Abstract
Plant phenology is one of the key regulators of ecosystem processes, which are sensitive to environmental change. The acceleration of urbanization in recent years has produced substantial impacts on vegetation phenology over urban areas, such as the local warming induced by the urban heat island effect. However, quantitative contributions of the difference of land surface temperature (LST) between urban and rural (ΔLST) and other factors to the difference of spring phenology (i.e., the start of growing season, SOS) between urban and rural (ΔSOS) were rarely reported. Therefore, the objective of this study is to explore impacts of urbanization on SOS and distinguish corresponding contributions. Using Hangzhou, a typical subtropical metropolis, as the study area, vegetation index-based phenology data (MCD12Q2 and MYD13Q1 EVI) and land surface temperature data (MYD11A2 LST) from 2006–2018 were adopted to analyze the urban–rural gradient in phenology characteristics through buffers. Furthermore, we exploratively quantified the contributions of the ΔLST to the ΔSOS based on a temperature contribution separation model. We found that there was a negative coupling between SOS and LST in over 90% of the vegetated areas in Hangzhou. At the sample-point scale, SOS was weakly, but significantly, negatively correlated with LST at the daytime (R2 = 0.2 and p < 0.01 in rural; R2 = 0.14 and p < 0.05 in urban) rather than that at nighttime. Besides, the ΔSOS dominated by the ΔLST contributed more than 70% of the total ΔSOS. We hope this study could help to deepen the understanding of responses of urban ecosystem to intensive human activities.
Highlights
Plant phenology is the time of a certain growth event in the growth cycle, such as germination, branching, leafing, flowering, fruiting, defoliation and dormancy [1,2,3,4]
The objective of this study is to explore impacts of urbanization on start growing season (SOS) and exploratively distinguish contributions of local warming induced by the urban heat island effect (∆land surface temperature (LST)) and other factors to the difference of spring phenology between urban and rural (∆SOS)
The results showed that there was a significant spatial heterogeneity in the LST of Hangzhou, showing a gradient of high in the urban and low in the rural
Summary
Plant phenology is the time of a certain growth event in the growth cycle, such as germination, branching, leafing, flowering, fruiting, defoliation and dormancy [1,2,3,4]. It directly or indirectly regulates several processes of plant growth, such as carbon and water cycle, playing a crucial role in the earth system [5,6]. An increase in spring temperature promotes the release of plant dormancy in spring, and generally extends the growth cycle of plants [9,10,11,12,13,14].
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