放牧对中国北方草地生态系统水分利用效率的影响

Effects of grazing on water-use efficiency of grasslandecosystem in northern China

解析草地生态系统植物水分利用效率对不同放牧强度的响应特征,对于提升草地生产和生态屏障功能具有重要意义。收集中国北方草地开展的38个放牧试验中关于放牧对植物水分利用效率影响的试验数据进行Meta分析。结果表明:放牧对中国北方草地植物水分利用效率影响的平均效应值为-0.18±0.04(95%置信区间:-0.27~-0.10),放牧极显著降低草地生态系统植物水分利用效率(P<0.01)。不同类型草地平均效应值降低幅度从高到低依次为典型草原>高寒草地>草甸草原>温性草原>荒漠草原。放牧对典型草原与高寒草地、草甸草原平均效应值具有极显著和显著影响,对荒漠草原与温性草原无显著影响。植物水分利用效率对放牧强度的响应顺序从高到低依次为重度、轻度和中度放牧,重度放牧极显著降低植物水分利用效率(P<0.001),中度放牧可以提高植物水分利用效率,轻度放牧对于植物水分利用效率影响不显著。土壤C/N、海拔和年均气温分别可以解释60.88%、11.81%和6.45%效应值变异。基于优化放牧制度以及对重度退化草地恢复的治理,提高草地土壤有机碳含量,将会提升草地生态系统植物水分利用效率。

Analyzing the response of plant water-use efficiency of grassland ecosystems to different grazing intensities is of great significance for improving grassland production and ecological barrier functions.Meta-analysis was conducted by collecting experimental data on the impact of grazing on plant water-use efficiency in 38 grazing experiments conducted on grasslands in northern China.The results showed that the average effect value of grazing on water-use efficiency of grassland plants in northern China was-0.18±0.04(95%confidence interval:-0.27~-0.10);grazing significantly reduced plant water-use efficiency of grassland ecosystems(P<0.01).The reduction in the average effect value among different types of grassland followed the order of typical grassland>alpine grassland>meadow grassland>temperate grassland>desert grassland.Grazing had extremely significant or significant impact on the average effect value of typical grassland,alpine grassland and meadow grassland,but had no significant impact on desert grassland and temperate grassland.The response of plant water-use efficiency to grazing intensity followed the order of heavy>light>moderate grazing.Heavy grazing extremely significantly reduced plant water use efficiency(P<0.001),moderate grazing improved plant water use efficiency,while light grazing had no significant negative effects.Soil C/N,altitude and annual average temperature explained 60.88%,11.81%and 6.45%of the variation of effect value,respectively.Based on the optimization of grazing systems and the restoration of severely degraded grasslands,increasing soil organic carbon content of grassland would improve plant water-use efficiency of grassland ecosystems.