Effects Of Different Age Of Larix Plantations On Soil Aggregates Enzyme Activities And The Distribution Of Labile Organic Carbon In Black Soil Region

In order to explore the differences of enzyme activities between in homogenized soil and dry or wet-sieved aggregates and reveal the effects of vegetation restoration on hydrolase activities in soil aggregates and the distribution of labile organic carbon,the topsoil(0-20 cm)in typical black soil region with vegetation restoration of 14,23 and 50 year-old Larix plantations and the farm-land was studied by measuring,calculating and analyzing invertase,?-D-glucosidase,phosphatase activities and labile organic carbon in homogenized soil and dry or wet-sieved aggregates.The result showed that aggregates had obvious protective effects on soil enzymes because of homogenized soil enzyme activity was significantly lower than enzyme activities in aggregates(p<0.05).Vegetation restoration improved enzyme activities in homogenized soil and aggregates in various degrees,in which every particle in ?1.0mm size of dry-sieved and <0.25 mm wet-sieved aggregates and integrative index of soil enzyme activities had reached a significant level(p<0.05).The effect of vegetation restoration on enzyme activity was as follows: dry-sieved aggregates> homogenized soil > wet-sieved aggregates.So we can consider that the enzyme activities in ?1mm size aggregates could be used as a sensitive index that characterize the quality changes in habitat of black soil regions.The results provide a reference for scientifically evaluating the effects of vegetation construction on the ecological restoration of soil quality in black soil regions.The content distribution of labile organic carbon in homogenized soil and aggregates was low activity > medium activity > high activity.Vegetation restoration promoted the accumulation of low,medium and high active organic carbon in homogenized soil and aggregates in varying degrees,in which the increased range of high active-organic carbon was the most significant in homogenized soil and wet-sieved aggregates,and low active-organic carbon increased most in dry-sieved aggregates.During the first 14 years of vegetation restoration,vegetation restoration promoted the accumulation of labile organic carbon of aggregates which less than 1mm.With the increase of forest age,the content of labile organic carbon which less than 1mm was increased significantly.There was a significant positive correlation between the activities of invertase,?-D glucosidase and phosphatase activity in the dry or wet-sieved aggregates.The protective effect of soil aggregates on enzyme was affected by enzyme types.Both hydrolases in dry-sieved aggregates and labile organic carbon showed significant positive correlation,which indicated that the increase of enzyme activity in the dry-sieved aggregates could promote the accumulation of active organic carbon.The results provide a reference for scientifically evaluating the effects of vegetation construction on the ecological restoration of soil quality in black soil regions.