Redai dili (Mar 2023)
Spatial and Temporal Changes in Urban Green Space Ecosystem and Evapotranspiration Response Mechanism in Guangzhou during 2000-2020
Abstract
Evapotranspiration is an important mechanism connecting earth surface and the atmosphere. One of the factors that affect regional transpiration include land cover type. With the speeding up of urbanization around the world, urban land cover change and its impact on surface evaporation have attracted extensive attention from academia. The change in land cover in Guangzhou China, which occupies the central area of the Pearl River Delta Urban Agglomeration, is more diverse and complex during a certain period. This can be attributed to the rapid urbanization of Guagnzhou since the reform and opening up of China. The urbanization process of Guangzhou is typical, and research findings from this study can be referred to ensure rational allocation of water resources and construction of sponge cities during the urbanization process of other large cities. The present study investigated the changes in land cover and urban green space structure in Guangzhou over the last two decades; this was based on the remote sensing interpretation of Landsat datasets for 2000, 2005, 2009, 2015, and 2020. Data were obtained from 38 meteorological stations in Guangzhou and its surrounding areas; thereafter, spatial interpolation of the data was conducted to assess the change in trends of precipitation, temperature, air pressure, wind speed, and relative humidity over the past 20 years. After the above two steps, the change of surface evapotranspiration in Guangzhou was investigated. The obtained results suggested are given below:1) The total area of urban green space in Guangzhou decreased during 2000-2020. The change in land cover was mainly characterized by a significant conversion of non-forest vegetation into construction land or unused land, such as urban residential, industrial, and commercial land. Some of the vegetation had also been converted into forest land. In the past 21 years, the proportion of forest land in the urban greenspace ecosystem of Guangzhou has shown an upward trend. 2) The proportion of forest land and annual average evapotranspiration in Guangzhou showed an overall upward trend during 2000-2020. The annual average evapotranspiration and proportion of forest land were positively correlated. Moreover, high spatial consistency was observed between the increase and decrease in evapotranspiration and the mutual transformation between land cover types with different evapotranspiration capacities. 3) During the study period, evapotranspiration in Guangzhou was positively correlated with precipitation, relative humidity, and temperature and negatively correlated with air pressure, sunshine hours, and wind speed. However, the area proportion of regions with significant or higher correlation between meteorological factors and surface evapotranspiration was too low to indicate that meteorological factors were the main driving factor behind increasing regional evapotranspiration. 4) The increase in surface evapotranspiration in Guangzhou from during the study period did not occur synchronously with the spatial changes of the urban green space ecosystem and showed a lag owing to different reasons, including forest growth cycle and climate conditions. In conclusion, the study summarized the land cover changes and achievements of urban green space ecological construction under the process of urbanization in Guangzhou and explored the comprehensive impact of land cover change on regional surface evapotranspiration in Guangzhou over the last 20 years. This study provides a theoretical basis and data reference for urban ecosystem management in Guangzhou.
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