Management practices and soil quality patterns in evergreen oak woodlands (montado)

Abstract

The sustainability of evergreen oak woodlands (montado) in Portugal is currently threatened in large areas, mainly due to limited tree recruitment constrains and soil degradation. It is therefore urgent to develop sustainable management options which enhance montado productivity, ensuring their long-term viability and all ecosystem services. The present study aimed specifically to evaluate trends in soil quality changes, associated with management practices currently followed in montado. Different montado areas, corresponding to different soil types and land use histories, with different management options, including sowed and natural pasture systems, and different stocking rates and grazer species, were considered; also, the specific influence of the tree cover on the soil characteristics was investigated. The soil quality of study areas was assessed by evaluating physical, chemical and biochemical soil properties. Carbon and the main nutrient fluxes were also evaluated, assessing GHG emissions and nutrient leaching. Results enabled the assessment of the benefits associated with the establishment of improved pastures, namely in soil hydrological conditions, nutrient availability and soil organic matter status, which was particularly enhanced in areas under the tree cover influence. Nevertheless, factors associated with the soil type (texture) and livestock management (stocking rate) might have strong influence on the extent and nature of such benefits. Pasture management influence over soil carbon and nutrient fluxes were found negligible, despite disturbance may occur. Scattered trees, in the montado, promote the creation of islands of improved physical conditions and soil fertility, where the organic carbon accumulation is strongly enhanced. Trees undoubtedly improve soil quality, enhance the soil resistance to face degradation threats, and contribute to carbon sequestration. This potential should be taken into account for policy and management decisions, at both local and regional scales