Abstract: Three urban parks along a building density gradient (indicating a gradient of human disturbance) in Shenzhen were chosen as the sampling sites, and in each park, three vegetation types (lawn, high forest and Lichi forest) were selected to sample soils, with a rural forest of Wutongshan as the reference. The results showed that soil bulk density and pH value in the urban sampling sites were higher than those of the rural forest, exceeding the optimal range of plant growth. Soil carbon and nitrogen concentrations and fine root biomass in urban sampling sites were lower than those of rural forest. However, soil phosphorus concentration in urban sampling sites was higher than those of rural forest, particularly indicated by phosphorus eutrophication in Lichi forests. Soil carbon concentration, nitrogen concentration and fine root biomass were positively related to each other, indicating that urban plant growth may be constrained by soil nitrogen, and that fine root inputs may have contributed substantially to soil organic matter. The results suggest that soil carbon, nitrogen, phosphorus and root biomass in urban green lands were affected by vegetation type and building density. The results may have important implications for green land construction and management: lawns are able to accumulate soil carbon and nitrogen rapidly in the shallow soil layer, and Lichi forests are better to accumulate soil carbon and nitrogen concentration in deeper soil layer. In addition, aboveground litter should not be removed in urban high forests in order to increase soil carbon and nitrogen concentrations.

Key words: urban green land, soil carbon, nitrogen, and phosphorus storage, root biomass, plantation type, building density

摘要： 在深圳市按建成区密度(体现人类活动干扰程度)递增梯度选取3个公园为采样地点, 每个采样地点选取草坪、乔木林和荔枝林3种植被类型采集土壤样品, 同时以远郊的梧桐山人工林为对照, 研究不同深度土壤碳、氮、磷含量和细根生物量。结果表明城区各植被类型土壤容重和pH值都显著高于远郊人工林, 并高出适合植物生长的范围。城区各植被类型土壤碳、氮含量及细根生物量都低于远郊人工林。城区土壤磷含量高于远郊人工林, 呈现明显的富磷化特征, 特别是荔枝林土壤的富磷化现象最严重。土壤碳、氮浓度与细根生物量三者之间显著正相关, 表明城市植物的生长受到土壤氮含量的限制。与此同时, 城市植物的细根周转和输入能够有效维持土壤有机质含量。研究表明, 城市绿地土壤碳、氮、磷含量和细根生物量受现有植被类型和建成区密度(人为干扰)的共同影响。在城市绿地建设中, 种植草坪可以较快地积累土壤表层碳和氮, 而荔枝林更有利于土壤深层碳和氮的积累, 同时, 对于城区乔木林应该减少枯枝落叶的清理以利于土壤碳、氮的积累。

关键词: 城市绿地, 土壤碳氮磷含量, 细根生物量, 植被类型, 建成区密度