Chin J Plan Ecolo ›› 2005, Vol. 29 ›› Issue (2): 304-310.doi: 10.17521/cjpe.2005.0039

• Research Articles • Previous Articles     Next Articles

CHARACTERISTICS OF SOIL NITROGEN AND CARBON OF PASTURES UNDER DIFFERENT MANAGEMENT IN NORTHWESTERN SICHUAN

SUN Geng WU Ning* and LUO Peng   

  1. (Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China)
  • Online:2005-03-10 Published:2005-03-10
  • Contact: WU Ning

Abstract: Different methods of pasture management have been adopted in individualized pastures of northwestern Sichuan, one of the most important pastoral areas in China. In this paper, common analytical chemistry and barometric process separation methods were used to determine soil N and C pools, denitrification rates, gross nitrification rates, and N2O and CO2 flux rates of pastures under different management methods, including natural pasture, fenced pasture, tilled pasture and artificial pasture. The results indicated that SOM (Soil organic matter) and total N in soils of the study area were 101.8 and 5.1 g·kg-1, respectively, which were notably lower than 181.3 and 7.4 g·kg-1 of other typical sub-alpine soils. In contrast to common belief, the content of NO3-N was three-to-eleven times higher than that of NH4+N, which was probably caused by the anthropogenic disturbance. There was a significant effect of different methods of pasture management to N and C pools, N transformation rates and soil respiration. After fence, SOM and total N increased notably. For example, fenced pasture was 61% and 58% and tilled pasture was 46% and 51% higher than natural pasture in these two respects, respectively. Accordingly, N transformation rates and soil respiration rates accelerated a lot, especially in soils of tilled pasture. For example, in soils of tilled pasture gross nitrification and N2O flux rate were 5.1 times and 2.4 times that of natural pasture. Thus, although tillage in spring might help to enhanced crop yields (or pasturage), it also runs a great ecological risk including increased emissions of CO2 and N2O to the atmosphere and leaching of NO3- to ground water. This research also found that the gross nitrification rates were 20-93 times higher than net nitrification rates, and thus net nitrification rates do not provide valuable information on the dynamic character of soil nitrification in this high-altitude region.

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