Nonlinear Responses of Vegetation Phenology to Climate Change and Urbanization: A Case Study in Beijing, China

Abstract

Vegetation serves as an indicator of ecological change and phenology is an important indicator for evaluating vegetation growth and development. Analyzing the spatiotemporal characteristics of vegetation phenology and its driving factors is of great significance for analyzing the carbon, water, and energy balance of terrestrial ecosystems. To better assess the impact of external environmental changes on vegetation phenology and comprehend the changing trends of phenology, this research employed phenological parameters as response variables and incorporated meteorological factors and urbanization factors as explanatory variables. A generalized additive model (GAM) was constructed meticulously to investigate how vegetation phenology responds to climate change and urbanization in Beijing, as well as to predict vegetation phenology. The results showed that there were non-linear relationships between the vegetation phenological parameters SOS (start of season) and EOS (end of season) and external environmental changes. GAM explained 68.1% and 73.9% of the variations in SOS and EOS, respectively. The R 2 of the GAM predicted SOS and EOS with respect to the observed data increased to 0.719 and 0.832, respectively. The prediction effects in each region of the urban-rural gradient zone were better with RMSE of approximately 4-7 d. This research demonstrates that GAM considers the non-linear relationships between vegetation phenology and external environmental factors. The validation results based on observed data show that the models are reliable, and the research findings can provide theoretical references for urban development planning and ecological environmental protection in Beijing.