Afforestations and its relationships with soil erosion and productivity in forest-steppe transition (Andinopatagonia, Argentina)

Abstract

In Andinopatagonian region —Neuquén province— forested areas for wood production, located in forest – steppe ecotone, have increased during the last decades, where one of the most serious environmental problems is desertification caused by over-grazing. This turn critical other functions of afforestations such as soil conservation. A regional simulation of forest land use and its effect on soil erosion was done. Erosion under forest was estimated and compared with actual erosion, on soil cartographic units from moderately to very apt. Potential forest control on erosion was evident in the cartographic units under steppe vegetation. Field erosion and its consequences on potential productivity was estimated and compared under Pinus ponderosa Dougl. —first stand from 14 to 19 years old— and under shrub gramineous steppe. Eleven paired plots were selected in representative sites of the cartographic units, distributed from west to east, each pair under each vegetation type with equivalent physiographic conditions. A-horizon depth was higher under pine than under steppe, which indicated soil losses under steppe about 136 t-1 ha-1 year. This determined a decrease on Site Index at 14 years between 0.53 and 0.43 m, which implied a decline on potential productivity of the ecosystem. Soil losses under steppe in relation to soil losses under afforestations evidenced forest effect on erosion control and sustainable productivity uphold. This has a temporal projection and its consideration is decisive for ecosystem management.