土壤溶解性有机碳（DOC）是土壤有机碳库的活性组分，DOC降解影响土壤有机碳的迁移转化过程、生态系统的养分平衡和微生物的能源供给。当前大气氮沉降的增加是影响我国南方森林生态系统碳固定过程的重要因素，已引起各方广泛关注。论文基于中亚热带红壤丘陵区三种人工针叶林过去5 a 的施肥试验，重点分析了不同树种土壤DOC季节及0~30 cm土壤垂直剖面上的动态变化特征，对比分析了施肥对于不同人工林土壤DOC的影响。研究发现：① DOC浓度季节变化：湿地松林为秋季 >春季 >夏季 >冬季；马尾松林为秋季 >春季 >冬季 >夏季；杉木林为秋季>夏季>冬季>春季。DOC浓度剖面变化特征如下：湿地松林为10 cm>20 cm>30 cm；马尾松林为20 cm >10 cm >30 cm；杉木林为20 cm >30 cm >10 cm。②湿地松林土壤DOC浓度：施P肥 >对照 >施N+P肥 >施N肥；马尾松林土壤DOC浓度：对照、施N+P肥>施N肥>施P肥；杉木林：对照>施P肥>施N肥、施N+P肥。论文通过研究不同施肥条件下人工林DOC浓度在季节和剖面上的变化，可为了解大气氮沉降对中亚热带人工针叶林土壤DOC的可能影响提供重要的科学依据。

Soil dissolved organic carbon (DOC) is an active fraction of soil organic carbon (SOC) pool, the degradation of DOC can affect soil carbon cycling, ecosystem nutrient dynamics and energy supply to microorganism. Elevated nitrogen deposition is an important factor affecting forest carbon pool, its effect on DOC dynamics has been discussed extensively. In the last five years, we investigated the seasonal and profile variabilities of DOC concentrations in soils of three types of planted forests in central subtropical region. Seasonal variation of DOC concentration in descending order for slash pine forest was: autumn (11.3 mg/L) > spring (10.4 mg/L) >summer (10.2 mg/L) > winter (8.0 mg/L); for masson pine forest: autumn (12.2 mg/ L) > spring (10.7 mg/L) > winter (8.9 mg/L) > summer (7.3 mg/L); and Chinese fir forest: autumn (9.4 mg/L) > summer (8.2 mg/L) > winter (7.2 mg/L) > spring (7.0 mg/L). Profile variability of DOC concentration for slash pine forest: 10 cm (12.7 mg/L) > 20 cm (10.6 mg/L) > 30 cm (8.7 mg/L); masson pine: 20 cm (13.1 mg/L) >10 cm (9.8 mg/L) > 30 cm (5.8 mg/L); and Chinese fir: 20 cm (8.1 mg/L) > 30 cm (8.0 mg/L) >10 cm (7.3 mg/L). The effects of four kinds of treatments on DOC concentration in different forests were compared. Variabilities of DOC concentration in descending order for slash pine were: P fertilization > CK > N+P fertilization > N fertilization; masson pine: CK, N+P fertilization > N fertilization > P fertilization; and Chinese fir：CK > P fertilization > N fertilization, N+P fertilization. This study highlighted the importance of DOC dynamics for the carbon cycle and provided evidence for DOC dynamics in soil of coniferous planted forests under nitrogen deposition in subtropical region.