Changes in Day and Night Temperatures and Their Asymmetric Effects on Vegetation Phenology for the Period of 2001–2016 in Northeast China

Abstract

Asymmetrical changes in day and night temperatures (Td, Tn) have become a hot topic in climate change research. Using the MODIS 8-day synthetic temperature (MOD11A2) and the SPOT-VGT/PROBA_V 10-day synthetic normalized difference vegetation index (NDVI), we analyzed the spatiotemporal trends of Td and Tn in spring and autumn in Northeast China during the period of 2001–2016 and the partial correlation between temperature and vegetation phenology (start of season, SOS; end of season, EOS). We revealed that spring Td was the main negative factor pertaining to SOS. An increasing Td resulted in a delayed SOS in arid and semiarid regions, while in boreal areas, an increasing Td ensured the heat required for vegetation growth and prompted the SOS to advance. Conversely, EOS was positively correlated with Tn in autumn. Areas showing positive correlations between Tn and EOS totaled 73.26%, and 14.19% of the areas had a significant correlation (p < 0.05). However, the effects of Td on EOS were not as significant as Tn, and only at a 10.62% correlation did Td achieve significance, which was mostly attributable to areas of high elevation and latitude. Our results are crucial for future improvements in dynamic vegetation activities in response to climate change.