How does grazing affect soil water availability in the Patagonian steppe?

GOLLUSCIO, RA; GARCÍA MARTÍNEZ,G; CAVAGNARO, FP

JOURNAL OF ARID ENVIRONMENTS

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2022 vol. 205

0140-1963

In the Patagonian steppe, grazing may or may not reduce soil water availability: it may increase evaporativelosses, because it reduces plant cover, but may decrease transpiration losses because it decreases plant biomass.Therefore, grazing could reduce soil water availability in the superficial layer, mostly affected by evaporation,but could increase it in the subsurface layers, mostly affected by transpiration. Our hypothesis is that such effectswould be most evident in the bare soil spaces, with higher evaporative losses and lower root density thanvegetated microsites. Therefore, we analyzed the proportion of four microsites (shrubs, bare soil, preferred- andunpreferred grasses), and their soil water availability at 0–5 and 5–15 cm depth in four sampling areas, each onewith an ungrazed, a moderately- and an intensely-grazed site. Our results supported the initial hypothesis: baresoil microsites had the lowest surface, but the highest subsurface water availability. However, grazing did notcause any change in the mean soil water availability (net effect) because it did not affect soil water availability inany microsite and depth (direct effects), and only caused a replacement of preferred-by unpreferred grasses(indirect effects), two groups that induced small differences in water availability.