions in the transformation process from a Soviet republic to an independent state.A first detailed analysis of mountain pasture vegetation in the Ferghana Range answers the following questions:What are the main plant community types among Kyrgyzstan’s mountain pastures? What are the main environmental gradients that shape their species composition? Which phytogeographical distribution types are predominant? How does grazing affect community composition and species richness in these grasslands? Species composition was classified by cluster analysis;underlying environmental gradients were explored using DCA.A dataset of 395 relevés was used for classification,and a subset of 79 relevés was used in a DCA to analyze the correlation between vegetation,environment,and grazing impact.The investigated pastures were classified into four distinctive plant communities.The site factors altitude,heat load,inclination and grazing impact were found to be the major determinants of the vegetation pattern.A significant overlap between floristic composition and structural and spatial properties was shown.The majority of the species pool consisted of Middle Asian endemics and Eurosiberian species.However,disturbance-tolerant species played a significant role with respect to species composition and coverage of the herbaceous layer in vast areas of southern Kyrgyzstan’s mountain pastures.In general,an intense grazing impact is clearly reflected by both species composition and structural variables of plant communities.The highly diverse and unique ecosystem is modified by an increasing utilization pressure.In order to maintain vital processes and functioning of this valuable ecosystem-in both economical and ecological terms-,it is indispensable to adopt appropriate pasture management strategies.     

Soil and vegetation seasonal changes in the grazing Andean Mountain grasslands

Andean grasslands ecosystems are fragile environments with rigorous climatologic conditions and low and variable food for the grazing. The Apolobamba area is located in the Bolivian Andean Mountains. Its high grasslands provide a natural habitat for wild and domestic camelids such as vicuna（Vicugna vicugna） and alpaca（Lama pacos）. The botanical diversity plays an essential role in maintaining vital ecosystem functions. The objectives of this research were to determine the seasonal changes in soil properties, to study the vegetation changes during the wet and dry seasons and the influence of soil properties and camelid densities on the vegetation in the Apolobamba grasslands. Four zones with different vicuna populations were selected to be studied. The following soil parameters were determined： total organic carbon, total nitrogen, available phosphorous, cation exchange capacity, exchangeable cations, pH and texture. The vegetation season changes were studied through botanical identification, above-ground biomass, plant cover and species richness. Results showed that some soil properties such as C/N ratio, CEC, silt and clay percentages kept stable against the seasonal changes. Generally, soil nutrients were relatively higher during the dry season in the surface and subsurface. The results did not point out the predominant vegetation growth during the wet season. The seasonal vegetation growth depended on each species. Thegood soil fertility corresponded to the highest plant cover. Soil fertility presented no influence on the above-ground biomass of the collected species. The negative influence of camelid grazing on soil properties could not be assessed. However, overgrazing could affect some plant species. Therefore, protection is needed in order to preserve the biodiversity in the Andean mountain grasslands.     

The potential contribution of wildlife sanctuary to forest conservation: A case study from binsar wildlife sanctuary

Forest vegetation of a protected area(Binsar Wildlife Sanctuary) in Kumaun region(west Himalaya) was analysed for structure,composition and representativeness across three different altitudinal belts,lower(1,600-1,800 m a.s.l.),middle(1,900-2,100 m a.s.l.) and upper(2,200-2,400 m a.s.l.) during 2009-2011 using standard phytosociological methods.Four aspects(east,west,north and south) in each altitudinal belt were chosen for sampling to depict maximum representation of vegetation in the sanctuary.Population structure and regeneration behaviour was analysed seasonally for two years to show the establishment and growth of tree species.A total of 147 plant species were recorded from the entire region of which 27 tree species were selected for detailed study.Highest number was recorded at upper(18 species),and lowest at lower altitudinal belt(15 species).The relative proportion of species richness showed higher contribution of tree layer at each altitudinal belt.The population structure,based on the number of individuals,revealed a greater proportion of seedling layer at each altitudinal belt.The relative proportion of seedlings increases significantly along altitudinal belts(p<0.05) while opposite trends were observed in sapling and tree layers.The density of sapling and seedling species varied non-significantly across seasons(p>0.05).The density values decreased in summer and increased during rainy season.As far as the regeneration status is concerned,middle and upper altitudinal belts showed maximum number of species with fair regeneration as compared to lower altitudinal belt.Overall density diameter distribution of tree species showed highest species density and richness in the smallest girth class and decreased in the succeeding girth classes.This study suggests that patterns of regeneration behaviour would determine future structural and compositional changes in the forest communities.It is suggested that the compositional changes vis-à-vis role of ‘New’ and ‘Not regenerating’ species need priority attention while initiating conservation activities in the sanctuary.This study calls for exploring other less explored Wildlife Sanctuaries in the Himalaya and across the world,to achieve overall biodiversity status in these protected areas and thus to justify their role in conserving biodiversity in the region.     

Herbage Production and Species Richness in Sub-alpine Grasslands of Different Soil Parent Material in Northern Greece

Several abiotic and biotic factors were investigated as possible predictors of local species richness in two sub-alpine grasslands of Jenna and Belles Mountains in Northern Greece.For species richness modelling a hierarchical modelling framework based on generalized additive models was adopted.The two sub-alpine grasslands differed in aspect,altitude and soil parent material（volcanic origin,mostly trachyte,and andesite（TA） for Jenna and metamorphic rocks,mostly gneiss（G） for Belles）.12 fenced squared plots,16 m2 each,were used per grassland,where soil properties,herbage production,species presence and cover of grasses,legumes and forbs were estimated.Mean herbage production was significantly affected by slope and altitude,soil K content and floristic composition as expressed by an ordination axis.Soil p H,floristic composition and average herbage production were significant predictors of forbs and total species richness.For the former,soil N content and for the latter the occurrence of Agrostis capillaris,were also included as significant terms in the predictive model.Thepredictors for grasses species richness were N content,having a positive effect,and average herbage production.In all cases higher species richness was predicted for intermediate values of average herbage production.Differential responses were found between forbs and grasses.The predictors of their species richness were different while for the case of the common predictor（N） the responses of the two groups were also different（grasses species numbers increase and forbs species numbers decreased with increasing N）.Maximum species richness of grasses was observed at relatively low production levels while forbs species richness maximized at relatively high production levels.     

Species richness and biodiversity significance of alpine micro-waterbody systems in Gaoligong Mountain,Northwest Yunnan,China

Water quality, size, connectivity and other physical properties of hydrological systems might have different functions in the formation and maintenance of biodiversity, but this remains mostly unclear due to the lack of undisturbed sites for experimental modelling. Alpine freshwater habitats such as micro-waterbodies(MWB) represent a kind of natural system suitable for biodiversity research. In order to assess potential linkages between environmental factors, connectivity of MWBs and aquatic species richness, we conducted a pilot study in two separated MWB systems located in Gaoligong Mountain, northwest Yunnan province, China. A total of 27 MWBs have been analyzed, including 22 connected and 5 isolated bodies. 13 conventional environmental factors were tested while all kinds of aquatic macro-organisms were collected and classified. Results showed a high environmental heterogeneity among MWBs and significant differences between the two systems but only a few environmental variables such as the depth of soil bottom, total Nitrogen and altitude were related to species richness and the formation of the community structure. As a benefit from the high environmental heterogeneity, the cascaded MWB systems provided divergent habitats able to support species richness at a higher level than the same number of randomly selected MWBs. This finding supports the idea that habitat connectivity matters also in extremely small aquatic ecosystems. Moreover, although still a preliminary result, a polarization effect within connected chains where edge MWBs host higher taxa and endemic taxa richness as well as larger populations, was detectable. This study gives interesting insights on the spatial processes driving community structure and a new prospective for biodiversity conservation. Since alpine MWBs have significant effects on the maintenance of watershed biodiversity, further research on such small and crucial ecosystems is encouraged.     

Species-area relationship within and across functional groups at alpine grasslands on the northern Tibetan Plateau,China

The species-area relationship(SAR) is one of the most fundamental concepts in community ecology and is helpful for biodiversity conservation.However,few studies have systematically addressed this topic for different alpine grassland types on the Tibetan Plateau,China.We explored whether the plant composition of different functional groups affects the manner in which species richness increases with increasing area at scales ≤ 1.0 m~2.We also compared species richness(S) within and across forbs,legumes,sedges and grasses,with sampling subplot area(A) increasing from 0.0625 m~2 to 1.0 m~2 between alpine meadow and steppe communities.We applied a logarithmic function(S = b_0 + b_1 ln A) to determine the slope and intercept of SAR curves within and across functional groups.The results showed that the logarithmic relationship holds true between species richness and sampling area at these small scales.Both the intercept and slope of the logarithmic forbs-area curves are significantly higher than those for the three other functional groups(P 0.05).Forb accounts for about 91.9 % of the variation in the intercept and 75.0% of the variation in the slope of the SAR curve when allfunctional groups' data were pooled together.Our results indicated that the different SAR patterns should be linked with species dispersal capabilities,environmental filtering,and life form composition within alpine grassland communities.Further studies on the relationship between species diversity and ecosystem functions should specify the differential responses of different functional groups to variations in climate and anthropogenic disturbances.