Soil health assessment of urban forests in Nanchang, China: Establishing a minimum data set model

Soil health plays an important role in environmental and ecosystem sustainability. Urban forest soil health has been gradually deteriorating, resulting in several challenges. Here, a soil health index was employed to explore the soil health conditions and spatial differences in urban forests. We assessed soil health in urban forests in Nanchang, China, by establishing a minimum data set model using 20 soil indicators. The results suggested that the minimum data set included soil organic carbon, clay, pH, soil moisture content, nitrate nitrogen, and mean weight diameter, which could be key indicators for assessing soil health conditions. The average of the soil health index-total data set was 0.45 and that of the soil health index-minimum data set was 0.49, both representing grade III moderate health. Soil health index-minimum data set was positively correlated with soil health index-total data set (p < 0.001), with an R² of 0.77, which suggests that the minimum data set can closely reflect the total data set. In different urban forest types, the average soil health index value represented a grade III moderate health level, among which the soil health index value in landscape forest was remarkably higher (0.51) than that in the other forest types (p < 0.05). With increasing urbanization intensity, the soil health index decreased significantly (p < 0.05), indicating that soil health differed across the components of urban expansion. Our findings, along with further analysis and assessment of urban forest soil health index, can help establish a theoretical basis for soil management in the mid-reaches of the Yangtze River and provide references for managing the adverse effects of urbanization on soil health.