Effects Of Plant Functional Group Removal On Soil Fungal And Nematode Communities In An Alpine Meadow On The Tibetan Plateau

Climate change and human activity cause rapid loss of plant diversity in alpine meadows on the Tibetan Plateau.Plant species loss in a local habitat was often non-random because not all plant functional groups were equally affected by these factors.Here we used a plant removal experiment to examine the effects of specific plant functional group on soil fungal and nematode communities.Five treatments are: no removal(CK),removal of both legumes and forbs(Graminoids),removal of both graminoids and forbs(Legumes),removal of both graminoids and legumes(Forbs),and removal all plant(None).We analyzed the impact of removing specific plant functional group on the structure and function of soil fungal and nematode communities,root properties and soil properties.The main results are as follows:(1)No effect of plant functional group removal on plant root properties(root carbon and nitrogen content,and root biomass)and the majority of soil properties(soil water content,the concentrations of total carbon,total nitrogen,carbon to nitrogen ratio,soil organic carbon,particulate organic carbon,mineral associated organic carbon,dissolved organic carbon,ammonium nitrogen,and nitrate nitrogen)were noted after three years.The plant root biomass was lowest in None,but the decrease was not significant.The content of soil organic carbon was 60.6-67.8 g/kg in all treatments.The value of carbon stability index significantly was higher in Legumes and None than that of in CK.It suggests that the stability of soil carbon pool increased.(2)Three phyla,Ascomycota,Mortierellomycota,and Basidiomycota,were the most abundant,representing more than 90% of the relative abundance in different treatments.There was no significant variation in the Alpha-diversity and composition of soil fungal community in different treatments.At the phylum level,the relative abundance of Glomeromycota was significantly higher in Forbs,whereas the relative abundance of Glomeromycota and Zoopagomycota were higher in Legumes.At the class level,the relative abundance of Sordariomycetes was higher in None than in others treatments.At the order level,the relative abundance of the Sordariales was higher in CK than in others treatments.The soil fungal richness index was negatively affected by the increase in root biomass,root C/N,and dissolved organic carbon.(3)In total,7775 nematodes belonged to 59 genera were extracted from the 25 samples with an average density of 570/100 g dry soil.The structure of soil nematode community varied,while the density of each trophic group had no significant variation in different treatments.Legumes was beneficial to bacterivores density,while Forbs were beneficial to the density of fungivores and plant parasites.Lower evenness index and higher dominance index were observed in Forbs.The community structure of freeliving nematode was strongly disturbed in Forbs.The structure and ecological indices(the Alpha-diversity index,the maturity index,the enrichment index,the structural index,the channel index,nematode channel ratio)of soil nematode community were not significantly different between CK and None,indicating that the proportion of plant functional groups had a greater impact than its biomass on soil nematode community structure.The correlation analysis showed that the density of bacterivores was positively correlated with the ratio of carbon to nitrogen in roots.The density of fungivores was positively correlated with root biomass,negatively correlated with carbon stability index and nitrate nitrogen.The density of plant parasites was positively correlated with soil water content.Nematode channel ratio was positively correlated with root total carbon.Overall,most soil properties did not show significant changes,while root properties have a significant impact on soil fungal and nematode communities.This study revealed whether and how specific plant functional group affected the composition,structure and function of soil fungal and nematode communities.Our results establish regional reference for the future consequences of plant diversity loss and sustainable use of grassland resources in alpine meadows on the Tibetan Plateau.