3种混交林造林初期土壤真菌群落结构特征

A comparative study on the soil fungal community structure across three mixed forests at the initial stage of afforestation

土壤微生物是参与陆地生态系统生物地球化学循环过程的重要成员。造林可以显著影响土壤微生物群落结构与功能,但造林初期驱动的土壤理化因子变化对土壤微生物结构与功能的影响尚不清楚。通过分析由珍稀乡土树种组成的三种新造混交林(BB:银杏Ginkgo biloba⁃桢楠Phoebe zhennan;CB:香椿Toona sinensis⁃红豆杉Taxus wallichiana⁃桢楠Phoebe zhennan;MB:鹅掌楸Liriodendron chinense⁃乐昌含笑Michelia chapensis⁃香椿Toona sinensis⁃玉兰Yulania denudata)表层(0—20 cm)土壤真菌群落组成、功能类群及其土壤理化因子,并以草灌化未造林地作对照(CK),研究土壤真菌群落结构和功能对不同林型造林初期的响应。结果表明:(1)不同林型土壤真菌群落丰富度、多样性指数高于CK,表现为MB>BB>CB>CK,主要受到土壤孔隙度、水解性氮的影响。(2)土壤真菌门水平优势类群在不同处理间无显著差异,其中子囊菌门占绝对优势,MB中的被孢霉门相对丰度显著高于CK(P<0.05)。与CK相比,球囊菌门与Leptodiscella相对丰度在各林型中均降低。(3)通过非度量多维尺度(NMDS)与置换多元方差(Adonis)分析表明,造林初期,造林土壤真菌群落结构与CK存在显著差异(P<0.01)。冗余分析(RDA)分析表明全钾、水解性氮、土壤容重及土壤碳氮比是影响真菌群落指示种的主要土壤理化因子;被孢霉门与水解性氮、碳氮比、全氮、非毛管孔隙度、含水率均呈正相关,与全钾呈负相关。(4)真菌群落主要以腐生营养型为主,病理营养型次之;造林后腐生营养型真菌相对丰度降低,而土壤腐生菌的相对丰度在BB与MB处理中反而显著增加(P<0.05);MB处理中动物病原菌的相对丰度显著增加(P<0.05);真菌优势功能类群主要受到土壤pH、土壤孔隙度、土壤碳氮比(C/N)、土壤有机质、全氮、全钾的影响。造林初期土壤真菌群落结构与功能类群发生了显著改变,阔阔混交林较针阔混交林变化更加明显,其中多种阔叶树混交林病原菌相对更高。

Soil microorganisms play an important role in biogeochemical cycles of terrestrial ecosystems.Afforestation significantly affected the structure and function of soil microbial community.However,the effects of variation of soil physical and chemical properties driven by afforestation in the initial stage on the structure and function of soil microorganisms remain unknown.In this study,we analyzed the soil fungal community composition and functional groups and soil physical and chemical properties of the surface layer(0—20 cm)in three newly mixed forests composed of precious native tree species(BB:Ginkgo biloba and Phoebe zhennan;CB:Toona sinensis and Taxus wallichiana and Phoebe zhennan;MB:Liriodendron chinense and Michelia chapensis and Yulania denudata and Toona sinensis),and compared them with an unforested land(CK),to explore the response of soil fungal community structure and function to the initial afforestation of three forest types.The results showed as follows:The richness and diversity index of soil fungal community in different forest types were higher than CK,showing MB>BB>CB>CK,which was mainly affected by soil porosity and available nitrogen(AN).There was no significant difference in the dominant groups of soil fungal community at phylum level among different treatments.Ascomycetes are predominant fungal group,and the relative abundance of Mortierellomycota in MB was significantly higher than that in CK(P<0.05).The relative abundance of Glomeromycota and Leptodiscella were lower in all forest types compared with CK.The results of NMDS and Adonis analysis showed that there were significant differences in soil fungal community structure between afforestation and CK(P<0.01).RDA analysis showed that the factors such as total potassium(TK),AN,soil bulk density(SBD)and carbon⁃to⁃nitrogen ratio(C/N)were the main factors affecting fungal community indicator species.Mortierellomycota were mainly positively correlated with AN,C/N,total nitrogen(TN),non⁃capillary porosity(NCP),soil water content(SWC),and mainly negatively correlation with TK.Saprotroph group was identified as the most dominate trophic group,followed by pathotroph.After afforestation,the relative abundance of Saprotroph decreased,while the relative abundance of soil saprotroph increased significantly in BB and MB(P<0.05).The relative abundance of animal pathogen significantly increased in MB(P<0.05).The dominant functional groups of fungi were mainly affected by soil pH,soil porosity,C/N,soil organic matter(SOM),TN and TK.The community structure and functional groups of soil fungi changed significantly in the early stage of afforestation,and the variation of broad⁃leaved mixed forest was more obvious than that of coniferous and broad⁃leaved mixed forest,and the pathogen was higher in a mixed broad⁃leaved forest consisted of more species than other forest type.