Abstract
Depending on the vegetation type, extreme climate and drought events have a greater impact on the end of the season (EOS) and start of the season (SOS). This study investigated the spatial and temporal distribution characteristics of grassland phenology and its responses to seasonal and extreme climate changes in Sichuan Province from 2001 to 2020. Based on the data from 38 meteorological stations in Sichuan Province, this study calculated the 15 extreme climate indices recommended by the Expert Team on Climate Change Detection and Indices (ETCCDI). The results showed that SOS was concentrated in mid-March to mid-May (80–140 d), and 61.83% of the area showed a significant advancing trend, with a rate of 0–1.5 d/a. The EOS was concentrated between 270–330 d, from late September to late November, and 71.32% showed a delayed trend. SOS was strongly influenced by the diurnal temperature range (DTR), yearly maximum consecutive five-day precipitation (RX5), and the temperature vegetation dryness index (TVDI), while EOS was most influenced by the yearly minimum daily temperature (TNN), yearly mean temperature (TEMP_MEAN), and TVDI. The RX5 day index showed an overall positive sensitivity coefficient for SOS. TNN index showed a positive sensitivity coefficient for EOS. TVDI showed positive and negative sensitivities for SOS and EOS, respectively. This suggests that extreme climate change, if it causes an increase in vegetation SOS, may also cause an increase in vegetation EOS. This research can provide a scientific basis for developing regional vegetation restoration and disaster prediction strategies in Sichuan Province.
Highlights
Phenology is defined as the study of the timing of recurrent biological events, the causes of their timing in terms of biotic and abiotic forces, and the interrelationship between the phases of the same or different species [1,2]
The end of the season (EOS) of grassland vegetation observed on the ground was between 280 and 320 days, but the EOS that was calculated from the MOD13A1 phenological product ranged from 275 to 325 days
Had earlier dates than the ground-based observations, and the error between the remotely sensed and ground-based phenology was less than 10 days; the results were still well correlated. These results showed that the normalized difference vegetation index (NDVI) of phenology data from MOD13A1 can be used to calculate the start of the season (SOS) and EOS of grassland vegetation in Sichuan Province, and Atmosphere 2021, 12, x FOR PEER REVIEW
Summary
Phenology is defined as the study of the timing of recurrent biological events, the causes of their timing in terms of biotic and abiotic forces, and the interrelationship between the phases of the same or different species [1,2]. The average surface temperature of the world has increased substantially since the twentieth century, especially in the last 20 years (from 1951 to 2012, the global average surface temperature increased by 0.72 ◦ C) [4,5], and vegetation phenology has changed dramatically in response [5]. Climate change encompasses both significance and severity [6,7].
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