Limited effect of hare grazing and short-term climatic variations on the most common alpine vegetation community in the Snowy Mountains,Australia

Background: In the alpine zone of the Snowy Mountains, grazing by mammals is limited. However, introduced European hare numbers have increased since the 1970s.

Aims: To estimate the density of hares and hence grazing pressure among years. To assess the response of biomass, vegetation height and composition to a cessation of hare grazing.

Methods: We used indices of hare abundance based on spotlighting and counts of hare pellets on a transect. The effect of hare grazing on tall alpine herbfield was assessed by using 15 paired exclosure and control quadrats for six years.

Results: The indices of hare abundance suggested densities similar to those in upland areas of Britain. Grazing did not affect the composition, cover of herbs or graminoids or, for 2010, vegetation height or biomass. Variation in vegetation and hare numbers among years was not correlated with climatic variables. Observations of selective grazing suggested that impacts on vegetation may be localised and restricted to certain species. Prior analyses of hare pellets indicated that hares might spread seed of native and exotic species.

Conclusions: Hares are having no general effect on tall alpine herbfield but may affect certain plant species via selective grazing or by spread of viable seed.     

Linking grazing response of species abundance to functional traits in the Tibetan alpine meadow

Whether grazing response of species abundance can be predicted by plant functional trait remains a challenge untested in a specific ecosystem. We measured species abundance and relevant functional traits for 30 common component species in a moderately grazed and a control community over 3 years (2005, 2006 and 2007) in a Kobresia capillifolia dominated alpine meadow on the Tibetan Plateau. Our objective was to examine species response to grazing and to test the relationship between the response of species abundance and functional traits in grazed and control habitats. Our results showed: i) in terms of species relative abundance and saturated height (the maximum height of an adult individual), most component species significantly decrease in response to moderate grazing and the effect differed among species and between functional groups. ii) The response of species abundance was significantly negatively correlated with saturated height, but not correlated with specific leaf area or seed size. We concluded that the response direction of species abundance to grazing can be predicted by functional traits, whereas it is a weak predictor of the extent of grazing response in species abundance.     

Grazing alters species relative abundance by affecting plant functional traits in a Tibetan subalpine meadow

Domestic livestock grazing has caused dramatic changes in plant community composition across the globe. However, the response of plant species abundance in communities subject to grazing has not often been investigated through a functional lens, especially for belowground traits. Grazing directly impacts aboveground plant tissues, but the relationships between above‐ and belowground traits, and their influence on species abundance are also not well known. We collected plant trait and species relative abundance data in the grazed and nongrazed meadow plant communities in a species‐rich subalpine ecosystem of the Qinghai–Tibet Plateau. We measured three aboveground traits (leaf photosynthesis rate, specific leaf area, and maximum height) and five belowground traits (root average diameter, root biomass, specific root length, root tissue density, and specific root area). We tested for shifts in the relationship between species relative abundance and among all measured traits under grazing compared with the nongrazed meadow. We also compared the power of above‐ and belowground traits to predict species relative abundance. We observed a significant shift from a resource conservation strategy to a resource acquisition strategy. Moreover, this resource conservation versus resource acquisition trade‐off can also determine species relative abundance in the grazed and nongrazed plant communities. Specifically, abundant species in the nongrazed meadow had aboveground and belowground traits that are associated with high resource conservation, whereas aboveground and belowground traits that are correlated with high resource acquisition determined species relative abundance in the grazed meadow. However, belowground traits were found to explain more variances in species relative abundance than aboveground traits in the nongrazed meadow, while aboveground and belowground traits had comparable predictive power in the grazed meadow. We show that species relative abundance in both the grazed and the nongrazed meadows can be predicted by both aboveground traits and belowground traits associated with a resource acquisition versus conservation trade‐off. More importantly, we show that belowground traits have higher predictive power of species relative abundance than aboveground traits in the nongrazed meadow, whereas in the grazed meadows, above‐ and belowground traits had comparable high predictive power.     

Linking sheep density and grazing frequency to persistence of herb species in an alpine environment

Large herbivores are important drivers in ecosystems worldwide. Changes in herbivore densities are predicted to especially affect herbs that are strongly preferred by herbivores. The persistence of herbs could be challenged by enhanced grazing, but also grazing cessation may affect persistence, especially for prostrate herbs, which might be out-competed. To test how different herbivore densities (high, low, and no sheep) affect grazing frequency and plant responses (plant height, flowering frequency, and plant density) at the herb community and species level, we conducted a fully replicated, landscape-scale experiment in an alpine environment. We found that none of the herb species changed their densities after 5 years with experimental changes in grazing pressure. Sheep density affected grazing and flowering frequency at the herb community level. Eight herb species were more grazed at high sheep density as compared to enclosures with no sheep. Herb height decreased at high sheep density as compared to no sheep for the two species with the highest grazing frequency. Increased height and flowering frequency were found for small herbs at high sheep density. Our experiment clearly shows that herbs do not constitute a homogeneous functional group and that, in particular, tall and small herbs are affected in contrasting ways but all species (n = 15) tolerated changes in grazing regimes as densities were maintained at both enhanced grazing and grazing cessation.     

Response of Polygonum viviparum species and community level to long-term livestock grazing in alpine shrub meadow in Qinghai-Tibet Plateau

Grazing by domestic herbivores is generally recognized as a major ecological factor and an important evolutionary force in grasslands. Grazing has both extensive and profound effects on individual plants and communities. We investigated the response patterns of Polygonum viviparum species and the species diversity of an alpine shrub meadow in response to long-term livestock grazing by a field manipulative experiment controlling livestock numbers on the Qinghai-Tibet Plateau in China. Here, we hypothesize that within a range of grazing pressure, grazing can alter relative allocation to different plant parts without changing total biomass for some plant species if there is life history trade-offs between plant traits. The same type of communities exposed to different grazing pressures may only alter relative species' abundances or species composition and not vary species diversity because plant species differ in resistant capability to herbivory. The results show that plant height and biomass of different organs differed among grazing treatments but total biomass remained constant. Biomass allocation and absolute investments to both reproduction and growth decreased and to belowground storage increased with increased grazing pressure, indicating the increasing in storage function was attained at a cost of reducing reproduction of bulbils and represented an optimal allocation and an adaptive response of the species to long-term aboveground damage. Moreover, our results showed multiform response types for either species groups or single species along the gradient of grazing Intensity. Heavy grazing caused a 13.2％ increase in species richness. There was difference in species composition of about 18％--20％ among grazing treatment. Shannon-Wiener (H') diversity index and species evenness (E) index did not differ among grazing treatments. These results support our hypothesis.     

Large scale experimental effects of three levels of sheep densities on an alpine ecosystem

Plant–herbivore dynamics is a major topic in ecological research, but empirical knowledge on the ecological effects of different densities of large grazers from fully replicated experiments is rare. Previous studies have focused on grazing vs no grazing, and our understanding of the extent to which different levels of grazing alter vegetation composition, and how quickly such effects can be measured, is therefore limited. We performed a fully replicated, short‐term (four‐year) experiment using large enclosures (each ～0.3 km²) with three different sheep densities (no grazing, low grazing and high grazing, respectively) in an alpine environment with summer grazing in southern Norway to address these issues. Sheep grazing mainly affected plant species at high densities of sheep as compared to no sheep after a four‐year treatment; few effects of low sheep densities were detectable. Highly selected herbs, herbs suggested vulnerable to trampling, and woody species decreased, while most graminoids, one ruderal, one prostrate species and two bryophyte taxa increased at high sheep densities. We found contrasting responses within main functional groups highlighting that fine details of plant life histories need to be known for responses to grazing to be successfully predicted. Vascular plant cover and bare soil responded to sheep density after two years of treatment, but only for one of the species was frequency change observed at this stage. Overall, plants in low grazing plots were found to be almost unaffected. Changes in abundance were mainly found at the no grazing and high grazing treatments. Plant species that decreased at high grazing generally increased at no grazing and vice versa, suggesting a response to both cessation of grazing and enhanced grazing respectively. Our study demonstrates, beyond a simple comparison of heavily grazed and non‐grazed sites, that herbivore effects on plants are typically non‐linearly related to herbivore density, and that the speed of plant responses will depend both on the plant property examined and the grazing pressure.     

围封与放牧管理对高寒草甸植物功能性状和功能多样性的影响

植物功能性状能够响应生存环境的变化并直接决定着生态系统功能。为了揭示围封与放牧管理对物种共存和驱动群落构建的影响机理,该研究以青藏高原东缘高寒草甸为对象,分析了围封与放牧处理对植物功能性状和功能多样性的影响。结果显示:(1)在群落水平,放牧显著降低了比叶面积和植物高度;在物种水平,放牧群落中多数杂类草比叶面积减小,而莎草类和禾草类的比叶面积在处理间无显著差异。(2)叶干物质含量与比叶面积在围封和放牧处理中均呈显著负相关关系,在放牧处理中,叶干物质含量与植物高度呈显著的二次函数关系,即随着叶干物质含量的增大,植物高度先减小后增大;在同等比叶面积的情况下,与围封相比,放牧降低了叶干物质含量;在相同叶干物质含量的情况下,与围封相比,放牧降低了植物高度。(3)放牧在总体上降低了种间性状的平均差异,植物性状表现出趋同响应,具体表现为放牧减小了叶干物质含量和植物高度的种间差异;与围封相比,放牧显著提高了功能均匀度,减小了功能分离度。研究表明,不同植物种对放牧的响应模式存在差异,放牧降低了种间对光资源的竞争,可能增加了对土壤养分的竞争,放牧驱动群落构建的过程中,土壤养分是非常重要的作用因子,说明放牧影响物种共存依赖于对多种资源的竞争。     

Decline in Medicinal and Forage Species with Warming is Mediated by Plant Traits on the Tibetan Plateau

Experimental studies of how global changes and human activities affect plant diversity often focus on broad measures of diversity and discuss the implications of these changes for ecosystem function. We examined how experimental warming and grazing affected species within plant groups of direct importance to Tibetan pastoralists: medicinal plants used by humans and palatable plants consumed by livestock. Warming resulted in species losses from both the medicinal and palatable plant groups; however, differential relative vulnerability to warming occurred. With respect to the percent of warming-induced species losses, the overall plant community lost 27%, medicinal plants lost 21%, and non-medicinal plants lost 40% of species. Losses of palatable and non-palatable species were similar to losses in the overall plant community. The deep-rootedness of medicinal plants resulted in lowered sensitivity to warming, whereas the shallow-rootedness of non-medicinal plants resulted in greater sensitivity to warming; the variable rooting depth of palatable and non-palatable plants resulted in an intermediate response to warming. Predicting the vulnerability of plant groups to human activities can be enhanced by knowledge of plant traits, their response to specific drivers, and their distribution within plant groups. Knowledge of the mechanisms through which a driver operates, and the evolutionary interaction of plants with that driver, will aid predictions. Future steps to protect ecosystem services furnished by medicinal and palatable plants will be required under the novel stress of a warmer climate. Grazing may be an important tool in maintaining some of these services under future warming. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Plant traits link hypothesis about resource-use and response to herbivory

Grazing by large herbivores, in interplay with environmental productivity, is a key driver of the composition of the vegetation with important consequences on the ecosystem and, consequently, for land management. We tested the predictions of the resource availability – resource–acquisition theory by assessing the extent to which community averages of plant traits, known to be related to plant growth, competitive ability and response to grazing were correlated with resource gradients within local (200 km²) geographical ranges. Second, we assessed the applicability of the same set of plant traits to make inferences on ecological effects of grazing by sheep in alpine ecosystems in Norway, using a data set consisting of 16 sites in central Norway. We estimated grazing intensity by free-ranging sheep based on GPS telemetry, soil properties, plant species composition and species traits i.e. specific leaf area (SLA), leaf dry matter content (LDMC), leaf size and plant height. Soil fertility and the interaction between soil fertility and grazing, but not grazing intensity alone, were significantly related to plant species and traits composition. Generally, average SLA showed lower correspondence with soil fertility and grazing than the other traits. Leaf size and plant height were lowest at sites with high grazing intensity and in sites with low fertility, and increased with soil fertility in little and moderately grazed sites, but declined at high fertility sites when grazing was intense. LDMC showed the opposite trend. Grazing intensity was more related to the variability in plant composition and average plant traits when environmental productivity was high. Our results therefore are indicative of a convergence of responses to grazing and nutrient limitation.     

Effects of grazing disturbance on plant diversity,community structure and direction of succession in an alpine meadow on Tibet Plateau,China

To elucidate the effects of grazing intensity and grazing time on plant diversity and community structure, as well as the successional differentiation in an alpine meadow, a controlled grazing trial, with six grazing intensities on an alpine meadow was conducted in the eastern Qilian Mountain region for four years. Using species accumulation curves, RDA ordination and variance decomposition, we analyzed the changes in proportion of dominant species, richness, abundance, as well as the life forms of plant communities under grazing disturbance. Both the grazing intensity and grazing time had a significant effect on these dominant species, richness, abundance, as well as the life forms in the plant community (P < 0.01). More detailed results showed that: (1) The richness and abundance of plant species were highest in the light grazing plot, and these increased as time passed. In the heavy grazing plot, the abundance of plant species decreased as time passed, but the richness of these species did not change significantly. (2) The abundance of Gramineae and Umbelliferae were negatively and significantly correlated with the duration of grazing treatments, whereas Plantaginaceae and Geraniaceae were positively and significantly correlated with the grazing intensity. Over time, the abundance of bunch-type plants decreased and other life forms of plants have increased. With the increase in grazing intensity, the plants' abundance with the rosette type did not change, but other life forms of plants decreased. The results of variance decomposition indicated that grazing disturbance has had greater effects on life forms and plant populations, followed by the changes in the dominant species and their abundance, with lesser effects on the richness of the species. Grazing intensity had a greater effect than the duration of the grazing treatment had. The results of PCA showed that the climax community in both the lowest and the highest grazing intensity plots had changed over time. In the sample plots with light grazing intensity, the plant community changed to an Elymus nutans + Poa crymophila community, but later changed to a Melilotoides ruthenicus + Kobresia humilis community under heavy grazing.     

Effects of grazing disturbance on plant diversity,community structure and direction of succession in an alpine meadow on Tibet Plateau,China

To elucidate the effects of grazing intensity and grazing time on plant diversity and community structure, as well as the successional differentiation in an alpine meadow, a controlled grazing trial, with six grazing intensities on an alpine meadow was conducted in the eastern Qilian Mountain region for four years. Using species accumulation curves, RDA ordination and variance decomposition, we analyzed the changes in proportion of dominant species, richness, abundance, as well as the life forms of plant communities under grazing disturbance. Both the grazing intensity and grazing time had a significant effect on these dominant species, richness, abundance, as well as the life forms in the plant community (P < 0.01). More detailed results showed that: (1) The richness and abundance of plant species were highest in the light grazing plot, and these increased as time passed. In the heavy grazing plot, the abundance of plant species decreased as time passed, but the richness of these species did not change significantly. (2) The abundance of Gramineae and Umbelliferae were negatively and significantly correlated with the duration of grazing treatments, whereas Plantaginaceae and Geraniaceae were positively and significantly correlated with the grazing intensity. Over time, the abundance of bunch-type plants decreased and other life forms of plants have increased. With the increase in grazing intensity, the plants' abundance with the rosette type did not change, but other life forms of plants decreased. The results of variance decomposition indicated that grazing disturbance has had greater effects on life forms and plant populations, followed by the changes in the dominant species and their abundance, with lesser effects on the richness of the species. Grazing intensity had a greater effect than the duration of the grazing treatment had. The results of PCA showed that the climax community in both the lowest and the highest grazing intensity plots had changed over time. In the sample plots with light grazing intensity, the plant community changed to an Elymus nutans + Poa crymophila community, but later changed to a Melilotoides ruthenicus + Kobresia humilis community under heavy grazing.     

放牧干扰下高寒草甸物种多样性指数评价与选择

在青藏高原东北缘高寒草甸设置6个放牧强度样地,连续4年研究10个多样性指数(Richness和Abundance 2个实测指数,优势度指数、均匀度指数、丰富度指数和综合指数各2个)对放牧强度和年限影响植物群落的解释能力.结果表明: 相对于重要值,利用多度计算的多样性指数对放牧干扰更敏感.优势度指数(Berger-Parker、Dominance)与放牧强度和年限均无关,不能将放牧干扰对群落优势种的影响有效区分.均匀度指数(Equitability、Evenness)均与放牧强度无关,但Evenness指数与放牧年限呈显著负相关,不受偶见种影响且与物种多度的变异系数呈显著正相关,在基于时间尺度的均匀度比较中可以选择Evenness指数.丰富度指数(Menhinick、Margalef)均与放牧年限无关,但Margalef指数与放牧强度呈显著正相关,且不受偶见种影响.综合指数(Shannon、Simpson)均与放牧强度无关,但Shannon指数与物种丰富度和多度呈显著正相关,且随放牧年限增加而显著升高,不受偶见种影响,Shannon指数可用于在长时间尺度下比较物种多样性变化.在所有多样性指数中,只有实测物种丰富度和多度均与放牧强度呈显著负相关,与放牧年限呈显著正相关,且不受偶见种影响,故实测物种丰富度和多度相结合可作为放牧干扰下多样性比较的首选指标.此外,多样性指数选择须考虑放牧干扰的强度与时间特征、多样性组分和研究目的.     

Regrowth capacity in relation to defence strategy in Stipa clarazii and Stipa trichotoma,native to semiarid Argentina

Abstract Plants can defend themselves against herbivores by either avoiding or tolerating herbivory. Since avoidance mechanisms divert resources to other than growth processes, it could be expected a lower regrowth capacity in species that avoid herbivory than in species that tolerate herbivory, particularly under competition for resources. We tested this hypothesis by quantifying the regrowth of a grazing‐avoidant (Stipa trichotoma Nees, synonymous Nasella trichotoma (Nees) Hackel ex Arechav.) and a grazing‐tolerant (Stipa clarazii Ball, synonymous Nasella clarazii (Ball) Barkworth) grass species native to semiarid Argentina, when growing either singly or in pairs (one individual of each species) under repeated defoliation in field conditions. Twenty pairs of plants were selected in an area codominated by both species. Plants were protected by a 60 cm‐diameter exclosure, in which the rest of the vegetation had been removed. The same procedure was followed with 20 single plants of each species. The same plants were clipped four times in 1996 and 1998 and five times in 1997. The response variable was the cumulative regrowth per plant at the end of each year. The regrowth was analysed for neutral detergent fibre and nitrogen content. Cumulative regrowth of S. clarazii was higher, similar, or lower than the cumulative regrowth of S. trichotoma in 1996, 1997, and 1998, respectively. Regrowth was reduced by interspecific competition, although there was no interaction between species and growing conditions (single or in pairs). Neutral detergent fibre content was consistently higher, whereas nitrogen content was consistently lower, in S. trichotoma than in S. clarazii. Collectively, our results did not support the hypothesis of higher regrowth capacity in the grazing‐tolerant species than in the grazing‐avoidant species. Further, our findings suggest herbivore tolerance is a previously unappreciated trait of S. trichotoma.     

物种多样性和功能性状驱动高寒草原地上生物量对长期禁牧的响应

围封对草地生物多样性和初级生产力的影响是草地生态学研究的热点问题之一。基于2013—2021年在青藏高原东北部紫花针茅(Stipa purpurea)高寒草原围栏内外植物群落长期调查数据,从物种多样性、功能性状的角度解析了高寒草原地上生物量对长期围封的生态响应过程。结果表明：(1)围封处理对高寒草原物种多样性的负效应具有强烈的时间依赖性。围封处理显著提高地上生物量,但也显著降低了生物量稳定性和异步性,意味着高寒草原稳定的、可持续的生态系统服务功能被长期围封处理削弱。(2)植物功能性状对长期围封处理表现出差异性响应模式;与叶绿素性状相比,叶形态性状对长期围封处理表现出更强的敏感性。(3)物种多样性和功能性状与地上生物量之间均存在显著相关关系,并且物种多样性的影响被功能性状调控进而对地上生物量发挥间接效应,群落加权性状和功能分异度共同对草地生物量发挥直接的主导效应。研究结果证明了植物功能性状通过介导物种多样性与其共同驱动高寒草原地上生物量对长期围封的响应。因此,在未来草地管理过程中,同步研究植物物种和功能属性对于全面揭示生态系统的响应机制至关重要。     

放牧扰动下高寒草甸植物多样性、生产力对土壤养分条件变化的响应

为了揭示高寒小嵩草草甸群落在放牧扰动下,探讨土壤养分供给水平的变化对生态系统初级生产力和多样性影响,为高寒草地的退化演替机理研究提供依据,以野外样地调查和室内分析法研究了放牧扰动下高寒草甸植物多样性、生产力对土壤养分条件变化的响应.结果表明,放牧干扰不仅改变了高寒小蒿草草甸群落土壤根系和蕴育土壤根系的"载体"量及根土比例,改变了植物群落的结构和功能,而且使土壤的物理和化学特性发生了明显的改变.随着放牧强度的增加,蕴育土壤根系的基质量逐渐减少,根土比特别是0～10 cm土层的根土比例增加;"载体"量减少导致大部分地下根系由于营养供给水平的降低而死亡,归还土壤中有机质的数量逐渐减少,加之地上部分持续利用,土壤养分也在不断消耗,土壤基质量的减少和土壤资源持续供给能力的下降,草地发生逆向演替(退化),表现在:物种数减少、多样性下降、能量的分配转向地下等;土壤性状上的某些改变(土壤容重、土壤湿度等),也会引起植被组成、物种多样性变化;放牧主要通过影响土壤环境及其养分含量来改变草地群落生物量(地上、地下);土壤表面的适度干扰和原有植物的适度破坏为新成员提供了小生境,从而允许新的植物侵入群落,并提高了植物的丰富度.但是,在受到强度干扰时,草地植物群落的主要物种的优势地位发生明显的替代变化.     

放牧和模拟增温对藏北高寒草地植物群落特征及生产力的影响

气候变化和放牧活动对草地植物物种多样性和生产力具有重要影响。为探索藏北高寒草地植物物种多样性和生产力对增温、放牧及其交互作用的响应, 于2011年在藏北高原开始建立增温实验平台, 2016年起增设放牧、增温+放牧实验, 连续2年(2016-2017年)观测了植物群落特征、群落组成、生产力和物种多样性。结果表明, 增温和放牧对高寒草地植物高度和净初级生产力具有显著交互作用。在放牧条件下, 增温对植物高度无显著影响; 但在不放牧条件下, 增温却显著增加了植物高度。在放牧条件下, 增温对净初级生产力的影响存在年际差异, 2016年增温对生产力无显著影响, 2017年增温显著降低了植物净初级生产力; 但在不放牧条件下, 增温对植物净初级生产力无显著影响。增温和放牧对高寒草地植物物种丰富度、盖度、重要值及多样性均无显著交互作用。植物盖度在增温和放牧条件下显著降低, 杂类草物种比例显著增加, 但物种多样性均无显著变化。研究表明, 增温和放牧显著改变高寒草地群落结构。未来气候变化条件下, 放牧活动加剧有可能导致高寒草地生产力降低。     

Response of soil bacterial communities to moisture and grazing in the Tibetan alpine steppes on a small spatial scale

As the Third Pole of the world, the Tibetan Plateau provides a typical alpine grassland environment for soil bacteria with its unique frigid and arid climate. Owing to clear changes in spatial moisture and increased grazing intensity, moisture and livestock grazing have become key factors influencing the microbial communities. Accordingly, we investigated the diversity and composition of soil bacteria in a selected alpine grassland within the dual gradients of moisture and grazing using high-throughput sequencing. Our results showed that grazing changed the soil bacterial diversity and composition, whereas moisture only influenced the relative abundance of the segmental community at the small spatial scale. Species richness was found to be increased by moderate grazing compared with that by high or low-grazing intensity. The relative abundance of dominant species and β-diversity of soil bacteria both showed differences with heavy, moderate, and low grazing. Some dominant bacteria were altered with the moisture content. However, there were no significant differences according to the moisture gradient in terms of the overall bacterial β diversity and composition. These results might be taken account into the small spatial scale as well as the compensation of grazing to moisture on this scale. This work provides new insights into the soil bacterial response to moisture gradients and grazing intensity in alpine steppe habitat.     

Grazing buffers the effect of climate change on the species diversity of seedlings in an alpine meadow on the Tibetan Plateau

Climate change predominated by warming over the past decades has affected plant biodiversity, distribution, and ecosystem functioning in alpine grasslands. Yet, little is known about the interactive effect of climate change and grazing on biodiversity and ecosystem functioning. Here, we conducted a vegetation translocation experiment (ten soil‐vegetation blocks were translocated from high‐altitudinal site 3,245 m to low‐altitudinal site 3,045 m) combined with grazing treatment in an alpine meadow on the Tibetan Plateau. The results showed that (a) translocation induced effect of climate change from harsh, high‐altitudinal site to benign, low‐altitudinal site significantly promoted species richness, and density of asexual and sexual seedling, with an increase in the proportion of asexual recruitment to sexual recruitment; (b) grazing decreased the proportion of asexual seedling to sexual recruitment within community, led to a shift in the dominant plant functional groups from graminoids and legumes to forbs; and (c) grazing partly offset the increased species richness of seedling, but not seedling density, induced by climate change. These findings suggest that moderate grazing may buffer the effect of climate change on the plant community composition, and thus, functional role in alpine meadows. Further understanding the influence of climate change on grassland ecosystems needs to consider the non‐additive effect of grazing and climate change to sustainability of grassland services.     

Does grazing induce intraspecific trait variation in plants from a sub‐humid mountain ecosystem?

Livestock grazing represents an important human disturbance for vegetation worldwide. We analysed the intraspecific differences in mean trait values between different grazing regimes (ungrazed and grazed) and explored whether these differences are consistent across species in a sub‐humid mountain ecosystem in Central Argentina. We selected 14 species of eight different families, co‐occurring in both regimes and comprising herbaceous (grasses and forbs) and woody (shrubs and trees) plants. For each species and grazing regime we measured 12 traits related to plant size, carbon fixation and water use. We found that plants in the grazed regime had consistently smaller leaves and shorter stature and internodal length than plants of the same species under the ungrazed regime. For the remaining traits the responses were species‐specific. Dry matter content, leaf tensile strength and minimum leaf water potential (Ψ_leaf) showed contrasting responses to grazing. Specific leaf area, wood density and potential water content of wood showed almost no significant responses except for very few species. Neither leaf area per shoot mass nor leaf area per sapwood area differed significantly between grazing regimes. Our study suggested that the intraspecific variation found for the size‐related traits would allow species to respond to grazing without modifying markedly other structural traits, a plastic response that might increase the probability of species success.     

Effects of grazing and fertilization on the relationship between species abundance and functional traits in an alpine meadow community on the Tibetan Plateau

Trait‐based approaches can provide a useful tool for linking plant attributes to community structure and ecosystem function. Seed mass and plant height play important roles in the dynamics of plant communities, but few empirical community level studies have tested this, especially in stressful environments. The aim of the present study was to determine if there is a relationship between functional traits (seed mass and plant height) and changes in species relative abundance (SRA) in response to grazing and fertilization. We measured SRA and plant functional traits for 40 common species in a Tibetan Plateau alpine meadow. In the fertilized meadow, seed mass and plant height was significantly positively correlated with the relative abundance of the species. In the grazed meadow, these variables were significantly negatively correlated. Our results demonstrates that plant functional traits can be used to predict the change of SRA in plant community. Grazing promotes the dominance of small‐seeded and short‐stature species, and fertilization facilitates the occurrence of large‐seeded and tall‐stature species.