Abstract:

Rapid urbanization has led to systematic degradation of urban green space soil, such as soil compaction, soil organic matter deficiency, soil acid-base imbalance‌, and soil biodiversity decline, which severely constrain the ecological service functions of these soils. Traditional restoration measures of urban green space soil are characterized by high costs and poor sustainability, necessitating the exploration of ecological remediation pathways based on nature. This study took Guangzhou as an example, conducted a comparative analysis of on-site investigation data and the local standard “DB4401/T 36—2019 for Garden Planting Soil”. The results showed that the soil quality of green spaces in Guangzhou generally failed to meet the standards. The average pH of the soil was pH 6.99, with a range of pH 3.16 to pH 10.29. 24.7% of the soil had a pH value above 7.5, and 2.63% of the soil had a pH value below 5.5. The average soil bulk density was 1.41 g/cm³, and the proportion of sample points with bulk density greater than 1.25 was 51.3%. The average soil organic matter content was only 15.1 g/kg, and the proportion of soil sample points below the standard limit was 63.1%. The proportion of soil sample points with soil hydrolyzable nitrogen, available phosphorus and available potassium content below the standard limit was 33.9%, 12.8% and 9.13% respectively. Soil compaction and acid-base imbalance were common problems. The multiple functions of earthworms as “soil ecosystem engineers” in improving soil physical structure, regulating nutrient cycling, constructing biological networks and purifying pollutants were summarized and sorted out, and the feasibility of their application was comprehensively evaluated from multiple dimensions such as resource conditions, economic costs, policy environment, market demand and ecological risks. It was considered that introduction of earthworm was an efficient and low-cost nature-based solutions (NbS) approach, which was suitable for soil ecological restoration of urban green space. This paper proposed an implementation pathway for ecological restoration of green space soils based on earthworm resource surveys, breeding of native species, scientific introduction, and supporting monitoring, evaluation, and adaptive management, aiming to provide a reference for enhancing the service capacity of urban ecosystems.

Key words: urban green space, soil, ecological restoration, earthworm introduction, nature-based solutions (NbS)