Predominant role of water in regulating soil and microbial respiration and their responses to climate change in a semiarid grassland
Predominant role of water in regulating soil and microbial respiration and their responses to climate change in a semiarid grassland
复制标题
半干旱草原水在调节土壤和微生物呼吸中的主导作用及其对气候变化的响应
DOI：
10.1111/j.1365-2486.2008.01728.x
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发表时间：
2009-01-01
影响因子：
11.6
通讯作者：
Wan, Shiqiang
中科院分区：
文献类型：
--
作者：
Liu, Weixing;Zhang, Zhe;Wan, Shiqiang
气候变化会深刻影响陆地生态系统的碳（C）循环。自2005年4月起，在中国北方的一个半干旱温带草原进行了一项田间实验，以研究土壤总呼吸、微生物呼吸以及微生物生物量对实验增温和降水增加的响应。我们在生长季节每月测量两次土壤呼吸，在2005年至2007年的生长季中期每年测量一次土壤微生物生物量碳（MBC）和氮（MBN）以及微生物呼吸（MR）。结果表明，土壤呼吸、微生物呼吸和微生物生物量的年际变化与降水的年际波动呈正相关。通过土壤水分梯度的实验室培养表明，低土壤水分含量限制了微生物呼吸对温度的响应。在这3年中，实验增温降低了土壤水分，进而导致土壤总呼吸、微生物呼吸以及微生物生物量显著减少，这表明增温引起的水分胁迫产生的负向间接影响比温度升高的正向直接影响更强。实验增温下蒸散量增加可能使土壤水分可利用性降低到胁迫阈值以下，从而抑制植物生长、根系和微生物活动。降水增加显著刺激了土壤总呼吸和微生物呼吸以及所有其他微生物参数，并且降水的积极影响随时间增强。我们的研究结果表明，在半干旱温带草原，土壤水分可利用性在调节土壤和微生物呼吸过程、微生物生物量及其对气候变化的响应方面比温度更为重要。实验增温导致土壤呼吸的减少量大于生态系统总生产力（GEP）的减少量。相反，降水增加对生态系统总生产力的刺激作用大于对土壤呼吸的刺激作用。我们的观察结果表明，气候变暖可能导致净碳损失，而降水增加可能导致半干旱温带草原的净碳增加。我们的研究结果强调，除非降水同时增加，否则中国北方干旱和半干旱地区的温带草原在气候变暖的情况下可能会成为一个净碳源。
Climate change can profoundly impact carbon (C) cycling of terrestrial ecosystems. A field experiment was conducted to examine responses of total soil and microbial respiration, and microbial biomass to experimental warming and increased precipitation in a semiarid temperate steppe in northern China since April 2005. We measured soil respiration twice a month over the growing seasons, soil microbial biomass C (MBC) and N (MBN), microbial respiration (MR) once a year in the middle growing season from 2005 to 2007. The results showed that interannual variations in soil respiration, MR, and microbial biomass were positively related to interannual fluctuations in precipitation. Laboratory incubation with a soil moisture gradient revealed a constraint of the temperature responses of MR by low soil moisture contents. Across the 3 years, experimental warming decreased soil moisture, and consequently caused significant reductions in total and microbial respiration, and microbial biomass, suggesting stronger negatively indirect effects through warming-induced water stress than the positively direct effects of elevated temperature. Increased evapotranspiration under experimental warming could have reduced soil water availability below a stress threshold, thus leading to suppression of plant growth, root and microbial activities. Increased precipitation significantly stimulated total soil and microbial respiration and all other microbial parameters and the positive precipitation effects increased over time. Our results suggest that soil water availability is more important than temperature in regulating soil and microbial respiratory processes, microbial biomass and their responses to climate change in the semiarid temperate steppe. Experimental warming caused greater reductions in soil respiration than in gross ecosystem productivity (GEP). In contrast, increased precipitation stimulated GEP more than soil respiration. Our observations suggest that climate warming may cause net C losses, whereas increased precipitation may lead to net C gains in the semiarid temperate steppe. Our findings highlight that unless there is concurrent increase in precipitation, the temperate steppe in the arid and semiarid regions of northern China may act as a net C source under climate warming.