Journal of Geographical Sciences ›› 2012, Vol. 22 ›› Issue (2): 315-328.doi: 10.1007/s11442-012-0929-y

• Ecological Environment • Previous Articles     Next Articles

Effects of a conversion from grassland to cropland on the different soil organic carbon fractions in Inner Mongolia, China

QI Yuchun1, DONG Yunshe1, PENG Qin1, XIAO Shengsheng1,3, HE Yating1,2, LIU Xinchao, SUN Liangjie1,2, JIA Junqiang1,2, YANG Zhijie1,2   

  1. 1. Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China;
    2. Graduate University of Chinese Academy of Sciences, Beijing 100049, China;
    3. Jiangxi Provincial Research Institute for Soil and Water Conservation, Nanchang 330029, China;
    4. Key Laboratory of Humid Subtropical Eco-geographical Process, Fujian Normal University, Ministry of Education, Fuzhou 350007, China
  • Received:2011-07-08 Revised:2011-10-20 Online:2012-04-15 Published:2012-04-15
  • Contact: Dong Yunshe (1961-), Ph.D and Professor, specialized in the global change and C, N biogeochemical cycle. E-mail: dongys@igsnrr.ac.cn E-mail:dongys@igsnrr.ac.cn
  • About author:Qi Yuchun (1972-), Ph.D and Associate Professor, specialized in the global change and C, N biogeochemical cycle. E-mail: qiyc@igsnrr.ac.cn
  • Supported by:

    National Natural Science foundation of China, No.40730105; No.40973057; No.41073061; Knowledge Innovation Program of the Chinese Academy of Sciences, No.KZCX2-EW-302

Abstract:

Cultivation is one of the most important human activities affecting the grassland ecosystem besides grazing, but its impacts on soil total organic carbon (C), especially on the liable organic C fractions have not been fully understood yet. In this paper, the role of cropping in soil organic C pool of different fractions was investigated in a meadow steppe region in Inner Mongolia of China, and the relationships between different C fractions were also discussed. The results indicated that the concentrations of different C fractions at steppe and cultivated land all decreased progressively with soil depth. After the conversion from steppe to spring wheat field for 36 years, total organic carbon (TOC) concentration at the 0 to 100 cm soil depth has decreased by 12.3% to 28.2%, and TOC of the surface soil horizon, especially those of 0-30 cm decreased more significantly (p<0.01). The dissolved organic carbon (DOC) and microbial biomass carbon (MBC) at the depth of 0-40 cm were found to have decreased by 66.7% to 77.1% and 36.5% to 42.4%, respectively. In the S.baicalensis steppe, the ratios of soil DOC to TOC varied between 0.52% and 0.60%, and those in the spring wheat field were only in the range of 0.18%-0.20%. The microbial quotients (qMBs) in the spring wheat field, varying from 1.11% to 1.40%, were also lower than those in the S. baicalensis steppe, which were in the range of 1.50%-1.63%. The change of DOC was much more sensitive to cultivation disturbance. Soil TOC, DOC, and MBC were significantly positive correlated with each other in the S. baicalensis steppe, but in the spring wheat field, the correlativity between DOC and TOC and that between DOC and MBC did not reach the significance level of 0.05.

Key words: temperate grassland, cultivation, soil, total organic carbon, dissolved organic carbon, microbial biomass carbon