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.