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Intra-annual stem increment patterns and climatic responses in five tree species from an Ecuadorian tropical dry forest

Abstract:

Key message: Intra-annual increment patterns and wood production are coupled with rainfall seasonality in five tree species of a Tumbesian tropical dry forest. However, climatic responses show variation among species. Abstract: In many tropical dry forests, information on radial-growth rates and phenology of wood formation is still lacking. However, such information is needed to better manage these forests, which have been severely disturbed by anthropogenic use and are also threatened by climate warming. To cover this research gap, we evaluated intra-annual variations in stem diameter and assessed cambial growth dynamics in five tree species of a Tumbesian tropical dry forest located in southern Ecuador. Using data from band dendrometers over a 5-year period, we modeled seasonal variations in stem increments through generalized additive mixed models. Monthly radial increments and annual growth rates were also correlated with monthly climatic variables (mean, maximum and minimum temperature, and total rainfall). Stem increments and xylem growth were clearly coupled with rainfall seasonality, although temperature effects were also detected. Interestingly, annual growth in all species did not respond similarly to climate, despite having similar growth rates and intra-annual growth patterns. At the inter-annual scale, climate effects were related to temperature and rainfall, emphasizing the relevance for tree growth of climatic conditions in standard years between “El Niño” events. Under a future scenario of climate warming, these contrasting growth responses to climate might imply changes in competitive dominance among coexisting species of tropical dry forests.