杉木幼林土壤垂直剖面CO_2通量对土壤增温的响应

Vertical profile of soil CO_2 flux in a young Chinese fir plantation in response to soil warming

研究土壤垂直剖面CO_2通量的分布是了解生态系统碳循环的重要环节.本研究以亚热带杉木幼林为研究对象,于2014年5月至2015年5月,采用气井法结合Fick扩散法则和扩散系数模型计算15、30、60 cm各层土壤的CO_2通量,探讨增温对其影响.结果表明:杉木幼林土壤增温影响可至60 cm土层,增温显著降低了各层土壤含水量(p<0.05).增温显著增加了杉木幼林土壤CO_2通量(p<0.05),深层尤为显著;增温处理(W)后15、30、60 cm土层的土壤CO_2通量年均值分别为1.35、0.73和0.36μmol·m-2·s-1,比对照(CT)相应增加了36%、180%和192%,并且增温显著影响了土壤基础呼吸速率F10和土壤温度敏感性指数Q10(p<0.05).土壤温度和含水量能够共同解释各层土壤CO_2通量季节变异的62%~87%,且增温处理后其R2增大.双因子模型拟合结果优于单因子模型.增温能够增加土壤呼吸,对全球大气CO_2浓度升高具有正反馈作用.

Continuous measurements were conducted to investigate the soil CO2 flux distribution in vertical profile of a young Chinese fir plantation in response to soil warming from May 2014 to May 2015. The results showed that the effect of soil warming was up to 60 cm soil depth,and soil moisture were reduced significantly at each soil depth by warming（ p〈0.05）. The annual average soil CO2 flux of warming plot（ W） at 15,30 and 60 cm were 1.35,0.73 and 0.36 μmol·m-2·s-1,respectively,and the growth factors of soil CO2 flux were of 36%,180% and 192%,which were higher than that of control（ CT）.Both soil basal respiration rate F10 and soil temperature sensitivity index Q10 were influenced by warming significantly（ p〈0.05）. Soil temperature and soil moisture explained the seasonal CO2 flux change from 62% to 87% in different soil layers of the monthly variations in soil respiration. The positive effect of soil warming was demonstrated by the R2 of soil respiration to soil temperature and moisture. It can be concluded that two-factor models,compared to singlefactor model,was more suitable for analyzing the impact of soil temperature and moisture on the seasonal variations of soil respiration in the area concerned in this study. Soil respiration increased by simulated soil warming,and there was a positive feedback on the global atmospheric CO2 concentration.