摘要:随着全球大气氮沉降的明显增加，将有可能显著影响我国西部地区受氮限制的亚高山森林生态系统。土壤微生物是生态系统的重要组成部分，是土壤物质循环和能量流动的重要参与者。由于生态系统类型、土壤养分、氮沉降背景值等的差异，土壤呼吸和土壤生物量碳氮对施氮的响应存在许多不确定性。而施氮会不会促进亚高山森林生态系统中土壤呼吸和微生物对土壤碳氮的固定？基于此假设，选择了川西60年生的四川红杉（Larix mastersiana）亚高山针叶林为研究对象，通过4个水平的土壤施氮控制试验（CK：0 g m^-2 a^-1、N1：2 g m^-2 a^-1、N2：5 g m^-2 a^-1、N3：10 g m^-2 a^-1），监测了土壤呼吸及土壤微生物生物量碳氮在一个生长季的动态情况。结果表明：施氮对土壤呼吸各指标和土壤微生物碳氮都有极显著的影响，施氮能促进土壤全呼吸、自养呼吸、异养呼吸通量和土壤微生物生物量碳氮的增长，施氮使土壤呼吸通量提高了11%-15%，土壤微生物量碳提高了5%-9%，土壤微生物量氮提高了23%-34%。在中氮水平下（5 g m^-2 a^-1）对土壤呼吸的促进最显著。相关分析发现，土壤呼吸与微生物生物量碳氮和微生物代谢商极呈显著正相关，微生物量碳氮与土壤温度呈极显著的正相关，与土壤湿度呈极显著负相关。通过一般线性回归拟合土壤呼吸速率与土壤10 cm温湿度的关系，发现土壤呼吸速率与土壤温度呈极显著的正相关，与土壤湿度极显著负相关（P < 0.001），中氮水平下土壤温度敏感性系数Q₁₀值（7.10）明显高于对照（4.26）。



Abstract:With rapid increase of global atmospheric nitrogen deposition, the nitrogen-limited subalpine forest ecosystem in western China maybe significantly affected. Soil microorganisms are important component part of the ecosystem and they are essential participants in the matter circulation and energy flow. Due to different background of ecosystem types, soil nutrients, and nitrogen deposition values, there are many uncertainties of soil respiration and soil microbial biomass carbon and nitrogen (MBC and MBN)in response to nitrogen application. Will nitrogen application promote the immobilization of soil carbon and nitrogen by soil respiration and microbial biomass in the subalpine forest ecosystem?Based on this assumption, a 60-year-old Larix mastersiana of subalpine coniferous forest in western Sichuan was taken as the research object.Dynamic of soil respiration and soil microbial biomass carbon and nitrogen were measured under four levels of nitrogen application control tests(CK:0g m^-2a^-1, N₁:2g m^-2a^-1, N₂:5g m^-2a^-1, N₃:10g m^-2a^-1)during a growing season (April-October).The results showed that nitrogen application had significant effects on soil respiration and soil microbial carbon and nitrogen, which significantly promote these indicators. Soil respiration flux increased by 11%-15%, soil microbial biomass carbon increased by 5%-9%, and soil microbial biomass nitrogen increased by 23%-34%. The promotion of soil respiration is most facilitatedunder the level of nitrogen (5g m^-2a^-1).Correlation analysis found that soil respiration had significant positive correlation with MBC, MBN and microbial metabolic quotient, and MBC and MBN had significant positive correlation with soil temperature and negative correlation with soil humidity.General linear regression analysis found soil respiration rate had significant positive correlation with soil temperature and negative correlation with soil moisture (P < 0.001),Soil temperature sensitivity coefficient Q₁₀value (7.10) was significantly higher than the control Q₁₀value (4.26).





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