A process-based model of climate-driven xylogenesis and tree-ring formation in broad-leaved trees (BTR).

The article focuses on the development and evaluation of the Broad-leaved Tree-Ring (BTR) model, a climate-driven process-based model designed to simulate xylem formation and radial growth in broad-leaved trees. Incorporating daily climate inputs—temperature, soil moisture, vapor pressure deficit, and daylength—the model simulates cambial activity, cell division, differentiation into vessel and fiber cells, and their growth processes to predict annual ring width and xylem anatomical traits. Calibrated and validated using data from two species, Fraxinus mandshurica (ring-porous) and Betula platyphylla (diffuse-porous), across multiple sites in northeast China, the BTR model effectively reproduces intra-annual and interannual variations in tree-ring width and xylem cell characteristics. While the model accurately simulates cell lumen areas and vessel differentiation dynamics, it has limitations in representing fiber cell wall thickening and long-term climate legacy effects, and it does not simulate complex vessel clustering. Overall, the BTR model offers a valuable tool for understanding broad-leaved tree growth responses to climate factors and supports further research in forest carbon dynamics and wood formation.