Assessing spring frost-induced production losses across China's apple planting regions

Spring frost poses a major threat to apple production in temperate regions, with severe implications for yield and fruit quality. China's apple production is particularly vulnerable to spring low temperature, yet comprehensive assessments of apple spring frost-induced production losses remain limited. In this study, we quantified frost-induced apple yield and production losses across China during 1991-2020 by integrating spring frost characteristics and simulated production losses. Frost hazard was characterized using the frequency (accumulated frost days, AFD) and intensity (accumulated frost degree-days, AFDD) of frost events occurring during frost-sensitive phenological stages of apple. Yield losses caused by frost were simulated using the process-based STICS model while spatial exposure was represented by the distribution of apple harvested regions derived from the Spatial Production Allocation Model (SPAM). Total apple production loss was estimated based on simulated yield, yield loss rate, and harvested region. The results show that the average annual AFD ranged from 0.04 to 1.20 d, while AFDD varied between 0.03 and 0.80 °C·d across major apple-planting regions. Frost events resulted in measurable yield reductions, with an average yield loss of 1.3%, and a maximum loss of 9.5% occurring in Region III. During the past three decades, spring frost-induced yield loss rates generally showed an increasing trend, particularly in the Loess Plateau.When combined with the spatial distribution of apple planting regions (averaging 760.7 ha), the estimated national average production loss reached 245.4 t. This study provides a quantitative assessment of frost impacts on apple production at the national scale and offers valuable insights for improving frost risk management, optimizing orchard distribution, and enhancing the resilience of apple production under increasing climate variability.