Land degradation affects shrub growth responses to precipitation in a semiarid rangeland of north-eastern Patagonia (Argentina)

CAMPANELLA, M. VICTORIA; ROSTAGNO, C. MARIO; VIDELA, LINA S.; BISIGATO, ALEJANDRO J.

AUSTRAL ECOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2018 vol. 43 p. 280 - 287

1442-9985

Arid landdegradation diminishes the proportion of precipitation conducted toinfiltration and increases the proportion lost to runoff and evaporation. Consequently,we expect that the effects of annual precipitation on shrub growth vary with landdegradation as a result of changes in soil available water. Chuquiraga avellanedae is the dominantshrub and the main indicator of land degradation in semiarid rangelands of north-easternPatagonia. We chose two communities with adifferent degree of land degradation: an herbaceous steppe with shrubs (HSS)and a degraded shrub steppe (SS). Vegetative growth of C. avellanedae was determined non-destructively using a double-samplingapproach. Soil water content was estimated for the two communities using a soilwater balance model. Linear regressions were used to evaluate the relationshipsbetween shrub growth and i) annual precipitation and ii) mean available waterduring the period of high vegetative growth in the soil layer that each plant communityconcentrates their roots. In SS, with elevated clay content, there were moreroots of C. avellanedae in the upperlayers of soil while in HSS, with coarse-textured soil, C. avellanedae had more roots in deeper layers. Vegetative growthof C. avellanedae, both in HSS and SScommunities, was positively related to annual precipitation but, for a givenprecipitation, C. avellanedaepresented higher vegetative growth in HSS than in SS. We also found a positiverelationship between vegetative growth and soil available water, and thisrelationship did not differ between communities. SS presented lower wateravailability because of lower infiltration rates. Our results showedthat, irrespective of the degree of land degradation, plants respond directlyto water content of the soil layers where most rootsare present at a specific window of time.