Alpine Grassland Communities Research Articles

Multitrophic Diversity of the Biotic Community Drives Ecosystem Multifunctionality in Alpine Grasslands.

Biodiversity and ecosystem multifunctionality are currently hot topics in ecological research. However, little is known about the role of multitrophic diversity in regulating various ecosystem functions, which limits our ability to predict the impact of biodiversity loss on human well-being and ecosystem multifunctionality. In this study, multitrophic diversity was divided into three categories: plant, animal, and microbial communities (i.e., plant diversity, rodent diversity, and bacterial and fungal diversity). Also, 15 ecosystem functions were divided into four categories-water conservation, soil fertility, nutrient cycling and transformation, and community production-to evaluate the significance of biotic and abiotic variables in maintaining ecosystem multifunctionality. Results indicated that species diversity at multiple trophic levels had a greater positive impact on ecosystem multifunctionality than species diversity at a single trophic level. Notably, the specific nature of this relationship depended on the niche breadths of plants, indicating that plants played a key role in linking above and belowground trophic levels. Abiotic factors such as altitude and pH directly acted on ecosystem multifunctionality and could explain changes in ecosystem functions. Overall, our study offers valuable insights into the critical role of multitrophic species diversity in preserving ecosystem multifunctionality within alpine grassland communities, as well as strong support for the importance of biodiversity protection.

Impact of functional groups on aboveground biomass in alpine grassland communities

Alpine grasslands on the Tibetan Plateau (TP) are highly vulnerable to various treatments and face significant degradation risks due to global environmental changes. However, the response of these grasslands to different external treatments remains uncertain, and the patterns behind functional group responses are unclear, impeding our ability to restore alpine grasslands under changing climate. To address this gap, we compiled a comprehensive database of 797 experimental observations of alpine grasslands in the TP, classified these communities into four common functional groups (e.g., grass and sedge), and conducted a meta-analysis to evaluate the response of aboveground biomass (AGB) to nine different treatments (e.g., grazing and nitrogen addition). Meta-regression was used to analyze the changes in AGB with treatment intensity and duration. We also used functional group asynchrony and unevenness to describe the complementary effects (CEs) and selection effects (SEs) of communities under these treatments. We found that among all the nine treatments, grazing had the biggest negative impact on the alpine grassland community by reducing AGB by 40.3%, mainly through decreasing the biomass of grass and sedge. Conversely, nitrogen and phosphorus addition had the largest positive effect, increasing AGB by 39.4% mainly by promoting the growth of grass. However, the increase in AGB was not significant in the interactive experiments involving grazing and nitrogen addition. The unevenness of the community decreased as grazing time prolongs, simplifying the structure of the community, with severe nutrient losses and weakened CE, while nitrogen addition could rapidly increase the AGB of grass and enhance the SE. CE or SE of communities can be enhanced through the restoration of specific functional groups, favoring the recovery of vegetation. Our study also revealed the potential of nitrogen compensation for repairing the damage caused by overgrazing on alpine grasslands.

Alpine grassland community productivity and diversity differences influence significantly plant sexual reproduction strategies.

Whether and how community structure variation affects plant sexual reproduction is crucial for understanding species' local adaptation and plant community assembly, but remains unrevealed. In Qinghai-Tibetan grassland communities that differed in aboveground biomass (AGB) and species diversity, we found significant influence of AGB on both species' reproductive biomass allocation (RBA) and flowering and fruiting time, but of species diversity only on species' reproductive time. In high-AGB or high-diversity communities, smaller and earlier flowering species generally advanced their reproductive phenology and increased their reproductive allocation for maximizing their reproductive success, whereas larger and later flowering species delayed their reproductive phenology and decreased their reproductive allocation for maximizing their vegetative growth and resource competition. This change in reproductive allocation with the variation in community structures was more pronounced in nonclonal as compared to clonal plant species. Thus, we evidence an important influence of community structure on plant sexual reproduction strategies, and the pattern of the influence depends largely on species biological attributes.

Pollen limitation and context‐dependent alleviating mechanisms in a co‐flowering alpine grassland community

The consequences of community metrics (e.g. co‐flowering diversity and floral density) and plant traits (e.g. pollinator dependency and trait similarity) on pollen limitation (PL) may depend on pollinator‐mediated competitive or facilitative interactions among plants in co‐flowering communities, which could vary with community contexts (i.e. different altitude communities) and under human disturbances (e.g. livestock grazing). However, the mechanisms to alleviate PL under different contexts, considering pollinator‐mediated interactions among neighboring plants are unclear. We investigated PL under grazing versus ungrazing conditions in low versus high altitude alpine meadows on the Tibetan Plateau to uncover the underlying mechanisms mediating PL associated with livestock grazing. We found that PL is prevalent in alpine grasslands, irrespective of community contexts. Grazing exclusion decreased PL in the two sites but in different ways. At the high‐altitude site, PL was reduced by the exclusion of grazers through increased trait similarity (suggesting facilitation). While PL was reduced by decreased trait similarity (suggesting competition avoidance) under grazing exclusion at the low‐altitude site. Our results provide a mechanistic understanding of PL in co‐flowering alpine grassland communities under distinct human disturbances at different altitudes, emphasizing the role of pollinator‐mediated interactions among plants on plant reproductive success.

Relationship between species distribution of sandy alpine grasslands and microtopography in the source regions of Yangtze river

Dynamic of sandy alpine grasslands affect the progress and reversal of desertification in source regions of the Yangtse Rivers. To understand geomorphic driving mechanism of species distribution pattern, we examined the species compositions and delineated the most important landform factors influencing species distribution of sandy alpine grassland using two-way indicator species analysis (TWINSPAN), detrended correspondence analysis (DCA), and canonical correspondence analysis (CCA). Field survey were conducted in summer of 2016 using stratified random methods in hilly sloped lands, floodplains, foothills, and valley land of study region. In total, 29 plant species grouped into 27 genera and 16 families were identified. Leymus secalinus, Elymus dahuricus and Corispermum declinatum are the dominant species of sandy alpine grassland communities in different microtopography. The present vegetation reflected xerosere character, which indicated that desertification of alpine grassland is in progress. Standard frequency distribution of species varied with different microtopography, the proportion of dominant species was generally lower than rare species, and the vegetation community was in a highly successional stage. Seven groups were distinguished through TWINSPAN, distribution of which in the DCA ordination graph showed species with similar ecotype is clustered together. The results of the CCA ordination revealed that slope and aspect are the dominant factors among microtopography determining the species distribution of sandy alpine grassland.

An Improved Method for Monitoring Multiscale Plant Species Diversity of Alpine Grassland Using UAV: A Case Study in the Source Region of the Yellow River, China.

Plant species diversity (PSD) is essential in evaluating the function and developing the management and conservation strategies of grassland. However, over a large region, an efficient and high precision method to monitor multiscale PSD (α-, β-, and γ-diversity) is lacking. In this study, we proposed and improved an unmanned aerial vehicle (UAV)-based PSD monitoring method (UAVB) and tested the feasibility, and meanwhile, explored the potential relationship between multiscale PSD and precipitation on the alpine grassland of the source region of the Yellow River (SRYR), China. Our findings showed that: (1) UAVB was more representative (larger monitoring areas and more species identified with higher α- and γ-diversity) than the traditional ground-based monitoring method, though a few specific species (small in size) were difficult to identify; (2) UAVB is suitable for monitoring the multiscale PSD over a large region (the SRYR in this study), and the improvement by weighing the dominance of species improved the precision of α-diversity (higher R2 and lower P values of the linear regressions); and (3) the species diversity indices (α- and β-diversity) increased first and then they tended to be stable with the increase of precipitation in SRYR. These findings conclude that UAVB is suitable for monitoring multiscale PSD of an alpine grassland community over a large region, which will be useful for revealing the relationship of diversity–function, and helpful for conservation and sustainable management of the alpine grassland.

Functional diversity outperforms taxonomic diversity in revealing short-term trampling effects

Alpine grasslands harbor diverse groups of flora and fauna, provide important ecosystem functions, and yield essential ecosystem goods and services, especially for the development of nature-based tourism. However, they are experiencing increasing anthropogenic perturbations such as tourist trampling. Although negative effects of tourist trampling on alpine vegetation have been frequently reported, previous studies have focused mainly on changes in taxonomic diversity after trampling, and rarely provide a mechanistic elucidation of trampling effects from a trait-based perspective. The present study evaluates the impacts of simulated trampling on taxonomic and functional diversity of a typical alpine grassland community in Shangri-La, China using a standardized protocol. The results showed that although taxonomic diversity was not statistically significantly affected by trampling, some functional attributes responded rapidly to trampling disturbance. Specifically, functional divergence decreased with an increase in trampling intensity, and characteristics of community-weighted mean trait values changed towards shorter species with reduced leaf area and lower leaf dry matter content. Such strong shifts in functional attributes may further affect ecosystem goods and services provided by alpine grasslands. Our inclusion of functional diversity in the analysis thus adds an important caution to previous studies predominantly focusing on taxonomic diversity, and it is urgent to keep alpine grasslands well managed and ecologically coherent so that their valuable functions and services can be safeguarded.

Land use and water availability drive community-level plant functional diversity of grasslands along a temperature gradient in the Swiss Alps

Functional traits of mountain grassland communities strongly depend upon temperature variation along elevational gradients. However, little is known to what degree the direction of such trait-temperature relationships is shaped by other environmental factors or land-use types. Here, we investigated context-dependent patterns of plant functional trait variation in alpine grassland communities. Specifically, we tested whether temperature (degree-days) variation along an elevational gradient, interacts with water availability, soil properties and land-use type to moderate such patterns. We used cover-abundance and plant-trait data from 236 grassland relevés of the Swiss Alps along an elevational range of 500–2400 m a.s.l. with plant traits being specific leaf area (L), seed releasing height (H) and seed mass (S). We used indices capturing different dimensions of plant functional diversity as response variables, i.e. community weighted mean (CWM), trait range (TR) and functional dispersion (FDis). Land-use type and water availability interacted significantly with degree-days determining the responses of multiple plant traits community attributes. Specific leaf area (CWML) and seed releasing height (CWMH) increased with temperature in meadows and pastures, while no significant trend was detected in fallows. In meadows, seed mass (CWMS) increased and was at the same time less constrained (higher TRS) with increasing temperature. In pastures and fallows, by contrast, no seed trait-temperature trends were detected. In addition, water availability interacted with increasing temperature affecting functional dispersion: FDisL decreased only in sites with higher site water balance and TRS and FDisS increased in sites with low mean summer precipitation. Our findings suggest that functional diversity of grasslands might respond to climate warming with strong ecological differences depending on land-use types and water availability. Based on our results, managed meadows and pastures most likely change in direction to species with more acquisitive strategies, whereas in fallows, no specific trajectory of change is expected.

Synergistic effects of nitrogen and CO2 enrichment on alpine grassland biomass and community structure.

Global environmental change is altering the Earth's ecosystems. However, much research has focused on ecosystem-level responses, and we know substantially less about community-level responses to global change stressors. Here we conducted a 6-yr field experiment in a high-altitude (4600m asl) alpine grassland on the Tibetan Plateau to explore the effects of nitrogen (N) addition and rising atmospheric CO2 concentration on plant communities. Our results showed that N and CO2 enrichment had synergistic effects on alpine grassland communities. Adding nitrogen or CO2 alone did not alter total community biomass, species diversity or community composition, whereas adding both resources together increased community biomass, reduced species diversity and altered community composition. The observed decline in species diversity under simultaneous N and CO2 enrichment was associated with greater community biomass and lower soil water content, and driven by the loss of species characterised simultaneously by tall stature and small specific leaf area. Our findings point to the co-limitation of alpine plant community biomass and structure by nitrogen and CO2 , emphasising the need for future studies to consider multiple aspects of global environmental change together to gain a more complete understanding of their ecological consequences.

Evaluation of Heavy Metal Level in Soil of Typical Alpine Grassland Communities

Objective: Through the investigation, determination and analysis of heavy metals in the soil of typical alpine grassland community, five kinds of alpine grasslands with different degeneration degree of Maduo County in Alpine area, two kinds of alpine grassland with high Maqu County, high Alpine desert along the coast of Qinghai Lake, alpine thickets in the yellow South region, Alpine wetlands, The condition of soil heavy metals in alpine meadow and other communities is analyzed, which provides scientific guidance for the ecological protection measures of typical alpine grassland communities, and provides a basis for the sustainable utilization of Alpine grassland. Methods: The content of various kinds of heavy metals in soil samples was determined by ICP-MS, and the pollution status of heavy metals was analyzed by means of single factor pollution index method, Nemero comprehensive pollution index method and potential ecological risk index method by using Excel. Results: (1) The content of Cd in Maduo, Maqu, Qinghai Lake and Huangnan was 1.74, 0.97, 1.84 and 1.06 times times the soil environment background respectively, and the content of Hg in Maqu was 1.36 times times that of soil environmental background value. The variation coefficient of Hg and Pb in Maqu and the coefficient of variation of Cd in Qinghai Lake are more than 100%, which is in the degree of high variation, which is greatly influenced by man. (2) The highest total pollution index in the 4 sample places was in the area of MA diversity, at 1.33. The second is the Huangnan sample, with an exponential value of 0.86. The Nemero comprehensive pollution Index of the Maqu sample is 0.77. The index value of Qinghai Lake sample is the lowest, at 0.61. (3) The highest potential ecological hazard index is the most diverse, in 0-10, 10-20, 20-30cm three soil layers are 96.96, 103.58, 102.46, Maqu in 0-10, 10-20cm soil, the potential ecological hazard index is 65.70, 71.01, the potential ecological hazard index of Huangnan in three soil layer is 78.23, 73.42 and 72.84 respectively, which refers to the smallest value of Qinghai Lake sample, three, 51.07 and 51.72 in 51.48 soil layer respectively. Conclusion: The Nemero comprehensive pollution Index of Qinghai Lake sample is less than 0.7, at the level of cleanliness, the exponential value of Huangnan and Maqu two samples is between 0.7~1, at the level of cordon, and the exponential value of ma variety is between 1~2, at the level of mild pollution. The comprehensive potential ecological hazard index of 80~160 has the potential ecological risk of strength, and the exponential value of the other three samples is between 40~80, which has medium potential ecological risk. Generally, the pollution degree of heavy metals is small in the whole alpine grassland area.

The competition-dispersal trade-off exists in forbs but not in graminoids: A case study from multispecies alpine grassland communities.

Much theoretical evidence has demonstrated that a trade‐off between competitive and dispersal ability plays an important role in facilitating species coexistence. However, experimental evidence from natural communities is still rare. Here, we tested the competition–dispersal trade‐off hypothesis in an alpine grassland in the Tianshan Mountains, Xinjiang, China, by quantifying competitive and dispersal ability using a combination of 4 plant traits (seed mass, ramet mass, height, and dispersal mode). Our results show that the competition–dispersal trade‐off exists in the alpine grassland community and that this pattern was primarily demonstrated by forbs. The results suggest that most forb species are constrained to be either good competitors or good dispersers but not both, while there was no significant trade‐off between competitive and dispersal ability for most graminoids. This might occur because graminoids undergo clonal reproduction, which allows them to find more benign microenvironments, forage for nutrients across a large area and store resources in clonal structures, and they are thus not strictly limited by the particular resources at our study site. To the best of our knowledge, this is the first time the CD trade‐off has been tested for plants across the whole life cycle in a natural multispecies plant community, and more comprehensive studies are still needed to explore the underlying mechanisms and the linkage between the CD trade‐off and community composition.

Floral usage partitioning and competition between social (Apis mellifera, Bombus terrestris) and solitary bees in New Zealand: Niche partitioning via floral preferences?

AbstractWorldwide, studies of interactions between introduced and native bees have produced contradictory evidence regarding the potential for competition. Different resource requirements and the impact of tongue length on resource use are often overlooked aspects of these studies. Here, we examine floral resource use and niche overlap between introduced social bees and native solitary bees over two flowering seasons on The Remarkables mountain range, South Island, New Zealand. The native bee fauna of New Zealand is composed of short‐tongued solitary bees in the families Colletidae and Halictidae. Long‐tongued social bees were introduced 150 years ago, and Apis mellifera and Bombus species are now widespread. We analysed floral resource utilization by introduced bees (mainly Bombus terrestris) and native bees in relation to resource abundance across elevations in montane to alpine grassland communities. We modelled resource utilization and overlap between bee taxa using a novel index of floral resource availability, developed to more accurately describe floral density. Additionally, we sought to quantify the impact of honey bees by introducing hives, however, low densities in study plots prevented direct conclusions from being drawn. Native and introduced bees did, however, have distinctly different floral preferences over the flowering season with more niche overlap within, rather than between, native and introduced groups. Introduced bees showed a preference for introduced species in the family Fabaceae which native bees could not access. Native bees heavily utilized introduced Asteraceae as well as native floral resources that introduced bees did not prefer. The limited resource overlap between bee taxa indicated that bee communities in New Zealand may have reduced potential for competition, owing to the different resource requirements of solitary versus social bees and their differing abilities to access floral resources. These findings provide some potential explanations for contradictory evidence worldwide regarding the perceived detrimental impacts of introduced social bees.

Contrasting response of coexisting plant's water-use patterns to experimental precipitation manipulation in an alpine grassland community of Qinghai Lake watershed, China.

Understanding species-specific changes in water-use patterns under recent climate scenarios is necessary to predict accurately the responses of seasonally dry ecosystems to future climate. In this study, we conducted a precipitation manipulation experiment to investigate the changes in water-use patterns of two coexisting species (Achnatherum splendens and Allium tanguticum) to alterations in soil water content (SWC) resulting from increased and decreased rainfall treatments. The results showed that the leaf water potential (Ψ) of A. splendens and A. tanguticum responded to changes in shallow and middle SWC at both the control and treatment plots. However, A. splendens proportionally extracted water from the shallow soil layer (0–10cm) when it was available but shifted to absorbing deep soil water (30–60 cm) during drought. By contrast, the A. tanguticum did not differ significantly in uptake depth between treatment and control plots but entirely depended on water from shallow soil layers. The flexible water-use patterns of A.splendens may be a key factor facilitating its dominance and it better acclimates the recent climate change in the alpine grassland community around Qinghai Lake.

Community-specific hydraulic conductance potential of soil water decomposed for two Alpine grasslands by small-scale lysimetry

Abstract. For central Europe in addition to rising temperatures an increasing variability in precipitation is predicted. This will increase the probability of drought periods in the Alps, where water supply has been sufficient in most areas so far. For Alpine grasslands, community-specific imprints on drought responses are poorly analyzed so far due to the sufficient natural water supply. In a replicated mesocosm experiment we compared evapotranspiration (ET) and biomass productivity of two differently drought-adapted Alpine grassland communities during two artificial drought periods divided by extreme precipitation events using high-precision small lysimeters. The drought-adapted vegetation type showed a high potential to utilize even scarce water resources. This is combined with a low potential to translate atmospheric deficits into higher water conductance and a lower biomass production as those measured for the non-drought-adapted type. The non-drought-adapted type, in contrast, showed high water conductance potential and a strong increase in ET rates when environmental conditions became less constraining. With high rates even at dry conditions, this community appears not to be optimized to save water and might experience drought effects earlier and probably more strongly. As a result, the water use efficiency of the drought-adapted plant community is with 2.6 gDW kg−1 of water much higher than that of the non-drought-adapted plant community (0.16 gDW kg−1). In summary, the vegetation's reaction to two covarying gradients of potential evapotranspiration and soil water content revealed a clear difference in vegetation development and between water-saving and water-spending strategies regarding evapotranspiration.

拉萨河谷草地群落的数量分类与排序

PDF HTML阅读 XML下载 导出引用 引用提醒 拉萨河谷草地群落的数量分类与排序 DOI: 10.5846/stxb201708121455 作者: 作者单位: 中国人民大学环境学院,中国科学院地理科学与资源研究所,中国人民大学环境学院,中国人民大学环境学院,中国科学院地理科学与资源研究所,中国科学院地理科学与资源研究所,中国人民大学环境学院,山东建筑大学测绘地理信息学院 作者简介: 通讯作者: 中图分类号: 基金项目: 西藏自治区重点科技计划项目（Z2016C01G01/08-004，Z2016C01G01/03）；国家重点研发计划（2016YFC0502006） Quantitative classification and ordination of grassland communities in Lhasa River Valley Author: Affiliation: Renmin University of China,Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences,,,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:采用TWINSPAN数量分类和DCA、CCA排序的方法，对拉萨河谷草地23个样点进行统计分析。结果显示：（1） TWINSPAN数量分类将拉萨河谷草地群落划分成8种类型，拉萨河谷的草地群落分布呈现明显的垂直地带性分布格局。（2） TWINSPAN分类所划分的各群落在DCA排序图上都有各自的分布范围和界限，说明DCA排序能较好的反应各群落与其环境资源之间的关系，同时，TWINSPAN的分类结果也在排序图上得到较好的印证。（3）样点DCA排序的第一轴基本反映了海拔高度的变化梯度，第二轴基本反映了坡向的变化。（4）样点CCA排序表明，影响群落分布的主要环境因子是海拔，其次是坡向。CCA排序进一步阐明了拉萨河谷草地群落分布决定于海拔和坡向等环境因子，并间接验证了TWINSPAN的分类结果。（5）物种CCA排序和TWINSPAN分类结果表明：植物群落中物种的分布格局与植物群落类型的分布格局存在一定的相似性，物种的分布格局在很大程度上影响着群落的分布格局。 Abstract:Alpine grasslands on the Qinghai-Tibetan Plateau play an important role in safeguarding the economic sustainability of local animal husbandry. However, these alpine grasslands have been degraded due to increased human disturbance and changing climate in the past few decades. Quantitative classification and ordination are necessary to reveal how alpine grasslands respond to the changing environments. In this study, the Two-way indicator species analysis (TWINSPAN) was used to classify 23 plots of alpine grassland communities in the Lhasa River Valley. Canonical correspondence analysis (CCA) and detrended canonical correspondence analysis (DCA) were used to clarify the geographical distribution patterns of these alpine grassland communities. Our results indicate that:(1) Alpine meadows in the study area can be classified into 8 subtypes:Elymus nutans + Tripogon bromoides; Carex moorcroftii; Kobresia pygmaea + Carex moorcroftii; Potentilla fruticose + Kobresia pygmaea; Rhododendron primuliflorum + Kobresia pygmaea; Rhododendron primuliflorum + Rhododendron nivale + Kobresia pygmaea; Rhododendron nivale + Kobresia pygmaea; and Kobresia pygmaea. (2) Each subtype identified by TWINSPAN had a specific distribution and boundaries on the DCA ordination diagram, suggesting that DCA ordination can explain the relationship between community composition and environmental factors, (3) The first and second axes of DCA reflected the influences of plot elevation and aspect, respectively, (4) CCA ordination also confirmed that altitude, followed by aspect, was the primary environmental factor controlling the distribution of alpine grassland communities, (5) The CCA of species and TWINSPAN of community subtypes were similar, indicating that the distribution patterns of the grassland community were largely affected by the species distribution pattern. Quantitative analysis is suggested to examine and assess the relative contributions of anthropogenic and natural factors to changes in the Tibetan alpine grasslands in the future. 参考文献 相似文献 引证文献

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 m2. We also compared species richness (S) within and across forbs, legumes, sedges and grasses, with sampling subplot area (A) increasing from 0.0625 m2 to 1.0 m2 between alpine meadow and steppe communities. We applied a logarithmic function (S = b0 + b1 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 all functional 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.

Sub‐alpine and alpine grassland communities in the northeastern Greater Caucasus of Azerbaijan

AbstractQuestionsWhich are the main sub‐alpine and alpine grassland communities in the northeastern Greater Caucasus of Azerbaijan and what are their environmental and anthropogenic drivers?LocationGrasslands at 1800 and 3500 m a.s.l. on northern macroslope of the Greater Caucasus in Azerbaijan near Shahdag Mt.MethodsWe established a randomized sampling design with stratification by geomorphology and altitude and validation using remote sensing data. The vegetation survey on 194 relevés in a nested plot design of up to 100 m² encompassed examiniation of various site conditions. We applied cluster and indicator species analysis for vegetation classification, and indirect multivariate ordination to assess vegetation–environment relationships.ResultsWe classified 13 unranked communities in two sub‐alpine groups and one alpine group, plus the very distinct vegetation around camp sites of semi‐nomadic herders. Important drivers for vegetation differentiation are altitude as proxy for temperature, latitude as proxy for orographically founded differences in bedrock and precipitation, aspect, soil factors, such as content of organic matter and variables connected to land‐use types and intensity (e.g. pasturing vs hay meadows, browsing tracks). In consequence, also effects on species richness are detectable. Furthermore, we found only partial concordance of our communities with existing vegetation classifications in the Greater Caucasus.ConclusionsA state‐of‐the‐art classification and ordination of regional high‐mountain grassland communities and their environmental drivers fills a gap in knowledge about this vegetation. It is widely unknown to international audience and remained almost unstudied during the last 25 yr, when severe shifts in land use remarkably changed the natural conditions. The study can help to identify problems in current grassland management and their consequences for biodiversity conservation. Desirable changes towards sustainable grassland utilization require combined socio‐ecological assessments beforehand.

Germination strategies of 20 alpine species with varying seed mass and light availability

Seed germination is a central component of plant life history. To investigate the proposed role of seed size on germination strategy in plant communities, a semifield experiment was conducted in alpine meadow of the Qinghai–Tibetan Plateau, China. Interspecies relationships of seed mass and seed germination characteristics were studied under semifield conditions with different light availability. Light availability and seed mass had significant effects on final germination percentage and time to germination for studied species. There was a significant negative correlation between the strength of light required for germination and seed mass. Fifteen study species (e.g. Ligularia przewalskii, Artemisia sieversiana Willd, Tripolium vulgare Ness. and Saussurea morifolia Chen) exhibited a synchronous germination strategy. Seeds from large-seeded species, such as Dracocephalum ruyschiana, Laniophlomis rotate (Benth.) and Salvia przewalskii Maxim., were less likely to require light for germination than those of small-seeded species, such as A. sieversiana Willd, Senecio diversipinnus Ling and Saussurea mongolica (Franch.). We propose that germination strategies of small-seeded species are well suited to unpredictable environmental variation in this alpine grassland community.

Simulations of phenology in alpine grassland communities in Damxung, Xizang, based on digital camera images

Simulations of phenology in alpine grassland communities in Damxung, Xizang, based on digital camera images

高寒草原植物群落种间关系的数量分析

Highland ecosystems are believed to be of vital importance in ecological study,partly due to the rapid climate change worldwide and the highest sensitive feature of this special system,not only its productivity and biodiversity but also its inter-specific relationship,to environmental alterations.The Bayabulak Steppe distributes in the middle part of Tianshan Mountains,and is situated at 42°18′—43°34′ N,82°27′—86°17′ E with altitude between 2460—2760 m.Climate here belongs to typical alpine cold climate with yearly mean temperature of-4.8 ℃,yearly mean precipitation here is 276.2 mm,yearly evaporation is(1 135.2±112.3) mm,the snow period in Bayabulak is about 150—180d,and there is no frost-free time in this region.Stipa purpurea and Festuca ovina grassland are the dominant vegetation types in our study site. In order to clarify the species composition and inter-specific association of the alpine grassland community of Bayanbulak in Xinjiang,China,variance ratio(VR) of the overall association,association coefficient(AC),Ochiai index(OI) and Spearman rank correlation coefficient,based on the 2 × 2 contingency table,were used in our quantitative analysis.Field data were collected in July 2009.Three parallel transect were firstly set up and the distance between each of them was 50 m,then 20 plots(0.50 m × 0.50 m for each unit) were randomly set within each transect,in so doing total of 60 plots were involved in the present work.Our results showed that: 1) There are 36 species with 14 common species of plants in Bayinbulak alpine steppe,and they belong to 26 Genus of 16 Family.W = 61.52,a statistic index to test whether the VR is significant or not,indicated that the overall correlation of all plant species was positive but not significant.2) Inter-specific associations of keystone species with others were neutral or not significant.Keystone species showed greater independence and occupied prior ecological niche in the community,and their distributions were not susceptible to other species.Values of OI were basically identical to those of association coefficient;Based on the measuring of OI,19.79% of total 91species-pairs composed by 14 common species was significant or very significant,and 72.21% of them showed positive correlation while 27.79% showed negative correlation for those significantly related species-pairs;3) Inter-specific associations of accompanying species or weeds with others were significant(negative or positive),suggesting higher dependency of accompanying species or weeds on other species,namely they were susceptible to other species and only occupied inferior ecological niche in the community.Furthermore,populations of these plant species are instability in the process of ecosystem development;4) This study provides new dimensions for the theory of species association.According to their adaptability to the environment and the relationships between plants and environment,the 14 common species were divided into three ecological species groups.Positive correlations occurred among the species in the same ecological species groups,while the negative correlations were found in the different ecological species groups.It mainly due to their different biological features induced by different adaptability to habitats or separated niches;5) Several suggestions were proposed to promote the ecological restoration of degraded steppe systems in the study region.