Response Of Active Organic Carbon And Enzyme Activities To Density Adjustment In Rhizosphere And Non-rhizosphere Soil Of Larix Principis-rupprechtii Plantation

The effects of thinning on active organic carbon and related soil enzyme activities were investigated in a 38-year-old Larix principis-rupprechtii plantation in Taiyue Mountain.According to different thinning intensities,four treatments were set up: control(0%),low thinning(15%),moderate thinning(35%),heavy thinning(50%).The differences of active organic carbon contents and enzyme activities under different thinning intensities and their changing rules were discussed.The correlation between organic carbon content and various enzymes revealed the effect of thinning on soil carbon cycle and nutrient transformation.The results showed that:(1)Thinning affected the basic physical and chemical properties of rhizosphere and nonrhizosphere soil of Larix principis-rupprechtii plantation.The basic physical and chemical properties of rhizosphere and non-rhizosphere soil under moderate and heavy thinning were the best.(2)Thinning increased the contents of active organic carbon in rhizosphere and non-rhizosphere soil,and the contents of active organic carbon in rhizosphere and non-rhizosphere soil were the highest in moderate thinning forest.The contents of readily oxidized carbon,microbial biomass carbon and dissolved organic carbon increased by 30.77% and 49.57%,272.04% and 117.25%,37.15% and 31.29% respectively in rhizosphere and non-rhizosphere soil.The content of active organic carbon in rhizosphere soil was higher than that in non-rhizosphere soil.(3)Thinning had a significant effect on soil enzyme activities in rhizosphere and non-rhizosphere of Larix principis-rupprechtii plantation.In rhizosphere and non-rhizosphere soil,the activities of cellulase and peroxidase were the highest under moderate thinning,the enzyme activities in rhizosphere and non-rhizosphere soil increased by 687.5% and 150%,42.86% and 50%,respectively;sucrase was the highest under heavy thinning and phenol oxidase was the highest under low thinning,the enzyme activities in rhizosphere and non-rhizosphere soil increased by 36.19% and 26%,143.41% and 76.27%.(4)Thinning affected the enrichment of rhizosphere soil to a certain extent.The nutrient enrichment rate of rhizosphere soil had a higher effect on enzyme activity and active organic carbon accumulation.(5)Thinning affected the correlation between active organic carbon and enzyme activity in rhizosphere and non-rhizosphere soil.In rhizosphere soil,the main nutrient affecting the activity of organic carbon was total nitrogen,and the enzymes were sucrase and peroxidase.In non-rhizosphere soil,the main nutrients affecting the activity of organic carbon were total nitrogen and phosphorus,and the enzymes were sucrase and peroxidase.