A missing sink in forest ecosystems, the effect of dwarf bamboo understory on soil carbon sequestration

为评价矮竹（Sasa senanensis）林下植被对森林生态系统土壤固碳的影响，比较了相邻两个落叶阔叶林样地地表矿物层土壤碳含量和溶解有机碳（DOC）通量。沙沙样地有机质层DOC通量比非沙沙样地高20%，主要是由于沙沙凋落物的存在。应用罗斯碳模型（Rothamsted carbon (Roth C)）估算了林下莎草林地土壤中有机质的固碳量。采用3个情景进行15年模拟：A（地上树木凋落物生产）、B（地上树木和莎莎凋落物生产）、C（地上和地下树木和莎莎凋落物生产）。情况C的年有机碳积累量（约0.7tC ha-1年-1）高于情况A和b。这表明莎草通过增加对DOC的吸收量对土壤固碳具有积极的启动作用，而莎草凋落物产量（特别是地下凋落物）对落叶阔叶林生态系统固碳具有重要作用。

To evaluate the effect of dwarf bamboo (Sasa senanensis) understory on soil carbon sequestration in forest ecosystems, we compared the soil carbon content and the dissolved organic carbon (DOC) flux for a surface mineral horizon between two adjacent deciduous broad-leaved forest sites. The DOC flux of the organic horizon at the Sasa site was 20% higher than that at the non-Sasa site because of a presence of Sasa litterfall. We also estimated the carbon sequestration of organic matter in forested soil with understory Sasa by applying the Rothamsted carbon (Roth C) model. A 15-year simulation was run three scenarios: A (aboveground tree litter production), B (aboveground tree and Sasa litter production), C (above- and belowground litter production of trees and Sasa). The annual SOC accumulation in case C (ca. 0.7tC ha-1 yr-1) was higher than that of case A and B. These results suggest that Sasa exerts a positive priming effect on soil carbon sequestration by increasing the amount of DOC sorption, and that litter production (especially for belowground) of Sasa are important to SOC sequestration in deciduous broad-leaved forestecosystems.