Analysis Of Soil Mycological Causes Of Pinus Sylvestris Var.mongolica Plantation Degradation In Inner Mongolia

Pinus sylvestris var.mongolica is an important tree species for the construction of ’three north ’ protection forest in China.In recent years,in view of a series of degradation problems of Pinus sylvestris var.mongolica plantation,researchers have analyzed the causes of degradation through factors such as climate,water,nutrients,pests and diseases.However,the problem of Pinus sylvestris var.mongolica degradation has not been really solved,and there is a lack of research on revealing the causes from the perspective of soil fungi.In this study,the reasons for the degradation of Pinus sylvestris var.mongolica were explored from the perspective of soil mycology.The natural forests of Pinus sylvestris var.mongolica and plantations with different health levels in Inner Mongolia were taken as the research objects.Through metagenomic sequencing technology and FUNGuild database,the characteristics and differences of soil fungal community structure of different functional groups of Pinus sylvestris var.mongolica were studied.The effects of geographical factors and different stands on the soil fungal groups of Pinus sylvestris var.mongolica were found out,and the core soil fungi that played a key role in the degradation of Pinus sylvestris var.mongolica were found out,which provided a theoretical basis for improving the ecological stability of Pinus sylvestris var.mongolica plantations in Inner Mongolia.The main results are as follows :(1)A total of 841 fungal OTUs were identified from soil samples of Pinus sylvestris var.mongolica natural forest and plantation.The analysis of their nutritional types showed that the proportion of symbiotic nutritional fungi in natural forests was greater than that of pathological nutritional fungi.The proportion of pathotrophic fungi in plantations was greater than that of symbiotic fungi.(2)From the perspective of symbiotic nutrient fungi in forest soil,Ascomycota was the absolute dominant phylum in both natural forest and artificial forest soil,accounting for more than 60%.Suillus and Phialocephala were dominant genera,and the abundance of natural forest was higher than that of artificial forest,which was 9.6% and 18.5% higher,respectively.In the analysis of pathotrophic type,Beauveria was the most dominant genus of pathotrophic fungi in both forests and its abundance in natural forests was higher than that in plantations,with an abundance of 8.5%.In the analysis of α diversity,the richness of symbiotic nutritional fungi in natural forests was higher,and the richness of pathological nutritional fungi was lower.(3)There are differences in soil fungal community structure under healthy Pinus sylvestris var.mongolica plantations in different regions of Inner Mongolia from east to west.From the perspective of symbiotic nutritional fungi,Ascomycota and Mucormycota were the dominant phyla,and the relative abundance of Ascomycota gradually decreased.The relative abundance of Mucormycota showed a trend of decreasing first and then increasing.Phialocephala was the dominant genus in Hulun Buir area and Chifeng and Tongliao area,Rhizophagus,Suillus and Tuber were the dominant genera in Chifeng to Alxa area,and Rhizopogon was the dominant genus in Hohhot to Alxa area.From the perspective of pathotrophic fungi,Beauveria is the most dominant genus in Hulun Buir area,and its abundance shows a downward trend from Hulun Buir area to Chifeng area,and the abundance shows an upward trend from Hohhot to Alxa area.Metarhizium was the most dominant genus in Hohhot to Alashan,and the abundance showed a downward trend.(4)The soil fungal communities of Pinus sylvestris var.mongolica plantations with different health degrees in Alashan,Ordos and Hohhot were compared,and the following rules were obtained : With the decrease of the health degree of Pinus sylvestris var.mongolica,the abundance of Scytinium,Claroideoglomus and Geopora in symbiotic nutritional fungi decreased,and the abundance of Suillus increased gradually.The abundance of Metarhizium and Beauveria in animal pathogenic fungi showed a decreasing trend,while the abundance of Clonostachys,Bipolaris and Ilyonectria in plant pathogenic fungi showed an increasing trend.(5)The interaction network between ectomycorrhizal(ECM)fungi and dark septate endophytic(DSE)fungi of Pinus sylvestris var.mongolica in different regions of Inner Mongolia was analyzed.The results showed that the important soil fungi related to the health of Pinus sylvestris var.mongolica plantation were Phialocephala subalpina,Phialocephala helvetica,Capronia coronata,Rhizopogon salebrosus,Tuber calosporum,Capronia epimyces,Mollisia scopiformis,Suillus bovinus,Laccaria bicolor and Cenococcum geophilum.