AbstractWinter chill accumulation is critical for the productivity and profitability of perennial tree fruit production systems. Several studies have quantified the impacts of global warming on risks of insufficient chill accumulation in the warmer tree fruit and nut production regions of the United States (US), such as the Southeast and California, where these risks are currently prevalent. In this work, we focus on the Pacific Northwest US – the largest production area in the US for apples, pears and cherries – and quantify the potential risk of insufficient chill accumulation. Our results highlight large spatial variations in response within the PNW, with northern areas projected to have reduced risks and southern areas projected to have increased risks. In the southern areas, rather than chill accumulation in and of itself, it is the combination of reduced and delayed chill accumulation with likely advancement in spring phenology that lead to production risks. In spite of future reductions to chill accumulation, risks of insufficient chill accumulation seem limited for apple even with advancement of spring phenology. Under the extreme “no climate policy” RCP 8.5 climate projections, the production risks are significant for early blooming crops (e.g. cherries) and varieties with relatively high chill portions requirements (e.g. Sam cherries), necessitating planning for management strategies such as frost protection and chemical management of budbreak to address potential risks which have not historically been a concern in the region. Under less extreme warming outcomes, the PNW tree fruit production systems are likely to remain resilient. Given that the convergence of the fulfillment of chilling requirements and environmental conditions promoting budbreak is where potential risk to perennial tree fruit production exists, future work should focus on understanding, modelling and projecting responses within this convergence space. Additionally, given significant spatial differences across a relatively small geographic range, it is also critical to understand and model these dynamics at a local landscape resolution for regions such as the PNW that faced limited risk historically, but could be exposed to new risks under a warming climate.
MONITORING OF PRODUCTION RISKS OF EXPERIMENTAL AND DESIGNED WORKS OF DEFENSE ENTERPRISES
