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University of Chinese Academy of Sciences (2019)

Characteristics of In-situ Mineralization of Soil Nitrogen under Erosion Environment in the Loess Plateau

孔维波;

Titre : Characteristics of In-situ Mineralization of Soil Nitrogen under Erosion Environment in the Loess Plateau

Auteur : Grade : Master’s Theses 2019

Université : University of Chinese Academy of Sciences

Résumé
Soil erosion is the extensive and influential form of soil degradation around the world,resulting in the redistribution of nutrients such as soil organic carbon and topsoil,reshaping the surface environment,affecting the productivity of terrestrial ecosystem and soil biogeochemical cycling(such as soil nitrogen cycling).Additionally,soil nitrogen(N)mineralization is one of the fundamental processes of soil N cycling,which not only controls N availability and supply to plants,but also affects ecosystem productivity and regulates global carbon balance.The Loess Plateau has fragmented terrain and widespread sloping land where suffers severe soil erosion,which provides a favorable platform for studying soil N cycling in erosion environment.Different small watersheds of the Loess Plateau,namely Shenmu Liudaogou watershed,Suide xindiangou watershed,Ansai Zhifanggou watershed,Guyuan Huochagou watershed and Changwu Wangdonggou watershed were selected to carry out in situ N mineralization experiments in eroding and depositional sites of every small watershed.The temporal and spatial differentiation characteristics of soil N mineralization in the erosion environment and their response to seasonality,environmental factors and vegetation status were clarified,and the variations in these responses between eroding and depositional sites were further elucidated.The main conclusions were as follows :(1)Soil organic carbon(SOC),total nitrogen(TN),pH,bulk density(BD),clay content,moisture and temperature were significantly discrepant across all five sites(five watersheds:Liudaogou(LD),Xindiangou(XD),Zhifanggou(ZF),Huochawan(HC)and Wangdonggou(WD)).Generally,the contents of SOC and TN in the eroding site were significantly higher than that in the depositional site,and related to site.The soil pH,clay content and BD in the depositional site were significantly higher than those in the eroding site and regardless of site.Soil moisture in the eroding site was significantly higher,while soil temperature was significantly lower than in the depositional site.(2)The soil inorganic nitrogen pool is dominated by ammonium(NH4+),but existing site-heterogeneity.The LD is dominated by ammonium,but ammonium and nitrate(NO3-)collectively composed of inorganic N pool in XD and HC sites,and were jointly dominated in the eroding site and 0-10 cm soil depth in ZF site.The eroding site in WD site is dominated by ammonium,while ammonium and nitrate collectively predominated the inorganic N pool in the depositional site.In addition,nitrification dominated soil nitrogen mineralization across five sites

Mots clés : The Loess Plateau; erosion environment; inorganic N pool; net N mineralization; temporal dynamics;

Présentation (CNKI)

Page publiée le 21 mai 2020