Soil physical changes after conversion of woodlands to pastures in Dry Chaco rangelands (Argentina)

MAGLIANO, PN; FERNÁNDEZ, RJ; FLORIO, EL; MURRAY, F; JOBBÁGY, EG

Rangeland Ecology and Management (ex JRM)

SOC RANGE MANAGEMENT

Lugar: Boulder, Colorado; Año: 2017 vol. 1 p. 225 - 229

1550-7424

The conversion of dry woody rangelands into pastures canalter key soil physical properties that regulate ecosystem water circulationand storage. Based on three paired stands of native woodlands and pastures established20 years ago in the southern Dry Chaco (San Luis, Argentina), we describedcontrasts in five soil physical properties using a systematic sampling of soilpatches (9-18 patches along a single transect within each of the three paired 1-hastands). Compared to woodlands, pastures displayed flatter micro-topography (mean± SD: 3.7±0.34 vs. 5.0±0.67% slope; p<0.05), lower infiltration rate (mean ±SD: 71.6±9.0 vs. 139.9±37.2 mm h-1; p<0.05), and higherpenetration resistance (mean ± SD: 4.2±0.10 vs. 1.9±0.17 kg cm-2;p<0.01) and bulk density (mean ± SD: 1.39±0.05 vs. 1.16±0.04 g cm-3;p<0.0001). On average, topsoil water content at field capacity was similarfor both types of cover (mean ± SD: 16.3±0.21 vs. 17.1±1.12%, pastures andwoodlands, respectively; p=0.29). However, at similar bulk density values,pastures presented a ~20% reduction in volumetric water content at fieldcapacity (16.3%) compared to woodlands (19.7%). The establishment of pastures led to more homogenous soils,with most variables having reduced spatial variability in comparison with woodlands.Our observations showed how the conversion of native woodlands to pastures producedstrong physical changes in the soils of Dry Chaco, and help to understand the mechanismsthat are most likely influencing the surface-soil water dynamics of these, and perhaps other, dry rangelands.