密云水库上游流域不同林分土壤有机碳分布特征

在全球气候变化背景下,森林土壤有机碳库作为全球土壤碳库的重要组成部分,已成为全球碳循环研究的重点之一。以密云水库上游流域天然次生山杨（Populus davidiana Dode）、白桦（Betula platyphylla Suk.）混交林、天然次生辽东栎（Quercus wutaishanica Blume）林、人工华北落叶松（Larix principis-rupprechtii Mayr.）林、人工油松（Pinus tabulaeformis Carr.）林和灌丛等5种典型林分为研究对象,选取典型样区,进行密集采样和试验分析,探讨了不同林分土壤有机碳质量分数和密度的分布特征。结果表明：在整个土壤剖面上（0~40 cm）,不同林分土壤有机碳质量分数和密度大小顺序均为：杨桦林〉辽东栎林〉灌丛〉落叶松林〉油松林,总体上呈现出随土地利用强度和人为干扰程度增加而降低的变化趋势,即天然次生林比人工林更有利于土壤有机碳的储存和积累;不同林分类型土壤有机碳质量分数和密度均在表层（0~10 cm）最大,并随着土层深度的增加呈下降趋势,剖面分布差异明显;此外,不同林分在0~20 cm土层中的单位面积土壤有机碳储量均占其剖面总储量的57%以上,即土壤有机碳富集在0~20 cm深的表层土体中。因此,为增加森林土壤固碳,应加强对天然次生林的保护,减少人类活动对森林及其表土层的干扰。

Distribution characteristics of soil organic carbon of different forest types in the upstream watershed of Miyun Reservoir in north China

In the context of global climate change,as an important component of the global soil carbon pool,the forest soil organic carbon（SOC） pool has become one of the hot issues in the global carbon cycle field.In this study,distribution characteristics of SOC content and density in the five kinds of typical forest types of the Upstream Watershed of Miyun Reservoir were investigated by soil sampling and laboratory analysis.The results showed as follows.In the whole soil profile（0-40 cm）,SOC content and density were both ranked in order of natural secondary Populus davidiana Dode-Betula platyphylla Suk.mixed forest natural secondary Quercus wutaishanica Blume forest shrub artificial Larix principis-rupprechtii Mayr.forest artificial Pinus tabulaeformis Carr.forest.That is to say,both SOC content and density decreased with the increasing disturbance intensity of land use and management practices.Natural secondary forest is more favorable for SOC storage and accumulation than artificial forest.Both SOC content and density in the top soil layer（0-10 cm） were greatest and declined greatly with the increase of soil depth under all the five forest types.Furthermore,more than half of SOC was accumulated in the top 20 cm soil layer under each kind of considered forest type.Therefore,protecting natural secondary forest and preventing unreasonable human disturbance to forest soil are very important to promote forest soil carbon sequestration.