Labile carbon (C) input to soils is expected to affect soil organic matter (SOM) decomposition and soil organic C (SOC) stocks in temperate coniferous forests. We hypothesized that the SOM decomposition rate, C content in soil fractions, and microbial and faunal abundance and activity were increased along the gradient in labile C input around wood ant nests. Three distances from the nest that differed in annual labile C input to soil were selected: 4 m with 6379 mg C m −2 , 30 m with 9060 mg C m −2 , and 70 m with 9215 mg C m −2 . Soil from the organic horizon (Oe+Oa), surface mineral horizon (A), and subsoil mineral horizon (B) was analyzed for C content in soil fractions and for activity and abundance of soil microorganisms and fauna. In addition, a 1-year litter-bag and soil-bag decomposition experiment was conducted. Although the rate of soil decomposition did not differ along the labile C input gradient, the rate of litter decomposition in the B horizon increased as labile C input increased with distance from the nest. Correspondingly, the C content in bulk soil and in the labile and less-protected soil fractions in the B horizon decreased as labile C input increased. We infer that, because the O and A horizons are less C-limited than the B horizon, the changes in the labile C input along the gradient affected the B horizon more than the surface O and A horizons. However, soil microbial and faunal activity and abundances were not consistently affected by the gradient. Apparently, C stocks in soil fractions are more important for microbial and faunal communities than labile C inputs. Although the results indicate that SOC content changes very slowly in the coniferous forest soil of the current study, increases in the input of natural labile C leads to decreases in the SOC stock in the B horizon. By increasing the labile C input to temperate forest soils, future increases in atmospheric CO 2 concentration may therefore lead to a significant loss of SOC in deep soil layers.

中文翻译：

---

受温带森林土壤不稳定碳输入梯度影响的土壤组分中的有机质分解和碳含量

预计土壤中的不稳定碳 (C) 输入会影响温带针叶林中的土壤有机质 (SOM) 分解和土壤有机碳 (SOC) 库。我们假设 SOM 分解速率、土壤组分中的 C 含量以及微生物和动物群的丰度和活动沿着木蚁巢周围不稳定 C 输入的梯度增加。选择了三个距离巢穴的三个距离，其中每年对土壤的不稳定 C 输入不同：4 m 具有 6379 mg C m -2 ，30 m 具有 9060 mg C m -2 ，以及 70 m 具有 9215 mg C m -2 。分析了有机层 (Oe+Oa)、表层矿物层 (A) 和底土矿物层 (B) 的土壤中土壤组分中的 C 含量以及土壤微生物和动物群的活性和丰度。此外，还进行了为期 1 年的垃圾袋和土袋分解实验。虽然土壤分解速率沿不稳定 C 输入梯度没有变化，但 B 层的凋落物分解速率随着不稳定 C 输入随着离巢的距离增加而增加。相应地，随着不稳定 C 输入的增加，散装土壤和 B 层中不稳定和保护较少的土壤部分的 C 含量降低。我们推断，因为 O 和 A 层级比 B 层级受 C 限制更少，所以沿梯度的不稳定 C 输入的变化对 B 层级的影响大于表面 O 和 A 层级。然而，土壤微生物和动物群的活动和丰度并未始终受到梯度的影响。显然，土壤组分中的碳库对微生物和动物群落比不稳定的碳输入更重要。虽然结果表明当前研究的针叶林土壤中 SOC 含量变化非常缓慢，但天然不稳定 C 输入的增加导致 B 层级 SOC 储量减少。通过增加温带森林土壤的不稳定 C 输入，未来大气 CO 2 浓度的增加可能会导致深层土壤中 SOC 的显着损失。