Possible impact of climate change on apple yield in Northwest China

Apples (Malus pumila Mill.) are widely cultivated in 95 countries and regions around the globe. China is the world's largest producer of apples. Prediction of apple yield in the context of climate change has become an important topic of research. The study sites in this investigation include 28 apple-producing base counties located in the Shaanxi province of the northwest Loess Plateau. In this study, grey relational analysis was used to examine 88 climatic factors and to extract those factors that significantly influence the meteorological yield (MY) of apples. A support vector machine (SVM) was used to make a quantitative prediction of changes in MY in the apple-producing areas of Shaanxi province from the years 2000-2099 under 2 climate change scenarios, RCP 4.5 and RCP 8.5. In addition, fuzzy information granulation was used to analyze the variation trends and variation spaces of MY from 2020 to 2049 and 2050 to 2099, compared with the 1990-2019 reference period. The results showed that for the 10-day and monthly climatic factors affecting the MY of apples, climate resource factors are more influential than meteorological disaster factors and spring factors are significantly more influential than other seasonal factors. Overall, there are more and broader climate resource factors affecting MY, and spring climatic conditions are more important for it. In the RCP 4.5 scenario, 9 base counties showed slight decreases, 2 counties showed significant decreases, 15 counties maintained or had slightly increased, and 2 counties showed significant increases. The variation of unit yield was -1.44-1.85 t/ha. In the RCP 8.5 scenario, 10 base counties showed slight decreases, 2 counties showed significant decreases, 12 counties maintained or had slightly increased, and 4 counties showed significant increases. The variation of unit yield was -2.43-2.78 t/ha. For both future climate change scenarios, the uncertainty of MY increased with time.