PDF(Pubmed)
Abstract：
Drought and nitrogen deposition are two major climate challenges, which can change the soil microbial community composition and ecological strategy and affect soil heterotrophic respiration (Rh). However, the combined effects of microbial community composition, microbial life strategies, and extracellular enzymes on the dynamics of Rh under drought and nitrogen deposition conditions remain unclear. Here, we experimented with an alpine swamp meadow to simulate drought (50% reduction in precipitation) and multilevel addition of nitrogen to determine the interactive effects of microbial community composition, microbial life strategy, and extracellular enzymes on Rh. The results showed that drought significantly reduced the seasonal mean Rh by 40.07%, and increased the Rh to soil respiration ratio by 22.04%. Drought significantly altered microbial community composition. The ratio of K- to r-selected bacteria (BK:r) and fungi (FK:r) increased by 20 and 91.43%, respectively. Drought increased hydrolase activities but decreased oxidase activities. However, adding N had no significant effect on microbial community composition, BK:r, FK:r, extracellular enzymes, or Rh. A structural equation model showed that the effects of drought and adding nitrogen via microbial community composition, microbial life strategy, and extracellular enzymes explained 84% of the variation in Rh. Oxidase activities decreased with BK:r, but increased with FK:r. Our findings show that drought decreased Rh primarily by inhibiting oxidase activities, which is induced by bacterial shifts from the r-strategy to the K-strategy. Our results highlight that the indirect regulation of drought on the carbon cycle through the dynamic of bacterial and fungal life history strategy should be considered for a better understanding of how terrestrial ecosystems respond to future climate change.
摘要：
干旱和氮沉降是两大气候挑战,改变土壤微生物群落组成和生态策略,影响土壤异养呼吸(Rh)。然而,微生物群落组成的综合影响，微生物生命策略，干旱和氮沉降条件下Rh的动态和胞外酶尚不清楚。这里,我们用高山沼泽草甸进行了模拟干旱（降水量减少50％）和多级添加氮的实验，以确定微生物群落组成的相互作用。微生物生命策略,和Rh上的胞外酶。结果表明，干旱显著降低了季节平均Rh40.07%，Rh与土壤呼吸比增加了22.04%。干旱显著改变了微生物群落组成。K-与r-选择的细菌（BK：r）和真菌（FK：r）的比例分别增加了20和91.43％，分别。干旱增加了水解酶活性，但降低了氧化酶活性。然而,添加N对微生物群落组成无显著影响,BK:r,FK:r,胞外酶，或Rh。结构方程模型表明,干旱和添加氮通过微生物群落组成,微生物生命策略,和胞外酶解释了Rh变异的84％。氧化酶活性随BK：r，但随着FK:r增加。我们的发现表明，干旱主要通过抑制氧化酶活性来降低Rh，这是由细菌从r策略转变为K策略引起的。我们的结果强调，应考虑通过细菌和真菌生活史策略的动态来间接调节干旱对碳循环的影响，以便更好地了解陆地生态系统如何应对未来的气候变化。
