Responses of soil organic carbon cycle to land degradation by isotopically tracing in a typical karst area, southwest China

PeerJ

article

Ruiyin Han¹  Qian Zhang³  Zhifang Xu¹ 

[1] Institute of Geology and Geophysics, Chinese Academy of Sciences;University of Chinese Academy of Sciences;Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences;CAS Center for Excellence in Life and Paleoenvironment

关键词: Soil organic carbon;    Stable carbon isotope;    Land management;    Karst soils;    Isotopic tracing;   

DOI  :  10.7717/peerj.15249

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

BackgroundThe loss of soil organic carbon (SOC) under land degradation threatens crop production and reduces soil fertility and stability, which is more reflected in eco-sensitive environments. However, fewer studies simultaneously compared SOC variations and δ13CSOC compositions under diverse land uses, especially in karst areas.MethodsSoil profiles from two agricultural lands and a secondary forest land were selected to analyze SOC contents and their stable isotope composition (δ13CSOC) in a typical karst area located in southwest China to understand the response of the SOC cycle to land degradation. Moreover, the relationships between SOC contents and mean weight diameter (MWD) and soil erodibility (K) factor were comprehensively analyzed for assessing the response of SOC to soil degradation risk.ResultsThe mean SOC content was found to be the lowest in abandoned cropland (6.91 g/kg), followed by secondary forest land (9.31 g/kg) and grazing shrubland (34.80 g/kg), respectively. Meanwhile, the δ13CSOCshrubland (mean: −25.33‰). The isotopic tracing results suggested that plant litter was the main contributor to SOC in the secondary forest land. Whereas abundant nitrogen from goat feces enhanced plant productivity and resulted in additional accumulation of SOC in the grazing shrubland. Conversely, long-term cultivation led to the depletion of SOC sequestration by the loss of calcium. In surface soils, the fractionation of δ13CSOC were considerably affected by the decomposition of SOC by soil microorganisms and covered vegetation rather than agricultural influences.ConclusionsThe findings indicate that the cycling of SOC and soil stability in the calcareous soil of southwest China are largely regulated by different land uses and the presence of vegetation cover. The depletion of SOC and soil physical degradation pose significant challenges for abandoned cropland, particularly in the karst area, where land degradation is inevitable. Nevertheless, moderate grazing enhances SOC levels, which is beneficial to the land fertility maintenance in the karst region. Therefore, more emphasis should be placed on the cultivation methods and management strategies for abandoned cropland in the karst area.

【 授权许可】

CC BY