Composition and mineralization of soil organic carbon pools in four single-tree species forest soils

Forest soil carbon (C) is an important component of the global C cycle. However, the mechanism by which tree species influence soil organic C (SOC) pool composition and mineralization is poorly understood. To understand the effect of tree species on soil C cycling, we assessed total, labile, and recalcitrant SOC pools, SOC chemical composition by C-13 nuclear magnetic resonance spectroscopy, and SOC mineralization in four monoculture plantations. Labile and recalcitrant SOC pools in surface (0-10 cm) and deep (40-60 cm) soils in the four forests contained similar content. In contrast, these SOC pools exhibited differences in the subsurface soil (from 10 to 20 cm and from 20 to 40 cm). The alkyl C and O-alkyl C intensities of SOC were higher in Schima superba and Michelia macclurei forests than in Cunninghamia lanceolata and Pinus massoniana forests. In surface soil, S. superba and M. macclurei forests exhibited higher SOC mineralization rates than did P. massoniana and C. lanceolata forests. The slope of the straight line between C (60) and labile SOC was steeper than that between C (60) and total SOC. Our results suggest that roots affected the composition of SOC pools. Labile SOC pools also affected SOC mineralization to a greater extent than total SOC pools.