摘要:人类活动导致氮和磷输入到草原生态系统，对土壤有机碳循环产生影响，但是土壤微生物呼吸（Soil microbial respiration，Rs）及其温度敏感性（Q₁₀）对于氮沉降和磷有效性增加的响应还存在争议。因此，依托多伦草原氮添加样地（0、50 kg N hm^-2 a^-1和100 kg N hm^-2 a^-1），并添加磷进行室内恒温培养（10℃和15℃），研究氮添加和磷有效性增加对Rs及其Q₁₀的影响。结果发现：氮添加显著降低胞壁酸含量和显著增加真菌丰富度（Fungal richness，F-richness）。与N0处理相比，N50和N100处理使累积呼吸量显著降低了61.2%和67.1%，但Q₁₀显著升高了32.7%和50.8%；磷有效性增加没有对累积呼吸量及其Q₁₀产生显著影响。逐步回归结果表明，F-richness和pH值分别是累积呼吸量及其Q₁₀最重要的影响因子。研究表明氮添加抑制Rs，减少土壤有机碳损失，但增加气候变暖对多伦草原土壤有机碳分解的影响，在全球变暖背景下增加土壤有机碳排放的不确定性。



Abstract:Increasing input of nitrogen (N) and phosphorus (P) into the grassland ecosystems induced human activities, may have effects on soil organic carbon (SOC) cycle. However, how soil microbial respiration (Rs) and its temperature sensitivity (Q₁₀) respond to N addition and increasing P availability remains unclear. Here, we collected soils from the long-term simulated N deposition site in a temperate grassland in Duolun, northern China (0, 50, 100 kg N hm^-2 a^-1), and then added available P before laboratory incubation at two constant temperatures (10℃ and 15℃) to investigate how N addition and P availability affect Rs and its Q₁₀. The results showed that N addition significantly decreased muramic acid content but increased fungal richness. In the N50 and N100 treatments cumulative respiration was significantly reduced by 61.2% and 67.1% than N0, but Q₁₀ was increased by 32.7% and 50.8% compared to the N0 treatment. However, increasing P availability had no effects on cumulative respiration and its Q₁₀. The results of stepwise regression analysis showed that fungal richness and pH were the most important influencing factors of cumulative respiration and its Q₁₀, respectively. These results suggest that N addition inhibits Rs and reduces SOC loss, but increases the sensitivity of response of SOC decomposition to elevated temperature in the Duolun grassland ecosystem, which may increase CO₂ emissions via SOC decomposition under the continuously warming scenario.





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