Dynamics in non-structural carbohydrates of trees might influence the variation of leaf phenology

Plant phenology is a key driver of plant growth and ecosystem-climate interactions, influencing canopy structure, surface albedo, and carbon and water fluxes. While the effects of environmental factors on phenology are well-documented, less attention has been given to intrinsic plant physiological processes. Non-structural carbohydrates (NSC), including sugars and starch, are essential for growth, metabolism, and osmotic regulation, serving as indicators of carbon availability. They reflect the balance between photosynthetic carbon supply (source activity) and the demands of growth and respiration (sink activity), suggesting that NSCs may influence phenological stages such as spring leaf-out and autumn senescence. However, the relationship between NSC dynamics in various plant organs and leaf phenology remains poorly understood.

By synthesizing current knowledge on the interplay between NSCs and leaf phenology, we outline seasonal NSC variations in deciduous and evergreen species. We further propose hypotheses on their interactions with phenological stages, namely leaf-out and autumn leaf senescence, and assess their alignment with existing conceptual carbon allocation models. To address existing gaps, we advocate for integrating NSC dynamics into carbon allocation models by leveraging insights from manipulative experiments, multi-scale observational networks, and remote sensing. These approaches will enable a more comprehensive understanding of NSC-phenology relationships across spatial and temporal scales. This could help us improve the modelling of plant phenology responses and carbon dynamics in diverse ecosystems.