Annual and differentiated growth-ring boundaries in the northern Andes: From dry to humid tropical forests

Abstract

Tropical forests play a critical role in global carbon and water cycles, yet long-term tree growth dynamics across different tropical climates remain poorly understood. This is due to scarce and unevenly distributed climate records in tropical regions and high species diversity, challenging studies about forest responses to environmental variability. Dendrochronology allows the reconstruction of tree-growth dynamics in relation to climate; however, its application in the tropics remains underappreciated due to the difficulty of identifying growth-ring boundaries in tropical species, determining whether these are formed annually, and the high species turnover across climate gradients. To address this gap, we describe the wood anatomy of 65 tree species along a tropical climate gradient from dry to humid forest on the Eastern Cordillera of the Colombian Andes and explore their dendrochronological potential, including numerous species not previously described. We find that ∼78% of the species exhibit distinguishable growth-ring boundaries. Ring visibility varies with wood structure, with well-defined boundaries associated with marginal parenchyma bands and vessel size variation, whereas poorly defined rings are linked to fiber structure. Radiocarbon (¹⁴C) dating confirms annual ring formation in several species but also reveals discrepancies in others, likely due to false rings, missing rings, or intra-annual and supra-annual growth variability. Our results confirm the broad dendrochronological potential of tropical tree species and expand the taxonomic and geographic scope of tropical dendrochronology. Exploiting the dendrochronological potential of tropical tree species could provide valuable insights into tropical forest functioning and resilience under future climate change.