南京城市林业土壤的肥力特征分析

采集南京市不同功能区林地0~20 cm和20~40 cm土壤,分别测定土壤的理化性质和酶活性。研究结果表明,南京城市林业表层土壤(0~20 cm)的容重大,孔隙度和渗透性小;土壤质地以粉壤土为主,所占比例为60.42%,土壤中普遍含有砾石,但含量不是很高;土壤以中性土和碱性土为主,非天然林土壤的pH明显高于城郊天然林下土壤;土壤有机质和全氮含量偏低,土壤的阳离子交换量(CEC)偏高,非天然林土壤中有效磷富集,但城郊天然林土壤有效磷缺乏,土壤速效钾富集。0~20 cm和20~40 cm土壤中,过氧化氢酶活性平均值分别为0.25 mL/g和0.31 mL/g,脱氢酶活性平均值分别为32.14 mg/g和20.91 mg/g,碱性磷酸酶活性平均值分别为16.7 mg/kg和9.5 mg/kg,纤维素酶活性平均值分别为0.002 1 mg/g和0.001 mg/g。过氧化氢酶活性、脱氢酶活性和碱性磷酸酶活性与土壤有机质和全氮含量都有显著相关性,是表征城市林业土壤肥力的重要生物指标。

A Study on Fertility Characters of Urban Forest Soil in Nanjing City

The physiochemical physical and chemical properties as well as enzyme activities of urban forest soil with the depth of 0~20 cm and 20~40 cm in different functional areas of Nanjing were analyzed.The result indicated that surface soil(0~20 cm) had a high bulk density,low porosity and permeability.Soil texture was dominated by silt loam which accounts for 60.42%.The content of gravel was low in most of the soil samples.The type of soil was dominated by neutral and alkaline soil,and the pH value of unnatural forest soil was distinctly high as compared with suburban natural forest soil.Soil organic matter and total nitrogen were low,cation exchange capacity(CEC) was high.Soil available potassium enriched,and soil available phosphorus enriched in unnatural forest soil but lacked in suburban natural forest soil.The average values of hydrogen peroxidase activity in soils with 0~20 cm and 20~40 cm depths were 0.25 mL/g and 0.31 mL/g respectively,while those of dehydrogenase activity were 32.14 mg/g and 20.91 mg/g respectively,those of alkaline phosphatase activities were 16.7 mg/g and 9.5 mg/g respectively,and those of cellulase activity were 0.002 1 mg/g and 0.001 mg/g respectively.Hydrogen peroxidase,dehydrogenase and alkaline phosphatase were important indicators for fertility of urban forest soil and all had significant relation with soil organic matter and total nitrogen.