Ecohydrological dynamics in the Central American and Andean Páramo: Insights from a modelling analysis using a Budyko-type model for non-stationary conditions

The Páramo is a high‐elevation tropical grassland ecosystem that plays an important role in the regional water cycle of Central America and the northern Andes. However, refined information about the ecohydrological partitioning in these mountainous biomes is scarce. This work aimed to assess sub-annual or monthly variations in the ecohydrological conditions along a N-S transect with three Páramo sites: Chirripó (Costa Rica) and El Carmen and Cajas (north and south Ecuador, respectively). A Budyko-type model for conditions under which evapotranspiration surpasses precipitation using monthly meteorological observations and evapotranspiration products (May 2016-April 2019) was applied to evaluate short-term ecohydrological dynamics based on the aridity index and precipitation partitioning in the Páramo sites. Stronger hydroclimatic variations were found in Chirripó than in the Andean Páramos, related with significant increments in the evaporative index (AET/P) during the dry season. We also found a clear separation between Chirripó and the Ecuadorian Páramos owing to a higher ecohydrological resilience (i.e., similar trajectories in the energy excess or 1- AET/PET and the water excess or Q/P) in Chirripó during dry season and a more effective regulation by the additional water available to evapotranspiration besides direct precipitation (y₀, range: 37 – 90 %). Our results reveal the complex ecohydrological functional properties of the Páramo and its sensitivity to future moisture changes (e.g., ENSO cycles) that could alter its water yield synchronicity.