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.

土壤有机碳（SOC）是森林生态系统中碳（C）循环的重要组成部分，并且受树种的影响很大。源自不同植被的凋落物将不同数量和质量的有机物质引入土壤，并影响土壤碳库的形成和稳定性。我们提出了在三种温带森林中的树种对SOC稳定性的影响的研究：松树（Pinus tabuliformis Carr。），落叶松（Larix principis-rupprechtii Mayr。）和桦木（Betula dahurica）颇尔（Pall。）。确定了0–5、5–10、10–20和20–30 cm土壤层中的SOC和高锰酸盐可氧化C（POXC）浓度。通过分析不同树种下土壤有机碳的化学组成和有机碳在土壤颗粒级分中的分布，评估土壤有机碳的稳定性。在所有四个土壤层中，桦树林的SOC和POXC浓度均明显高于松树和落叶松。这些差异可能与海拔高度有关，也可能是由桦木和两种针叶树种的凋落物特性差异引起的。在桦木林土壤中，有机碳富集于粘土大小的部分，但在松树下，粗砂部分（2000-250μm）中的有机碳含量较高，这表明桦木林在稳定的SOC池中积累碳的潜力更大。SOC的化学组成由固态确定¹³ C核磁共振光谱显示，在前5名中，桦木林土壤的松树和落叶松林土壤的烷基C / O-烷基C，芳族C / O-烷基C和疏水性C /亲水C的比率更高厘米的土壤层，比桦树和落叶松下的桦树更能反映顽固的SOC成分。我们得出的结论是，白桦林不仅可以增加矿质土壤中的SOC浓度，而且在稳定的土壤碳库中具有更高的积累C的潜力，因此比松木和落叶松林更有利于SOC稳定。这项研究强调，除了SOC浓度外，树种选择的未来策略还需要考虑树种对稳定性的潜在影响。