间伐初期马尾松根际细菌群落物种多样性的季节动态及驱动因子

Seasonal dynamics of species diversity of the bacterial community in Pinus massoniana rhizosphere and its driving factors in the early thinning stage

根际细菌在促进植物生长、对非生物胁迫耐受性以及抗病性方面发挥着重要作用,但间伐对马尾松(Pinus massoniana)根际细菌群落影响的研究尚未见报道.以川东低山区马尾松人工近熟林为研究对象,对不同强度间伐(0、10%、30%、50%)两年半后马尾松根际细菌群落组成和多样性季节动态进行研究.结果表明:变形菌门(Proteobacteria)、放线菌门(Actinobacteria)和酸杆菌门(Acidobacteria)是各处理中相对丰度前三大门,平均相对丰度分别为61.94%±17.30%、9.52%±11.07%和6.09%±4.09%,间伐强度的增大可以提高根际中变形菌门细菌的相对丰度,降低放线菌门、酸杆菌门细菌的相对丰度;根际细菌群落α多样性指数在夏季表现出谷值,间伐强度对根际细菌群落α多样性和NMDS结构空间排序没有显著影响;RDA分析结果表明土壤有机碳(SOC)、季节(SE)和pH是影响马尾松根际细菌群落结构的前三大环境变量,决定系数分别为0.348、0.317、0.266.综上所述,间伐初期间伐强度能改变富/贫营养型菌群丰度的相对比例,但不能显著影响群落整体结构,季节仍然是决定群落结构的关键因素.本研究阐明了间伐对根际细菌群落组装的初期作用,对川东低山区马尾松人工林功能恢复和保护具有现实意义.

Rhizosphere bacteria play an important role in promoting growth,abiotic stress tolerance,and disease resistance in plants.However,research on the effects of thinning on the bacterial community in the rhizosphere of Pinus massoniana is lacking.This study aimed to investigate the initial responses of microbial community composition and diversity in the rhizosphere of P.massoniana to tree thinning.An artificial,near-mature P.massoniana forest in the low mountainous area of eastern Sichuan was used as the study object.The seasonal dynamics of bacterial community composition and diversity in the P.massoniana rhizosphere were studied after two and a half years of thinning at different intensities(0,10%,30%,and 50%).The results of the analysis indicated that Proteobacteria,Actinobacteria,and Acidobacteria were the most abundant phyla in each treatment,with average relative abundances of 61.94%±17.30%,9.52%±11.07%,and 6.09%±4.09%respectively.An increase in thinning intensity increased the relative abundance of Proteobacteria and reduced the relative abundance of Actinobacteria and Acidobacteria in the rhizosphere.Theαdiversity index values of rhizosphere bacterial communities were lowest in summer,and the thinning intensity had no significant effect on theαorβdiversity of the bacterial communities in the rhizosphere.The results of redundancy analysis suggested that soil organic carbon,season,and pH were the top three environmental variables affecting the bacterial community structure in the rhizosphere of P.massoniana,with coefficients of determination of 0.348,0.317,and 0.266,respectively.Therefore,thinning intensity can change the relative proportions of the abundance of eutrophic/oligotrophic flora but does not significantly affect the community structure in the early stage of thinning.Season remains a key factor in determining bacterial community structure.This study clarified the initial effects of tree thinning on bacterial community assembly in the rhizosphere,which has practical value for the functional restoration and protection of P.massoniana plantations in the low mountainous areas of Eastern Sichuan.