干旱荒漠区灌木生物量与土壤水分动态耦合研究

The amount of biomass of a given species assimilated per unit area of the landscapemay serve as a proxy for its competitiveness and evolutionary success. The coupled dynamics of shrub biomass and soil moisture is of vital importance for evaluating the stability as well as the sustainability of arid desert ecosystems. Shrub biomass and soil moisture dynamics is driven by stochastic rainfall. At the same time, it is closely related to the photosynthesis, transpiration and respiration. The research proposal takes the xerophytic shrubs Salsola passerina and Reaumuria soongarica in the desert ecosystem at the southeast edge of the Tengger Desert as the target plants, based on the multi-time scale and multi-factor observation of the biomass and soil moisture variation, to study the competition between different species and individuals for soil moisture is driven by variations in physiology and metabolic regulation strategies, expressed by such parameters as rooting depth, stomatal opening or wilting point, and to quantify the biomass variation during the growing seasons. Accordingly, to analyze the responses and feedback mechanism of photosynthetic carbon assimilation, respiratory carbon loss and transpiration water consumption to soil moisture, and to construct a nonlinear probability density function of biomass and soil moisture. Furthermore, the proposal is aimed to develop an analytical scheme for the description of the photosynthetic biomass dynamics undergoing seasonal cycles with different rainfall characteristics in detail, to characterize the stable state and transient state of the biomass and soil moisture, and to test the accurate representation of the analytically predicted statistics of biomass per unit area throughout the wet and dry seasons. The overall objections are to reveal the sustainable maintenance mechanism of desert ecosystem, to expand the theory of water stability of water-controlled desert vegetation, and to provide scientific basis for reasonable regulation of vegetation-water relations in vegetation restoration.

生物量反映了生态系统尺度上植物对土壤水分的竞争力及适应干旱生境的能力，是表征植被稳定演替的理想指标。准确认识生物量与土壤水分的动态耦合特征，是揭示荒漠生态系统稳定性及可持续性的基础。干旱荒漠区灌木生物量与土壤水分动态既受随机降水驱动影响，同时与灌木光合、蒸腾、呼吸作用密切相关。本项目以腾格里沙漠东南缘荒漠生态系统优势灌木红砂、珍珠为研究对象，以生物量与土壤水分变化的多时间尺度、多要素观测为主线，基于灌木通过根系分布、气孔调节及凋萎湿度变化等策略实现充分吸收利用有限土壤水分的事实，从机理上解析光合碳同化、呼吸碳损失、蒸腾耗水对土壤水分的响应与反馈，构建生物量与土壤水分非线性变化的概率密度函数；界定生物量、土壤水分稳态及瞬态分布范围，阐明生物量和土壤水分对随机降水驱动的响应模式；分析生物量与土壤水分的动态耦合关系，论证生长季干湿交替变化对生物量累积的影响；发展水分限制型荒漠植被的水分稳定性理论，揭示维持荒漠生态系统稳定性的生态水文学机制，为干旱区植被恢复中合理调控植被-水分关系提供理论依据。

准确认识生物量与土壤水分的动态耦合特征，是揭示荒漠生态系统稳定性及可持续性的基础。干旱荒漠区灌木生物量与土壤水分动态既受随机降水驱动影响，同时与灌木光合、蒸腾、呼吸作用密切相关。本项目以我国腾格里沙漠东南缘荒漠生态系统优势灌木红砂、珍珠为研究对象，以生物量与土壤水分变化的多时间尺度、多要素观测为主线，以灌木光合、呼吸、蒸腾作用与土壤水分动态耦合的生物物理过程为切入点，探明了灌木通过生物量异速增长分配模式、根系构型变化、气孔调节等策略实现充分吸收利用有限土壤水分养分的生态适应机制，从机理上解析了光合碳同化、呼吸碳损失、蒸腾耗水对土壤水分的响应与反馈，建立了基于根、茎、叶等性状指标的植物生物量-土壤水分定量关系。当灌丛斑块空间分布符合截尾幂律分布时，其生态系统状态优于符合对数正态分布的植被样方。不同灌木种内和种间的相互关系对空间格局有显著影响，小尺度上竞争关系为主导是斑块破碎化的首要原因。小灌木种内的互利作用能促使其形成多样化的斑块形态，而大灌木种间的互利关系，能够增强灌丛斑块的异质性，形成更为复杂的空间格局，揭示了维持荒漠生态系统稳态性及可持续性的生物量-土壤水耦合机制，对退化生态系统恢复具有重要的参考价值。发表论文12篇（其中在SCI收录刊物发表论文9篇），培养博士研究生5名。