黄土高原次生林演替对团聚体有机碳含量及化学稳定性的影响OA北大核心CHSSCDCSTPCD

The secondary forest succession is conducive to the accumulation of soil organic carbon.It has a significant impact on the protection of soil physical structure and chemical composition of organic carbon.Aggregates are important storage units of soil organic carbon,and their stability directly affect the sequestration of organic carbon.However,the accumulation mechanism and chemical stability of soil aggregate organic carbon in the process of secondary forest succession are rarely studied.In order to investigate the effect of secondary forest succession on the organic carbon content of soil aggregates and the stability of their chemical composition,the experiments were conducted as follows.This study selected three secondary forest successions:Betula platyphylla(initial stage),Populus davidiana Dode,Quercus wutaishanica Blume(mid-term),and Quercus wutaishanica Blume(late stage)on the Loess Plateau.We analyzed the changes in organic carbon,soil bulk density,total nitrogen,total phosphorus,total potassium,available phosphorus,and available potassium through whole surface soil.We classified the soil aggregates into different particle sizes(2,1,0.5,0.25,and 0.053 mm),and then used Fourier Transform Infrared Spectroscopy(FTRI)to determine the chemical composition.After that,we calculated the chemical composition stability(IC/AC)and analysed its response mechanism and influencing factors.The results showed that the organic carbon content of soil aggregates presented a gradually increasing trend during the process of secondary forest succession and there was a significant difference between different communities(P＜0.05),with the highest content of medium particle size aggregates in the top-level community(37.63 g/kg).The content of polysaccharide organic carbon in soil aggregate AC was the highest(55.87%),while the content of aromatic organic carbon in IC was the highest(94.45%).During the succession process,both IC and AC showed a first decrease and then increase trend.IC/AC showed a trend of firstly decreasing and then increasing with succession,with the highest chemical composition stability of organic carbon in microaggregates at the late stage is the strongest,reaching 3.95.The proportion of microaggregate content,along with soil total nitrogen,total phosphorus,and total potassium,significantly promoted the chemical composition stability of organic carbon in aggregates(P＜0.05).In conclusion,the secondary forest succession is beneficial to the accumulation of organic carbon in soil aggregates and the stabilization of the chemical structure of organic carbon,where micro-agglomerates play a key role during this process.Future management of secondary forest on the Loess Plateau may appropriately take corresponding measures to increase the content of soil microaggregates,which can help the Loess Plateau to form a more stable soil carbon pool.