Eco-hydrological Functions in Forested Catchments of Southern Chile

Abstract

Ecosystem functions in forests can vary significantly after disturbance, depending on changes in vegetation structure during succession and soil biophysical characteristics. We examined streamflow regulation, water storage and soil protection functions in small catchments covered by evergreen temperate rain forests, developed over volcanic ash soils, in southern South America. Our aims were to understand the differences in ecosystem functioning among catchments representing different forest stages following human disturbance, from scrubland to old-growth forest condition. In these catchments (n = 3 per condition), we assessed and compared eco-hydrological functions over 21 months. In old-growth (OG) forest catchments, streamflow for the entire study period averaged 2102 ± 110 mm, followed by secondary forest (SF) catchments with an average of 1770 ± 284 mm and finally scrub catchments (CH) with 1684 ± 267 mm. Evapotranspiration showed higher values in SF catchments (643 mm), followed by CH catchments (612 mm) and OG catchments (346 mm). OG and CH catchments had the lowest sediment export in streamflow, without statistical difference between them, while SF catchments had the highest sediment concentrations in all seasons of the year. Principal component analysis revealed that soil physical properties, vegetation structure and catchment morphometry were all relevant to explain the differences among the three forest successional stages compared. We validate the hypotheses that streamflow regulation and soil water storage capacity are greatly enhanced in old-growth forests, while the soil protection function is maximized in both early (bamboo-dominated) and advanced forest stages.