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西藏高寒草地植被生物量及其分配机制研究
Alternative TitleStudy on the Biomass Characteristics and Their Allocation Mechanism in Tibetan Alpine Grassland
Language中文
孙建
Thesis Advisor程根伟
2013
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Name博士
Degree Discipline自然地理学
Keyword植被指数 生物量分配 环境因子 等速分配假说 高寒草地 多尺度
Abstract作为世界上最为独特的生态地域单元,青藏高原的气候变化特征比其它地区更明显,对周围地区的影响也可能更大。作为气候变化的敏感区和先兆区的青藏高原,研究环境变化对高寒草地生态系统的植被状况,生物量分配,对认识青藏高原草地生态系统运行机制具有十分重要的意义。通过对植被覆盖变化与气候因子的关系、不同尺度地上部生物量、地下部生物量以及根冠比与环境因子关系的研究,确立环境效应。同时利用等速分配假说检验不同尺度生物量分配机制。主要成果如下: 1) 对1982到2002年时间序列植被变化以及对应时间序列的气候因子的分析,温度和降雨分别是影响青藏高原植被的主要气象因子。不同尺度的植被指数与温度降雨气象因子分析表明,在整个区域尺度上降雨为主要主导因子,且促进植被指数的增加,年均降雨与生长季年均降雨均与MNDVI呈现正相关关系,相比之下温度系列指标与MNDVI的关系很弱。 2)基于区域尺度上、生态系统尺度,研究环境因子与植物地上部生物量、地下部生物量以及根冠比的关系,结果表明生物量受环境因子的影响。由于尺度效应的存在,导致在不同尺度上植物生物量(地上部,地下部以及根冠比)受不同的环境因子所主导,且效应大小也不相同。 3)研究不同草地管理措施对地下部生物量的分布影响,结果表明严重放牧、围栏两年、长期放牧以及围栏五年表层地下部生物量呈现递减趋势,以严重放牧均值最大,放牧可能促使地下部生物量浅层化。土壤有机碳、全氮、速效氮、总磷和速效磷均以围栏两年为最高,其次为严重放牧,最小值均出现在长期放牧。说明围栏能够很好的增加地力,提升土壤中的营养。相关关系分析结果显示群落生物量受土壤营养状况调节。 4)区域尺度、生态系统尺度的群落生物量,站点尺度上不同植物群落、植物个体,以及不同草地管理措施(人类干扰)下植物生物量分配(地下部/地上部生物量)均符合等速分配假说,但是植物地上部生物量,地下部生物量以及根冠比(R/S)又受环境因子的影响。而等速分配假说不能定量地描述环境因子对植物光合产物分配的影响,因此我们提出“自身约束--适应环境假说” 使其能合理的解释高寒草地植物生物量分配机制。分析认为在长期的诸多选择压力和约束过程中进化出了变化的生长关系,也就是说环境因子对植物的等比分配不断的进行着微调,以适应当前的生境。但是该变化的比例关系约束于等速生长关系(与标准等速生长关系斜率差异不显著)。
Other AbstractTibetan Plateau not only plays a vital role in improving the ecosystem and achieving sustainable development in China, but also contributes to safeguarding Asian, and even global ecological security. Tibetan Plateau is the sensitive to climate change, To analyse the alpine grassland vegetation dynamic and biomass allocation, which has great significance for us to understand the ecosystem mechanism of grassland in Tibeyan Plateau. In this study, the relationship between vegetation and climate factors at different scales, the relationship of aboveground biomass, belowground biomass, the ratio of root and shoot with environmental factors are explored and the hypothesis of allometric allocation is verified and revised, the conclusions are as follows: 1) Temperature and precipitation have been separately reported to be the main factors affecting NDVI(Normalized Difference Vegetation Index)in the Tibetan Plateau. The effects of the main climatic factors on MNDVI (Yearly Maximum NDVI) in the Tibetan Plateau were examined on different scales. The result underscored the observation that both precipitation and temperature affect MNDVI based on weather stations or physico-geographical regions; precipitation is the main climatic factor that affects the vegetation cover in the entire Tibetan Plateau. Both annual mean precipitation and annual mean precipitation of the growing period are related with MNDVI, and the positive correlations are manifested in a linear manner. By comparison, the weakly correlated current between MNDVI and all the temperature indexes are demonstrated in the study area. 2) On the regional and ecosystem-scale, the relationships of environmental factors with aboveground biomass, belowground biomass, and the ratio of root to shoot showed that the effects of environmental factors on the biome. However, the crtical environmental factors as well as the size of the environmental effects are different on different scales.. 3) With the reduction of grazing gradients, the community belowground biomass showed a decreasing trend, and then the maximum appeared in fence two years, the maximum of aboveground biomass and the ratio of root and shoot are in serious grazing and fences for two years, respectively. The belowround biomass distribution in different soil depths are ordered as severe grazing, fence for two years, long-term grazing and fence five, which showed a decreasing trend. The maximum is in severe grazing, so we conclude that grazing may encourage belowground biomass is shallow. The maximum of soil organic carbon (SOC) and soil total nitrogen (TN), soil available nitrogen (TAN), soil total phosphorus (TP) and available phosphorus (TAP) are in the fence two years, followed by severe grazing, and the long-term grazing. So the fence may be increase soil fertility, accelerated soil nutrition.transfromation. 4) On the different scales, the biomass allocation (the ratio of root to shoot) was analysed, we concluded that all the allocation of biomass belong to the hypothesis of allometric allocation. But environmental factors also affect aboveground biomass, belowground biomass and the ratio of root to shoot ratio (R/S), due to the presence of scale effects, resulting in biomass allocation is dominated by different environmental factors on different scales. Under the long-term selection pressures and constraints, the environmental factors regulate the allocation of vegetations to adapt to the current habitat.
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/7052
Collection山地表生过程与生态调控重点实验室
Recommended Citation
GB/T 7714
孙建. 西藏高寒草地植被生物量及其分配机制研究[D]. 北京. 中国科学院研究生院,2013.
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