林火干扰对广东马尾松林土壤有机碳密度及其活性有机碳的影响

【目的】森林在全球碳循环中发挥着重要作用。林火干扰是全球生物地球化学循环的关键驱动因子,影响植被结构变化及森林演替方向,从而对森林生态系统土壤有机碳密度及碳周转产生重要作用,进而影响森林碳循环与碳平衡。笔者定量研究林火干扰对森林生态系统土壤有机碳密度及其活性有机碳的影响,科学阐明林火干扰对森林生态系统土壤有机碳的影响机制,为火烧迹地恢复与森林碳减排增汇提供参考。【方法】以广东省佛冈马尾松林为研究对象,采用相邻样地比较法、化学分析法,在森林生态系统水平上,定量测定不同林火干扰强度对土壤有机碳密度、土壤活性有机碳含量和细根生物量的影响,对林火干扰后土壤有机碳密度的变化进行定量研究,探讨林火干扰对土壤有机碳密度以及活性有机碳的影响机制,深入分析森林生态系统土壤有机碳的循环与分配过程。【结果】林火干扰对马尾松林的土壤有机碳密度、活性有机碳含量和细根生物量均有影响,不同林火干扰强度下土壤有机碳密度与土壤活性有机碳含量变化趋势均表现为对照>轻度林火干扰>中度林火干扰>重度林火干扰。轻度林火干扰对土壤有机碳密度的影响差异不显著(P>0.05),而中度和重度林火干扰则显著降低土壤有机碳密度(P<0.05)。林火干扰的马尾松林土壤细根生物量均低于对照样地,变化趋势为重度林火干扰>中度林火干扰>轻度林火干扰,轻度林火干扰只显著降低土壤表层细根生物量(P<0.05),而中度和重度林火干扰显著降低了土壤表层和浅层细根生物量(P<0.05)。【结论】林火干扰减小了土壤有机碳密度,减少幅度随土壤剖面深度增加而逐渐变小。轻度林火干扰仅显著降低了表层土壤有机碳密度,而中度和重度林火干扰显著降低了土壤表层和浅层土壤有机碳密度,进而导致土壤有机碳密度显著变化。林火干扰对土壤活性有机碳含量产生了影响。林火干扰后马尾松林4种土壤活性有机碳含量均呈下降趋势,但仅中度和重度林火干扰差异显著。活性有机碳含量各组分随林火干扰强度增加沿土壤剖面递减的幅度呈现一定差异,重度林火干扰后的递减趋势最强。此外,林火干扰还降低了马尾松林土壤细根生物量。

Effects of forest fire disturbance on soil organic carbon density and labile organic carbon of Pinus massoniana forests in Guangdong Province,China

【Objective】Forests play an important role in the global carbon (C) cycle. Fire disturbance in forests is a key driving factor of the global biogeochemical cycle, as it affects vegetation structure and the direction of forest succession, which play important roles in soil organic C density and C turnover in forest ecosystems, thus affecting the forest C cycle and C balance. A quantitative study of the effects of forest fire disturbance on soil organic C density and active organic C in forest ecosystems was conducted. It also contributed to clarification of the mechanism of forest fire disturbance on soil organic C in forest ecosystems, and provided information about the recovery of burned land and forest C emission reduction effects.【Method】In a subtropical P. massoniana forest in Guangdong Province, adjacent plot comparison and chemical analysis methods were used to quantitatively determine the soil organic C density, soil active organic C content and fine root biomass at different levels of fire disturbance (low, moderate and high) in the forest ecosystem. The impact of forest fire disturbance on soil organic C density, and the mechanism of forest fire disturbance on soil organic C density and active organic C were investigated and an in-depth analysis of the C cycle and partitioning of soil organic C in the forest ecosystem process was undertaken.【Result】The results showed that forest fire disturbance had an effect on soil organic C density, soil labile organic C content and fine root biomass in P. massoniana forest, and the trend for soil organic C density and soil labile organic C content was: control > low forest fire disturbance > moderate forest fire disturbance > high forest fire disturbance. There was no significant difference in the effect of low forest fire disturbance on soil organic C density (P > 0.05), whereas moderate and high forest fire disturbances significantly reduced soil organic C density (P < 0.05). The soil fine root biomass in P. massoniana forest was lower than that in the control plots, and the trend was: high forest fire disturbance > moderate forest fire disturbance > low forest fire disturbance. Low forest fire disturbance only significantly reduced the soil surface fine root biomass (P < 0.05), whereas moderate and high forest fire disturbances significantly reduced the soil surface and shallow fine root biomass (P < 0.05). 【Conclusion】The results show that forest fire disturbance reduces soil organic C density, and the decrease gradually declines as the soil profile depth increases. The low forest fire disturbance significantly reduced the soil organic C density only at the soil surface, whereas the moderate and high forest fire disturbances significantly reduced the soil organic C density at the soil surface and in shallow soil, which led to significant changes in soil organic C density. Forest fire disturbance had an effect on the soil active organic C content. The contents of soil active organic C in the four species of P. massoniana forest decreased after forest fire disturbance but only moderate and high forest fire disturbances were significantly different. The components of active organic C content showed some difference along the decreasing profile of the soil profile with an increase in forest fire disturbance intensity, and the decreasing trend after high forest fire disturbance was the greatest. Forest fire disturbance had an effect on the fine root biomass of P. massoniana forest.