Warming and increased precipitation alter soil carbon cycling in a temperate desert steppe of Inner Mongolia

增温增雨调控内蒙古荒漠草原土壤碳循环的机制

Warming and precipitation are key global change factors driving soil carbon(C)dynamics in terrestrial ecosystems.However,the effects of warming and altered precipitation on soil microbial diversity and functional genes involved in soil C cycling remain largely unknown.We investigated the effects of warming and increased precipitation on soil C cycling in a temperate desert steppe of Inner Mongolia using metagenomic sequencing.We found that warming reduced plant richness,Shannon-Wiener and Simpson index.In contrast,increased precipitation signifcantly infuenced Shannon-Wiener and Simpson index.Warming reduced soil microbial species by 5.4%while increased precipitation and warming combined with increased precipitation led to increases in soil microbial species by 23.3%and 2.7%,respectively.The relative abundance of Proteobacteria,which involve C cycling genes,was signifcantly increased by warming and increased precipitation.Warming signifcantly reduced the abundance of GAPDH(Calvin cycle)and celF(cellulose degradation)while it enhanced the abundance of glxR(lignin degradation).Increased precipitation signifcantly enhanced the abundance of pgk(Calvin cycle),coxL(carbon monoxide oxidation),malZ(starch degradation),and mttB(methane production).Moreover,a wide range of correlations among soil properties and C cycling functional genes was detected,suggesting the synergistic and/or antagonistic relationships under scenario of global change.These results may suggest that warming is benefcial to soil C storage while increased precipitation negatively affects soil C sequestration.These fndings provide a new perspective for understanding the response of microbial communities to warming and increased precipitation in the temperate desert steppe.

增温和降水是驱动陆地生态系统土壤碳循环的关键因素,但是增温和降水改变对土壤碳循环过程中微生物多样性和功能基因的影响并不十分清楚。因此,本研究利用宏基因组测序技术,研究了增温和增雨对内蒙古温带荒漠草原土壤碳循环的影响。研究结果表明,增温降低植物丰富度、Shannon Wiener指数和Simpson指数,增雨显著影响Shannon Wiener和Simpson指数。增温减少5.4%土壤微生物种类,增雨增加23.3%土壤微生物种类,二者交互增加2.7%土壤微生物种类。增温增雨显著增加碳循环相关的变形杆菌属基因的相对丰度。增温显著降低卡尔文循环相关基因GAPDH和纤维素降解基因celF的丰度,提高木质素降解基因glxR的丰度。增雨显著提高卡尔文循环基因pgk、一氧化碳氧化基因coxL、淀粉降解基因malZ和甲烷产生基因mttB的丰度。而且,土壤性质和碳循环功能基因之间均存在显著相关性,表明全球变化背景下二者具有协同或拮抗关系。以上结果表明,增温有利于土壤碳的固定,而增雨则降低碳的固定。本研究结果为温带荒漠草原微生物群落对增温增雨的响应提供了理论支撑。