Effects Of Exogenous Carbon On Particulate Organic Carbon And Enzyme Activities

In this research,the study objects were natural forest(Altingia gracilipes),secondary forests(Castanopsis carlesii),plantation(Cunninghamia lanceolata)and orchard(Citrus orchard),all of which had the same background conditions in the subtropical region.Soil samples were collected from the soils under vegetations of Altingia gracilipes forest,Castanopsis carlesii forest,Cunninghamia lanceolata forest,and Citrus orchard,respectively.Based on a soil incubate experiment which joined the 13C labeled fir sample and screening experiment,light fraction organic matter(LF)which included in 2000-250LF and 250-53LF,occluded particulate organic carbon which included in coarse particulate organic carbon in 2000-250?m(250c),fine particulate organic carbon in 2000-250?m(250f)and fine particulate organic carbon in 250-53?m(53f),mineral-associated organic carbon(mSOC)could be obtained.The quality percentage,the soil organic carbon(SOC)values,?13C values of soil and different particle sizes and urease,polyphenol oxidase(PPO)were estimated.Then those values were used to study the effects of different land use on the distribution of SOC among different particle sizes,the characteristics of soil enzyme.renewal andturnover of SOC,and further to study its dynamic change under organic matter input in soil.Eventually,the effects of different land use on different particle sizes soil and enzyme activities were revealed.The results showed that:1.After incubating 90 days,the quality percentage of soil which was input in residual existed significant differences among different particle sizes,presented that mSOC>250c>53f>250f>LF.It existed differences among different land uses:in LF,it showed that C.carlesii>A.gracilipes>C.lanceolata>C.orchard;in 250c,it showed that A.gracilipes>C.lanceolata>C.carlesii>C.orchard;in 250f,C.lanceolata and A.gracilipes were bigger,C.orchard and C.carlesii were smaller;in 53f,A.gracilipes was biggest,C.lanceolata was smallest,C.orchard and C.carlesii were in the middle;in mSOC,it showed that C.orchard>C.lanceolata>C.carlesii>A.gracilipes.In the same particle size,it existed significant differences after inputting different quantity residual(CK,0.2%leaf,1.2%leaf)in soil.In LF,showed that 1.2%leaf>CK>0.2%leaf.In 250c and 250f,the quality percentage reduced significantly,but had no relationship with the quantity of residual.In 53f and mSOC,it increased significantly,but had no relationship with the quantity of residual.In the same particle size,it existed significant differences after inputting different quality residual(CK,leaf,root)in soil.In LF and mSOC the quality percentage increased significantly,and the increasing degrees showed root>leaf.In 250c and 250f,it significant decreased,and the decreasing degrees showed root>leaf.In 53f,it significant increased after inputting in leaf,but it significant decreased after inputting in root.2.After incubating 90 days,the organic carbon content of soil which was input in residual existed significant differences among different particle sizes,presented that mSOC>LF>53f>250c>250f.It existed significant differences among different land uses in the same particle sizes:in LF and53f,it presented that A.gracilipes>C.carlesii>C.lanceolata>C.orchard;in 250c and mSOC,it presented that A.gracilipes>C.lanceolata>C.carlesii>C.orchard;in 250f,it presented C.lanceolata>A.gracilipes>C.carlesii>C.orchard.With the increase of the residual quantity,the content of organic carbon was increasing.After inputting in 0.2%leaf,the carbon content of LF decreased,however after inputting in 1.2%leaf,the content increased.Overall,along with the residual increase,the carbon content of 250c,250f significant decreased,and decreasing degrees showed 0.2%leaf>1.2%leaf;the carbon content of 53f significant increased,and increasing degrees showed 1.2%leaf>0.2%leaf;the carbon content of mSOC increased,but had no relationship with the quantity of residual.After inputting different quality residual(CK,leaf,root)in soil,the content of organic carbon increased,and increasing degrees showed root>leaf.In LF,the carbon content increased with addition of residual,and increasing degrees showed root>leaf.In 250c,the content decreased and the decreasing degrees showed leaf>root.In 250f,the content decreased and the decreasing degrees showed root>leaf.In 53f,the content increased after inputting in leaf,but had no change after inputting in root.In mSOC,the content increased significant,but had no relationship with the quality of residual.3.After inputting in residual incubating 90 days,the carbon content which coming from the residual was showed that:it existed differences among different land uses,presented C.orchard>C.lanceolata>C.carlesii>A.gracilipes.And it existed differences among different particle sizes:2000-250LF>250-53LF;53f>250c>250f.Moreover,in LF and 250f showed C.orchard>C.lanceolata>A.gracilipes>C.carlesii;in 250c showed C.orchard>C.carlesii>C.lanceolata>A.gracilipes;in 53f showed C.orchard>C.lanceolata>C.carlesii>A.gracilipes.With the increase of the residual quantity,the carbon content which coming from the residual was increasing in soil and all particle sizes.After inputting in different quality residual(CK5 leaf,root),the carbon content which coming from the residual showed root>leaf in soil,LF,250c and 53f.In 250f,A.gracilipes and C.carlesii showed leaf>root,while C.orchard and C.lanceolata showed root>leaf.4.After inputting in residual incubating 90 days,the activities of urease presented A.gracilipes>C.carlesii>C.lanceolata>C.orchard and the activities of PPO presented C.orchard>C.lanceolata>C.carlesii>A.gracilipes.With the increase of the residual quantity,the activities of urease and PPO significant decreased and the decreasing degrees showed 0.2%leaf>1.2%leaf.After inputting in different quality residual,the activities of urease and PPO significant decreased and the decreasing degrees showed root>leaf.