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

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