The impact of global dimming on crop yields is determined by the source–sink imbalance of carbon during grain filling

• Published in: Global change biology 2021-02, Vol.27 (3), p.689-708
• Main Authors: Shao, Liping, Liu, Zijuan, Li, Haozheng, Zhang, Yaling, Dong, Mingming, Guo, Xuanhe, Zhang, Han, Huang, Baowei, Ni, Rongbing, Li, Gang, Cai, Chuang, Chen, Weiping, Luo, Weihong, Yin, Xinyou
• Format: Article
• Language: English
• Subjects: Agricultural production; Biological fertilization; Biomass; Carbon; Crop production; Crop yield; Crops; Diffuse radiation; diffuse radiation fertilization effect; Dimming; Edible Grain; Fertilization; Field tests; global dimming; Grain; Growth; Nitrogen; Oryza; Radiation; Rice; Source-sink relationships; source–sink relationship; Triticum; Wheat
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.15453

Global dimming reduces incident global radiation but increases the fraction of diffuse radiation, and thus affects crop yields; however, the underlying mechanisms of such an effect have not been revealed. We hypothesized that crop source–sink imbalance of either carbon (C) or nitrogen (N) during grain filling is a key factor underlying the effect of global dimming on yields. We presented a practical framework to assess both C and N source–sink relationships, using data of biomass and N accumulation from periodical sampling conducted in field experiments for wheat and rice from 2013 to 2016. We found a fertilization effect of the increased diffuse radiation fraction under global dimming, which alleviated the negative impact of decreased global radiation on source supply and sink growth, but the source supply and sink growth were still decreased by dimming, for both C and N. In wheat, the C source supply decreased more than the C sink demand, and as a result, crops remobilized more pre‐heading C reserves, in response to dimming. However, these responses were converse in rice, which presumably stemmed from the more increment in radiation use efficiency and the more limited sink size in rice than wheat. The global dimming affected source supply and sink growth of C more significantly than that of N. Therefore, yields in both crops were dependent more on the source–sink imbalance of C than that of N during grain filling. Our revealed source–sink relationships, and their differences and similarities between wheat and rice, provide a basis for designing strategies to alleviate the impact of global dimming on crop productivity. The source–sink balance is a key factor in determining crop yields, while source and sink during grain filling are usually imbalanced under climate change, such as global dimming. We demonstrated that despite a diffuse radiation fertilization effect, source supply and sink growth decreased under dimming, for both carbon and nitrogen. Dimming increased the post‐heading carbon deficit in wheat, but decreased it in rice. Wheat and rice yields depended more on the source‐sink imbalance of carbon rather than that of nitrogen during grain filling. These results provide a basis for designing strategies to alleviate global dimming impact on crop productivity.