Exploring the potential of multiple tropical tree species for dendroclimatology in the Ecuadorian Andes

Climate change projections for the equatorial Ecuadorian Andes are contradictory due to topographic diversity and interplay of multiple climatic influences. Intensifying droughts and increasing precipitation variability impact the livelihood of local populations which depend on agriculture and hydroelectric energy sources and thus are highly vulnerable to long- and short-term climatic changes. Overall, the hydroclimate of the northern tropical Andes is influenced by multiple climate systems such as the Intertropical Convergence Zone (ITCZ), the Pacific Decadal Oscillation (PDO) and El Niño Southern Oscillation (ENSO) (Dominguez-Castro et al., 2017). The interaction of these large-scale climate systems across the complex Andean topography results in strong variability of local climate conditions. As a result, the available instrumental climate data is spatially and temporally limited. Tree-rings and stable isotopes can be used as high-resolution climate proxy to complement and extend instrumental records and investigate local climate impacts.

This study focuses on exploring the potential of multiple tropical Ecuadorian tree species, beyond the Polylepis-focused approaches common in Andean dendroclimatology. For a feasibility study, five tree species of the western cordillera located about 30 km north of Quito were selected. Dendrocores were retrieved at an elevation of 2000 – 3000 m a.s.l in the protected Cambugán primary forest, a primary and secondary forest in the Piganta river catchment (Atahualpa) and a private agroforest area. Although uncertain seasonality in the Andean tropics complicates the use of standard dendrochronological applications, preliminary observations suggest that growth patterns and potential annual tree-rings may be influenced by local precipitation patterns characterized by a dry season. Other potential growth-limiting factors appear largely persistent across the research area. Overall, the identification and description of growth-ring boundaries across multiple tropical tree species will provide the foundation for robust chronologies and future dendroclimatological analyses using stable isotopes. This could enable further investigation in the reconstruction of local precipitation and drought patterns in relation to large-scale climate influences (ENSO, ITCZ, PDO).