全球变暖背景下多年冻土区高寒草地生产力对冬春降水量增加的响应过程与作用机制

Precipitation plays a crucial role on plant growth suffering from warming at arctic and alpine region. But little about the effects of precipitation on alpine grassland at the Tibetan Plateau was conducted compared with warming study. Particularly, how strongly and how to influence spring-up onset observed evident increase in winter and spring precipitation in recent decades of year, which keep unknown till now. Even, It is not clear for us what kind of lagging effects and potential mechanism from increasing precipitation and temperature in winter and spring will be. The temperatures of air and active soil were passively increased using open-top chambers (OTCs), snow fences was erected for the purpose of manipulating the snowpack, which simulate increased precipitation in winter and spring in the present study. All of these field sites were conducted in two most widespread alpine grassland types, alpine meadow and alpine swamp, at the Tibetan Plateau, China, which is very sensitive to climate change. The aim of this study is to contrast the contribution rate of increasing precipitation and temperature on green-up onset, to clearly identify what ratio of species/functional group biomass accounts for above net primary production (ANPP), and to clarify the relationship of production distribution pattern and functional traits between above- and below-ground, respectively. These results would be help us to reveal how climate change influences plant net primary production and what potential mechanism it will be in the future. The present study will be helpful to understand what direction of alpine community will be marching toward and what principle community would be in future climate change. Moreover, the obtained results here will also provide scientific guidance for estimating the effects of climate change on plant production and function of carbon source/sink, and planning the protective policy of alpine ecosystem to adapt near climate change.

降水量是影响增温背景下高寒植物生长的重要限制因子，但相比温度影响研究，对降水量变化的青藏高原高寒草地影响研究较少，尤其是近10年冬春降水量显著增加多大程度和如何影响增温引起高寒植被返青期提前至今仍不清楚，这种影响对植被生产力产生何种滞后效应及其机制更不明确。本项目选定对气候变化十分敏感的多年冻土区广泛分布的高寒草地为研究对象，通过野外原位设置开顶式气室模拟增温，积雪栅栏增加积雪厚度模拟降水增加，对比分析增温和冬春降水增加对返青期提前的作用大小，辨识物种/功能群地上生物量对地上净初级生产力的贡献率，探明地上/地下生产力分配格局及其功能属性的关系，揭示气候变化影响高寒植被净初级生产力作用过程与潜在机理。研究结果有利于系统地认知高寒植物群落响应气候变化的演变方向和内在机制，为准确评估气候变化对青藏高原高寒生态系统生产力及碳源汇功能的影响、制定适应气候变化的高寒生态系统保护对策提供重要的科技支撑。

本项目选择对气候变化十分敏感的多年冻土区广泛分布的高寒草地为研究对象，通过野外原位设置开顶式气室模拟增温，积雪栅栏增加积雪厚度模拟降水增加，对比分析增温和冬春降水增加对草地返青期提前的作用力大小、功能群生物量对地上净初级生产力的贡献、以及根系生物量分布格局及其功能属性关系。阐明了联合的温度和水分增加对返青期提前最为显著的现状，探明了温度升高对草地枯黄期推迟的可能生物学机制；明确了杂类草和禾本科功能群的物种丰富度和地上生物量对变化环境的响应更敏感，显示出更高的贡献率对草地生产力变化；辨识了温度和水分对根系生物量分布格局和资源利用策略的影响差异，揭示了不同水分条件的植被对温度响应的演变过程差异；从样方尺度证实了过去十年青藏高原多年冻土区高寒草地“变绿”的现状，但是伴随着高寒草地牧草质量下降和毒杂草数量上升的现状，凸显了遥感影像结果与地面植物群落真实情况的差异，强调了地面调查工作的重要性，建议开展更多高海拔敏感脆弱生态系统的长期定位观测研究。