Spatial And Seasonal Dynamics Of The Structure And Diversity Of Soil Fauna Communities On The Eastern Slope Of Gongga Mount

Soil fauna play an important role in soil organic matter decomposition and nutrientcycling, improving soil structure, and soil quality and plant succession. On the other hand,they are extremely sensitive to the changes of environmental factors. Soil fauna can beaffected by the changes in temperature, precipitation and vegetation. Gongga Mount, thethird highest mountain in China with an altitude up to7556m, is located in the middle ofHengduan Mountains. In this region, temperature decreases about0.43℃and precipitationincreases about68mm with an100m increasing in elevation. The different vegetationtypes distributed on Gongga Mountain accompanied with elevations, temperature,precipitation, and other environmental factors. At present, No investigations has beenconducted on vertical distributions of soil fauna in this area. Therefore, this study aimed to:1) examining the vertical distributions of soil fauna communities on Gongga Mount;2)revealing the determined factors for the vertical distributions of soil fauna communities.Four vegetation types, including evergreen broad-leaved Forest (EBF), deciduousbroad-leaved forest (DBF), coniferous and broad-leaved mixed forest (CBF) and darkconiferous forest (DCF), were selected on the eastern slope of Gongga Mount along theelevation, and the invetigations had been conducted on soil fauna in March, May, July,October, and December,2012. A total of558individuals of soil macrofauna were captched,which belonged to10classes,29orders,66families and75taxonomic groups. TheSpirobolus、Lumbricus、Orsiboe and other24groups were the dominant groups, accountingfor81.22%of the total individuals of soil macrofauna. Total8581individuals of soilmeso-microfauna, belonging to8classes,28orders,120families and149taxonomicgroups, were extracted, and the dominant and common groups included Paranurophorus,Paranura, Belba and other20taxonomic groups, accounted for77.19%of the totalindividuals. There were57846individuals of soil nematode extracted from soil samples,which classified into2classes,8orders,43families and109taxonomic groups. thedominant groups were Dorylaimus, Prodorylaimus, Chrysonema and other22taxonomicgroups, accounting for86.99%of the total. These groups are the principal component ofsoil fauna in the east slope of Gongga Mount. The diversity index of soil macrofauna, meso-microfauna and soil nematode showedthe similar tendency under four vegetations, which was EBF> DBF> CBF> DCF. Thatmeans the diversity index of soil fauna significantly reducing with increasing elevation,and the density of soil macrofauna and meso-microfauna also decreased, while the soilnematode’s density increased with the elevation increasing. The S rensen andMorisita-Horn similarity index showed that the similarities were low for soil macrofaunacommunities among different vegetation types, but high for the soil meso-microfauna andnematode communities. The similarities of soil macrofauna, meso-microfauna andnematode community among different months were also low.The functional groups of soil macrofauna were detritivore, predator, omnivore andherbivore, the biomass of detrivorous accounted for57.11%of total biomass and was themain functional groups of soil macrofauna. The functional groups of soil meso-microfaunawere omnivores, herbivore, predator, dertritivore and fungivores, the the density ofomnivores accounted for41.83%of the total density, and was the main functional groupsof soil meso-microfauna. The functional groups of soil nematodes were predacious,bacterial feeding, hyphal feeding and plant feeding, the density of predacious accounted for76.87%of the total density, and was the main functional groups of soil nematodes. Theproportion of each functional group varied in four different vegetation types, but they havesimilar seasonal variation. Therefore, the vegetation type has greater influence on thestructure of functional group than the seasonal variation.The Shannon-Wiener index, Pielou index, Richness and density of soil macrofaunawere significantly negatively correlated with elevation, but positively correlation with thesoil pH and soil temperature. The Shannon-Wiener index, Richness and density ofmeso-microfauna were significantly positively correlated with the content of soil totalphosphorus, but negatively correlated with the available phosphorus. The Shannon-Wienerindex, Pielou index, Richness and density of soil nematode were significantly andpositively correlated with elevation. The influence of environment factors varied betweendifferent soil fauna groups and the biggest impact factors to the soil fauna is soil pH andthe content of soil phosphorus.The results showed that soil fauna communities were abundant in the eastern slopeGongga Mount and the community structure and diversity varied along the elevation. But there were different tendencies among soil macrofauna, meso-microfauna and nematodes,and among different function groups. The results also indicated that the content of soilphosphorus, pH and elevation were the main factor that impact the variation of thecommunity structure, diversity and the functional groups.