|Alternative Title||Study on the response of plant community in alpine grassland to climate change|
|Place of Conferral||北京|
|Keyword||气候变化 高山草地 种群动态 圆叶小堇菜 开花物候|
The Earth has warmed by about 0.74 °C in the last 100 years, and global mean temperatures are projected to increase fur-ther by 4.3 ± 0.7 °C by 2100. Alpine ecosystems are vulnerable to climate change due to specific characteristics, such as short-distance habitat limitations and alterations of environmental key factors determining plant life. Mountain ecosystems represent invaluable resources, both in terms of biodiversity and the ecosystem services they provide. Mountain ecosystems offering steep environmental gradients also represent exciting biological experiments of nature which have stimulated research for centuries. Mount Yajiageng is situated at the eastern fringe of the Tibetan Plateau and belongs to cold and wet area. It includes subalpine grasslands and alpine grasslands forming under grazing conditions along the elevational gradient, which is ideal to study the effects of climate warming on alpine grasslands. We selected four sites in the grasslands along its elevational gradient. Firstly we studied plant community characteristics of alpine grasslands and soil microbial community composition along elevation gradient, and their driving factors. Secondly we combing with experimental manipulation studied the influence of climate change on the population dynamics of a small alpine forb and the response of flowering phenology in an alpine meadow to climate warming. The main results are as follows:1）There were obvious differences in plant community characteristics along the elevation gradient. Aboveground biomass was significantly reduced with altitude increasing, while underground biomass and root-shoot ratios of community had significant increase. Community diversity indexes showed significant change between lower altitude sites, but did not change significantly between higher altitude sites. Overall community diversity and evenness increased with altitude increasing. Variation in community characteristic of different altitude was mainly controlled by meteorological factors, and the temperature played a leading role. The interpretation of the variance from soil factors can be ignored. Other factors not considered in this study, such as herding, interspecific interactions might also play important roles on characteristics of grassland community. Community diversity indexes showed negative correlation with aboveground biomass along the elevation gradient, which support root competition hypothesis and light competition hypothesis.2）There were obvious differences in soil microbial communities along the elevation gradient. However, microbial biomass and various microbial groups did not show elevational trend on the whole. Leguminous plant coverage and soil TN had important effects on soil microbial community composition. Other factors may influence the soil microbial community through interaction with leguminous plant coverage and soil TN. Soil chemistry and plant functional group composition respectively affect the different aspects of soil microbial community. The interaction between them had no impact on the soil microbial community maybe because long-term grazing greatly reduces litter.3）Though Viola biflora var. rockiana (Vio.bif) as alpine species is small, its phenotypic plastics has obvious adaptation strategy for light competition. In the community with intensive competition for light it increases investment in stem growth and single leaf area, and however decreases investment in increasing leaf number, and vice versa. This strategy ensures effective access into light per biomass.The adaptation is embodied not only in the natural gradient formating from the long time and in the short-term change of environment. Vio.bif is sensitive to competition for light and adaptive adjustment of phenotypic plasticity is closely related to the level of competition for light.4）Clonal reproduction is a main contributor to population growth of Vio.bif in closed vegetation. Survival and clonality were the most important vital rates contributing to reduce in population growth rate in warming treatment.The reduce of these two viato ratios should be attributed to the enhanced competition from the surrounding community. The population of higher altitude was affected by warming through greater impact on clonality, whereas the poputation of lower altitude was affected by warming through greater impact on survival. Population growth rate and clonality showed anomalous change at the early stage of greater warming treatment, which may be attributed to increased re-sprouting after vegetative dormancy in the environment with high precipitation pulse. Sharp decrease of population growth rate at the subsequent stages of greater warming treatment should be attributed to the dramatically increased competition from surrounding community with immigrating species. Vio.bif is similar to fugitive species with low competitive abilities and certain colonization and dispersal abilities. Persistence for Vio.bif may become increasingly dependent on management interventions (i.e. grazing, mowing) to reduce competition from surrounding community in a future climate.5）We find striking diversity in the phenological shifts of individual plant species under warming. Assuming that phenological firsts represent overall phenological change can lead to inaccurate assessments of the magnitude of change and the number of responsive species within an ecological community. This diversity of species-level shifts in phenology ultimately leads to altered patterns of coflowering, expansion of the flowering season, and community-level redistribution of floral abundance. The response of flowering phenology and flowering abundunce to warming showed a certain regularity and difference beween plants belonging to different functional groups (forb or graminoid ) or with different life history characteristics (flowering early or late). Life-history traits, phenotypic plasticity, sensitivity to environmental factors may affect the plant sexual reproduction investment, affect plant population and competitiveness, and thus affect the community-level floral abundance. The suite of changes in phenology caused by climate change will likely create powerful selection pressure not only on plant species themselves but possibly also on species at higher trophic levels that depend on these plants. A community pattern of blooming in which the flowering of various species is staggered in an unbroken progression over a growing season, which may indicate a dynamic evolutionary consequence of the reproductive phenology of the species and the resources available in the environments to which they have been adapted. The climate-induced disruption of phenological patterns potentially initiates changes that over time might affect community organization and have far-reaching consequences for ecology and evolution.
|崔海军. 高山草地植物群落对气候变化的响应研究[D]. 北京. 中国科学院大学,2016.|
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