Do improved pastures enhance soil quality of cork oak woodlands in the Alentejo region (Portugal)?

Abstract

Portuguese forest sustainability is currently threatened by forecasted climate changes and inappropriate management practices. Specifically, large cork oak woodland areas (montados) are subjected to soil degradation and tree recruitment impeachment. A study was developed to compare soil properties in cork oak woodlands with improved pastures (IP) grazed by cattle and natural understorey management (NU) without grazing. The IP system did not lead to soil organic C concentration increase, soil organic C stock being 0.7 kg m−2 lower in the upper 30 cm soil layer, compared to the NU system. Under the IP management, soil N content was 39.7 g m−2 higher up to 30 cm depth, and N mineralization potential was increased by 50% in the 10 cm top soil layer. Soil bulk density and C mineralization potential were similar in both systems. Sowing legume-rich pastures can result in an immediate soil quality improvement, especially regarding N availability, although grazing may hamper tree recruitment. Managing the natural understorey appears suitable for soil organic C maintenance, and also allows tree recruitment, while soil N availability limitation could be overcome by fertilizer applications.