Remote sensing monitoring of the spatiotemporal dynamics of urban forest phenology and its response to climate and urbanization

Urban forests are an important part of urban ecosystems, and urban forest phenology is of extraordinary significance for exploring climate change in terrestrial ecosystems and related issues arising from urbanization. In this study, the urban forest phenology of Hangzhou was extracted using the dynamic thresholding method based on MODIS EVI data from 2001 to 2020 by reconstructing the time series through the double logistic function. Additionally, this study combines climate data (temperature, precipitation) and urbanization indicators (impervious surface, urban-rural gradient) to analyze the response of Hangzhou urban forest phenology to climate and urbanization. The results of the study showed that the urban forest phenology in Hangzhou as a whole tended to have an advanced start of the growing season (SOS), delayed end of the growing season (EOS), and extended length of the growing season (LOS). The greater a region's urbanization, the more obvious the trend. In response to climate change, temperature had the most significant effect on urban forest phenology, with the SOS advancing by 0.4 days and the EOS delaying by 0.3 days for every 1 degrees C increase in temperature. Our study contributes to the understanding of urban forest phenology in Hangzhou and serves as a reference for the study of subtropical urban forest phenology.