Enhancing Establishment of Young Chestnut Trees Under Water-Limited Conditions: Effects of Ridge Planting and Foil Mulching on Growth, Physiology, and Stress Responses

The successful establishment of young chestnut orchards is increasingly challenged by drought stress and limited irrigation availability, especially in areas with limited water access. This study evaluated the effects of ridge planting and plastic foil mulching, individually and in combination, on the early growth and stress physiology of vegetatively propagated Castanea sativa × C. crenata ‘Marsol’ trees under rainfed conditions. Over a two-year field trial, vegetative traits, photosynthetic pigments, and leaf phenolic profiles were assessed to determine treatment effects. Ridge planting combined with foil mulching significantly improved tree growth, leading to a 2.6-fold increase in leaf number and 1.6-fold increase in height compared to control (flat planting without foil). This treatment also minimized stress indicators, such as chlorosis and elevated phenolic content. Notably, the ellagitannin chestanin emerged as a dominant stress-related metabolite in the first year, suggesting its potential as an early biochemical marker of transplantation stress. Over time, a compositional shift in phenolic groups, from hydroxycinnamic acids and flavanols to flavonols and hydroxybenzoic acids, was observed, reflecting the plant’s transition from acute stress response to developmental acclimation. These results support ridge planting with foil as a practical, climate-adaptive solution for chestnut orchard establishment and highlight chestanin as a candidate marker for stress monitoring in young trees.