Response of plant production to growing/non-growing season asymmetric warming in an alpine meadow of the Northern Tibetan Plateau.

Abstract

A field growing/non-growing season asymmetric warming experiment (C: control, i.e., no warming in the entire year; GLNG: growing season warming lower than non-growing season warming; GHNG: growing season warming higher than non-growing season warming) was conducted in an alpine meadow of the Northern Tibetan Plateau in early June 2015. The effects of growing/non-growing season asymmetric warming on the normalized difference vegetation index (NDVI), soil adjusted vegetation index (SAVI), aboveground biomass (AGB) and gross primary production (GPP) in 2015-2017 were examined. The GLNG and GHNG treatments significantly increased the annual mean air temperature (Ta) by 2.95\u202f°C and 2.76\u202f°C, and the vapor pressure deficit (VPD) by 0.23\u202fkPa and 0.28\u202fkPa but significantly reduced the annual mean soil moisture (SM) by 0.02\u202fm3\u202fm-3 and 0.02\u202fm3\u202fm-3 respectively; however, changes in the annual mean Ta, VPD and SM were the same between the GLNG and GHNG treatments over the three years in 2015-2017. There were no significant differences in the SAVI and GPP among the C , GLNG and GHNG treatments over the three growing seasons in 2015-2017. The GLNG and GHNG treatments did not significantly affect the NDVI and AGB compared to C , whereas the NDVI and AGB under the GLNG treatment were significantly greater than those under the GHNG treatment over the three growing seasons in 2015-2017. The significant differences in NDVI and AGB between the GLNG and GHNG treatments may be attributed to the different effects under the GLNG and GHNG treatments on the non-growing season Ta, growing season water availability and soil nitrogen availability. Therefore, the non-growing season with a higher warming magnitude may have stronger effects on the aboveground plant production than did the growing season with a higher warming magnitude in the alpine meadow of the Northern Tibetan Plateau.