半干旱区灌-草复合系统结构和功能对增强的降雨变异的响应

Climate change simulations project increase in precipitation variability as a result of global warming. Enhanced precipitation variability has an important effect on the whole ecosystem, especially for the arid and semiarid ecosystems limited by water. Studying the responses of structure and function of shrub-grass ecosystem to the enhanced precipitation variability has important theoretical and practical significance on predicting the occurrence and development process of shrub encroachment. We study the widely distributed Caragana korshinskii Kom. and the grasses under the canopy in northern arid and semi - arid area. By controlling the intra- and inter- annual precipitation variability, we study the changes of the leaf physiological and ecological traits, species abundance and turnover, and species diversity, functional diversity and above-ground primary productivity. Then we compare and analyze the threshold of state transition of shrub - grass ecosystem , and derive the corresponding early warning signal. The expected results will not only enhance understanding of the shrub -grass ecosystem sensitivity to enhanced precipitation variability, but also strengthen the predicting ability of ecosystem state transition under global climate change scenarios. The results would provide data support and theoretical basis to develop the adaptive management strategies.

气候变化研究表明，全球变暖将导致未来降雨变异的增强。增强的降雨变异将对整个陆地生态系统，尤其是对受水分限制的干旱和半干旱生态系统产生重要影响。深入研究半干旱区灌-草复合系统结构和功能对增强的降雨变异的响应对于预测和控制灌木入侵以及半干旱区天然草原的管理具有重要的理论和实践意义。本项目拟以我国北方干旱和半干旱区广泛分布的柠条锦鸡儿及其灌丛内外的草本植物构成的灌-草复合系统为研究对象，从叶、物种和群落水平研究灌-草复合系统结构和功能对增强的年内降雨变异和年际间降雨变异的响应过程和机制，揭示灌-草复合系统发生状态转变的阈值，并推导出相应的前期预警信号。该研究结果不仅有利于增加对半干旱区灌-草复合系统响应增强的降雨变异的敏感性认识，而且将增强在全球气候变化背景下对灌-草复合系统状态转变的预测能力，可为制定保证区域社会经济可持续发展的适应性管理策略和措施提供数据参考和理论依据。

气候变化研究表明，全球变暖将导致未来降雨变异的增强。增强的降雨变异将对整个陆地生态系统，尤其是对受水氮限制的干旱和半干旱生态系统产生重要影响。深入研究半干旱区灌-草系统结构和功能对增强的降雨变异的响应对于预测和控制灌木入侵以及半干旱区天然草原的管理具有重要的理论和实践意义。本项目以我国北方草原区广泛分布的柠条锦鸡儿及其灌丛内外的草本植物构成的灌-草系统为研究对象，从叶、物种和群落水平研究了灌-草复合系统结构和功能对增强的降雨变异的响应过程和机制。研究结果表明：灌丛斑块和草地斑块对降雨变异增强的时间尺度敏感性存在差异。年内降雨变异增强（先干后湿）显著增加了灌丛斑块和草地斑块的物种丰富度；年际降雨变异增强（先干后湿）显著降低了灌丛斑块和草地斑块的物种丰富度；降雨变异增强对地上生产力没有显著影响。灌丛和灌丛下的草本植物之间表现为正相互作用；草地斑块物种之间的相互作用取决于环境条件，水养条件较好时一般以竞争为主，水养条件较差时表现为中性作用；短时间降雨变异的增强并不会影响群落功能丰富度和功能离散度。该研究结果不仅有利于我们增加对半干旱区灌-草复合系统响应增强的降雨变异的敏感性认识，也可为全球气候变化背景下对灌-草复合系统状态转变的预测提供一定的数据支撑，同时可为制定保证区域社会经济可持续发展的适应性管理策略和措施提供参考和理论依据。

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