Land-use diversity can better predict urban spontaneous plant richness than impervious surface coverage at finer spatial scales

Spatiotemporal correlations of PM2.5 and O3 variations: A street-scale perspective on synergistic regulation

PM2.5 and O3 are major pollutants affecting air quality and posing serious health risks in China. While many studies focus on their control at urban and regional scales, their co-regulation at the street level-closely tied to traffic emissions and commuting patterns-remains unexplored. This study addressed the gap by using nonlinear statistical methods to analyze the spatiotemporal evolution of PM2.5 and O3 from street-scale mobile measurements in Fuzhou, China. A random forest (RF) model was applied to elucidate factors influencing PM2.5-O3 synchronicity. Key findings revealed that street-scale variations in PM2.5 and O3 exhibited multifractality and long-term persistence. Co-directional changes between PM2.5 and O3 peaked at noon, compared to traffic peak hours and midnight. An 800 m threshold was identified for analyzing PM2.5-O3 synchronicity-below this spatial scale, local factors weaken their concordance, while beyond it, the concordance strengthened. RF models showed that PM2.5 was primarily influenced by precursor substances in winter and meteorological conditions in summer, while O3 was consistently affected by meteorological conditions across both seasons. Road traffic and construction disrupted the co-directional changes of PM2.5 and O3, whereas high humidity partially mitigated high concentrations of both pollutants but enhanced their synchronicity.

Urbanization and plant diversity in urban fringes: Differential responses across life forms

Urban fringe areas, as critical transition zones between urban expansion and natural environments, provide essential ecosystem services that enhance the overall health and sustainability of urban environments. However, previous studies have focused on urban built-up areas while neglecting the unique conditions of urban fringe zones. This study investigated the spatial distribution patterns of plant diversity across different life forms in Jiangdong New District and their responses to urbanization levels. The results indicate that hot and cold spots of diversity for trees and shrubs show similarity, while diversity in herbaceous plants differs significantly. Nighttime light intensity, POI (Point-of-Interest) density, and road density are primary influencing factors, with nighttime light intensity and POI density having the greatest combined impact, and herbs showing the highest sensitivity to these factors. Further analysis reveals that in the northwestern forest, grassland, and farmland mosaic areas, urbanization levels are positively correlated with tree and shrub diversity but negatively correlated with herb diversity. In the southeastern nursery planting area, urbanization levels consistently relate to the diversity of these three plant types. These findings underscore the necessity of adopting diverse conservation and management strategies in urban fringe areas to address the ecological needs and functional contributions of different plant types. This provides new perspectives on urban planning and ecological conservation that can help improve the overall health and sustainability of urban ecosystems.

Small but irreplaceable: The conservation value of landscape remnants for urban plant diversity

The widespread decline of biodiversity due to increasing urban development raises the need to timely identify areas most relevant to the conservation of native species, particularly within cities where natural areas are extremely limited. Here, we assess the multiple role of local geomorphological features in shaping patterns and dynamics of plant diversity, with the aim of identifying conservation values and priorities in an urbanised area of Southern Italy. Based on recent and historical lists of vascular plants, we compared the floristic composition of different portions of the area by considering species' conservation value, ecological and biogeographical traits. We found that landscape remnants, accounting for 5% of the study area, harbour over 85% of the whole plant diversity and a considerable set of exclusive species. Results of Generalised Linear Mixed Models show an outstanding role of landscape remnants for the conservation of native, rare and specialised species. Based on the compositional similarities among sampled sites resulting from hierarchical clustering, these linear landscape elements also play a key role in maintaining the floristic continuity and potential connectivity throughout the urban landscape. By comparing current biodiversity patterns with data from the early XX century, we also show that the considered landscape elements are significantly more likely to host populations of declining native species, underlining their role as refugia against past and future extinctions. Taken together, our findings represent an effective framework to tackle the challenging conservation of nature in cities, namely providing a valuable approach for the identification of priority areas for the conservation of diversity within anthropogenic landscapes.

Driving effects of land use and landscape pattern on different spontaneous plant life forms along urban river corridors in a fast-growing city

River corridors are critical in connecting fragmented greenspace and providing habitats for plants and animals. There is a paucity of information on the detailed influence of land use and landscape patterns on the richness and diversity of distinct life forms of urban spontaneous vegetation. This study aimed to identify the variables that dramatically affect spontaneous plants and then disentangle how to manage such a variety of land types to maximize the biodiversity-supporting function of urban river corridors. The total species richness was remarkably influenced by the amount of commercial, industrial, and waterbody area and the landscape complexity of water, green space, and unused land. In addition, the spontaneous plant assemblages of different life forms significantly differed in their responses to land use and landscape variables. Vines were more sensitive to urban sites, i.e., strongly negatively affected by residential and commercial areas but positively supported by green space and cropland. Multivariate regression trees indicated that the total plant assemblages were clustered most remarkably by the total industrial area, and the classified responding variables differed among distinct life forms. The colonizing habitat of spontaneous plants explained a high proportion of the variance and was also closely related to the surrounding land use and landscape pattern. These scale-specific interaction effects ultimately determined the variation in richness among various spontaneous plant assemblages in urban sites. Based on these results, in future city river planning and design, spontaneous vegetation could be protected and promoted by a nature-based solution according to their adaptability and preference for distinct landscape characteristics and habitat features.