Variation of seasonal wood growth in the Central-African semi-decidious forest of the Luki Biosphere Reserve.

Abstract

Understanding the seasonal dynamics of radial growth in tropical trees is essential for predicting forest responses to climate change. This study, conducted within the framework of the CANOPi project, investigated growth patterns in canopy trees from the Luki Biosphere Reserve (DRC) using high-resolution dendrometer data collected over 20 months. Growth curves were classified into distinct patterns through breakpoint analysis, and their relationships with tree traits (e.g. diameter, wood density, leaf habit) and climatic variables from ERA5 were explored. Four growth types were identified: highly seasonal, moderately seasonal, non-seasonal, and no-growth, with deciduous species largely dominating the seasonal groups. Strong inter- and intra-specific variability was observed in growth period timing, duration, and intensity. The growth period of seasonal patterns was closely aligned with the wet season, with growth onset and cessation largely driven by rainfall and soil water content thresholds. Non-seasonal trees were predominantly evergreen or exhibited potential rapid leaf exchange. Gompertz modelling of the highly seasonal group revealed a consistent inflection point between January and February, coinciding with a brief dry spell within the wet season. These findings confirm the strong climatic control over growth seasonality in Central African forests and highlight the need to integrate fine-scale monitoring with phenological and anatomical analyses to improve growth modelling under changing climate conditions.