Qinghai-Tibet Plateau Research Institute, Southwest Minzu University
【Objective】Aggregate is an important storage unit of soil organic carbon, and its stability directly affects the sequestration of organic carbon. The purpose of this study is to investigate whether grassland shrubby affects the stability of soil aggregates and their cementing materials.【Method】Four typical shrubby grasslands (Spiraea alpina、Sibiraea angustata、Caragana microphylla、Potentilla fruticosa) in the eastern margin of the Qinghai-Tibet Plateau were studied, the content of aggregates and their cementing materials (soil aggregate organic carbon, Fe-Al oxides, Ca bond and Fe-Al bond organic carbon) and the stability of aggregates (the content of aggregates >0.25?mm/R0.25、mean weight diameter/MWD and fractal dimension/D) were determined, in order to explore the main contributing factors to the stability of the aggregates under the impact of shrub encroachment. 【Result】 Results show that: 1) Shrub encroachment decreases the aggregate content of 2~0.25?mm and <0.002?mm and aggregate stabilitySin Caragana microphyllaSSplot; However, it has no significant effect on the other three shrub grasslands. 2) Shrub encroachment mainly changes the content of cementing substances in the aggregates of Caragana microphylla plot and Sibiraea angustata plot. 3) The results of boosted regression tree analysis (BRT) between cementing materials and MWD show that the main contribution factors to the stability of aggregates in Spiraea alpina polt are complexed iron (Fep) and amorphous iron and aluminum (Feo, Alo); The major contributors to grassland and other shrub plots are soil aggregate organic carbon (SAOC) and Free iron oxides (Fed). 【Conclusion】 Although shrub encroachment increases the content of SAOC in <0.053?mm, but reduces the content of large aggregates and clay, as well as the content of Fed in Caragana microphylla plot. Thus, the stability of aggregates is reduced, which may be detrimental to the retention of organic carbon. The study intended to provide theoretical knowledge for the stability theory of aggregates and the dynamic change of organic carbon pool in this region.
Chen Hong, Ma Wenming, Zhou Qingping, Deng Zengzhuoma, Di Liyaer, Tang Sihong, Hou Chen. Effects of shrub-encroached grassland on the stability of soil aggregates and cementing materials in alpine grassland of Qinghai-Tibet Plateau[J]. Acta Pedologica Sinica,,[In Press]