摘 要 ：川西北地区是我国的主要牧区之一。草地承包后，草地建设中出现了各种草地经营管理方式——围栏、翻耕和完全的人工建设。采用常规化学分析和气压过程分离（Barometric Process Separation，BaPS）法，对不同类型草地（天然放牧草地、围栏草地、翻耕草地和人工草地）的土壤氮、碳库以及反硝化速率、总硝化速率、N2O和CO2排放速率进行了研究。结果表明：研究地点土壤有机质、全氮含量分别为101.8和5.1 g·kg－1 ，比典型的亚高山土壤有机质和全氮含量（分别是181.3和7.4 g·kg－1）明显低，而且，与通常的观念不同的是，土壤NO3－N含量是NH4+N含量的3～11倍。这可能是由于研究地过度的人为干扰造成的。研究还发现，不同管理措施对土壤氮、碳库，氮转化速率和土壤呼吸有显著影响。天然放牧草地围栏后，土壤有机质和全氮含量明显升高，比如，围栏草地和翻耕草地的有机质、全氮含量分别比天然放牧草地高61％、58％和46％、51％。氮转化速率和土壤呼吸大大加快，尤其是在翻耕草地，比如，翻耕草地的总硝化速率和N2O排放速率分别是天然放牧草地的5.1和2.4倍。因此，虽然春季翻耕可能提高作物（包括牧草）产量，但它同时也承担了巨大的生态学风险，包括增加排放到大气中的CO2 和 N2O的量以及淋溶到地下水的NO3－的量。因此，建议在川西北亚高山区的人工草地建设中慎重选择翻耕措施。研究还发现，研究地土壤的总硝化速率是净硝化速率的20～93倍，净硝化速率不能反映高海拔地区土壤硝化的准确状况。
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.