冰川融水增加对冰川末端高寒草甸生态系统碳循环关键过程的影响

Due to climate warming, 82% of the Tibetan plateau’s glaciers have retreated, which significantly increased glacial meltwater runoff flowing into the alpine meadows at glacier terminus. Plant community characteristics, soil temperature, water content, and microbial community properties of the alpine meadows were altered as a consequence of the increased meltwater, which should further alter the ecosystem carbon dynamics, such as plant net primary productivity (NPP) and microbial organic matter decomposition processes. However, there has been very little research reported on the effects of increased Tibetan glacial meltwater on alpine meadow ecosystem carbon dynamics and we can’t further assess their effects on climate change and freshwater ecosystems draining from the meadows. Here, to study the response of plant NPP and microbial organic matter decomposition processes in alpine meadow ecosystem to current and future glacial meltwater runoff increases, we will conduct quantitative and controllable glacial meltwater addition experiments in alpine meadows at terminus of two Tibetan glaciers, which melt significantly and are mainly under the dominance of the Indian monsoon and westerlies, respectively. In situ plant primary production and ecosystem carbon exchange monitoring and lab microbial structure and function analysis will be performed. Our results will provide a basis for prediction and assessment of ecological consequences of increased glacial metlwater runoff.

由于气候变暖，青藏高原82%的冰川出现了消融和退缩。冰川融水大量流入冰川末端的高寒草甸，对草甸植物群落特征、土壤温度、含水量和微生物群落特征等产生影响，继而影响植物净初级生产力（NPP）和微生物有机质分解等生态系统碳循环过程。然而当前对青藏高原冰川融水增加的现象关注较少，对其导致的高寒草甸生态系统碳循环过程的变化及其机制还不清楚，无法进一步评估预测融水增加对气候变化和下游水体的影响。本项目在青藏高原选择2处消融显著并且分别受季风和西风影响的冰川，在冰川末端高寒草甸设计定量可控的冰川融水添加实验，模拟现在和100年后冰川融水增加情形。结合原位生态系统碳交换、植被生产力监测和实验室微生物碳循环功能分析，研究青藏高原气候变暖背景下高寒草甸植物NPP和微生物有机质分解等生态系统碳循环关键过程对冰川融水增加的响应及其主要机制。本研究结果将为准确预测和评估冰川融水增加的生态后果提供数据支持和理论基础。

气候变暖导致青藏高原冰川加速消融，冰川融水增加将显著影响冰川前缘高寒草甸生态系统碳循环过程。然而高寒草甸生态系统关键碳循环过程对冰川融水增加的响应过程和机制尚不清楚。针对这一科学背景，本项目按照任务书完成了西藏唐古拉山中部龙匣宰隆巴冰川前缘高寒草甸关键碳循环过程对冰川融水增加的响应过程及其机制的相关研究内容。通过原位的野外调查及移栽试验并应用微生物分子生物学、宏基因组测序等技术，本项目发现1）冰川融水增加后高寒草甸甲烷排放显著增加，生态系统由甲烷汇转变为甲烷源；2）冰川融水增加后显著增加了高寒草甸植物地上生物量和土壤含水量、电导率、总碳、总氮和易分解碳组分含量，但是显著降低了土壤的pH、总磷和硝态氮，并且各个土壤深度都有相似的响应；3）冰川融水增加后显著增加了微生物生物量，改变了高寒草甸土壤的微生物群落组成和功能；4）高寒草甸土壤理化性质和微生物特征对夏季的冰川融水增加和秋冬季节的融水减少过程的响应是不对称的。这些研究结果对于更好的认识气候变化和冰川消融情形下，青藏高原冰川区高寒草甸的碳循环过程具有重要意义。本项目已在包括Global Change Biology和Frontiers in Plant Science等国内外学术期刊上发表研究论文9篇，还有部分研究结果待发表。本项目研究论文也获得了中国生物地理学青年优秀论文奖和梁希青年论文奖2项学会论文奖。项目执行期间培养博士研究生1名，硕士研究生6名，完成了项目书中制定的研究目标。