The Comparison Of Physical Composition And Chemical Structure Of Soil Organic Carbon Pool Among Different-Age Moso Bamboo Plantations

Moso bamboo(Phyllostachys edulis)is the most important economic and ecological bamboo species in southern China.Because of its fast growth and high biomass.Moso bamboo is considered to be the most potential plant type for carbon sequestration.However,to date,few studies focused on the formation and stabilization mechanism of soil organic carbon in Moso bamboo plantations.In this study,the bamboo forests with different planting ages(19a,37a,64a)were selected as the experimental sites,and an adjacent secondary deciduous broad-leaved forest was selected as a control to study changes in soil basic properties,organic-carbon composition and its chemical structures.The main results are presented as follows:1.The physical and chemical properties of the surface(0-20cm)and deep(20-40cm)soil were significantly changed after Moso bamboo cultivation.Compared with the control secondary forest,bulk density and contents of ammonium nitrogen,nitrate nitrogen,water-soluble organic nitrogen,total phosphorus,available phosphorus and available potassium were significantly reduced,but soil aggregate stability,pH,total nitrogen content.C/N ratio and C/P ratio were significantly increased in soil planting Moso bamboo for a long time.2.The content and storage of organic carbon in bamboo soil increased significantly with the extensive of bamboo planting time.The contents of active carbon components such as hot water soluble organic carbon(DOC),easily oxidized carbon(ROC),free particle organic carbon(fPOC)and closed storage particle organic carbon(oPOC).and stable organic carbon components including mineral bound organic carbon(MOC)and humus carbon(HOC)were significantly increased by 23.2%?270.8%.The mineralization rate of organic carbon in soil also increased with the extension of planting years.The distribution ratio of organic carbon in Moso bamboo forests was the highest for MOC(52.12-73.3%),followed by oPOC(11.51-20.73%)and fPOC(7.98-12.76%),and then Microbial Biomass Carbon(MBC)(1.46-6.62%),ROC(1.82-4.45%)and DOC(1.43-1.68%).3.The organic carbon in the bamboo forest soil was dominated by alkoxy carbon and aromatic carbon,while the proportion of carbonyl carbon and alkyl carbon was small.Alkyl carbon,alkyl carbon/alkoxy carbon and hydrophobic carbon/hydrophilic carbon gradually increased by 75%,80%and 28%respectively with the increase of planting years in 0-20cm soil layer;aromatic carbon and aromaticity increased by 33%and 66%respectively with the increase of planting years in 20-40cm soil layer,demonstrating that the chemical structure stability of soil organic carbon was improved in long-term bamboo forest.Based on the changes of soil properties,organic carbon components and chemical composition,it is concluded that long-term planting of Phyllostachys pubescens and moderate disturbance are of great significance to improve soil structure,maintain and increase soil carbon(nitrogen)fixation capacity,and promote soil carbon sink.