Abstract:

Based on normalized difference vegetation index (NDVI), vegetation type, and meteorological data, this study revealed the seasonal variations of the day- and nighttime warming in growing seasons using unitary linear regression analysis. It examined different effects of asymmetric seasonal warming on vegetation activities in China's temperate zone using the two-order partial correlation analysis method. The results are as follows. (1) The day- and nighttime warming trends from 1982 to 2015 in growing seasons were extremely significant. The day- and nighttime warming rates were featured by asymmetry; daytime warming was slightly faster than nighttime warming in spring and summer. Contrarily, in autumn, nighttime warming was faster than daytime warming. (2) The effects of the day- and nighttime warming on vegetation activity were obviously different; daytime warming had significantly greater and more extensive effects on vegetation than nighttime warming did, and the areas impacted by diurnal warming were broader in spring than in summer and autumn. (3) Different vegetation types responded differently to the seasonal asymmetry in day- and nighttime warming, and the degree of responses showed distinct variations by season.

Key words: day- and nighttime warming, vegetation dynamics, seasonal variation, China's temperate zone