高寒草甸温室气体排放与土壤生物群落特征对气候变化的响应机制

The grassland ecosystem structure and function was changing under global change which based on the characteristics of climate warming, precipitation pattern change and atmospheric nitrogen deposition and so on. At present, the effect of the single factor and the interaction of multiple factors on the greenhouse gas emissions, soil biological community structure and composition research become an important topic for the research of global change ecology. But so far, the greenhouse gas emissions, the characteristics of soil biological community and the relationship between the two was influenced by the interaction of multiple factors was seldom reported in alpine meadow of the Qinghai-Tibet plateau which was sensitive to climate change. In this study, the effect of simulation climate change experiment by increasing temperature, precipitation, nitrogen and interaction on the greenhouse gas emissions, the characteristics of soil animal and microbial community will be researched. The change trend and its influencing factors in greenhouse gas emissions, soil animal and microbial community structure and composition will be clarified in alpine meadow of northern Tibet under the background of climate change. The potential influence mechanism on greenhouse gas emissions and the characteristics of soil biological community response to climate change will be revealed in alpine meadow of northern Tibet. The effect of climate change on greenhouse gas emissions will be clarified by the relationship between soil biological community and greenhouse gas emissions in the Tibetan plateau, and provide a scientific basis for the sustainable use of alpine grassland resources and address future climate change in the alpine grassland.

以气候变暖，降水格局变化及大气氮沉降等为特征的全球变化，正在改变着草地生态系统结构与功能。目前，关于全球变化单因子及多因子间的交互作用对温室气体排放、土壤生物群落结构与组成影响的研究成为全球变化生态学研究的重要议题。但迄今为止，在气候变化敏感的青藏高原地区，有关模拟气候变化交互作用对高寒草甸温室气体排放及土壤生物群落特征及其相互关系影响的报道还较少。本研究以藏北地区高寒草甸为研究对象，通过增温、增雨和增氮及其交互模拟实验，研究气候变化对温室气体排放、土壤动物、微生物群落特征的影响，阐明气候变化背景下藏北高寒草甸温室气体排放、土壤动物、微生物群落结构与物种组成变化趋势及其影响因素，揭示高寒草甸温室气体排放与土壤生物群落特征对气候变化潜在的响应机理。本研究将从温室气体排放与土壤生物群落特征间关系的角度阐明气候变化对青藏高原温室气体排放的影响机理，也为高寒草地资源可持续利用和应对气候变化提供科学依据。

以气候变暖，降水增加以及氮沉降增加等为主要特征的气候变化，正在改变着藏北高原高寒草甸草地生态系统的结构与功能。本项目选择藏北典型高寒草甸开展模拟增温(W)、增雨(P)、增氮(N)及增温与增氮(WN)，增温与增雨(WP)，增雨与增氮(NP)耦合作用的实验，研究与分析不同处理下温室气体排放通量、土壤生物(线虫与微生物)群落组成、植物与土壤因子的变化规律及彼此间相互关系，揭示温室气体排放、线虫以及微生物群落对气候变化的响应特征及其响应因素。主要结论如下：⑴气候变化改变了土壤线虫群落组成，且其交互作用对其影响比单一因素的影响更为复杂。W处理显著降低了线虫密度(ND)，而显著提高了Fu数量和CI指数，N处理显著降低了Om数量而显著提高了PPI指数，P和NP处理显著增加了ND、Om数量、H指数、种类及MI和SI指数。P和NP处理通过增加BGB、SM和SOC而对提高土壤线虫群落多样性、稳定性及食物网复杂性。(2)不同处理通过影响BGB、SM和SOC、NO3-N而导致土壤细菌和真菌群落组成差异，但不同处理间其群落组成和多样性变化无规律性。(3)温室气体的排放通量受取样时间与实验处理的影响，且3种温室气体对不同处理的响应趋势也有差异。6月份NP与P处理通过提高土壤SM而导致土壤CO2 排放通量显著高于CK和W处理；7月与8月份，CO2 排放通量对各气候变化耦合作用的响应更为明显，NP和WN处理通过增加土壤SM、NH4-N、NO3-N含量、BGB及ND而显著促进CO2 排放通量，由此，W、P、N、NP、WN均显著影响其排放通量。就N2O而言，6月NP处理、7月NP和N处理和8月NP和WN处理均显著增加了N2O排放通量。P、N、NP和WP处理通过增加土壤温湿度、NO3-N含量、BGB和nirS和AOA基因数量直接或者间接促进土壤N2O排放，显著影响土壤N2O排放通量。就CH4而言，W和WN处理通过增加土壤TC和pmoA基因数量而促进土壤CH4 吸收，NP处理通过增加土壤SM和NH4-N含量而降低CH4吸收降低。在未来气候变化背景下，由于植物特征、土壤环境因子、土壤微生物和线虫群落组成的变化可能增加藏北高寒草甸CO2、N2O排放通量和增温潜势。