Effects Of Litter And Understory Vegetation On Soil Microbial Activity In Chinese Fir Plantation

Litter and understory vegetation are important components of forest ecosystem and play important roles in soil carbon and nutrient cycling in forest ecosystem.Researchers had conducted extensive studies on the effects of litter and understory vegetation on soil physical and chemical properties in the past years.However,the mechanism of litter and understory vegetation effects on soil microbial activity was unclear.In this paper,different litter and understory vegetation treatments were established in subtropical Chinese fir forest to study the effects of litter and understory vegetation on soil physical and chemical properties,microbial biomass,hydrolase activity and catalytic efficiency.Our purpose was to reveal the microbial mechanism of litter and understory vegetation effects on soil properties by analyzing the relationship between soil physical and chemical properties,microbial biomass and soil hydrolytic enzyme activity and kinetic parameters.We hoped that our findings would provide some recommendations for ecosystem management practices in Chinese fir forest.Main findings were as follows:?1?In the 2nd-year treatment,litter removal had a tendency to decrease the activities of?G,NAG and AP as well as pH and NH₄⁺-N content,although the effects were not significant?P>0.05?.And in the 3rd-year treatment,litter removal reduced the catalytic efficiency?K_a?of NAG,while it also reduced soil pH and DOC content?P<0.05?.?2?In the 2nd-year treatment,understory vegetation removal significantly reduced soil?G activity and DOC content?P<0.05?,and it also had a trend to reduce NAG activity,SMC,pH and NH₄⁺-N content?P>0.05?.Understory vegetation clipped but left on the floor was more beneficial to improve soil NAG and AP activities and DOC content than understory vegetation normal growth.In the 3rd-year treatment,understory vegetation removal decreased the K_a value of?G as well as the contents of DOC,SOC and NH₄⁺-N?P<0.05?.When compared with understory vegetation normal growth,Understory vegetation clipped but left on the floor was merely reduced soil pH value?P<0.05?.?3?In the 2nd-year treatment,the coexist of litter and understory vegetation was significantly enhanced the activities of soil?G,NAG and AP,while it also increased the soil pH value and improved the contents of soil DOC and NH₄⁺-N?P<0.05?.Litter and understory vegetation coexist increased the contents of soil bacteria,fungi,total PLFAs and improved the contents of DOC,POC,SOC,NH₄⁺-N simultaneously in the 3rd-year treatment?P<0.05?.?4?Soil hydrolytic enzyme activities showed obvious seasonal variation,and they were mainly affected by soil physical and chemical properties,i.e.,soil hydrolytic enzyme activities were positively correlated with SMC and DOC contents?P<0.05?.?5?The catalytic efficiency of soil hydrolytic enzymes was more affected by soil physical and chemical properties than microbial biomass.The K_a value of?G was positively correlated with ST,SMC,DOC and POC,bacteria?including G⁺and G^-?,fungi and total PLFAs contents;the K_a value of NAG was positively correlated with ST,SMC,POC,SOC,NH₄⁺-N,TN,bacteria?including G⁺and G^-?,fungi and total PLFAs contents;the K_a value of AP was positively correlated with ratio of F/B,and was negatively correlated with SMC,POC,SOC and TN contents.In conclusion,litter and understory vegetation were important sources of soil carbon and nitrogen in Chinese fir forest.Maintaining litter and understory vegetation biomass could improve soil nutrient status and microbial activity.Therefore,we proposed to keep litter and understory vegetation in forest management measures in order to maintain the soil quality and productivity of Chinese fir forest.