Preferential allocation of carbohydrate reserves belowground supports disturbance-based management of American chestnut (Castanea dentata)

Abstract

Non-structural carbohydrates (NSCs) are critical for the survival of trees, but the ability to accurately predict NSC levels for a given forest tree species is lacking. We evaluated NSC dynamics in American chestnut (Castanea dentata), a species of high restoration interest, to test the conventional model of seasonal and inter-organ dynamics and to facilitate informed conservation efforts. Chestnut trees were sampled over the course of one year at different phenological stages. Then, organ-specific NSC concentration data were paired with biomass estimates from a custom-built allometric model to generate NSC pool sizes. Organ-level NSC concentrations and pools generally peaked at leaf fall (October) and were lowest during shoot expansion (June), although interactions between organ type and collection period drove variation in pool sizes. Whole-tree NSC pools increased from 2.47 ± 0.42 kg at shoot expansion to 4.29 ± 0.65 kg at leaf fall. Coarse roots were the most important NSC reservoir, accounting for 46.5% − 56.6% of the total whole-tree NSC reserves, depending on the time of year. Coarse root NSC pools were larger and more dynamic than in previous studies with other temperate deciduous trees, and they were the primary supplier of NSCs to support spring leaf-out. Preferential belowground NSC allocation and the ability to mobilize root NSCs to fuel growth and metabolism suggest that chestnut could thrive under disturbance-based management.