Reforestation is an important step toward recovering soil quality and wildlife habitats that are degraded due to deforestation. However, little is known about how soil C and N compositions in subtropical forests evolve after decades of reforestation. This study comprehensively evaluated the differences in soil C and N fractions in 40‐ and 80‐year‐old secondary (reforested) coniferous forests and a natural broadleaf forest. Although reforestation with coniferous plants appeared to increase soil organic matter and labile C levels, the ratio of soil labile C to total organic C was lower in the reforested coniferous forests than the natural broadleaf one. The trend in the labile N to total N ratio as coniferous reforestation progresses follows that of C. Furthermore, the percentage of recalcitrant C as total soil organic C was higher in the reforested coniferous forests than the natural broadleaf one. This feature of C composition in reforested coniferous forest causes environmental stress to microbes (as indicated by a high metabolic quotient) in the forest, even several decades after reforestation of a former broadleaf forest site. Results from this study demonstrate that it takes a very long time for reforestation with coniferous vegetation to restore the soil chemical properties of the previous natural forest.

中文翻译：

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亚热带低山林区造林40年和80年后土壤碳氮含量的改善

植树造林是恢复因毁林而退化的土壤质量和野生动植物栖息地的重要一步。然而，关于几十年的重新造林后，亚热带森林中土壤碳和氮成分如何演变的消息鲜为人知。这项研究综合评估了40和80岁的次生（重新造林）针叶林和天然阔叶林中土壤C和N分数的差异。尽管用针叶植物造林似乎增加了土壤有机质和不稳定碳水平，但在重新造林的针叶林中，土壤不稳定碳与总有机碳的比率比天然阔叶林低。随着针叶林再造的进展，不稳定氮与总氮之比的趋势遵循碳的趋势。此外，在重新造林的针叶林中，顽固性碳占土壤有机碳总量的百分比高于天然阔叶林。在重新造林的针叶林中，C成分的这一特征甚至对原阔叶林地进行重新造林后的几十年，都会对森林中的微生物造成环境压力（由高代谢商表示）。这项研究的结果表明，用针叶植被重新造林需要很长时间才能恢复以前天然林的土壤化学特性。