摘要:以欧亚温带草原东缘生态样带为平台，以样带上未放牧和重度放牧配对样地为研究对象，开展重度放牧对欧亚温带典型草原土壤氮矿化及其温度敏感性的影响研究。结果表明：（1）在室内培养条件下，土壤氮积累量和土壤净氮矿化速率呈现出干燥度指数较大的样点显著大于干燥度指数最低的样点（P < 0.05）。在相对湿润的样点，土壤氮素矿化周转速率较快；（2）重度放牧对不同样点土壤氮积累量和土壤氮矿化速率的影响是不同的。在干燥度指数较高样点，重度放牧样地土壤铵态氮减少量和速率较未放牧样地低（P < 0.05），重度放牧显著降低了土壤硝态氮积累量、无机氮积累量、硝化速率、净氮矿化速率（P < 0.05）；在干燥度指数较低样点，重度放牧样地土壤铵态氮减少量和速率较未放牧样地高（P < 0.05），重度放牧对土壤硝态氮积累量、无机氮积累量、硝化速率、净氮矿化速率影响不大（P > 0.05）；（3）土壤氮矿化作用温度敏感性（Q₁₀）变化范围在1.61-2.06，重度放牧对Q₁₀无显著影响。随着纬度的升高，Q₁₀呈升高趋势。Q₁₀与基质质量指数以及表观活化能与基质质量指数均呈显著的负相关关系（P < 0.05）；（4）土壤硝态氮积累量、无机氮积累量、硝化速率、净氮矿化速率对重度放牧的响应比与干燥度指数呈极显著负相关（P < 0.01），重度放牧对欧亚温带典型草原土壤氮矿化的影响受气候条件（温度和降水）的调控。



Abstract:Effects of heavy grazing on soil nitrogen mineralization and temperature sensitivity in the Eastern Eurasian Steppe were studied using laboratory incubation methods by comparing non-grazing plots with heavy grazing plots at different sites. The results showed that accumulations of soil nitrogen and soil nitrogen mineralization rates were significantly higher in sites with a higher aridity index (AI) than sites with a lower AI (P < 0.05), which indicated that soil nitrogen turnover rates were high in relatively humid sites. In sites with a higher AI, the amount and rate of soil ammonium nitrogen reduction in heavy grazing plots were lower than that of non-grazing plots (P < 0.05), and heavy grazing significantly decreased accumulations of soil nitrate nitrogen (A_nit), accumulations of soil inorganic nitrogen (A_min), soil nitrification rate (R_nit), and net nitrogen mineralization rate (R_min) (P < 0.05). In sites with lower AI, the amount and rate of soil ammonium nitrogen reduction in heavy grazing plots were higher than that of non-grazing plots (P < 0.05), and heavy grazing had little effect on A_nit, A_min, R_nit, and R_min (P>0.05). The temperature sensitivity of net nitrogen mineralization (Q₁₀) ranged from 1.61 to 2.06 and heavy grazing had little effect on Q₁₀. Q₁₀increased with increasing latitude and showed a significant negative correlation with the substrate quality index (P < 0.05). There was a significant negative correlation between substrate quality index and apparent activation energy (P < 0.05). Furthermore, the response ratios of A_nit, A_min, R_nit, and R_min to heavy grazing were significantly negatively correlated with AI (P < 0.01). Our results emphasized that the effects of heavy grazing on soil nitrogen mineralization in the Eastern Eurasian Steppe was regulated by climate (temperature and precipitation).





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