模拟牲畜采食对高寒草甸土壤潜在氧化亚氮排放的影响

The Response of Potential N_(2)O Emission from an Alpine Meadow Soil to Simulated Livestock Grazing

探明牲畜采食对土壤氧化亚氮(N_(2)O)排放的影响,是准确预测放牧干扰下高寒草甸生态系统温室气体变化的关键。本研究通过刈割留茬模拟牲畜不同强度采食行为(无采食,CK;轻度采食,LD:留茬高度3 cm;重度采食,HD:留茬高度<1 cm),利用室内培养法测定土壤潜在N_(2)O排放,并测定了土壤理化性质、酶活性以及硝化和反硝化功能基因丰度等指标。结果表明:LD处理对土壤潜在N_(2)O排放无显著影响,但HD处理显著降低了潜在N_(2)O排放(P<0.05)。重度采食导致输入土壤铵态氮(NH+4-N)和碳减少,降低土壤AOA-amoA,nirS和nosZI基因丰度及反硝化潜势(Denitrification potential,DP),减弱土壤硝化和反硝化作用从而降低N_(2)O排放。综上,轻度采食对土壤潜在N_(2)O排放无显著影响,但重度采食可能通过降低土壤硝化和反硝化作用,减弱土壤潜在N_(2)O排放。

Clarifying the impact of livestock defoliation on soil nitrous oxide(N_(2)O)emissions is pivotal for accurately predicting the alterations in greenhouse gas of the alpine meadow ecosystems under grazing disturbance.This study simulated the grazing behavior of livestock at different intensities by mowing stubble(no grazing,CK;light grazing,LD:stubble height 3 cm;heavy grazing,HD:stubble height<1 cm).By using incubation methods,we measured the potential N_(2)O emissions from the soil,and assessed soil physicochemical properties,enzyme activities,and the abundance of nitrification and denitrification functional genes.The results showed that the LD treatment had no significant effect on soil potential N_(2)O emissions,but the HD treatment significantly reduced potential N_(2)O emissions(P<0.05).Heavy defoliation resulted in the decrease of ammonium nitrogen(NH+4-N)input and carbon input,decreased the abundance of soil AOA-amoA,nirS and nosZI genes and denitrification potential(DP),weakened the nitrification and denitrification of soil,thereby reducing soil denitrification and N_(2)O emissions.In conclusion,light defoliation does not have a significant impact on potential N_(2)O emissions from alpine meadow soil,but heavy defoliation may reduce potential N_(2)O emissions by jointly reducing nitrification and denitrification in soil.