非生长季与生长季增温增水对北方温带草原生态系统碳循环的影响

Anthropogenic activities induced climate change including climate warming and changes of precipitation regime seriously affects grassland ecosystem carbon cycling. However, less attention has been paid on the responses of ecosystem carbon flux to seasonal variation of climate warming and precipitation regime changes, which increases uncertainty to predict the climate change-ecosystem carbon cycling feedback in the future. This project will perform a four factors experiment including non-growing season warming (warming vs ambient temperature), non-growing season precipitation addition (increased snow vs ambient snow), growing season warming (warming vs ambient temperature), and growing season precipitation addition (increased rainfall vs ambient rainfall) in a typical temperate steppe in Inner Mongolia. Net ecosystem carbon flux, ecosystem respiration, and gross ecosystem productivity under different treatment are monitored to test the interactive effect of no-growing season and growing season climate change on ecosystem carbon cycling. Plant phenology, as well as biodiversity of plant and microorganisms is investigated to document the response mechanisms of ecosystem carbon cycling to seasonal variation of climate change. The results will enhance the understanding on the responses of grassland ecosystem carbon flux to climate change; facilitate model projections on ecosystem carbon cycling under climate change scenario. The research findings will have significant implications for the sustainable and adaptive management of the temperate steppe in northern China.

人类活动导致的全球气候变化，包括气候变暖和降水格局变化严重影响了生态系统碳循环。但目前关于气候变化幅度在非生长季与生长季的差异对生态系统碳循环的影响还缺乏足够的认识，极大的增加了气候变化-陆地碳循环反馈关系预测的不确定性。本项目拟选择我国内蒙古北方温带草地为研究对象，建立一项包括非生长季增温（增温、自然温度）、非生长季增水（增雪、自然降雪）、生长季增温（增温、自然温度）、生长季增水（增雨、自然降雨）的四因素控制实验平台。通过监测生态系统净碳交换、生态系统呼吸、生态系统总初级生产力变化，揭示不同季节温度与降水变化对温带草原生态系统碳循环的交互影响。通过对植物物候、植物及微生物群落生物多样性的调查，分析气候变化背景下生态系统碳循环变化的内在机制。提高对草地生态系统碳循环响应气候变化的认识，为陆地生态系统碳循环预测模型提供参数估计，为未来气候变化情景下我国温带草原的适应性管理提供决策支持。

研究气候变化的季节性差异对温带草原生态系统碳循环的影响机制，以及增温与降水格局变化对生态系统碳循环的交互影响，有助于提高对草地生态系统碳循环响应气候变化的认识，本项目以温带典型草原为研究对象，围绕气候变化对草地生态系统碳循环的影响研究了1）非生长季与生长季气候变化对生态系统碳循环的交互影响，2）非生长季与生长季气候变化对生态系统碳循环调控因子的交互影响。结果发现1）仅在生长季进行实验处理与监测的碳循环相关指标响应幅度，与全年进行增温或降水处理的相关指标响应幅度存在明显区别，表明非生长季气候变化及碳通量在该地区碳循环中占有重要的地位。2）该地区生态系统碳循环对降水变化的响应更为敏感。非生长季与生长季增水均显著提高了生态系统净碳交换速率。气候变暖的效应虽然小于降水，但是也显著影响了生态系统呼吸与土壤呼吸。3）降水显著提高了该地区植物群落的盖度与生物量，而增温处理对植物群落结构的影响并不明显。4)非生长季降水增加显著提前了生长季的开始时间，推迟了生长季的结束时间，延长了生长季长度。生长季增温、非生长季增温、生长季降水对植物物候的影响均不显著。本研究结果证实非生长季气候变化与碳循环在气候变化研究中应受到充分关注，可以为陆地生态系统碳循环的预测模型提供参数估计，同时为未来气候变化情景下我国温带草原的适应性管理提供决策支持。