Understory changes associated with the replacement of natural vegetation by Pinus ponderosa Dougl. under different plantation management (SW Neuquén, Argentina)

Abstract

Influence of different plantation management intensity on understory vegetation of Ponderosa pine plantation was studied in plots distributed through a W-E transverse. Five under Nothofagus forest and ten under Ponderosa pine plantation —five with 90-100% soil cover and five with an overstory reduction to 60-70%—; and other two under steppe vegetation and their equivalents under non-thinned and thinned pine plantations. Shannon diversity index was calculated, and topsoil was characterized and compared. Under pines diversity was lower than under natural vegetation—Nothofagus and steppe— which together with the lower carbon content showed the ecosystem alteration. Diversity was higher under thinned plantations and dominated by non-native herbal species and native shrubs, this was reflected on top soil structure which tended to be granular as under native vegetation, showing its resilience capacity. Overstory reduction promoted shrub and herbal understory development in Ponderosa pine plantation, showing a tendency to biodiversity restoration, probably due to the higher radiation which reaches the soil. From the information gathered on the species composition of the understory vegetation and its consequences on top soil properties, strategies for the effective management can be derived to enhance productivity diversification.