COS 38-1 - Climate and topography control variation in the tropical dry forest–rainforest ecotone

Abstract: Ecotones, the transition zones between ecosystems, are gradients in ecosystem properties controlling flows of energy and organisms between them. Ecotones are sensitive indicators of global change, but the potential for spatiotemporal dynamics of ecotones to act as global change indicators is limited by methodological and logistical constraints. Here, we use a novel combination of satellite remote sensing and analyses of spatial synchrony to identify the tropical dry forest-rainforest ecotone in Area de Conservación Guanacaste, Costa Rica. We further examine how climate and topography influence the spatiotemporal dynamics of the ecotone, showing that ecotonal forests are most prevalent at mid-elevations where the topography leads to moisture accumulation, and that climatic moisture availability influences up- and downslope inter-annual variation in ecotone position. We found no evidence for long-term (22-year) trends toward upslope or downslope ecotone shifts, as suggested by others in both tropical and extra-tropical regions. However, we demonstrate that the regional climate mediates topographic controls on ecotone formation, suggesting the ecotone boundary on the dry forest side may be less resilient to future precipitation reductions and that if drought frequency increases as predicted, ecotone reductions are more likely to occur along the dry forest boundary.