The influence of tree species on soil organic carbon stability under three temperate forests in the Baihua Mountain Reserve, China

Abstract Soil organic carbon (SOC) is an important component of the carbon (C) cycle in forest ecosystems, and is largely influenced by tree species. Leaf litter originated from different vegetations introduce organic materials into soil with different quantities and qualities, and influence the formation and stability of soil C pool. We present a study on the influence of tree species on SOC stability under three temperate forests: pine (Pinus tabuliformis Carr.), larch (Larix principis-rupprechtii Mayr.) and birch (Betula dahurica Pall.) in the Baihua Mountain Reserve. The SOC and permanganate oxidizable C (POXC) concentrations in the 0–5, 5–10, 10–20 and 20–30 cm soil layers were determined. The SOC stability was evaluated by analyzing the chemical composition of SOC and the distribution of organic C in soil particle-size fractions under different tree species. The birch forest had significantly higher SOC and POXC concentrations than pine and larch in all the four soil layers. These differences might be partly related to the altitude, and also caused by the differences in litter characteristics between birch and the two coniferous species. The organic C was enriched in clay-sized fraction in birch forest soil, but showed higher concentrations in coarse sand fraction (2000-250 μm) under pine, suggesting a higher potential of birch forest for C accumulation in stable SOC pools. The chemical composition of SOC was determined by solid-state 13C nuclear magnetic resonance (NMR) spectra and showed that the birch forest soil had higher alkyl C/O-alkyl C, aromatic C/O-alkyl C and hydrophobic C/hydrophilic C ratios than pine and larch forest soils in the top 5 cm soil layer, reflecting a more recalcitrant SOC composition under birch than under pine and larch. We concluded that the birch forest could not only increase SOC concentration in mineral soils but also had a higher potential to accumulate C in stable soil C pools, and thus is more beneficial to SOC stabilization than the pine and larch forests. This study highlights that future strategy of tree species selection needs to consider the potential effects of tree species on the stability in addition to the concentration of SOC.