Impact of tussock grasses removal on soil water content dynamics of a tropical mountain hillslope

Abstract

© 2019 John Wiley & Sons, Ltd. Land use impacts on soil water content (SWC) are scarcely studied in mountain humid ecosystems, such as the Andean páramos, despite its influence on ecohydrological processes. Our objective was to analyze the impacts of extensive grazing on SWC of an Andean páramo hillslope with native tussock grasses. Along two parallel transects in a hillslope, we monitored SWC through pairs of SWC sensors placed at different soil depths (Ah horizon= 10 –35 cm; C horizon= 65 – 75 cm). The tussock grasses were cutout from one transect (Experimental) as an emulation of extensive grazing (without soil destruction), whereas the second transect (Control) remained intact. Both transects were hourly monitored for 10 months (post-intervention period). Post-intervention period was compared with a pre-intervention period of similar precipitation characteristics to minimize the influence of precipitation in the interpretation of the results. We analyzed both periods through differences in SWC between the pairs of sensors (Experimental minus Control) and differences in SWC dynamic of the pairs of sensors through linear regressions (slope and intercept values). Results suggest that the emulation did not change the mean SWC, but caused a reduction of SWC dynamic. Causes of SWC attenuation were a lower interception and transpiration, a higher amount of effective rainfall infiltrated, and similar evaporation from the soil than under unchanged conditions. These observations were done at all the soil depths. Probably, extensive grazing does not negatively affect the hydrological functioning of páramo ecosystems, particularly its water yield, as long as the soil remains undisturbed.