The Evolution Of Soil Carbon Sequestration Mechanismsin The Process Of Ecological Restoration In Degraded Red Soil

In this study we selected erosion of degraded mountain as the study area,choosing the different periods of Pinus massoniana mixed forest,Pinus massoniana forest and the erosion of bare land as ecological recovery sequence. Through the method of density, size and acid hydrolysis on soil aggregates separation and processing,Analysing the relationship between forest soil aggregates organic carbon content,stock,carbon fractions in aggregates and soil layer, Soil particle size, Woodland.The results are as flows:(1)The aggregate mass fraction ranking from high to low is roughly followed by>2mm,2-0.25mm,0.25-0.053mm,<0.053mm,the greater particle size(grain) the higher mass,after wet sieve separation.With the increase of soil depth the different size of aggregates organic carbon content is reduced,>2mm aggregate organic carbon content is the highest, physical protection is the strongest,2-0.25mm aggregate organic carbon content is the lowest, physical protection is the weakest;The average carbon content of Pinus massoniana mixed forest higher than Pinus massoniana forest,physical protection action is stronger.Soil carbon reserves increased significantly after vegetation restoration, The average carbon reserves of Pinus massoniana mixed forest higher than Pinus massoniana forest, Soil organic carbon storage is mainly assigned in the large aggregates(>0.25mm).(2)The content of f-LF and m-LF increased significantly after vegetation restoration,But the content reduced with the increase of soil depth as well as the carbon and nitrogen content,The content of f-LF more than m-LF in each soil layer;According to the content of f-LF and m-LF,different aggregates from high to low ranking are>2mm,2-0.25mm,0.25-0.053mm(Feng Shui forest except);The f-FL carbon content of big aggregates (>0.25mm) is higher than the micro-aggregates, The f-FL carbon content of big aggregates of Pinus massoniana forest is higher,however the f-FL carbon content of micro-aggregates of Pinus massoniana mixed forest is higher; The carbon content of fine particle fraction is higher than the coarse particle fraction’s,Micro-aggregates plays a greater role in the physical protection. The organic carbon content of fine particle fraction(2000f、250f、53f) from different forest had significant difference.According to the content from high to low,the forest ranking are Pinus massoniana mixed forest>Pinus massoniana forest>bare land;Soil organic carbon reserves exist primarily in the fine particle fractions of aggregates,whose average carbon storage is approximately5times that of the coarse particle fraction’s.(3)mineral soil organic carbon content increased in each soil layer after ecological restoration,The carbon content of Pinus massoniana mixed forest is higher than Pinus massoniana forest,With the increase of soil depth the mineral soil organic carbon content is reduced;The mineral soil organic carbon content of different aggregates had significant difference(P<0.05),the mineral organic of>2mm aggregate is the highest,then the2-0.25mm aggregate is second,the0.25-0.053mm is the lowest. All kinds of mineral carbon content of fengshui forest is higher than the other’s.According to the reserves of mineral,different fractions of aggregates from high to low ranking are2000msoc>250msoc>53msoc,but the fraction of250msoc is the highest from fengshui forest.Large aggregate within the mineral organic carbon fractions(2000mso、250msoc) on chemical protection is more important.(4)With the increase of soil depth the recalcitrant organic carbon(RC) content is reduced;According to the content of RC,different aggregates from high to low ranking are>2mm、<0.053mm、0.25-0.053mm、2-0.25mm; On the regression analysis about RC and organic carbon content found they have the extremely significant linear correlation(P<0.01);RI value with the increase of soil depth increases,indicating that the biochemical stability are mainly embodied in the soil below the surface.In the same soil layer, According to the index of recalcitrant (RI),different aggregates from high to low ranking are>2mm,2-0.25mm,0.25-0.053mm,<0.053mm.Large aggregates on soil organic carbon of Biochemistry protection action is stronger, larger aggregates is the main carrier of Biochemistry protection.