Effects Of Precipitation Change On Soil Microbial Community Of The Monsoon Evergreen Broad Leaved Forest In Dinghushan Biosphere Reserve

With the global climate changing,global rainfall patterns has changed obviously.The soil moisture has reduced,that impacting the forest soil carbon stock gradually,as the changes of the precipitation intensity and precipitation frequency in the south subtropical area.Soil microbial community structure is an effective indicator to reflect this change.In the paper,we take the soil of the south subtropical monsoon evergreen broad-leaved forest soil in Dinghushan Biosphere Reserve as research object.Experimental treatments are included of the constant precipitation but the times of precipitation increaseing,the amounts of precipitation reduced by 50%,and the normal precipitation as control group.We collected soil in different soil layers both 0¹0cm and 10²0cm.Soil microbial comminity structure was measured by the method of phospholipid fatty acid（PLFA）.Soil organic carbon mineralization rate was measured by the method of indoor culture.Than the changes of the soil microbal biomass,relative abundance and the soil organic carbon mineralization rate are analyzed by the precipitaion treaments.There are different characteristics of the soil physical and chemical properties.The soil pH is effected significantly between the rainy and dry season（P<0.05）,but others are not effected significantly（P>0.05）.In the layer 0²0cm,the soil moisture,soil organic carbon content,total nitrogen（N）and phosphorous（P）decrease as the soil layer deepens.The soil acidity weakens with the soil layer deepens.In the rainy and dry seasons,the two experimental treatments the times of precipitation increaseing and the amounts of precipitation reduced by 50%,increase the soil organic carbon content.It is not significantly affected the amount of soil microbial total PLFAs,bacteria PLFAs,fungi PLFAs,arbuscular mycorrhizal PLFAs of the same layer in the treatments.The actinomycetes PLFAs are affected not significantly in the rainy season but significantly in the dry season（P<0.05）.In the layer 0¹0cm,the actinomycetes PLFAs are reduced in a 50% reduction in precipitation treatment.This may be the reason that during the dry season,the soil organic carbon content and nitrogen inhibits the growth of actinomyces.In the rainy season,the soil microbial PLFAs are not significant difference with the dry season.At the same time,the treatment of 50% less can promote the growth of soil microbial in the rainy season.Relative abundance of arbuscular mycorrhizal fungi was not significantly affected under the precipitation process in the soil.But relative abundance of soil bacteria,gram-positive and gram-negative bacteria,fungi and actinomycetes are affected significantly in different level.The soil fungi and bacteria rate was not significant in the rainy season but significant in the dry season in the treatments.Soil organic carbon mineralization rate rises first but falls instabily after overall.The soil organic carbon mineralization cumulative rate tends to be linear.In the layer 0²0cm,the soil mineralization accumlative rate was 1000.04±166.87mgCO₂·kg^-1·h^-1 in the treatment of constant but times increasing.The soil mineralization accumlative rate was 967.26±97.60mgCO₂·kg^-1·h^-1 in the treatment of 50% less precipitation.The soil mineralization accumlative rate was 948.18±108.47mgCO₂·kg^-1·h^-1 in the control group.This indicates that the rate of the soil carbon emissions was improved by times increasing.