Divergent climate feedbacks on winter wheat growing and dormancy periods as affected by sowing date in the North China Plain

Fengshan Liu,Huizi Bai,Nini Bai,Ying Chen,Dengpan Xiao,Quansheng Ge,Fulu Tao

doi:10.5194/bg-18-2275-2021

Abstract

Abstract. Crop phenology exerts measurable impacts on soil surface properties, biophysical processes and climate feedbacks, particularly at local or regional scales. Nevertheless, the response of surface biophysical processes to climate feedbacks as affected by sowing date in winter wheat croplands has been overlooked, especially during winter dormancy. The dynamics of leaf area index (LAI), surface energy balance and canopy temperature (Tc) were simulated by a modified SiBcrop (Simple Biosphere) model under two sowing date scenarios (early sowing, EP; late sowing, LP) at 10 stations in the North China Plain. The results showed that the SiBcrop model with a modified crop phenology scheme well simulated the seasonal dynamic of LAI, Tc, phenology and surface heat fluxes. An earlier sowing date had a higher LAI with earlier development than a later sowing date. But the response of Tc to the sowing date exhibited opposite patterns during the dormancy and active-growth periods: EP led to higher Tc (0.05 K) than LP in the dormancy period and lower Tc (−0.2 K) in the growth period. The highest difference (0.6 K) between EP and LP happened at the time when wheat was sown in EP but was not in LP. The higher LAI captured more net radiation with a warming effect but partitioned more energy into latent heat flux with cooling. The climate feedback of the sowing date, which was more obvious in winter in the northern areas and in the growing period in the southern areas, was determined by the relative contributions of the albedo radiative process and partitioning non-radiative process. The study highlights the surface biophysical process of land management in modulating climate.

Highlights

Land–atmosphere interactions are key components of the climate system
The analyses focused on the dynamics of leaf area index (LAI) and Tc and the surface energy balance components, such as Rn, latent heat flux (LH) and sensible heat flux (SH), which were used to explain the climate feedback mechanism
The dynamics of winter wheat LAI and Tc under two sowing date scenarios were simulated by the SiBcrop model in the NCP, and the Tc disparity between the two scenarios was explained by the surface energy balance

Summary

Introduction

The land cover and management changes have strong feedbacks with climate through surface biophysical and biochemical processes (Mahmood et al, 2014). Cropland surface characteristics have been and will continue to be changed through crop management, such as the cropping system (Jeong et al, 2014; Cui et al, 2018), sowing date and phenology shifts (Sacks and Kucharik, 2011; Richardson et al, 2013), and cultivar selection (Seneviratne et al, 2018), to keep a high yield under climate change conditions. The changed cropland properties further generate feedback to regional climate through surface energy partitioning and albedo (α) mechanisms (Cooley et al, 2005; Zhang et al, 2015). It is important to quantify the climate feedback of crop phenology for regional climate prediction and sustainable agriculture development.

Methods

Results

Discussion

Conclusion