Species In Alpine Meadow Research Articles

Ecology of Trifolium elazizense, an endemic alpine meadow species from Türkiye

This study presents some ecological characteristics of Trifolium elazizense, a local endemic alpine meadow plant species in the East Anatolian region of Türkiye. Elemental analyses were carried out in plants and soils. Soil-plant relationships were evaluated. The results obtained from all plant parts of Trifolium elazizense (root, stem and leaves) showed that the elemental concentrations of boron, calcium, copper, potassium, manganese, lead and zinc were within the limit values; cadmium, iron and magnesium were above the limit values. The general concentration of all elements in the soil samples is generally within acceptable limits.

Species richness and dominant functional groups enhance aboveground biomass, with no effect on belowground biomass in Qinghai-Tibet Plateau's grasslands

Understanding the role of plant diversity in maintaining grassland ecosystem functioning is of great importance in ecological research. Despite decades of research, ecologists have struggled to understand the biodiversity-ecosystem functioning relationships and how the dominance of plant functional groups impacts ecosystem function. In attempting to understand (i) the temporal patterns of above- and below-ground biomass (AGB and BGB) and species richness, (ii) whether species richness is consistently associated with AGB and BGB, and (iii) the relative contributions of plant functional groups (forb, grass, legume, and sedge) in stabilizing ecosystem function, we used biomass productivity data of meadow steppe and alpine meadow in the Qinghai-Tibet Plateau (QTP) for the period 2015–2019. Our results show that AGB for both grasslands increased, but BGB stayed steady over 5 years. The rising tendency of AGB was caused by the upward trend of AGB in forbs and grasses, which are the dominant functional groups in QTP, stressing the importance of dominant functional groups to ecosystem functioning. The biodiversity-ecosystem functioning relationships were significantly positive for AGB, stable for BGB, and negative for the BGB:AGB ratio, which highlights the crucial role of higher species richness in ecosystem functioning. Significant differences in mean species richness among sites (9–19 species in meadow steppe and 8–22 species in alpine meadow) highlight the varying levels of species diversity across sites in the QTP. While 42% of the sites showed stable species richness, the reported increasing trends in species richness at 58% of the sites indicate the potential for ecological changes or processes in these areas. AGB in both grasslands increased, while BGB remained stable with increasing precipitation. The top soil layer (0–10 cm) dominated the observed BGB in both grasslands, as abundant nutrients in the top layer provide favorable conditions for root proliferation. In meadow steppe, AGB formed an isometric relationship with BGB, indicating that AGB increased with BGB. This study concludes that species richness influenced ecosystem functioning, and forbs and grasses dominated biomass productivity, of which the topsoil layer contributed three-quarters of BGB. Our study (i) provides empirical evidence of stable to increasing species richness in both grasslands over 5 years, and (ii) highlights the role of greater species richness in enhancing ecosystem functioning. These findings serve as a scientific reference for policymaking regarding ecosystem stability.

Effects of warming conditions on plant nitrogen–phosphorus stoichiometry and resorption of three plant species in alpine meadows on the Tibetan Plateau

Abstract Global climate change is expected to have a significant impact on ecosystems worldwide, especially for alpine meadows which are considered as one of the most vulnerable components. However, the effects of global warming on the plant nitrogen–phosphorus stoichiometry and resorption in alpine meadows remain unclear. Therefore, to investigate the plant nitrogen–phosphorus stoichiometry and resorption in alpine meadows on the Qinghai-Tibet Plateau, we conducted an artificial warming study using open-top chambers (OTCs) over the 3 years of warming period. We selected three dominant species, four height types of OTCs (0.4, 0.6, 0.8 and 1 m) and four warming methods (year-round warming, winter warming, summer–autumn–winter warming and spring–summer–autumn warming in the experiment) in this experiment. In our study, soil temperature significantly increased with increasing the height of OCTs under the different warming methods. Kobresia pygmaea presented an increase in nitrogen (N) limitation and Kobresia humilis presented an increase in phosphorus (P) limitation with increasing temperature, while Potentilla saundersiana was insensitive to temperature changes in terms of nitrogen and phosphorus limitations. Both nitrogen resorption efficiency:phosphorus resorption efficiency and N:P trends in response to rising temperatures were in the same direction. The differential responses of the chemical stoichiometry of the three species to warming were observed, reflecting that the responses of nitrogen and phosphorus limitations to warming are multifaceted, and the grassland ecosystems may exhibit a certain degree of self-regulatory capability. Our results show that using chemical dosage indicators of a single dominant species to represent the nitrogen and phosphorus limitations of the entire ecosystem is inaccurate, and using N:P to reflect the nutritional limitations might have been somewhat misjudged in the context of global warming.

Warming affects leaf light use efficiency and functional traits in alpine plants: evidence from a 4-year in-situ field experiment.

Light use efficiency (LUE) is a crucial determinant of plant productivity, while leaf functional traits directly affect ecosystem functions. However, it remains unclear how climate warming affects LUE and leaf functional traits of dominant species in alpine meadows. We conducted a 4-year in-situ field warming experiment to investigate the eco-physiological characteristics for a dominant species (Elymus nutans) and a common species (Potentilla anserina) on the Tibetan Plateau. The leaf traits, photosynthesis and fluorescence characteristics were measured, along with the soil physical-chemical properties associated with the two species. Experimental warming increased the leaf LUE, maximum photochemical efficiency, non-photochemical quenching, relative water content and specific leaf area for both species. However, there was a decrease in leaf and soil element content. Different species exhibit varying adaptability to warming. Increasing temperature significantly increased the photosynthetic rate, stomatal conductance, transpiration rate, total water content, and specific leaf volume of E. nutans; however, all these traits exhibited an opposite trend in P. anserina. Warming has a direct negative impact on leaf LUE and an indirectly enhances LUE through its effects on leaf traits. The impact of warming on plant photosynthetic capacity is primarily mediated by soil nutrients and leaf traits. These results indicate that the two different species employ distinct adaptive strategies in response to climate change, which are related to their species-specific variations. Such changes can confer an adaptive advantage for plant to cope with environmental change and potentially lead to alterations to ecosystem structure and functioning.

Interspecies variation in plant surface water storage capacity in alpine meadows: Prediction based on plant ecological strategies

Rainfall interception by vegetation is essential in precipitation redistribution within ecosystems and greatly affects water services. However, the patterns of interspecies variation in plant surface water storage (PWS) remain unclear, which greatly limits our understanding of the relationship between species composition and vegetation rainfall interception. Thus, we aimed to examine whether the plant ecological strategy, which is an internal driving force and comprehensive characteristic of plant traits, can serve as a PWS predictor. The PWS of thirty-nine common plant species in natural, degraded, and restored alpine meadows within the Ruoergai wetland was compared, and the variability in PWS between these species was examined from both plant trait and ecological strategy perspectives. The results showed that PWS per plant (IWSC) ranged from 0.12 to 9.32 mL plant−1, and PWS based on projected area (PSCI) and fresh weight (PMS) ranged from 0.01 to 0.94 mm and 0.11 to 1.29 g g−1, respectively. The PSCI was comparatively lower in Cyperaceae, whereas the PMS was relatively lower in Polygonaceae, and Poaceae. The correlations between PWS and multidimensional plant traits are complex for predicting PWS but can be clarified by considering plant ecological strategies. Further regression analysis revealed that as an evolutionary representation of the crucially related plant traits, plant competition significantly positively affected both IWSC and PSCI, and stress tolerance obviously negatively affected these two parameters (P < 0.05). The correlation between plant strategy and PSCI implied that the increased dominance of competitive species in alpine meadows may intensify interception loss, thereby hindering rainfall allocation to soil and exacerbating water scarcity.

Decoupling of uptake‐ and transport‐related traits in absorptive roots across coexisting herbaceous species in alpine meadows

Abstract The anatomical structure of roots determines their function. Coexisting species complementarily forage nutrients by roots themselves (e.g. root strategy) and their fungal partners (e.g. mycorrhizal strategy), leading to a trade‐off between root strategy and mycorrhizal strategy. However, few studies have specifically evaluated whether and how the root anatomical structures are involved in this trade‐off, especially for species in alpine ecosystems limited by extreme climate. Here, absorptive root anatomical and chemical traits and three key root traits commonly associated with nutrient foraging strategies, that is root strategy indicated by first‐order root length and root branching intensity and mycorrhizal strategy indicated by arbuscular mycorrhizal fungal colonization, were examined across 68 herbaceous species in alpine meadows of the Tibetan Plateau. We observed that absorptive roots with higher branching intensity had more protoxylem poles, thinner cortices and smaller cortical cells, whereas absorptive roots with higher mycorrhizal colonization and longer first‐order roots consistently had thicker cortices and larger cortical cells. Unexpectedly, root cortical traits responsible for nutrient uptake were decoupled from stelar traits specialized in water and nutrient transportation. The decoupling may be related to the non‐coordinated changes in soil water and nutrient availability in the meadows of the Tibetan Plateau. In addition, we found that root cortical thickness and stelar radius increased at a similar rate rather than well‐reported different rates with increasing root diameter. Synthesis: Our results demonstrate that root internal makeup plays an integral role in forming the diverse nutrient foraging strategies in below‐ground. These findings provide new insights into our understanding of plant coexistence and the responses of alpine meadows to climate change on the Tibetan Plateau.

Dry storage alters intraspecific variation in phenotypic traits at early life stages: evidence from a dominant alpine meadow species

AbstractThe intraspecific variations of phenotypic traits in the early life stages, such as seed germination and seedling establishment, are important components affecting species adaptation and differentiation. As one of the most common ways in which seeds are maintained, dry storage usually affects these traits, by either increasing or decreasing variation among populations. However, little is known about how the interaction between dry storage and population variation of a species affects the performance and adaptability of early life-cycle traits. In this study, we conducted experiments with seeds from ten populations of Elymus nutans along an altitudinal gradient on the eastern Qinghai-Tibet Plateau. Fresh seeds and seeds stored dry for 6 months were used to quantify the temperature thresholds for germination, determine seedling emergence and survival in two common gardens and examine the correlation between these traits and environmental conditions of population provenance. Dry storage increased germination percentage, germination speed and seedling emergence, and decreased intraspecific variation in germination traits of seeds (reduced by 33.36, 52.05 and 20.45% for Tb, θT(50) and σθT, respectively). Dry storage had little effect on the intraspecific variation of seedling emergence and survival. In addition, the temperature threshold for germination cannot be used to predict seedling emergence and survival in either common garden, regardless of whether seeds were stored or not. These results indicated that it is feasible to use dry-stored seeds to evaluate and select suitable provenances in ecological restoration, and using dry-stored seeds in ecological restoration projects is expected to achieve better vegetation restoration results than fresh seeds. On the other hand, the status of seeds (fresh vs. dry stored) should be considered in an evaluation of the adaptive value of plant functional traits, especially in the early life stages, otherwise, inconsistent conclusions may be drawn.

Effects of dominant plant species change on soil multifunctionality in alpine meadows of the three-river source region

Alpine meadows are an important ecosystem in the Three-River Source Region of the Qinghai-Tibet Plateau. The dominant plant species in alpine meadows undergo changes during degradation that may directly or indirectly influence soil functionality. In this study, the effects of variations in the dominant plant species on soil physicochemical properties and multifunctionality were analyzed. Quadrats with different dominant plant species were classified as CY (for Cyperaceae), CGF (for Cyperaceae-Gramineae-Forbs), and FB (for Forbs). The results showed that, for all cases, there were significant correlations among TN (Total Nitrogen), SOC (Soil Organic Carbon), TP (Total Phosphorus), soil water, and bulk density, whereas TK (Total Kalium) showed no clear correlations with other properties. The most significant correlation between plant community characteristics and soil physicochemical properties was found in CGF because of the higher biodiversity and intensity of intermediate competition. Species with absolute dominance had stable positive or negative effects on soil multifunctionality at almost all thresholds. The effects of Cyperaceae decreasing and Forbs increasing on soil multifunctionality were nonlinear. Turning points of important values of Cyperaceae (∼0.38 and 0.66) and Forbs (∼0.34 and 0.69) were observed in dominant species changes. The different effects of Cyperaceae and Forbs on soil multifunctionality before and after the turning point indicate that the effect of plant communities on soil multifunctionality depends more on the interactions between species that remain rather than those that depart. The results of this study can guide efforts to maximize both plant communities and soil multifunctionality for the protection and restoration of alpine meadows.

Structural changes in vegetation coincident with reseeding Elymus nutans can increase perceived predation risk of plateau pikas (Ochotona curzoniae)

The perceived predation risk of animals is often influenced by the structure and complexity of vegetation communities. Plateau pikas (Ochotona curzoniae) are considered a pest species in alpine meadows when their densities exceed a certain threshold. The changes in vegetation structure caused by reseeding Elymus nutans can reduce pika densities, which may result from the increased risk of predation for pikas. However, whether the changes in community structure caused by reseeding of E. nutans is sufficient to alter the perceived predation risk for pikas, remains unknown. In this study, we measured the running speed (spontaneous without stimulation), alert distance (AD) and vigilance to a potential human predator in E. nutans habitat and open habitat by video review to assess perceived predation risk for plateau pikas in the two habitat types. Our results showed that body mass and habitat type influenced the running speed, group size and the habitat type influenced AD, and habitat type and group size influenced vigilance. The running speed of pikas was 1.67 times faster in the E. nutans compared to in open habitat, the AD of pikas was 1.79 times longer in the open than in the E. nutans habitat, and pikas were more vigilant in E. nutans than pikas in open habitat. The shorter AD indicates pikas have poor visibility due to higher vegetation height. The faster running speed and higher vigilance suggest a higher perceived predation risk for pikas in E. nutans habitat. Therefore, we believe that structural changes in vegetation following reseeding of E. nutans can increase the perceived predation risk for pikas, and could be responsible for the decrease in the pika population densities in these areas.

Deterministic process shape coexistence of alpine meadow species based on DNA barcode sequences

Deterministic and stochastic processes can simultaneously construct plant community assemblages. However, how they shape herbaceous plants’ phylogeny and functional structure in alpine meadows is unclear, hindering the understanding of species’ coexistence processes and diversity maintenance in herbaceous communities. We established a permanent research sample plot of 3.76 × 105 m2 in alpine meadows on the northeastern Qinghai-Tibet Plateau of China, investigated the flora, measured nine functional traits, analyzed inter- and intraspecific variation, and visualized phylogenetic signals. The results show that: (1) The phylogenetic structure based on DNA barcode sequences exhibits a range from competitive exclusion (NRI < 0, NTI < 0) to habitat filtering (NRI > 0, NTI > 0) along an altitude gradient. (2) The interspecific functional structure varied with altitude, reflecting different survival strategies of plants. In contrast, intraspecific trait variation was associated with environmental screening processes. (3) Except for PH and LPC, none of the functional traits showed a phylogenetic signal (K < 1, P > 0.05), suggesting that they are more influenced by environmental heterogeneity; with increasing altitude, enhanced environmental filtering favors species with conservative strategies of selection. These results suggest that deterministic processes (interspecific competition, habitat filtering) may be the main mechanisms of species coexistence in alpine meadows. Low altitude drives niche differentiation of coexisting species through competitive exclusion to reduce competition for resources. In contrast, high altitude species lead to the coexistence of functionally similar species through habitat filtering.

Dwarfing and the Underlying Morphological Changes of Poa alpigena Plants in Response to Overgrazing Conditions.

Poa alpigena is a dominant grass species in alpine meadows, which is sensitive to environmental conditions. In this study, we analyzed the characteristics of the anatomical structure of the stems and leaves of Poa alpigena in overgrazed and enclosed conditions in order to determine the dwarfing morphological mechanism associated with overgrazing. The results show that leaf thickness, leaf epidermal thickness, epidermal cell area, and phloem thickness increased with increased grazing intensity (p < 0.05). In contrast, xylem thickness, mesophyll cell area, and guide wall thickness decreased with an increase in grazing intensity (p < 0.05). Mesophyll cell density was relatively unaffected by grazing intensity. Additionally, the plasticity indices of leaf area, upper epidermal cutin layer thickness, and leaf xylem thickness were higher than 0.5. The plasticity indices of stem tube diameter, epidermal cell size, and epidermal cuticle thickness were greater than 0.4. The results of our study indicate that the structural stem and leaf changes in Poa alpigena are induced by the water and mechanical stresses that occur under grazing conditions. Thus, plateau plants adapt to grazing stress by increasing the thickness of their leaves, cuticles, and phloem. The mesophyll cell area, as well as the stem epidermal cell area of Poa alpigena decreased in response to minor variations in grazing intensity, yet overgrazing did not change its density. However, overgrazing induced a shortening of the leaves and stems, indicating that overgrazing has a dwarfing effect on Poa alpigena.

非生长季降水对青藏高原高寒草甸优势种生物量稳定性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 非生长季降水对青藏高原高寒草甸优势种生物量稳定性的影响 DOI: 10.5846/stxb202103200741 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家科学基金（U20A2007-01）；第二次青藏高原综合科学考察研究（2019QZKK0307）；山西省博士毕业生、博士后研究人员来晋工作奖励资金科研项目（SXBYKY2021067）；山西农业大学博士科研启动项目（2021BQ34） Non-growing season precipitation facilitated the biomass stability of dominant species in alpine meadow of the Qinghai Tibet Plateau Author: Affiliation: Fund Project: National Natural Science Foundation of China 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:受全球气候变化的影响，青藏高原在过去的几十年间整体上呈现暖湿化的趋势，相比于年际之间温度和降水的变化外，生长季和非生长季气候变化模式的差异可能会对生态系统产生更重要的影响，但相关的研究尚不充分。以青藏高原东部的高寒草甸为研究对象，基于2001年至2017年17年的野外观测数据，包括优势植物紫花针茅的高度、多度以及生物量、次优势物种洽草的生物量，结合生长季和非生长季平均温度和降水量的变化，通过线性回归以及结构方程模型，探究生长季/非生长季不对称气候变化对于青藏高原高寒草甸优势物种生物量稳定性的影响。研究结果表明：1）青藏高原东部年均温和年降水在过去的17年间显著增加，呈现暖湿化的趋势，但是非生长的降水却变化不明显；2）紫花针茅的高度、多度以及生物量在过去17年没有显著的趋势，但是洽草的生物量稳定性显著减少；3）非生长降水结合紫花针茅的高度、多度以及洽草的生物量稳定性促进了紫花针茅的生物量稳定性。研究结果可以为青藏高原高寒草甸在未来气候变化的背景下合理保护与利用提供科学依据。 Abstract:In the past few decades,the Qinghai-Tibet Plateau showed warming and humidifying with global climate change. Compared with the interannual changes of temperature and precipitation, the difference of climate change patterns between growing season and non-growing season may have a more important impact on the ecosystem, but the relevant research is still insufficient. Based on the field observation data of 17 years from 2001 to 2017, including the height, abundance and biomass of dominant plant Stipa purpurea, and biomass of Subdominant species Koeleria cristata, combined with the changes of mean temperature and precipitation in growing season and non-growing season, the growth season/non growing season was explored by linear regression and structural equation model to explore the effects of asymmetric climate change in growing season and non-growing season on biomass stability of dominant species in alpine meadow of Qinghai Tibet Plateau. The results show that:1) the annual mean temperature and annual precipitation in the eastern Tibetan Plateau have increased significantly in the past 17 years, showing a trend of warming and wetting, but the non-growing precipitation has no significant change; 2) The height, abundance and biomass of Stipa purpurea had no significant change trend in the past 17 years, but the biomass stability of Koeleria cristata decreased significantly; 3) The non-growth precipitation combined with the height and abundance of Stipa purpurea and the biomass stability of Koeleria cristata promoted the biomass stability of Stipa purpurea. The results can provide scientific basis for the reasonable protection and utilization of alpine meadow in the context of climate change in the future. 参考文献 相似文献 引证文献

Moderate Grazing Increases Water Use Efficiency for Environmental Health in Alpine Meadows of the Tibetan Plateau

Water use efficiency is an important indicator of drought tolerance in plants. The response of the water use efficiency to different grazing intensities and adaptive mechanisms in alpine meadows remains unclear. To understand the changes in water use in alpine meadow ecosystems under different grazing gradients, grazing systems have to be optimized, and severely receding grasslands should be effectively restored. This study analyzed the response of water use efficiency of plant dominant species, coexisting species, and functional group-level plants to grazing intensity using the δ13C index in an alpine meadow. We found that grazing increased the leaf carbon isotope composition in plants (δ13C) of Gramineae by 3.37% and grazing at a moderate level significantly increased it by 4.84% (P &amp;lt; 0.05). In addition, an increase in δ13C was observed in the functional groups of Cyperaceae (3.45%), Leguminosae (0.81%), and Forb (1.40%). However, some dominant species and coexisting species showed the highest δ13C values under moderate grazing. These results indicate that moderate grazing may significantly improve the water use efficiency of species in alpine meadows. The path analysis showed that water use efficiency was negatively correlated with evapotranspiration (P &amp;lt; 0.05), soil water content, soil organic carbon, and soil bulk density. Nevertheless, there was a positive correlation between water use efficiency and the available nitrogen. This study concluded that moderate grazing could improve the efficiency of grassland water use to a certain extent. Additionally, soil evapotranspiration was the main driving factor affecting the water use efficiency of alpine meadows.

Effect of vegetation mosaic on spatial heterogeneity of soil organic carbon mineralization and nitrification in an alpine meadow

Patchy distribution of herbaceous species is common in degraded grasslands on the Qinghai-Tibetan Plateau, but the effects of such a mosaic pattern on soil biochemical properties have rarely been studied. We compared soil organic carbon (SOC) mineralization, nitrogen (N) availability, ammonia oxidation and plant N uptake between the following vegetation patch types (plant communities) in an alpine meadow: grass (dominated by Elymus nutans, Poa crymophila and Leymus secalinus), sedge (Kobresia capillifolia and Kobresia humilis), Polygonum viviparum (P. viviparum only), Artemisia smithii (A. smithii only) and Oxytropis kansuensis (O. kansuensis only). All patches had a diameter ranging from about tens of centimeters to several meters. SOC mineralization was faster in patches beneath grass or A. smithii than in those beneath sedge or O. kansuensis, but the faster SOC mineralization beneath grass and A. smithii patches did not result in a difference in SOC storage in the top 30 cm of soil compared with that in other patches. Greater litter production beneath grasses or belowground carbon input (largest root/shoot ratio) beneath A. smithii may have offset the negative effect of rapid SOC mineralization on SOC storage under grass and A. smithii patches. Productive grasses were associated with the highest level of N availability in the soil, consistent with their greater demands for N uptake. Sedge species and A. smithii inhibited nitrification by decreasing the abundance of ammonia oxidation bacteria in soil, in contrast to grasses. The inhibition of biological nitrification under A. smithii explained the finding that the soil beneath this vegetation patch type had the lowest nitrate content as a percentage of total inorganic N. However, the inhibition of nitrification beneath sedges did not induce a decrease in the nitrate content as a percentage of total inorganic N under sedge patches compared with that under grass patches. This suggests that sedges preferentially use ammonium instead of nitrate as their N source. It is concluded that patchy distribution of herbaceous species in alpine meadows created significant spatial heterogeneity in soil biological and biochemical properties at the field scale. Sampling in ecosystem studies clearly needs to take into account such heterogeneity of soil properties and processes in grasslands with patchily distributed vegetation.

Alpine forbs rely on different photoprotective strategies during spring snowmelt.

Snowmelt in alpine ecosystems brings ample water, and together with above-freezing temperatures, initiates plant growth. In this scenario, rapid activation of photosynthesis is essential for a successful life-history strategy. But, strong solar radiation in late spring enhances the risk of photodamage, particularly before photosynthesis is fully functional. We compared the photoprotective strategy of five alpine forbs: one geophyte not particularly specialised in subnival life (Crocus albiflorus) and four wintergreens differing in their degree of adaptation to subnival life, from least to most specialised: Gentiana acaulis, Geum montanum, Homogyne alpina and Soldanella alpina. We used distance to the edge of snow patches as a proxy to study time-dependent changes after melting. We postulated that the photoprotective response of snowbed specialists would be stronger than of more-generalist alpine meadow species. Fv /Fm was relatively low across wintergreens and even lower in the geophyte C. albiflorus. This species also had the largest xanthophyll-cycle pool and lowest tocopherol and flavonoid glycoside contents. After snow melting, all the species progressively activated ETR, but particularly the intermediate snowbed species G. acaulis and G. montanum. The photoprotective responses after snowmelt were idiosyncratic: G. montanum rapidly accumulated xanthophyll-cycle pigments, tocopherol and flavonoid glycosides; while S. alpina showed the largest increase in plastochromanol-8 and chlorophyll contents and the greatest changes in optical properties. Climate warming scenarios might shift the snowmelt date and consequently alter the effectiveness of photoprotection mechanisms, potentially changing the fitness outcome of the different strategies adopted by alpine forbs.

Effects of abiotic factors on plant diversity and species distribution of alpine meadow plants

The alpine meadow is a type of vegetation with significant ecological and economic values. Plant diversity and species distribution are affected by ecological environment. To study the influence of abiotic factors (topographic factors and soil chemical and physical properties), it can understand plant communities' formation and the adaptation of plants to abiotic factors. Here, we explored the influence of the abiotic factors on the plant diversity and species distribution through the investigation of alpine meadow vegetation and abiotic factors at the northeast Tibetan Plateau, the results of the laboratory experiments, and the representative difference analysis (RDA) to find the ordination differences. Our results revealed that 11 ordered abiotic factors explained the 25.5% of the distribution of the alpine meadow species. The slope, soil total nitrogen (STN), and soil organic matter (SOM) have a significant influence on the distribution of the alpine meadow species. According to the RDA analysis of the correlation between plant diversity and abiotic factors, the cumulative interpretation value of the four ordination axes was 39.0%. Slope and STN has a strong correlation with plant diversity, respectively. STN, soil total phosphorus (STP), soil total potassium (STK), and soil water content (SWC) has positive relationships with the plant diversity index, respectively, suggesting that those factors above mentioned are the main factors affecting the diversity of species in alpine meadows. Slope, aspect, and soil temperature (ST) has negative relationships with the Partrick index, Simpson's diversity index, and Shannon-Wiener diversity index, indicating that with the slope increases, the plant diversity decreases, and the plant diversity also decrease at the sunward aspect. The soil has a more significant impact on the Pielou's evenness index, but the topography has a weaker influence on the Pielou's evenness index. The plant diversity and species distribution of alpine meadow in Tibet Plateau are affected by many abiotic factors. In our study, we found that slope and STN were the main factors affecting the plant diversity and species distribution in alpine meadows.

植物功能群去除对高寒草甸群落结构、多样性及生产力的影响

群落中物种的丧失在干扰下普遍存在，但对生态系统过程和功能的影响仍存在较大不确定性。选取青藏高原东缘典型高寒草甸为对象，开展优势植物功能群的梯度去除试验，以模拟长期过牧干扰下物种的损失。经过连续两个生长季的功能群去除，我们对群落的物种组成、结构、多样性和生物量等特征进行了分析，探讨了上述指标的响应过程和机制。研究结果表明：（1）功能群的去除降低了群落高度，增加了物种均匀度，并显著影响了禾草、杂草优势比以及功能群多样性和优势度；（2）同时，去除操作显著减小了凋落物量与禾草生物量，并显著影响了群落地上生物量；（3）进一步分析还发现，禾草、莎草和杂草功能群之间存在显著的竞争关系，群落生产力主要取决于禾草功能群并随物种均匀度的增大而显著减小。上述结果表明，禾草在高寒草甸群落中占据竞争优势地位，植物功能群的损失主要通过改变种间竞争关系、引起有机物质丢失影响群落过程和功能。;Impacts of biodiversity loss on ecosystem dynamics and functioning have aroused considerable attention and controversies. Loss of plant species is common in natural assembled community, whereas the response of ecosystem process remains unclearly. The continuous overgrazing of livestock has resulted significant plant species loss, like palatable grass and sedge species in alpine meadow on the Qinghai-Tibet plateau. In this study, we conducted a plant removal experiment to simulate the species loss along retrogressive succession gradient of alpine meadow resulting from long term overgrazing. A typical alpine meadow located on the eastern edge of the plateau was selected as the object to conduct the removal manipulation. The study site was fenced in April 2014 after the long term moderate winter grazing of yaks to exclude grazing of herbivores. Six removal treatments including: remove no plant species, remove Grass, remove Grass and Sedge, remove all species, randomly remove 25% of community aboveground biomass, and randomly remove 50% of community aboveground biomass. In middle July 2014 and 2015, we removed aboveground part of specific plant species individuals in 1 m×1 m plots. In late July 2016, the community coverage, height, species composition, diversity indices and biomass were investigated based on 0.5 m×0.5 m quadrats to detect response of alpine meadow to the removal experiment. The results showed that (1) removal of plant functional group (PFG) decreased the weighted-average height of community, but had no significant effect on the cumulative coverage of community. (2) Removal manipulation significantly influenced the summed dominance ratio (SDR) of Grass and Forb group, while no significant for Sedge group. (3) Removal of PFG increased the species evenness, and significantly influenced PFG diversity and dominance, whereas showed no significant effects for other diversity indices. (4) Removal of PFG reduced the litter biomass and Grass biomass. Only the removal of all plant reduced the community aboveground biomass. (5) In addition, further analysis showed that the community aboveground biomass was mainly depending on the Grass group, and decreased significantly with the increase of species evenness. And significantly competitive relationships were found among Grass, Sedge and Forb groups. The results showed that Grass species in the alpine meadow community have the greatest competitive advantage, the loss of plant species could change the community properties by means of influencing the inter-specific competitive relationships and significant plant biomass loss. The successive long-term monitoring on the response of community functioning to plant species loss should be strengthened.

Rainy season onset mainly drives the spatiotemporal variability of spring vegetation green-up across alpine dry ecosystems on the Tibetan Plateau

It is still debatable whether temperature or precipitation mainly triggers spring vegetation green-up (SVG) in alpine dry ecosystems on the Tibetan Plateau. As phenological sensitivity to the arrival of monsoon-season rainfall would allow plants to simultaneously avoid drought and frost damages in the early growing season, we hypothesize that rainy season onset (RSO) rather than temperature mainly drives the spatiotemporal variability of SVG across alpine dry ecosystems over the Tibetan Plateau. Dates of RSO and SVG across 67 target areas nearby 67 weather stations over the Tibetan Plateau were calculated from time-series data of daily mean temperature and precipitation (1974–2013) and of the Normalized Difference Vegetation Index from the Moderate Resolution Imaging Spectroradiometer (2001–2013), respectively. Satellite-derived SVG was validated by 7-year observations (2007–2013) for leaf emergence of dominant species in alpine meadows along elevations (4400–5200 m) in Damxung of Tibet. We found that SVG generally synchronized with or was somewhat later than RSO although seasonal air temperatures were already continuously above 0 °C in 1 month before SVG dates. In pooled data across sites and years, the analysis of linear mixed model indicated that RSO (F = 42.109) and its interactions with pre-SVG precipitation (F = 6.767) and temperature (F = 4.449) mainly explained the spatio-temporal variability of SVG, while pre-SVG temperature and its interaction with precipitation did not have significant effects on SVG. Our data supported the hypothesis, suggesting that synchronization of SVG and RSO is a general spring phenological strategy across alpine dry ecosystems under influence of monsoon climate.

Plant community of alpine steppe shows stronger association with soil properties than alpine meadow alongside degradation

The interaction between soil properties and plant community determines the efficacy to restore the degraded grassland via improving soil properties. We conducted a field survey to investigate the relationship between plant community composition and soil physical and chemical properties alongside different degradation stages of alpine grassland. Results showed that with the increasing severity of degradation, the dominant plants shifted from sedge and graminoid species, respectively, to forbs species in alpine meadow (AM) and alpine steppe (AS). Species richness and diversity indices were unchanged until the severely degraded stage in both AM and AS. Forward selection showed bulk density (BD) and ammonia nitrogen (NH4+) at 10–20 cm, pH and the ratio of soil organic carbon to total nitrogen (C/N) at 0–10 cm were the four important variables being responsible for the species community variation alongside degradation of AS, which explained 18.7% of the total variance. Soil nitrate nitrogen (NO3−) and C/N at 20–30 cm, NH4+ at 10–20, and BD at 0–10 cm were the important variables in driving the community variance alongside degradation stages, which only explained 9.5% of the total variance of AM. The loss of dense root layer and the species community change induced change in BD, and difference in plant competition for available resources would lead to the stronger association between vegetation community and soil properties in AS than that in AM. Our results indicate that though improving soil nutrients and soil texture to restore the degraded AS may be more effective than to restore degraded AM.

Effects of simulated N deposition on photosynthesis and productivity of key plants from different functional groups of alpine meadow on Qinghai-Tibetan plateau

Nitrogen (N) deposition may alter physiological process of plants in grassland ecosystem. However, little is known about the response mechanism of individual plants in alpine regions to N deposition. We conducted a field experiment, and three treatments including 0 kg Nha-1year-1 (CK), 8 kgNha-1year-1 (Low N), and 72 kg N ha-1 year-1 (High N) were established to simulate N deposition in alpine meadow of Qinghai-Tibetan plateau. Our objectives were to determine the influence of N deposition on photosynthesis of different functional types of herbage species in alpine meadow, and finally characterize the links of plant productivity and photosynthesis with soil nutrients. The results showed that responses of alpine plants were species-specific under N deposition. Compared with grass species Agropyron cristatum and forb species Thalictrum aquilegifolium, the sedge species Carex melanantha was much more sensitive to N deposition; a lower N load (8 kgNha-1year-1) can cause a negative effect on its photosynthesis and productivity. Additionally, N deposition can promote plant N uptake and significantly decreased the C (carbon)/N (nitrogen) ratio. Compared with CK and low N deposition, high N deposition inhibited the photosynthesis and growth of the forb species Thalictrum aquilegifolium and sedge species Carex melanantha. In all three functional types of herbage species, the grass species A.cristatum tended to show a much higher photosynthetic capacity and better growth potential; thus, suggesting that grass species A.cristatum will be a more adaptative alpine plants under N deposition. Our findings suggested that plant photosynthetic responses to N deposition were species-specific, low N deposition was not beneficial for all the herbage species, and N deposition may change plant composition by the differential photosynthetic responses among species in alpine grassland. Plant composition shift to grass-dorminant in alpine regions might be attributed to a much higher photosynthetic potential and N use efficiency of grass species.