Abstract
Abstract. The Neotropical Andean grasslands above 3500 m a.s.l., known as páramo, offer remarkable ecological services for the Andean region. The most important of these is the water supply of excellent quality to many cities and villages in the inter-Andean valleys and along the coast. The páramo ecosystem and especially its soils are under constant and increased threat by human activities and climate change. In this study, the recovery speed of the páramo soils after drought periods are analysed. The observation period includes the droughts of 2009, 2010, 2011, and 2012 together with intermediate wet periods. Two experimental catchments – one with and one without páramo – were investigated. The Probability Distributed Moisture (PDM) model was calibrated and validated in both catchments. Drought periods and its characteristics were identified and quantified by a threshold level approach and complemented by means of a drought propagation analysis. At the plot scale in the páramo region, the soil water content measured by time domain reflectometry (TDR) probes dropped from a normal value of about 0.84 to ∼ 0.60 cm3 cm−3, while the recovery time was 2–3 months. This did not occur at lower altitudes (Cumbe) where the soils are mineral. Although the soil moisture depletion observed in these soils was similar to that of the Andosols (27 %), decreasing from a normal value of about 0.54 to ∼ 0.39 cm3 cm−3, the recovery was much slower and took about 8 months for the drought in 2010. At the catchment scale, however, the soil water storage simulated by the PDM model and the drought analysis was not as pronounced. Soil moisture droughts occurred mainly in the dry season in both catchments. The deficit for all cases is small and progressively reduced during the wet season. Vegetation stress periods correspond mainly to the months of September, October and November, which coincides with the dry season. The maximum number of consecutive dry days were reached during the drought of 2009 and 2010 (19 and 22 days), which can be considered to be a long period in the páramo. The main factor in the hydrological response of these experimental catchments is the precipitation relative to the potential evapotranspiration. As the soils never became extremely dry nor close to the wilting point, the soil water storage capacity had a secondary influence.
Highlights
In the northern Andean landscape, between ca. 3500 and 4500 m a.s.l., an “alpine” Neotropical grassland ecosystem – locally known as “páramo” – covers the mountains
The potential reference Ep for the period from 16 July 2010 until 15 November 2012 was calculated by the FAO Penman– Monteith approach with the solar radiation estimated by Hargreaves–Samani
The páramo ecosystem has a pivotal role in the hydrology and ecology of the highlands above 3500 m in the Andean region and it is a major source of water for human consumption, irrigation, and hydropower
Summary
In the northern Andean landscape, between ca. 3500 and 4500 m a.s.l., an “alpine” Neotropical grassland ecosystem – locally known as “páramo” – covers the mountains. 3500 and 4500 m a.s.l., an “alpine” Neotropical grassland ecosystem – locally known as “páramo” – covers the mountains. The major ecological characteristics of this ecosystem have been documented by several authors The páramo is an endemic ecosystem with high biodiversity. Its soils contain an important carbon storage and provide a constant source of drinking water for many cities, villages, irrigation systems and hydropower plants. A high vulnerability to changes induced by human activities and climate change in mountainous regions has been recognized in these systems. Most of the research in páramos has been focussed on its hydrological capacity as well as the soil characteristics under unaltered and altered conditions
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