Comparative study on the effects of soil quality improvement between urban spontaneous groundcover and lawn

Abstract

Ecological restoration of today's urban soils is a global challenge. Soil quality improvement through groundcover is one of the practical ways in urban ecological restoration practice, and the selection of suitable groundcover types is the key to successful soil ecological restoration. Spontaneous groundcover and lawn, as the two typical urban groundcovers, are mostly used for urban soil restoration. However, few studies have quantified and compared their effects on improving soil quality in urban environments, making it difficult to make scientific choices in practice. Furthermore, the improving mechanism of groundcovers on soil quality is still not quite clear. First, root biomass is commonly considered to be a direct factor affecting soil quality, however, most of the current studies focus on the relationship between a single soil quality index and root mass, and few studies systematically explore the relationship between soil quality index and root mass. Second, species richness and functional group are two main differences in species composition between autochthonous groundcover and lawn, one of which must be the driving factor for the difference in soil improvement effect. At present, there are inconsistent results on whether the driving factors of groundcover for soil quality improvement are species richness or functional groups. In order to explore the above problems, this study sets up a comparative experiment in the urban environment. this study. Twelve typical groundcovers (including six urban groundcovers and six lawns) covering five functional groups (grass (G), forbs (F) and grass (L), G + F and G + F + L) were selected for experiments. Soil quality indicators including nitrogen (N), phosphorus (P), potassium (K), boron (B), iron (Fe), soil organic carbon (SOC), catalase (CAT), root biomass and species richness were tested, and the soil quality index (SQI) reflecting soil quality was calculated. The results showed that the soil quality index (SQI) of autochthonous groundcover was 35 % higher than that of lawn, and the contents of N, P, K and SOC in autochthonous groundcover were significantly higher than those in lawn. N, P, SOC, CAT showed a response to the root mass of groundcovers. Among all the indicators, only CAT was significantly correlated with groundcover species richness, while N, P, K, and SOC were significantly dependent on their functional diversity, and showed significant differences in different functional combinations. This study shows that the improvement effect of urban autochthonous groundcover on soil quality is significantly better than that of lawn. Functional groups may be the driving factors for the change of groundcover soil quality. Different functional groups may affect the root system of groundcover through compensation effect, thus affecting soil quality, which ultimately leads to the difference in the improvement effect of spontaneous groundcover and lawn on soil quality. This study provides a theoretical basis for the application of groundcover and lawn in urban soil ecological restoration in the future. In the practice of ecological restoration, if the goal is to improve soil quality, groundcover will be a more sensible choice than lawn. At the same time, attention should be paid to the diversity of functional groups to maximize the benefits of soil ecological restoration.