Diversity And Community Structure Of Ectomyrorrhizal Fungi Associated With Larix Chinensis In Taibai Mountain

The alpine timberline region in Taibai Mountain has an ecological transition zone from the forest stand to the alpine krummholz.Larix chinensis was only constructive tree species in the timberline ecotone,which could form typical mutualistic symbioses with ectomycorrhizal(ECM)fungi.With ecological methods and modern molecular biology methods,we investigate the ectomycorrizal(ECM)fungal community in the alpine timberline ecotone where was divided into five zones(Treeline zone,Timberline zone,Pure forest stand,Mixed forest stand and Upside down forest stand).This study aims to provide knowledge about the ECM community in the extreme conditions of the alpine treeline ecotone and to assess the importance of ECM fungi supporting the survival of trees growing in harsh growing conditions.In addition,by analyzing the major environmental factors explaining the changes of ECM community,we could assess the important driving factors of the ECM community change.The main results of the research are as follows:A total of 60 ECM species associated with L.chinensis were detected in the study,which belonged to 22 genus and 17 families.Most of ECM speices belonged to Basidiomycetes(78.3%)and Ascomycetes(8.3%).Tomentella?Sebacina?Inocybe?Heyderi and Lactarius were the dominant genera in the ECM communities.The biodiversity indexes for the ECM communities in treeline zone and timberline zone were higher than the closed forest stands.The indicator species analysis showed that the treeline zone had the most indicator species.The Venn diagram showed that the longer the distance is between two zones,the fewer species the share.With clustering analyses,the ECM communities associated with L.chinensis showed significant variation between the no-closed forest stands and closed forest stands.In the treeline and timberline zones,the dominant genus were Sebacina,Inocybe and Heyderia,while Heyderia,Lactariu and Russula were the dominant genus in closed forest stands.With Matastats analyses,we found that the relative abundances of Sebacina,Heyderia and Tomentella were significantly different among five zones.This illustrated that the variations of ECM communities were due to the distributions of the main genera.However,the change of ECM community structure was the gradient type,which present the adjacent zones had some same genera.The richness of ECM fungi showed significantly correlated with the elevation and soil organic matter,and the infection rate of ECM fungi was significantly correlated with the soil pH and total phosphorus.At the species level,only the occurrences of Clavulina sp.1 and Heydeira sp.were showed a strong correlation with the various environmental factors.And Inocybe sp.1 was olny related with soil pH,while Thelephora caryophyllea was only related with the soil nitrogen.At the genus level,the occurrences of Heyderia and Bisporella showed significantly relationship with the environmental factors.The structure of ECM communities associated with L.chinensis were influenced by the site,elevation,soil pH,soil organic carbon and soil total nitrogen.With varpart analyses,the site was the main influence among the environmental factors.In addition,the cross explanatory variable was the highest value.Therefore,we summarize that the change in the ECM community structure could be ascribed climatic factors,soil factors and geographical factors in the alpine treeline ecotone.