关键词: 城市绿地分类, 土壤有机质及氮磷钾, 土壤理化性质, 土壤肥力分级, 内梅罗综合肥力评价, 空间结构特征, 空间分布图

Abstract: [Objective] This study aims to provide a scientific basis to the construction and management of urban green land, hence, improving the ecological functionality of urban vegetation in Harbin City, through investigating the characteristics of fertility and its spatial distribution in the urban green land.[Method] 257 soil samples were collected from the following sites:roadside forests, institution-affiliated forests, landscape forests, ecological and public welfare forests, farmland. Nine indicators of soil fertility, including soil organic matter, total N, total P, total K, available N, available P, available K, pH, and soil density were measured. Classification of the 9indicatorsfollowed the classification criteria for soil nutrients listed in the 2nd National Soil Survey (6-grade evaluation) and a modified Nemorow formula. Additionally, spatial distribution of the 9parameterswas obtained by employing ArcGIS software.[Result] The results showed that the content of soil organic matter was graded as level 2 (high) with content of organic matters of 30-40 g·kg^-1 for most regions. For total N, available N and available P, they were graded as level 3, based on the contents of them of 1-1.5 g·kg^-1, 90-150 mg·kg^-1 and <20 mg·kg^-1 respectively. Considering the total K and available K, the levels were in the range of 50-100 g·kg^-1 and 150-200 mg·kg^-1, for most regions, which were graded as level 2 or higher. The total P reached the mid-low level(level 4), which showed a value ranging from 0.4 to 0.6 g·kg^-1 for most regions on the spatial map. The pH of the urban soil on the spatial map was 7.5-8.5, and soil density was 1.3-1.4 g·cm³. By reference to the value of, significant (P<0.05) differences were found among different types of green lands for all the studied parameters, with an exception of the available K. Spatial structure of soil indexes reveled that nugget/sill (C₀/C₀+C) of total P, available N, available P, available K and F were in the range of 25%-75%, while the values of both SOM and soil density were above 75%.[Conclusions] The total P content was low, while the content of total K was high the soil of green land in Harbin City. It was found that the total P, total N, soil density and available N were the main restraining factors for the soil fertility. In particular, the spatial variability of the studied parameters depended on various factors, showing that the total P, available N, available P, available K and F were influenced by structural factors and random factors, while the soil organic matter and soil density were influenced by random factors. Therefore, based on the findings in this study, measures such as application of N-P fertilizer, restricting the use of K fertilizer, and/or growing N-fixing plants, are needed to improve the soil fertility of green-land soil in Harbin City.

Key words: urban green space classification, soil organic matter and N, P, K, soil physical and chemical properties, grade of soil fertility, soil comprehensive fertility index via modified Nemorow formula, spatial structure, spatial distribution map