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大气CO2浓度升高和N沉降持续增加已是不争的事实,影响着森林生态系统碳循环。为深入了解CO2浓度升高和N沉降增加对中亚热带森林土壤碳循环的共同影响,本研究通过模拟CO2浓度升高和N沉降增加,利用Li-Cor 8100测定了土壤呼吸1年的变化。结果表明:CO2浓度升高和N沉降显著促进了土壤呼吸,其单独处理的土壤呼吸速率分别比对照高24.4%和27.9%(P<0.01);CO2浓度升高和N沉降同时作用下,土壤呼吸速率比对照高46.5%(P<0.01)。表明,N沉降和CO2浓度升高对土壤呼吸的促进作用存在非加和效应。相关性分析显示,土壤呼吸与土壤温度呈显著正相关,而与土壤含水量呈负相关。CO2浓度升高和N沉降增加改变了土壤呼吸的温度敏感性。CO2浓度升高略微增加了土壤呼吸的温度敏感性,而N沉降则降低了土壤呼吸的温度敏感性。因此,在全球CO2浓度升高和N沉降增加的背景下,中亚热带森林土壤有机碳向大气中的排放可能会增加,但有机碳分解对环境温度变化的敏感性降低。
It is an indisputable fact that atmospheric CO2 concentration and N deposition increase continuously, affecting the carbon cycle of forest ecosystem. In order to further understand the common effects of elevated CO2 and increased N deposition on soil carbon cycling in the subtropical forests, this study measured the changes of soil respiration for one year by simulating the increase of CO2 concentration and N deposition. The results showed that soil CO2 respiration increased significantly with the increase of CO2 concentration and N deposition, and the respiration rate of soil alone was 24.4% and 27.9% higher than that of the control (P <0.01). Under the simultaneous action of CO2 concentration and N deposition, The respiration rate was 46.5% higher than the control (P <0.01). The results showed that the promotion effect of N deposition and CO2 concentration on soil respiration had the effect of non-additive. Correlation analysis showed that there was a significant positive correlation between soil respiration and soil temperature, but negatively correlated with soil moisture content. The increase of CO2 concentration and the increase of N deposition changed the temperature sensitivity of soil respiration. The increase of CO2 concentration slightly increased the temperature sensitivity of soil respiration, while the N deposition decreased the temperature sensitivity of soil respiration. Therefore, under the background of the increase of global CO2 concentration and N deposition, the release of soil organic carbon to the atmosphere in the subtropical forest may increase, but the sensitivity of organic carbon decomposition to the change of ambient temperature is reduced.