Asymmetric effects of monthly maximum and minimum temperature on temperate grasslands in China

Based on GIMMS NDVI, maximum temperature (Tmax) and minimum temperature (Tmin) data during 1982-2006, this study investigated the impacts of Tmax and Tmin changes on temperate grasslands in China during the growing season of 1982-2006 (April–October). Results showed that monthly NDVI, Tmax and Tmin increased for temperate grasslands of China during 1982-2006. The largest increase rate of NDVI was found in August for temperate meadow (0.020/decade), temperate steppe (0.023/decade) and temperate desert steppe (0.011/decade). The effects of temperature change on temperate grasslands differed according to vegetation type and month. The increase of both Tmax and Tmin will promote vegetation growth in April, September and October for all the grassland types. However, the increase of temperature (both Tmax and Tmin) will prohibit the growth of temperate grasslands in June. There are opposite (asymmetric) effects of Tmax and Tmin on temperate grasslands in May, July and August: Tmax had negative effect but Tmin exerted positive effect on vegetation growth in May for temperate desert steppe and temperate steppe, July for temperate steppe and temperate meadow, and August for temperate desert steppe and temperate steppe. The results suggest that the increase of Tmin may prohibit vegetation growth by promoting the evaporation when water limitation reaches a certain degree. In the context of global asymmetric warming of daytime Tmax and night-time Tmin, we should more attention to these asymmetrical effects of Tmax and Tmin on temperate grassland vegetation, especially when we attempt to estimate the productivity of China’s temperate grasslands in the future. © 2015 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.