Soil carbon (C) reservoirs held in forests play a significant role in the global C cycle. However, harvesting natural forests tend to lead to soil C loss, which can be countered by the establishment of plantations after clear cutting. Therefore, there is a need to determine how forest management can affect soil C sequestration. The management of stand density could provide an effective tool to control soil C sequestration, yet how stand density influences soil C remains an open question. To address this question, we investigated soil C storage in 8-year pure hybrid larch (Larix spp.) plantations with three densities (2000 trees ha⁻¹, 3300 trees ha⁻¹ and 4400 trees ha⁻¹), established following the harvesting of secondary mixed natural forest. We found that soil C storage increased with higher tree density, which mainly correlated with increases of dissolved organic C as well as litter and root C input. In addition, soil respiration decreased with higher tree density during the most productive periods of warm and moist conditions. The reduced SOM decomposition suggested by lowered respiration was also corroborated with reduced levels of plant litter decomposition. The stimulated inputs and reduced exports of C from the forest floor resulted in a 40% higher soil C stock in high- compared to low-density forests within 8 years after plantation, providing effective advice for forest management to promote soil C sequestration in ecosystems.

森林中的土壤碳（C）库在全球碳循环中起着重要作用。但是，天然林的采伐往往会导致土壤碳流失，这可以通过在砍伐后建立人工林来抵消。因此，需要确定森林管理如何影响土壤碳固存。林分密度的管理可以提供控制土壤碳固存的有效工具，但是林分密度如何影响土壤碳仍然是一个悬而未决的问题。为了解决这个问题，我们调查了8年纯杂种落叶松（Larix spp。）人工林中三种土壤密度（2000公顷ha ^- 1、3300公顷ha ^-1和4400公顷ha ^-1）的土壤C储量），是在采伐次生混合天然林后建立的。我们发现，土壤碳储量随树密度的增加而增加，这主要与溶解有机碳以及凋落物和根系碳输入的增加有关。此外，在温暖潮湿的最丰产时期，土壤呼吸随着树木密度的增加而降低。降低的呼吸所提示的SOM分解减少也与植物凋落物分解水平降低有关。在种植后的8年内，受刺激的投入和林地碳出口减少导致高密度森林中的土壤碳储量比低密度森林高40％，为森林管理提供了有效的建议，以促进生态系统中的土壤碳固存。