Urban green spaces (UGSs) play a crucial role in supporting urban ecological systems and improving human well-being in cities. The spatial patterns of UGS are vital bases for analyzing various ecological processes. However, few studies have investigated morphological UGS patterns, especially in high-density cities. The Guangdong–Hong Kong–Macao Greater Bay Area (GBA) in China is one of the four major bay areas in the world. The aim of this study was to investigate the patterns and distributions of UGS in the core GBA cities (Guangzhou, Shenzhen, Zhuhai, Hong Kong, and Macao), and discuss the shortcomings and potential environmental impacts of the contemporary patterns of UGS. Morphological spatial pattern analysis (MSPA) was used to analyze the spatial UGS pattern. Seven MSPA metrics (core, islet, perforation, edge, loop, bridge, and branch) were assessed to measure morphological UGS patterns. The results showed that: (1) Hong Kong has the highest quality habitat, with a large and continuous distribution of UGSs, and a few smaller green spaces scattered in built-up areas; (2) Guangzhou’s UGSs are unevenly distributed, with large green spaces concentrated in the northern part of the city and many small, scattered green spaces distributed in built-up areas, demonstrating the most prominent pattern of green space fragmentation; (3) green space patches in the Shenzhen–Hong Kong region exhibit a relatively complex form; and (4) the UGS in Zhuhai–Macao is relatively discrete, and its connectivity is relatively low. These findings not only improve the depth of understanding of the spatial pattern of UGS in the GBA, but also confirm the applicability of MSPA in the analysis of spatial patterns of UGS.

Zingiberaceae plants are distributed in the tropical and subtropical regions of the world, being used in many famous medicinal materials. Meanwhile, some Zingiberaceae plants are important horticultural flowers because they are green all year round and have special aromas. To conduct an extensive investigation of the resources of Zingiberaceae plants, the volatile compounds of ten species of Zingiberaceae were extracted and analyzed by GC–MS, including Costus comosus var. bakeri (K.Schum.) Maas, Curcuma rubescens Roxb., Curcuma aeruginosa Roxb., Curcuma attenuata Wall., Hongfengshou, Hedychium coronarium Koeng, Zingiber zerumbet (L.) Smith, Hedychium brevicaule D. Fang, Alpinia oxyphylla Miq., and Alpinia pumila Hook.F. A total of 162 compounds were identified, and most of those identified were monoterpenes and sesquiterpenes. (E)-labda-8(17),12-diene-15,16-dial, n-hexadecanoic acid, 4-methoxy-6-phenethyl-2H-pyran-2-one, and L-β-pinene were found in high concentrations among the plants. These ten species of Zingiberaceae contained some of the same volatiles, but their contents were different. Pharmacological effects may be associated with the diversity of volatiles in these ten plants.

Purpose: Urban trees play a key role in ameliorating extreme urban climates in cities. At the micro-level, it is crucial to investigate the variations in microclimates affected by the canopies of different tree species. The significance of this research is to provide scientific evidence for the selection of tree species in urban planning that can improve the local microclimate. This study examines the factors of microclimate (air temperature, relative humidity, wind environment, and solar radiation) underneath the canopy of four different evergreen tree species in hot and humid areas. Furthermore, the correlation between the physiological characteristics of these tree species and microclimate was statistically analyzed using data on the physiological parameters of the trees and microclimate factors.Methods: In this study, four tree species were selected for field measurements: Ficus microcarpa L. f., Ficus virens Aiton, Bauhinia x blakeana Dunn, and Cinnamomum camphora (L.) Presl. We used the HOBE (H21-0024, onset) to measure three climatic parameters (Temperature, Relative Humidity, and Instantaneous Wind Speed), and the Li-6400 Portable Photosynthesis System to measure five plant physiological parameters: Stomatal Conductance (Gs), Leaf Temperature (Tleaf), Leaf Surface Relative Humidity (RHsfc), Photosynthetically Active Radiation (PAR), and Leaf-level Vapor Pressure Deficit (Vpdl). The observations were conducted during winter (January 16 - January 22) and summer (August 7 - August 22). The investigation periods were 9:00–11:00, 12:00–14:00, and 16:00–18:00, and data were recorded at 15-min intervals. The observational data obtained were analyzed using statistical methods, including one-way analysis of variance, Pearson correlation coefficient, and multiple regression analysis.Results: The results of this study indicated that the four tree species being measured had different effects on the microclimate at the sites in both the winter and summer seasons. During the 7-day observation in the summer, the cooling effect of the four tree species was significant. The relative humidity underneath the canopies was 3%–11% higher than that of weather stations. The instantaneous wind speed in the afternoon was relatively higher than at other times. The solar radiation intensity was dramatically reduced by 85%–95%. During the 7-day observation in the winter, the trees had a warming effect in the morning. The relative humidity underneath the canopies was 10%–20% higher than that of the weather stations. The areas underneath the canopies were windless in the afternoon. The solar radiation intensity was reduced by 78%–95%. Ficus microcarpa was found to be one of the most effective tree species for increasing the relative humidity and reducing solar radiation intensity in hot and humid areas. Additionally, the highest instantaneous wind speed was observed in the areas underneath the canopies of F. virens and C. camphora. Statistical tests revealed that the air temperature and the instantaneous wind were extremely significantly correlated with Tleaf and RHsfc.Conclusion: The four urban tree species studied had varying degrees of effect on air temperature, relative humidity, wind speed, and reducing solar radiation intensity in the areas underneath their canopies. Furthermore, these trees demonstrated varying abilities to improve microclimate conditions in different seasons. The four trees had a cooling effect in the summer. The instantaneous wind speed was calm in the afternoons during the winter in contrast to being relatively high speed in the afternoons during the summer. This characteristic is beneficial to warmth in winter and coolness in summer. In terms of the internal influence mechanisms, the results of the analysis indicated that microclimate factors were significantly correlated with the physiological parameters of the trees. Tleaf, RHsfc, and Vpdl were significant physiological parameters and had different contribution rates to microclimate factors.

Introduction: The Guangdong-Hong Kong-Macao Greater Bay Area (GBA) is located in the south subtropical area along the southeast coast of China, which is one of the world-class urban agglomerations and an important part for economic development. In order to investigate the change of vegetation indexes and its response to climate factors in such circumstance of climate change, this study is an important component in the protection and establishment of the ecological environment in the GBA.Methods: The Moderate Resolution Imaging Spectroradiometer-Enhanced Vegetation Index (MODIS-EVI) and climate data were recorded from National Aeronautics and Space Administration (NASA) and Resource and Environment Science Data Center of the Chinese Academy of Sciences. Trend analysis, Mann-Kendall (MK) Test and rescaled range analysis (R/S Analysis) offer an effective way of analyzing the correlation between the vegetation cover change and climate factors.Results: The results provide important insights into the following aspects: (1) The changes of climate factors (temperature, precipitation, wind speed, humidity, and sunshine radiation) are fluctuated in GBA, with no obvious increasing or decreasing trend. It comprehensively exhibited an extremely slow development of humidify and warming. (2) It presents an increasing trend of EVI in GBA, with the rate of 0.0045/a. The range of increase is in the middle level (0.4 ≤ EVI<0.6) based on the EVI. The vegetation cover in GBA is improved comprehensively, the area of vegetation improvement is larger than the area of vegetation degression, with the extremely improved vegetation cover area (66.98%) and the extremely degraded vegetation cover area (5.70%). There are obvious differences and agglomerations in the distribution of the EVI trends. (3) In future, the changing trends will be combinedly affected be various factors, and there is no obvious factor temporarily. The improved vegetation cover area (over 80%) are predicted. (4) There are significant spatiotemporal differences in the annual effects of EVI on various climate factors comprehensively. Wind speed and relative humidity have the strongest correlations with EVI; the area of significant correlation is more than 40% of the pixels. The correlation between temperature and EVI is second, with the area of significant correlation over 20% of the pixels. The precipitation and sunshine radiation weakly correlated with EVI, with the area of significant correlation is less than 5% of the pixels.Discussion: The result of this study indicated that the EVI changing trend in the future by R/S analysis method is affected by climate and human factors together and there are no significant factors. The result indicated precipitation has no significant correlation with EVI trends in the Hot and humid area with mean precipitation of 1800mm. However, there is a significant positive correlation between the EVI trend and two climate factors (relative humidity and wind speed). In the terms of spatial distribution, the influence of temperature to EVI is complex in GBA, the spatial distribution of correlation is scattered.

Corrigendum: Microclimate effects and influential mechanisms of four urban tree species underneath the canopy in hot and humid areas