The positive relationship between species richness and area is a fundamental principle in ecology. However, this pattern deviates on small islands, where species richness either changes independently of area or increases at a slower rate—a phenomenon known as the Small-Island Effect (SIE). While the SIE has been well documented in natural ecosystem, its presence in highly fragmented and disturbed urban ecosystem remains unexplored, posing challenges for urban vegetation conservation. Urban remnant vegetation, isolated by surrounding infrastructures, preserves intact zonal vegetation characteristics, serves as a benchmark for restoring near-natural habitats and offers ideal conditions to test the existence of the SIE in urban area landscapes. In this study, we surveyed 17 remnant vegetation patches in Qingdao City, China. A total of 331 plants attributed to 255 genera in 81 families have been recorded. Firstly, by using six species–area relationship regression models testing the SIE for remnant vegetation with different plant life forms, we found the SIE in only woody plants, with the land surface area threshold ranging from 6.38 ha (tree) to 11.91 ha (shrub). Our finding revealed that the drivers of the SIE in shrubs were landscape shape index, perimeter–area ratio, and the proportion of sealed surfaces within the patch. For trees, the SIE was influenced by the distance to the source of species, GDP, night light intensity, and perimeter–area ratio. This finding justifies that conservation in urban planning, construction, and development should focus not only on protecting large areas but also on maintaining and promoting diverse habitats within these areas. At the same time, reducing anthropogenic disturbance and enhancing the connectivity of green spaces are important for the persistence of metacommunities and can contribute to the local species pool, thus potentially improving the ecological resilience of urban environments.

Urbanization profoundly transforms ecosystems, often resulting in habitat loss and biodiversity decline. Urban spontaneous plants, which are established naturally without human intervention, play a critical role in urban ecosystems by providing habitats, mitigating urban heat islands, and acting as indicators of environmental changes. Multidimensional urbanization, encompassing vertical and horizontal scale, exerts a significant influence on the biodiversity of green space. While previous studies have extensively examined the effects of horizontal spatial scales (such as land use and population density), the impacts of vertical spatial scales remain understudied. To elucidate the spatial patterns and driving factors of spontaneous plant diversity under multidimensional urbanization, we conducted a comprehensive survey of spontaneous plants across Changchun, a rapidly urbanizing city in northeast China. We established 1147 herbaceous plots within 245 urban green space patches across 38 sites and analyzed the effects of multidimensional urbanization metrics on spontaneous plant diversity. A total of 408 species of spontaneous plants were recorded, with herbs as the dominant life-form (89.2%), 322 are native species (78.9%), and 21.1% non-native species (of which 65.1% are invasive), primarily dispersed by autochory. Significant differences in plant diversity indices were observed across various urban green spaces and habitat types in Changchun, with native plant diversity generally highest in square green spaces and scrub gaps, while non-native plant diversity was most prominent in brownfield sites and showed no significant variation among habitat types. Regression analyses revealed that, in addition to patch characteristic factors (including patch area, perimeter–area ratio, and landscape shape index), the richness of total, native, and autochorous spontaneous plants was primarily influenced by vertical urbanization (as indicated by building volume), with building volume positively associated with species richness. In contrast, the richness of non-native and anemochorous plants was also significantly affected by horizontal urbanization factors, such as the proportion of impervious surface within a 100 m buffer zone and distance from patch to city center. The results reveal distinct spatial patterns of spontaneous plant diversity driven by both urbanization of horizontal spatial scales and vertical spatial scales. Our study provides new insights into the interplay between multidimensional urbanization and biodiversity, offering a theoretical foundation for integrating biodiversity conservation into sustainable urban planning and ecosystem management.

The Qinghai‐Tibet Plateau (QTP) is ecologically significant due to its unique biodiversity and vulnerability to climate change and rapid urbanization. Among its emerging urban habitats, wastelands with relatively low anthropogenic disturbances offer key refuges and stepping stones for spontaneous plants. However, the patterns and drivers of spontaneous plant diversity in these habitats remain poorly understood. To address this, we surveyed spontaneous plant communities across 17 cities on the QTP. We found that native species dominated urban wasteland flora (85.8%), whereas invasive species constituted over half (65.8%) of the non‐native species. The results showed that land‐use legacy effects and environmental filtering shape community assembly. GLMM analyses further reveal that the climatic background constitutes a key factor shaping community diversity variations across the QTP, exerting the most significant influence on species richness, particularly through precipitation and wind speed. Urbanization and habitat quality factors jointly shape the diversity structural characteristics of communities. However, non‐native and invasive species exhibit heightened sensitivity to local habitat quality. Furthermore, differences between communities across all groups were due to species turnover, though the driving factors differed between groups. Native species exhibited stronger overall ecological adaptability, whereas differences between communities of non‐native and invasive species were primarily driven by human disturbance and habitat conditions. These findings underscore the ecological value of urban wastelands on the QTP for biodiversity conservation and invasion management under rapid urbanization and climate change.

Urbanization greatly impacts both the diversity of soil seed banks and the spatial dynamics of species. These seed banks serve as a window into the ecological history and potential for recovery in urban wastelands, which are continually evolving due to urbanization. In this study, we selected 24 plots along urban-rural gradients in Shanghai, China. Soil samples were collected from each plot for seed bank germination experiment in both spring and autumn. We tested whether the seed density, species diversity, and composition of soil seed banks in wasteland varied along an urban-rural gradient. The results showed that seed density was higher in autumn than in spring and no significant difference was found along urban-rural gradients. A total of 74 species, belonging to 26 families and 69 genera, was recorded in soil seed banks, in which annuals were the dominant life form and autochory was the dominant dispersal model. The proportion of exotic species was nearly 40%. There is no significant difference along urban-rural gradients for functional composition, species diversity, and species composition, excepting that marginal significant for autumn Shannon-Wiener index and species composition among urban-rural gradients. The relative homogeneity in the seed bank across urban-rural gradients may primarily be due to the young age of the wastelands.

The positive relationship between species richness and area is a fundamental principle in ecology. However, this pattern deviates on small islands, where species richness either changes independently of area or increases at a slower rate—a phenomenon known as the Small-Island Effect (SIE). While the SIE has been well-documented in natural ecosystem, its presence in highly fragmented and disturbed urban ecosystem remains unexplored, posing challenges for urban vegetation conservation. Urban remnant vegetation, isolated by surrounding infrastructures, preserves intact zonal vegetation characteristics, serves as a benchmark for restoring near-natural habitats and offers ideal conditions to test the existence of SIE in human-altered landscapes. In this study, we surveyed 17 remnant vegetation patches in Qingdao City, China. In total of 331 plants attributed to 255 genus in 81 families been recorded. Firstly, by using six species-area relationship regression models tested SIE for remnant vegetation with different life form (i.e. annual herb, perennial herb, shrub and tree), we found SIE detected in only woody plants, with area threshold ranging from 6.38 ha (tree) to 11.91 ha (shrub). According to stepwise and generalized linear regression mode analysis we found SIE detected in only woody plants, with area threshold 6.38 ha for tree and 11.91 ha for shrub. Further analysis revealed that the SIE in shrub was driven by landscape shape index, perimeter-area ratio, and the proportion of sealed surface within patch. For trees, the SIE was influenced by the distance to the source of species, GDP, night light intensity and perimeter-area ratio. This finding justifies that conservation in urban planning, construction and development should focus not only on protecting large areas, but also on maintaining and promoting diverse habitats within these areas. At the same time, reducing anthropogenic disturbance and enhancing the connectivity of green spaces are important for the persistence of metacommunities and can contribute to the local species pool, thus potentially improving the ecological resilience of urban environments.

Urbanization and climate change are rapidly altering large-scale plant distributions and local community compositions, profoundly impacting ecosystem functions and services. However, it remains unclear how life form compositions, one of the key functional biodiversity components, respond jointly to urbanization and climate gradients. Here we investigated the life form compositions of 2,864 naturally regenerated spontaneous plant species across 129 cities in Yunnan province of China, a global biodiversity hotspot with diverse environmental condition. Our results showed perennial herbs (45.0%) predominated in urban ecosystem, followed by annual herbs (29.2%) and woody plants (25.8%). Bayesian hierarchical models revealed that as urban expansion, the proportions of annual herbs rise, while the proportions of both perennial herbs and woody plants decline, indicating urban expansion favors short-lived plants but is detrimental to long-lived plants. Increasing mean annual temperature with a decline in perennial herbs and a concurrent increase in woody plants, suggesting divergent adaptive responses to thermal stress. Our results highlight the complex, divergent responses of plant life forms to urbanization and climate change, emphasizing the need for targeted conservation strategies that consider both the resilience of short-lived species and the vulnerability of long-lived plants.