Effects Of Different Planting Patterns On Soil Organic Carbon Pool

Southern Xinjiang has been recognized as one of the largest high-quality fruit production bases in China due to its special climate and soil conditions.During the agricultural restructuring,most of the farmland in Southern Xinjiang has been replaced by orchards or intercropping,which greatly promote the socio-economic development.However,the planting patterns change may greatly affect the soil organic carbon pool,and thus regulate the soil quality and soil organic carbon stability.In order to reveal the impact on soil organic carbon pool after the conversion of farmland into orchards and intercropping in Kizil Town,Wensu County,Xinjiang,we chose three different planting patterns(sole wheat,sole jujube and jujube wheat intercropping)of different tree age sections(<5a,5～10a,>10a)with basically the same soil conditions and management level in Kizil Town,Wensu County.The content and storage of soil organic carbon components(dissoloved organic carbon,light fraction organic carbon,and readily-oxidable organic carbon)under different planting patterns were studied and explored the relationship between total organic carbon and soil organic carbon components,and clarified the effects of different planting patterns on soil organic carbon pool and its stability.The main results are as follows:1.Soil total organic carbon content and storage declined with the increase of soil depth.In the soil depth of 0-100cm,the content and storage of soil total organic carbon under different planting patterns was 10a jujube-wheat intercropping>15a jujube orchard>15a jujube-wheat intercropping>10a jujube orchard>5a jujube-wheat intercropping>5a jujube orchard>wheat.The results showed that the carbon sequestration capacity of soil was improved under different planting patterns after the conversion of farmland into orchards or intercropping.2.The content of soil labile organic carbon was consistent with that of soil total organic carbon in the vertical section.Soil labile organic carbon content were different under different planting patterns,dissolved organic carbon content were significant different in 0～30 cm,60～80 cm soil layers(P<0.05),light fraction organic carbon content were significant different only in 10～30 cm soil layer(P<0.05),readily oxidizable carbon content were significant different in 0～30 cm,40～60 cm soil layers(P<0.05).The content of dissolved organic carbon and readily oxidizable carbon in different tree age sections were improved in some degree after the conversion of farmland into orchards or intercropping,while the content of light fraction organic carbon were improved only in the orchards and intercropping of 10 and 15 tree age sections.It indicates that different planting patterns have different effects on soil labile organic carbon.3.In the soil profile of 0～100 cm,the ratio of soil labile organic carbon to soil total organic carbon is different.Under different planting patterns,the proportion of soil dissolved organic carbon to total organic carbon decreased first and then increased with the increase of soil depth,while the proportion of soil light fraction organic carbon and soil readily oxidizable carbon to total organic carbon decreased with the increase of soil depth.The correlation between soil labile organic carbon and soil total organic carbon and between soil labile organic carbon under different planting patterns in this study area reached an extremely significant level.The results showed that the soil total organic carbon was closely related to the labile organic carbon,and the most closely related was the soil readily oxidizable carbon,followed by the light fraction organic carbon.