Climate warming outweighed agricultural managements in affecting wheat phenology across China during 1981–2018

Abstract

Investigating crop phenology change has important implications to understand crop response and adaptation to climate change. The spatiotemporal changes of wheat phenology had been investigated before, nevertheless some key scientific questions remain inconclusive. Here, the updated phenological observations with the longest time period (1981–2018) and the largest number of records (7,659 records at 357 stations) for wheat in China were applied to investigate whether the response of wheat phenology to recent climate warming declined, how wheat responded to asymmetric warming, and how different drivers affected wheat phenology change. The results showed wheat sowing date delayed but heading and maturity date advanced generally during 1981–2018. Trends in wheat sowing date, heading date, maturity date, vegetative growing period (VGP), reproductive growing period (RGP) and whole growing period (GP) between 1981–1999 and 2000–2018 changed heterogeneously across the agro-ecological zones. This inconsistence may be ascribed to the compound impacts of climate change and agricultural managements such as cultivar shifts. Climate warming impacts on GP increased for winter wheat but declined for spring wheat in most regions from 1981–1999 to 2000–2018. Daily minimum temperature increased more than mean and maximum temperature, however VGP, RGP and GP were more sensitive to mean and maximum temperature than to minimum temperature. Maximum and minimum temperature had contrasting effects. Spring wheat was more sensitive to temperature than winter wheat, and RGP was more sensitive to temperature than VGP and GP because the later was also subject to photoperiod and vernalization. During 1981–2018, climate warming shortened GP on average by 4.2 and 4.6 days/decade for winter and spring wheat, respectively. Cultivar shifts prolonged it by 2.0 and 2.9 days/decade, respectively. Changes in sowing date shortened it on average by 0.5 and 0.4 days/decade, respectively. The effects of other factors such as fertilization and irrigation changed it on average by 0.1 and -0.3 days/decade, respectively. And the effects of all agricultural managements together prolonged it on average by 1.6 and 2.4 days/decade, respectively. Our findings provide new insights into the spatiotemporal changes of wheat phenology, as well as their drivers, across China in the past four decades.