Meta分析中国不同类型草地放牧强度对土壤氮素矿化作用的影响

Effects of grazing intensity on soil nitrogen mineraliza-tion in different type of grasslands in China basedon meta-analysis

摘要:

氮是草地生产功能的重要限制因素,氮素矿化作用为草地肥力的重要指标。草地生态系统净氮矿化速率对放牧干扰存在不同的响应特征,本研究采用Meta分析方法,通过对中国草地已开展的32个有关放牧对草地矿化作用影响的试验结果进行整合分析。结果表明:放牧轻微增加我国草地土壤净氮矿化速率,增幅约0.68%,平均效应值为0.01±0.13(置信区间为-0.24~0.25)。放牧极显著增加了高寒草甸矿化作用(P＜0.05),平均效应值约为0.38±0.10。放牧降低了温性草原、温性荒漠和沼泽湿地(P＞0.05)土壤净氮矿化速率。放牧强度对平均效应值具有极显著影响(P＜0.000 1),轻度和中度放牧提高氮素矿化速率分别为13.88%和5.12%,而重度放牧降低草地氮素矿化速率约9.42%。土壤湿度和海拔对平均效应值具有显著正效应影响(P＞0.05),分别可以解释14.30%和13.61%的效应值变异。轻度和中度放牧有利于提高我国草地生态系统氮素矿化作用和供给能力,可以作为草地生产管理的重要利用方式。暖湿化气候情景有助于提升草地生态系统氮素矿化作用和供给能力。

Abstract:

Nitrogen is a primary limiting factor of grassland production function.Nitrogen mineralization is an important index of grassland nitrogen fertility.The net nitrogen mineralization rate of grassland ecosystem had different response characteristics to grazing disturbance in China.In this study,the data from 32 experiments on the effects of grazing on grassland mineralization in China were analyzed by a meta-analysis method.The results indicated that grazing slightly increased soil net nitrogen mineralization rate by~0.68%,with an average effect value of 0.01±0.13 (95% confidence interval: -0.24~0.25).Grazing significantly increased the mineralization of alpine meadow (P＜0.01),with an average effect value of 0.38±0.10.Grazing reduced soil net nitrogen mineralization rate in temperate steppe,temperate desert and swamp wetland (P＜0.05).Grazing intensity had significant effects on the average effect value (P＜0.000 1).Light and moderate grazing increased nitrogen mineralization rate by 13.88% and 5.12% respectively,while heavy grazing reduced nitrogen mineralization rate by 9.42%.Soil moisture and altitude had significant positive effects on the average effect value (P＜0.05),which could explain 14.30% and 13.61% of variation in effect value,respectively.Light and moderate grazing are beneficial to improve the nitrogen mineralization and supply capacity of grassland ecosystem,while heavy grazing may aggravate the nitrogen limitation of grassland ecosystem biomass production.