Abstract: Nitrogen mineralization and nitrification had important effects on soil nitrogen conversion in grassland. Grazing disturbance affected soil nitrogen mineralization and nitrification in grassland. Based on the meta-analysis method,this study conducted an integrated analysis of the results of 59 experiments on the effects of grazing on soil nitrogen mineralization and 55 experiments on the effects of grazing on soil nitrogen nitrification in Chinese grassland. The results showed as follows:1) Grazing reduced the mineralization and nitrification of soil nitrogen in grassland with the average effect values of -0.09 and -0.08,as a decrease of 8.61% and 7.69%,respectively;but both of them did not reach the significant test level. 2) The average effects of different grazing intensities on soil nitrogen mineralization and nitrification took an order of light grazing >heavy grazing >moderate grazing. 3) Soil total nitrogen significantly affected the average effect value of mineralization,accounting for 4.91% of effect value variation. Soil organic carbon and total nitrogen significantly affected the average nitrification effect value,accounting for 18.35% and 19.17% of the effect value variation,respectively. The purpose of this study was to provide a theoretical basis for deepening the insight into the N cycle in grazing grassland.

Key words: Grazing intensity, Nitrogen in grassland soil, Mineralization, Nitrification, Average effect values

摘要： 氮素矿化和硝化作用对草地土壤氮素转化过程具有重要影响。放牧干扰影响草地土壤氮素矿化和硝化作用。本研究基于Meta分析方法，对已开展的59个放牧影响中国草地土壤氮素矿化作用、55个放牧影响中国草地土壤氮素硝化作用影响的试验结果进行整合分析。结果表明：放牧降低草地土壤氮素矿化、硝化作用，平均效应值分别为—0.09和—0.08，降幅分别为8.61%和7.69%，但均未达到显著性检验水平；不同放牧强度对草地土壤氮素矿化作用和硝化作用平均效应值的影响呈现出轻度放牧>重度放牧>中度放牧；土壤全氮含量显著影响矿化作用平均效应值，可解释4.91%的效应值变异；土壤有机碳和全氮含量显著影响硝化作用平均效应值，分别可以解释18.35%和19.17%的效应值变异。本研究旨在为明晰放牧草地氮素循环提供理论基础。

关键词: 放牧强度, 草地土壤氮素, 矿化作用, 硝化作用, 平均效应值