Spatial Pattern And Driving Factor Of Soil Fungal Communities In The Huoditang Region,qinling Mountains

As one of the important groups of biodiversity in forest ecosystems,soil fungi play an important role in their nutrient cycling and soil carbon storage.Previous studies showed that soil fungal community and diversity were significantly affected by elevation gradient and horizontal distance in subtropical forest.However,the altitudinal distribution pattern of soil fungal community and diversity(FUNguild functional fungi)and influencing factors remain unclear.The horizontal spatial patterns of soil fungal communities and their drivers in small regional scales of subtropical forest ecosystems remain poorly studied.As the boundary and transition zone of geography and climate between north and south of Qinling Mountains,which have diverse forest vegetation types and obvious vertical distribution characteristics.Therefore,a plot was set up in the Huoditang region in the southern Qinling Mountains to determine the vertical distribution of soil properties and fungal communities and diversity.The spatial heterogeneity of fungal community structure,diversity and functional fungal community was explored by combining traditional statistics(regression analysis and variance analysis,etc.),geostatistics and GIS spatial interpolation methods.Topographic factors,soil characteristics and vegetation characteristics(NDVI)were used to determine the environmental variables affecting fungal community and diversity.The main conclusions are as follows:1.The soil available potassium(AK)and soluble total salt contents(EC)decreased first and then increased along the elevation gradient in a U-shaped distribution pattern.In addition,elevation had a direct driving effect on soil total carbon(TC)and available phosphorus(AP)content,but had a significant indirect driving effect on soil AK and EC.Under the influence of different dominant tree species,soil moisture(SM),AP and p H were significantly different.The contents of TC,p H and EC were the highest in Quercus aliena var.acuteserrata forest,which might be related to the organic acids produced by litters.The contents of SOM and AP were the highest in Tsuga chinensis forest,while the contents of TN were the highest in Pinus armandii forest,which may be caused by the difficulty of decomposition and accumulation of litter in coniferous forest.Soil moisture(SM)was the highest in Betula forest,which may be related to internal fluid flow rate.2.Ascomycota and Basidiomycota were the dominant phylum in Huodtang area with the elevation gradients(1500～2300 m);The dominant classes-families were Agaricomycetes,Sordariomycetes,Archaeorhizomycete Agaricales,Archaeorhizomycetales,Archaeorhizomycetaceae,Sebacinaceae,Archaeorhizomyces and Sebacina.The relative abundance of Ascomycota decreased along the elevation gradient;The distribution of Mortierella was “U”-shaped along the elevation;Agaricomycetes appeared "bimodal" distribution pattern.Archaeorhizomycetes increased along the elevation gradient;Sebacinaceae and Thelephoraceae all showed "double peak" pattern distribution;Archaeorhizomyces showed an obvious upward trend along the elevation;Sebacina appeared a "bimodal" distribution.3.Soil p H,AP and EC were significant driving factors of fungal community structure at different elevations.The relative abundance of ectomycorrhizal fungi(Ec M)was the largest in the functional fungal community,the relative abundance of the whole functional fungi did not show a significant distribution pattern with the elevation.The dominant fungal genera had strong spatial heterogeneity.The α-diversity(Chao1 richness index and Observed＿species index)showed a “U”-shaped distribution pattern along the elevation gradient.However,βdiversity did not have obvious altitudinal differentiation.In addition,soil TN and ST were the most significant factors affecting α diversity.Soil p H,C/N ratio and AP were significant drivers of β diversity.The relative abundance of Ascomycota generally decreased and that of Basidiomycota generally increased with elevation in Q.aliena var.acuteserrata forest.In general,the changes of soil p H,SOC and AP contents with elevation indirectly changed the soil fungal community structure.The phyla Ascomycota and Basidiomycota and the classes Agaricomycetes and Archaeorhizomycetes dominated the fungal communities in the P.armandii forest soils.The relative abundance of Ec M fungi decreased with increasing elevation.The richness of fungal community decreased with the elevation.Overall,soil p H,SOM and AK showed significant influence on soil fungal community and functional fungi.4.In the horizontal direction,the dominant phyla and class of fungi had strong spatial dependence.Agaricales had the highest spatial dependence,and Agaricales,Archaeorhizomycetales,Russulales and Hypocreales had relatively similar spatial structures and had certain spatial dependence.Mortierellaceae,Trichocomaceae and Cordycipitaceae were spatially dependent.The best fitting model of Sebacina,Simplicillium and Inocybe was gaussian model with strong spatial variation.In terms of α-diversity,the average richness index(Chao 1)and Obesrved＿species index had large variation coefficients.In functional fungal communities,the spherical model was applied to all functional fungal communities except for AM fungi.5.The dominant fungi in Huoditang soil showed several different spatial distribution characteristics,and Ascomycota had the largest number of patches in the highest category.Among the dominant groups,Ascomycota,Sordariomycetes,Hypocreales,Cordycipitaceae and Aspergillus accounted for the largest patch area,respectively.The area of the lowest grade plaque categories were Pezizomycetes,Pezizales,Strophariaceae,and Hymenogaster.Functional fungi showed different spatial distribution patterns except for AM.The highest degree of fungal diversity occurred in two regions with high values and local sporadic distribution.The distribution of Chao1 richness index was similar to Observed＿species diversity index.The patch area of the highest abundance grade of Pielou＿e index was the largest,while the patch area of the lowest Shannon index was the largest.6.The dominant species community only had significant influence on the dominant fungi genus in Huoditang of Qinling Mountains.Ascomycota was the highest in soft broadwood forest,Basidiomycota abundance was the highest in Betula forest,and Mortierellomycota abundance was the highest in Pinus tabuliformis forest.The highest of Agaricomycetes was found in Betula forest,while the highest of Sordariomycetes was found in Q.aliena var.acuteserrata forest.Agaricales were the largest in Tsuga chinensis forest and the smallest in Pinus tabuliformis forest.Both Sebacinales and Archaeorhizomycetales were highest in Betula forest.The relative abundance of Sebacinaceae,Archaeorhizomycetaceae and Thelephoraceae reached the highest values in Betula forest.The average relative abundance of Ec M was the highest in Q.aliena var.acuteserrata forest.The relative abundance of Unclassified Saprophytes was the highest in softwood forest.The relative abundance of Animal Pathogens and Soil Saprophytes was the highest in Pinus armandii forest.The average relative abundance of Plant Pathogens was the highest in Q.aliena var.acuteserrata forest,and Saprophytes was the highest in Tsuga chinensis forest.Among the differential species,Mortierellomycota(class-genus)was the most representative differential species among different dominant species.7.Compared with topographic characteristics,soil properties were the main factors affecting the horizontal spatial distribution of fungal community structure in Huoditang area of Qinling Mountains.Among the soil properties,soil p H,EC,AP and SOM were four significant driving factors.Among topographic factors,elevation was a significant factor affecting the horizontal spatial distribution of fungal communities.In addition,AP,AK and aspect were the main factors affecting the spatial distribution of soil functional fungi community.The dominant species community only had a significant effect on the dominant fungal genus.