Distribution Characteristics Of Soil Organic Carbon And Its Composition Under Erosion Enviroment In Different Vegetabale Regions Of Loess Plateau

The Loess Plateau is an area with severe soil erosion. In this area, slope soil erosion isextremely common and serious. Since the implementation of the “Grain for Green” project,the ecological environment and soil quality were improved. Also, the recovery of thevegetation effectively maintain soil and water to reduce soil erosion. Meanwhile, soil organiccarbon pool is sensitive to changes of the soil-plant system. In this study, we determined soilbulk density, soil moisture, nitrogen contents and total organic carbon and its compositionduring different erosion environment, to unearth the effect of the vegetation zones and erosionenvironment on soil organic carbon and its composition, evaluating the degree of erosion tofind out effective measures of vegetation recovery. The results showed that:The difference of physicochemical characteristics between soil0~10cm and10~20cmlayers was remarkable in arbor-brush-grass vegetation zone, brush-grass vegetation zone andgrass zone. In arbor-brush-grass vegetation zone, soil moisture, total organic carbon and totalnitrogen showed Shady low slope> Sunny lower slope> Shady middle slope> Sunny middleslope> Hill top, while bulk density showed: Shady middle slope <Sunny lower slope <shady middle slope <Sunny middle slope <Hill top. In brush-grass vegetation zone, soilmoisture, total organic carbon and total nitrogen showed: low slope> middle slope> Hill top,while bulk density showed: low slope <middle slope <Hill top. And the differenccesbetween sundy and shade slope was remarkable. In grass zone, physicochemicalcharacteristics fluctuated slightly. Overall, soil physiochemical characteristics ofarbor-brush-grass zone was superior than brush-grass and grass zones, while the latter twohad little difference.In both layers of arbor-brush-grass vegetation zone and0~10cm layer brush-grassvegetation zone, The difference of LOC（labile organic carbon）, MBC（microbial biomasscarbon）, LFOC（light fraction organic carbon） and DOC（dissolved organic carbon） wereremarkable, showing low slope> middle slope> hill top. And their contents in Shade slopewas larger than Sundy slope. In10~20cm layer of brush-grass vegetation zone, contents of LOC, MBC, LFOC and DOC in Shade slope were larger than Sundy slope. In grass zone,LOC, MBC, LFOC and DOC hardly were sensitive to slope soil erosion. In low slope, LOCand LFOC were surperer.The difference of LOC, MBC, LFOC and DOC of soil0~10cm and10~20cm layer isremarkable in arbor-brush-grass vegetation zone, brush-grass vegetation zone and grass zone.And LFOC had the biggest difference, followed by MBC, DOC and LOC. LOC and DOCwere sensitive to slope soil erosion dramatically. In both layers, there were significatedifferences of LOC and DOC between arbor-brush-grass vegetation zone, brush-grassvegetation zone and grass zone. In0~10cm layer, LFOC and LOC were sensitive to slope soilerosion.LOC, MBC, LFOC and DOC were significantly positively correlated with soil totalorganic carbon and total nitrogen, while bulk dentity showed negative correlation. Amongthese four, LOC was significantly positively correlated with MBC, as well as LOC and DOC.MBC was significantly positively correlated with LFOC, as well as LFOC and DOC.Degree of soil humification differed btween0~10cm and10~20cm layer. The contentsof soil humus fractions showed: HM> FA> HA, except the sunny low slope of brush-grassvegetation zone. The contents of soil humus fractions were highest in arbor-brush-grassvegetation zone. The content of HM was similar between brush-grass vegetation zone andgrass zone. But the contents in brush-grass vegetation zone of HA and FA were higher thanthem in grass zone. Overall, the content of FA showed: lower slope> middle slope> Hill top.The difference of HM was remarkable. And HA:FA ratio was between0.5~1.0.Principal component analysis of soil organic carbon and its composition showed that:The soil organic carbon pool in arbor-brush-grass vegetation zone was the most healthy. Andsoil organic carbon pool of0~10cm layer was greatly affected by type of vegetable zoneand slope direction. The soil organic carbon pool in brush-grass vegetation zone wassignificantly affected by EROSION ENVIROMENT. THE soil organic carbon pool inSunny middle slope and hill top was least healthy. And The soil organic carbon pool in grassvegetation zone was less healthy than the other two.