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2008年1月至2009年2月,对华西雨屏区撑绿杂交竹(Bambusa pervariabilis×Den-drocala mopsi)人工林进行模拟氮沉降试验,氮沉降水平分别为对照(CK,0 g N·m-2·a-1)、低氮(5 g N·m-2·a-1)、中氮(15 g N·m-2·a-1)和高氮(30 g N·m-2·a-1),采用红外CO2分析法测定土壤呼吸速率.结果表明:杂交竹林土壤呼吸呈明显的季节变化,7月最高,1月最低.对照样方土壤呼吸年累积量为(389±34)g C·m-2·a-1.土壤呼吸速率与10 cm土壤温度和气温呈极显著正指数关系,与微生物生物量碳、氮呈极显著正线性关系.模拟氮沉降显著促进了土壤呼吸,低氮、中氮处理与对照之间差异达显著水平,但高氮处理与对照之间差异不显著.自然状态下,杂交竹林土壤表层微生物生物量碳和氮分别为0.460和0.020 mg·g-1,而所有氮处理中土壤微生物生物量碳和氮均显著增加.杂交竹林土壤表层(0～20 cm)细根密度为388 g·m-2,模拟氮沉降对杂交竹林细根密度的影响不显著.基于土壤10 cm深度温度和空气温度计算的杂交竹林土壤呼吸Q10值分别为2.66和1.87,短期模拟氮沉降并未显著影响土壤呼吸温度敏感性.杂交竹林土壤呼吸变异主要受温度和微生物生物量的控制,模拟氮沉降可能通过增加土壤微生物生物量促进了该系统土壤CO2排放.
From January 2008 to February 2009, simulated nitrogen deposition experiments were carried out on Bambusa pervariabilis × Den-drocala mopsi plantations in the rain-west China. The nitrogen deposition levels were CK, 0 g N · m -2 · a-1), low nitrogen (5 g N · m -2 · a -1), middle nitrogen (15 g N · m -2 · a -1) and high nitrogen (30 g N · m -2 · A-1), the soil respiration rate was measured by infrared CO2 analysis.The results showed that the soil respiration of the hybrid bamboo forest showed a significant seasonal variation, the highest in July and the lowest in January. The cumulative annual soil respiration in the control plot was (389 ± 34) ) g C · m-2 · a-1. The soil respiration rate showed a very significant positive exponential relationship with soil temperature and temperature at 10 cm, and had a significant positive linear relationship with microbial biomass carbon and nitrogen. Simulated nitrogen deposition significantly promoted soil The difference between respiration, low nitrogen, medium nitrogen and control was significant, but the difference between high nitrogen and control was insignificant.Under the natural condition, the microbial biomass carbon and nitrogen of the hybrid bamboo soil were 0.460 and 0.020 mg · g-1, while the soil microbial biomass carbon and nitrogen in all treatments increased significantly.The density of fine roots in surface soil (0-20 cm) of hybrid bamboo was 388 g · m-2, The effect of soil density on root density was not significant.The soil respiration Q10 values of hybrid bamboo forests calculated based on soil depth of 10 cm and air temperature were 2.66 and 1.87, respectively, and the short-term simulated nitrogen deposition did not significantly affect soil respiration temperature sensitivity. Under the control of temperature and microbial biomass, simulated nitrogen deposition may promote the soil CO2 emission by increasing soil microbial biomass.