Objective  In the context of urban densification and continuous expansion, the creation of new green spaces faces enormous financial and spatial challenges, placing considerable strain on urban biodiversity conservation efforts. The ongoing process of urbanization brings forth a multitude of wastelands, characterized by the exuberance of spontaneous plants due to poor management and utilization. These plants offer a range of ecosystem services such as regulation, aesthetics, and recreation for the city. Taking Harbin, a representative old industrial city, as an example, this research investigates the species diversity of spontaneous plants in urban industrial wastelands, with a focus on the influence of habitat type, succession stage, disturbance intensity, and surface type on diversity distribution of spontaneous plants. Additionally, the research explores the potential of utilizing spontaneous plants in industrial wastelands as a strategy for creating sustainable and low-maintenance landscape while safeguarding biodiversity.

Methods Utilizing historical maps from Google Earth 7.3.0, along with urban and rural planning data, the research selects seven industrial wasteland sites within Harbin City’s Third Ring Road for investigation. The research, spanning from September 2020 to June 2021, involves a combination of desk analysis and fieldwork. Employing both the grid system sampling method and the typical sample plot method, the research records a total of 875 quadrats, and meticulously documents. information on the species name, height, cover, habitat type, succession stage, disturbance intensity, and surface type of spontaneous plants. Specifically, habitat types are classified as grassland, woodland, building periphery, wall edge, road edge, and forest edge habits. Succession stages are classified as pioneer, intermediate, mature, and spontaneous woodland stages. Surface types are classified as soil, gravel, cinder, railroad track, and waterlogging surfaces. Disturbance intensity, based on human trampling and occupancy, is categorized as low, medium, and high intensities. Using Excel, the research calculates the Patrick richness index, Shannon-Weiner diversity index, and Pielou evenness index for each quadrat. Moreover, the research employs the Kruskal-Wallis test in SPSS 24.0.0 to compare differences in the diversity of spontaneous plants across various habitat types, succession stages, disturbance intensities, and surface types, with comparative results being graphically depicted using GraphPad Prism 9.5.1. The research also conducts canonical correlation analysis (CCA) using CANOCO 5.0 to explore the relationship between the four factors and the distribution of spontaneous plants species.

Results The results show that: 1) The industrial wastelands in Harbin sustain a variety of spontaneous plants, with 168 species of 120 genera in 43 families recorded. The most abundant plant family is Asteraceae, followed by Gramineae, and the dominant species include Ulmus pumila, Geranium sibiricum, Setaria viridis, etc. The abundance of spontaneous plants species in Harbin’s industrial wastelands is notable. In terms of life-type composition, perennial plants hold dominance at 44.05%, followed by annual plants at 30.95%. Native species constituted 114 out of the total, accounting for 67.86% of the recorded species. 2) While the Patrick richness index of road edge and forest edge habitats surpass that of other habitat types, grassland habitats exhibit higher Pielou evenness index. The diversity of spontaneous plants peaks during the intermediate succession stage compared to other stages. Moderate disturbance intensity positively influences the diversity of spontaneous plants, whereas high-intensity disturbances may lead to the reduction of diversity. There is no significant difference in diversity indices across various land surface types. 3) The explanation of changes in the distribution of spontaneous plants driven by four types of influencing factors is 1.79%, indicating that the distribution of spontaneous plants is influenced by more complex factors. Of these factors, succession stage has the greatest effect on the composition and distribution of spontaneous plants, followed by habitat type and disturbance intensity, and surface type has the least effect.

Conclusion Industrial wastelands serve as a crucial habitat for urban spontaneous plants in Harbin, playing a positive and supportive role in upholding the diversity of these plants in the urban environment. Compared with other urban lands, wastelands may be more conducive to the preservation of perennial and woody spontaneous plants. The research proposes the following recommendations: Firstly, forest edges and road edges should be further protected and monitored in urban ecosystem management. Measures such as invasive species control and plants structure regulation should be implemented if necessary. Secondly, in the renewal or temporary use of industrial wasteland, a permissible intensity of human trampling may be considered. However, precautions should be taken to avoid disturbances like garbage dumping and frequent vehicle access. Furthermore, when renewing industrial wasteland for temporary or permanent open spaces, the utilization of native ornamental spontaneous plants, particularly those displaying high frequency under different environmental conditions in the research, can be maximized. This research may contribute to the creation of low-maintenance urban wilderness landscape.