城市化梯度上亚热带常绿阔叶林土壤有机碳及其组分特征

以珠江三角洲城区(广州)、近郊(鼎湖山)及远郊(怀集)梯度上的亚热带常绿阔叶林为对象,研究不同土层土壤总有机碳、惰性有机碳、活性有机碳(易氧化有机碳、微生物生物量碳和水溶性有机碳)沿城市化梯度的变化,分析城市化对森林土壤有机碳的影响.结果表明: 0～5 cm土层土壤总有机碳和惰性有机碳含量均在城市化梯度上差异不显著,在5～60 cm土层,土壤总有机碳含量在远郊森林显著高于近郊和城区森林,而惰性有机碳含量在近郊森林最高,城区与远郊森林差异不显著.易氧化有机碳含量在近郊森林显著低于远郊(0～60 cm)和城区(0～10 cm)森林,微生物生物量碳含量在城区森林显著低于近郊和远郊森林,而水溶性有机碳含量在近郊森林(0～10 cm)显著低于城区森林.在0～20 cm土层,城区、远郊森林土壤活性有机碳占总有机碳的比例显著高于近郊森林,而惰性有机碳占总有机碳的比例在远郊森林最低;近郊与城区森林惰性有机碳占总有机碳的比例仅在5～10 cm差异显著.城市化增加了土壤活性碳组分,降低稳定性碳组分,不利于总有机碳积累,远郊森林土壤对城市化的响应更敏感.

Characteristics of soil organic carbon and its fractions in subtropical evergreen broad-leaved forests along an urbanization gradient.

Subtropical evergreen broad-leaved forests were selected along an urban (Guangzhou) - suburban (Dinghushan) - rural (Huaiji) gradient in the Pearl River Delta, from which soil samples in different layers were collected. The changes in total organic carbon (TOC), recalcitrant organic carbon (ROC), and active organic carbon (AOC) including readily oxidizable organic carbon (ROOC), microbial biomass carbon (MBC), and water-soluble organic carbon (WSOC) of samples were examined along this urbanization gradient to reveal the influence of urbanization on forest soil organic carbon. Results showed that no significant differences in both TOC and ROC contents were observed in 0-5 cm soil layer along the gradient. In 5-60 cm soil layer, the TOC content was significantly higher in the rural forest than that in the suburban and urban forests, the ROC content was the highest in the suburban forest and no significant difference was observed between the urban and rural forests. The ROOC content was significantly lower in the suburban forest than in the rural (0-60 cm soil layer) and urban (0-10 cm soil layer) forests. The MBC content was significantly lower in the urban forest than that in the suburban and rural forests. The suburban forest had significantly lower WSOC than the urban forest (0-10 cm soil layer). In 0-20 cm layer, the percentage of AOC to TOC of the urban and rural forests was significantly higher than those of the suburban forest, while the percentage of ROC to TOC was the lowest in the rural forest. The significant difference in the percentage of ROC to TOC was only observed in 5-10 cm depth layer between the suburban and urban forests. The results indicated that urbanization increased the active components of soil organic carbon and reduced the stable ones, which could be detrimental to organic carbon accumulation in soils. The rural forest soils were more sensitive to the urbanization.