As the basic component of urban green-spaces, plant communities regulate both the microclimate and air particle levels. Understanding the regulatory mechanism of plant communities represents the theoretical basis for using green spaces to improve the urban climate and mitigate air particle pollution. Based on field investigations, differences in the daily air temperatures (AT), relative humidity (RH), and PM₁₀ and PM_2.5 concentrations in eight compositional types of plant communities were quantitatively analyzed. In addition, the correlations between these variables and various canopy parameters were further established in order to detect critical thresholds. The results showed that, among the eight compositional types, significant differences existed in daily AT, RH, PM₁₀ and PM_2.5 levels. The mixed tree, shrub and grass (M-TSG) community had the strongest cooling and PM₁₀ reduction effects; the broad-leafed tree, shrub and grass (B-TSG) community had the best humidifying effect; while the mixed tree and grass (M-TG) community most effectively reduced PM_2.5 concentrations. The daily AT and PM₁₀ concentrations were significantly negatively correlated with canopy density (CD) and leaf area index (LAI), but positively correlated with canopy porosity (CP) and sky view factor (SVF), while these correlations were opposite for daily RH. The response of daily PM_2.5 concentrations to canopy characteristics was complex, featuring multiple non-linear relations. Critical thresholds were found in some cases. Overall, M-TSG or M-TG communities with about 75% CD, 55% CP, 2.5 LAI and 0.18 SVF perform most noticeable both microclimate and air particle regulation services.

Karst rocky desertification (KRD) is one of the biggest challenges in the karst ecological restoration of Southwest China, and a thorough understanding of the plant community characteristics in various karren habitats provides a basis for mitigating KRD and restoring the degraded ecosystem. To improve our knowledge of the detailed characteristics and impact mechanisms of karren habitats on the species distribution and species diversity patterns of woody and herbaceous plants to benefit sustainable management and planting design for revegetation establishment in the karst region, a field investigation was carried out in the natural restoration vegetation of Shilin Geopark. The results indicated that karren habitats apparently determine the species diversity and composition. At the arbor layer, the habitat with the highest α diversity was solution corridor (SC), and at the shrub layer, grikes (GR) were the karren habitats with the most diverse communities. At the herb layer, solution rock debris (SRD) showed the highest richness of herbaceous species. The karren habitat features and topographic factors significantly influence plant α diversity and distribution. Soil area (SA) and canopy density (CD) were the dominant factors influencing plant diversity at the arbor, shrub and herb layers, soil thickness (ST) was significantly effective at the arbor and herb layers. Karren habitat height (KHH), litter thickness (LT), and slope gradient (SG) were significantly influential at the herb layer. The impacts of the karren habitat width (KHW), slope aspect (SAS), and SG on woody species distribution were significant. Knowledge obtained from this study will be helpful guidance for future sustainable restored vegetation design and management with high biodiversity and regional characteristics in the karst area of Southwest China and other fragile karst ecosystems in the world.