Effects Of Thinning On Soil Aggregate,Active Organic Carbon And Microorganism Of Larix Gmelinii Natural Forest

Larix gmelinii natural forest is an important part of ecosystem in Great Xing' an Mountain.The study about effects of thinning on soil aggregate,active organic carbon and microorganism plays a role in revealing the changes of soil after thinning.We select the natural Larix gmelinii forest of Great Xing'an Mountain with 3 thinning intensities(30%thinning intensity(T3),20%intensity thinning(T2),10%intensity thinning(T1)as research object,and investigate the soil aggregate,active organic carbon,microorganism and physical and chemical properties with different depths of soil(0-10 cm,10-20 cm,20-30 cm)after 4 years.Analyze the relationship among 3 thinning densities to reveal effects of thinning intensity on soil.The results showed:1.The agglomerates with greater than 5 mm on diameters decreased with the depth of soil layer increasing.The agglomerates with diameters of 2-5 mm increased with the depth of soil layer increasing.The agglomerates with diameters of 2-5 mm were tended to form aggregates with greater than 5 mm on diameter.The effect of thinning on soil aggregates stability mainly concentrated in 0-10 cm layer of soil,and there was obvious difference.Soil aggregates after dry sieving with greater than 5 mm on diameter accounted for 29.54%in soil on T3,and it significantly increased 6.54%than CK(P<0.05).Soil aggregates after wet sieving with greater than 5 mm on diameter accounted for 26.52%in soil on T3,and it significantly increased 7.59%than CK(P<0.05)and was better than other intensities.So water stability of soil aggregate on T3 was better than others.Stability of soil aggregates was better than others on T3.2.The content of soil water-soluble organic carbon and microbial biomass carbon decreased with increase of soil layer under different thinning intensities,but effect of thinning on active organic carbon of soil mainly concentrated in 0-10 cm layer of soil.The amount of active organic carbon in the soil can be increased by reasonable thinning.In this study,the content of soil water-soluble organic carbon in 0-10 cm layer was the highest after 30%thinning(T3),which significantly increased 64.97mg/kg,72.72mg/kg and 49.14mg/kg than T2,T1 and CK respectively(P<0.05).The content of microbial biomass carbon on T3 was 659.52mg/kg,which significantly increased 231.31mg/kg than CK(P<0.05),and it was also higher than other thinning intensities,but there was no obvious difference(P>0.05).There was no significant difference about carbon mineralization of average daily among different thinning intensities,but 30%thinning was higher than others at the beginning(30d).Therefore,the content of active organic carbon of soil was highest.3.Soil bacteria,fungi and actinomycetes decreased with the increase of soil layer under different thinning intensities(P<0.05).In this study,the content of soil bacteria and fungi on T3 was the highest(69.25 mol/g,4.58 mol/g),and the content of soil actinomycetes on T2 was higher than T3,but the difference was not significant(P>0.05).The content of Soil microorganism on T3 was the highest.In this study,content of soil aggregates,active organic carbon and microorganism showed that effect of different thinning intensities on soil 0-10 cm layer was significant.Aggregate stability,active organic carbon and microorganism of soil on T3 were the best,and the correlation among soil organic carbon,microbes and aggregates was best too.