半灌木扩张草原土壤细菌群落特征及其影响因素

Characteristics and Influencing Factors of Soil Bacterial Communities in Subshrub Encroachment Grasslands

半灌木扩张频繁发生在干旱半干旱草地中,显著改变了地上/地下过程。然而,黄土高原半灌木扩张过程对土壤微生物群落的影响尚不清楚。因此,本文研究了不同半灌木(白莲蒿Artemisia sacroorum)扩张强度(轻度、中度和重度)草地的土壤性质和细菌群落变化及其相互关系。结果表明,中度和重度半灌木扩张草地具有沃岛效应,即中度和重度半灌木扩张显著提高了土壤有机碳、全氮、碱解氮、全磷、有效磷和土壤水分含量(P<0.01)。半灌木扩张改变土壤细菌群落组成(OTUs水平),重度半灌木扩张显著增加土壤细菌群落α-多样性(P<0.01),Shannon,Chao1和ACE指数分别增加1.47%~1.80%,4.62%~6.77%和4.39%~6.82%。相关分析结果表明,土壤细菌优势门相对丰度和细菌群落多样性与土壤性质显著相关。冗余分析进一步表明,土壤碱解氮、全氮、水分、有机碳和全磷含量是影响土壤细菌群落组成的关键因子,对土壤群落组成差异的解释方差为39.04%。总体而言,本研究结果提高了我们对黄土高原半灌木扩张影响下土壤细菌群落变化过程的认识。

Subshrub encroachment occurs frequently in arid and semi-arid grasslands,and significantly alters the above and belowground processes.However,the effects of the subshrub encroachment process on soil microbial communities are poorly understood on the Loess Plateau.Therefore,we assessed the changes in soil properties and bacterial communities,and their association in grasslands subjected to different subshrub(Artemisia sacrorum)encroachment intensities(light,moderate,and heavy).Our results showed that moderate and heavy subshrub encroachment grasslands had fertile-island effect,that was,moderate and heavy subshrub encroachment significantly increased soil organic carbon,total nitrogen,alkali-hydrolyzed nitrogen,total phosphorus,available phosphorus and soil water content(P<0.01).Subshrub encroachment altered the composition of soil bacterial communities(OTUs level),and heavy subshrub encroachment significantly increased theα-diversity of soil bacterial communities(P<0.01)and Shannon,Chao1 and ACE indices increased by 1.47%~1.80%,4.62%~6.77%and 4.39%~6.82%,respectively.The results of correlation analysis showed that the relative abundance of soil bacterial dominance phylum and diversity were significantly correlated with soil properties.Redundancy analysis further showed that the contents of soil alkali-hydrolytic nitrogen,total nitrogen,water,organic carbon and total phosphorus were the key factors affecting the composition of soil bacterial community,and the explanatory variance of soil bacterial community composition difference was 39.04%.Overall,the results of this study improved our understanding of the processes underlying the alterations in the soil bacterial community by subshrub encroachment in Loess Plateau.