Impacts of land use and cover type on runoff and soil erosion in a marginal area of Portugal

Abstract

This paper presents the results of soil hydrological and erosional responses to different land use and cover types in a marginal area of Portugal. The six land uses and vegetation covers studied (cereal crop, fallow land, shrub cover, recovering autochthonous vegetation, land afforested with Pinus pinaster and pastureland) are representative of situations commonly found throughout central and northern Portugal and also in other Mediterranean systems. The specific goals were to evaluate and compare the hydrological and erosional response of soils representing different land uses and vegetation types, to establish the influence of climatic variability and soil surface characteristics, and to assess the efficiency of alternative land uses proposed by the Common Agrarian Policy in terms of hydrogeomorphic behaviour. The results show significant hydrogeomorphic responses among land uses/covers, indicating arable land and coniferous afforestation as the most serious in terms of runoff and soil erosion. With these types of land use, the soil transported by runoff peaks during autumn/winter coincided with the highest and most erosive rainfall in the experiment area. Conversely, shrub cover and recovering oak, resulting from land abandonment and plant succession, and pastureland, as consequence of conversion to arable land, showed the greatest rainfall infiltration capacity and the lowest rate of soil erosion. According to the results, vegetation dynamics emerges as a key factor in quantifying and interpreting the hydrological and erosional response of the land use/covers monitored. Soil erosion can subsequently be controlled by changing land use and increasing the ground cover, which was revealed as one of the basic approaches to controlling soil erosion in all types of land use.