Water storage dynamics across different types of vegetated patches in rocky highlands of central Argentina

Abstract

Rivers originating in the granitic highlands of seasonally dry central Argentina provide water to 2 million people. These highlands comprise a complex landscape where a matrix of outcropping rock hosts vegetated patches that vary in response to long‐term grazing and fire. We characterized water storage dynamics across 20 sites representing 6 vegetation‐soil conditions with similar mid‐upslope positions in the landscape. We measured temporal and spatial variability of water inputs (rain and fog) and water stored at the unsaturated and saturated zones. We found that rainfall was highly seasonal, but fog occurred year‐round, likely representing an extra water source in areas with complex vegetation structure. Moreover, fog seems to regulate evapotranspiration/topsoil water dynamics. Water was stored in the saturated zone only during the rainy season. Piezometric response to rainfall was rapid but transient (dropping an average 15 cm/day), possibly buffering peak stormflows, reducing sediment yield, and delivering subsurface water downslope for potential storing throughout the year. Spatially, a reduction in soil depth (from 100 up to 9 cm) and vegetation structure (from woodlands to stonelands), with a degradation of topsoil conditions for infiltration were accompanied by a decline in water storage at the unsaturated (from 32% up to 14%) and saturated (from 46.3 up to 0 cm) zones. Taken together, our results support the infiltration trade‐off hypothesis, which states that vegetation structure benefits fog interception, soil properties that enhance water infiltration, subsurface flow paths, and storage. Long‐term disturbances have likely triggered a degradation of the hydrological function of seasonal highlands in central Argentina.

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

“…These observations are in according with Famiglietti, Rudnicki, and Rodell (1998) and Poca, Cingolani, Gurvich, Saur Palmieri, and Bertone (2018), who reported that controlling aspects of SWC dynamic are soil porosity and hydraulic conductivity and topography of the studied hillslope/site. These observations are in according with Famiglietti, Rudnicki, and Rodell (1998) and Poca, Cingolani, Gurvich, Saur Palmieri, and Bertone (2018), who reported that controlling aspects of SWC dynamic are soil porosity and hydraulic conductivity and topography of the studied hillslope/site.…”

“…Climate characteristics such as (a) low temperature, (b) high air humidity, (c) high precipitations such as continuous rains-ranging between 47.5 and 149 mm month -1 -drizzles present during the 80% of the rainy days and that represent 30% of the water input (Padrón et al, 2015) and the presence of fog even during less humid periods (Poca et al, 2018), and (d) low evapotranspiration (evapotranspiration = 635 mm year -1 ; evapotranspiration-precipitation ratio = 0.51) due to the extended presence of fog and a dense cloud cover that limit incoming solar radiation (Carrillo-Rojas, Silva, Rollenbeck, Célleri, & Bendix, 2019). Reasons for this are the previously mentioned Andosols properties, the presence of perennial tussock grasses without seasonal changes that have a constant water consumption along the hydrological year and páramo climate characteristics.…”

“…the slope of 20% that prevented water accumulation. These observations are in according with Famiglietti, Rudnicki, and Rodell (1998) and Poca, Cingolani, Gurvich, Saur Palmieri, and Bertone (2018), who reported that controlling aspects of SWC dynamic are soil porosity and hydraulic conductivity and topography of the studied hillslope/site.…”

“…Reasons for this are the previously mentioned Andosols properties, the presence of perennial tussock grasses without seasonal changes that have a constant water consumption along the hydrological year and páramo climate characteristics. Climate characteristics such as (a) low temperature, (b) high air humidity, (c) high precipitations such as continuous rains-ranging between 47.5 and 149 mm month -1 -drizzles present during the 80% of the rainy days and that represent 30% of the water input (Padrón et al, 2015) and the presence of fog even during less humid periods (Poca et al, 2018), and (d) low evapotranspiration (evapotranspiration = 635 mm year -1 ; evapotranspiration-precipitation ratio = 0.51) due to the extended presence of fog and a dense cloud cover that limit incoming solar radiation (Carrillo-Rojas, Silva, Rollenbeck, Célleri, & Bendix, 2019). Together, all these climate characteristics diminished the loss of water from soil profiles, an affirmation corroborated by Schneider, Huisman, Breuer, Zhao, and Frede (2008), who indicated that atmospheric variables control the periods of soil wetting and drying.…”

Plant and soil carbon stocks in grassland patches maintained by extensive grazing in the highlands of central Argentina

“…Probably, the combined effect of erosion agents with grazing use could be especially stronger in grazing lawns located at higher topographic positions, which are less protected by vegetation cover; there, SOC stocks would be reduced due to the reduction of soil profile depth. In that case, greater efforts should be directed to protect vulnerable upland soils, which have been described as invaluable buffers of peak stormflows and sediment yields in these headwater catchments (Poca et al 2018b).…”