大兴安岭火烧迹地土壤呼吸及其与水热因子的关系

Soil respiration and its relationships with hydrothermic factors in the burned areas of Daxingan Mountain.

林火对森林生态系统碳循环起着重要的干扰作用，森林火烧迹地的土壤碳动态直接关系到森林生态系统碳循环过程。本文采用LI-6400-09土壤呼吸测定系统对内蒙古大兴安岭北部兴安落叶松林未过火区、2003年（轻度、重度）和2008年（轻度、重度）的火烧迹地土壤呼吸速率（Rs）进行生长季观测。结果表明：不同年份和不同程度火烧迹地土壤呼吸的日动态和生长季动态均呈单峰曲线的特点，日峰值出现在14：00，生长季峰值出现在8月份，Rs的整体特征表现为2008年重度〉2003年重度〉2008年轻度〉2003年轻度〉未过火区；多因素方差分析显示，月份、火烧年份和火烧程度对Rs均产生极显著的影响（P〈0．01）；不同火烧迹地5cm土壤温度（T5）与Rs之间具有极显著的指数回归关系（P〈0．01），而10em土壤含水量（W10）与Rs表现为二次函数关系，当W10达到30％～40％时，Rs达到峰值。初步认为，土壤温度是影响火烧迹地土壤呼吸的主要非生物因素之一，而林火对冻土环境的干扰导致了冻土区土壤水分形态的转变，因此土壤水分对土壤呼吸的影响存在较大的不确定性，有待于进一步研究。

Forest fire disturbs the carbon cycle of forest ecosystems, and the soil carbon dynamics of forest burned area is an important part in forest carbon cycle process. In this study, the LI- 6400-09 soil respiration measurement system was used to measure soil respiration （Rs ） of two burned areas during the growing season in northern Daxingan Mountain of Inner Mongolia in 2011. The sites had experienced fires in 2003 and 2008, respectively. The measurements were taken in unburned, lightly burned, and severely burned plots. The results showed that, at a dai- ly time scale, Rs occurred in a unimodal curve with the maximum at 14：00. In the growing months, RS also showed a unimodal curve with the maximum in August. Rs occurred in the order of 2008 severely burned 〉 2003 severely burned 〉 2008 lightly burned 〉 2003 lightly burned 〉 unburned. The post-fire duration and fire intensity significantly affected Rss（P〈0.01 ）. By using multi-way ANOVA, it was found that the time of field measurement, post-fire duration, and fire intensity significantly affected Rs（ P〈0.01 ）. Regression analysis showed that an exponential rela- tionship occurred between Rs and soil temperature at 5 cm depth and a quadratic relationship oc- curred between Rs and soil water at 10 cm depth. When soil water was 30% to 40% , Rs reached the maximum. Our study indicated that soil temperature was one of the main abiotic factors affecting Rs, but the form of soil water was changed by fire disturbance in the permafrost region. This uncertainty between soil respiration and soil water form needs to be further studied.