Effects of thinning on soil aggregation, organic carbon and labile carbon component distribution in Larix principis-rupprechtii plantations in North China

The forest ecosystem is the ecosystem with the largest terrestrial carbon pool in the world. Afforestation, cutting and tending mutually affect the forest carbon source and the carbon sink. However, few studies have explored the effects of larch plantation management on soil aggregate stability and soil aggregate carbon storage. The effects of the four thinning intensities (unmanaged control (CK), 15% reduction, mild thinning (LT), 30% reduction, intermediate thinning (MT), and 50% reduction, severe thinning (HT)) on soil aggregate stability and carbon storage were investigated in Larix principis-rupprechtii plantations in North China. The results showed that soil aggregates with a particle size of >2 mm or 1–2 mm under all thinning intensities were the most abundant. At the same time, organic carbon and labile carbon were mainly distributed in >0.25 mm soil aggregates. The MT treatment corresponded with the highest organic carbon and labile carbon levels. The distribution of soil macro aggregates was greatly affected by stand density, while the distribution of micro aggregates was most affected by nutrient-related factors. Forest thinning reduces the stability of soil aggregates, though intermediate thinning can improve the carbon sequestration potential of soil aggregates. These findings will provide essential evidence for carbon sequestration of soil aggregates in plantations after thinning, and provide reference for those formulating plantation management strategies in North China.