Soil physical changes after conversion of woodlands to pastures in dry Chaco Rangelands (Argentina)

The conversión of dry woody rangelands into pastures can aler key soil hysical ropertis that regulate ecosystem wáter circulation and storage. Based on three paired stands of native woodl and sand pastures established 20 years agoin the southern Dry Chaco (SanLuis, Argentina) ,wed escribed contrasts in five soil physical properties usin gasy stematics ampling of soil patches (9−18 patches along a single transect with inea chofthe three paired -hastands). Compared with woodl and ,pastures displayed flatter microtopography (mean more or less standarddeviation [SD]:3.7 plus sign minus sign 0.34vs.5.0 plus sign minus sign 0.67%slope; P b 0.05), lowerin filtration rate (mean plus sign minus sign SD:71.6 plus sign minus sign 9.0vs.139.9 plus sing minus sign 37.2mmh−1; P b 0.05), and higher penetration resistance (mean plus sign minus sign SD:4.2 plus sign minus sign 0.10vs.1.9plus sign minus sign 0.17kgcm−2; P b 0.01) and bulk density(mean plus sign minus sign SD:1.39plus sign minus sign 0.05vs.1.16 plus sign minus sign 0.04gcm−3; P b 0.0001). On average,top soil water contentat field capacity was similar forbothty pesof cover (meanplus sign minus sign SD:16.3 plus sign minus sign 0.21vs.17.1plus sign minus sign 1.12% ,pastures and Wood lands, respectively; P equal sign 0.29). However,at similar bulk density values,pastures presenteda approximately 20%reduction involumetric wáter contentat field capacity(16.3%)compared with Wood lands(19.7%). The establishment of pastures led tomore homogenous soils,with most variables havin greduced spatial variability in comparison with Wood lands. Our observations showed how the conversión of native Wood lands to pastures produced strong physical changes in the soil sof Dry Chaco and help tounder stand the mechanisms that arem most likely influencing the surface - soil wáter dynamics of these,and perhaps other,dry rangelands.