Deforestation of water‐repellent soils in Galicia (NW Spain): effects on surface runoff and erosion under simulated rainfall

Abstract

At three adjacent sites in steeply sloping woodland in Galicia (NW Spain), surface runoff and associated erosion under simulated rainfall (64 mm h 1 ) were measured on five occasions between June 1998 and July 1999. Two of the three sites had recently been deforested and topsoil added, and one of these two had been sown with grass, which was germinating at the onset of the study. Deforestation greatly increased runoff and erosion rates, and the recovery of plant cover reduced erosion. All three soils were very hydrophobic due to high levels of poorly humified organic matter, which led to higher runoff rates than expected, especially during dry periods. However, great structural stability prevented there being a significant correlation between runoff rate and soil erosion.

Seasonal changes in the soil hydrological and erosive response depending on aspect, vegetation type and soil water repellency in different Mediterranean microenvironments

“…This reduction of SWR was not observed in the case of inter-shrub areas of the southfacing hillslope, given that soils were already wettable during the transition season. Thus, SWR results highlighted the seasonal character of this property, reported widely in the literature in temperate humid areas as well as in semiarid environments (Witter et al, 1991;Kaiser et al, 2001;Benito et al, 2003;Whal, 2008;Zavala et al, 2009). SWR is commonly associated to dry soils and it is supposed to disappear when soil water content increases to a critical soil moisture threshold (Crockford et al, 1991;Imeson et al, 1992;Ritsema and Dekker, 1994;Moody et al, 2009;Santos et al, 2013).…”

“…On the other hand, the events with higher R c occurred in the transition season, being independent of precipitation. This seasonal behaviour of overland flow in Mediterranean conditions could be related to soil crust formation (Nunes et al, 2010), but soil surface layer on the north-facing hillslope had more than 5 % of organic matter, so surface crusting was not the reason for the enhanced overland flow (Hillel, 1998;Beven, 2001). This suggests SWR as the more probable cause (Doerr et al, 2003).…”

“…It has been widely accepted that the infiltration capacity of soils is higher under dry conditions, owing to the higher matric suction and the action of capillarity forces (Cerdà, 1998;Beven, 2001). This has been demonstrated by means of experiments and measurements in contrasted seasonal climates such as the Mediterranean (Cerdà, 1996(Cerdà, , 1997a(Cerdà, , 1999.…”

Concentrated flow erosion as a main source of sediments in Galicia, Spain

“…Even though soil erosion was studied comprehensively on Galician forest lands (Díaz-Fierros et al, 1982Soto et al, 1995;Soto and Díaz-Fierros, 1998;Benito et al, 2003), this topic has been a recent matter of interest on cultivated lands (Rodríguez Martínez-Conde et al, 1998;Dafonte, 1999;Valcárcel Armesto, 1999). Field observations over the last decade indicate that interrill, rill and ephemeral gully erosion are important sediment sources, which can cause diffuse water pollution and eutrophication problems (Valcárcel Armesto, 1999;Taboada Castro, 2001;Valcárcel et al, 2003).…”

Aplicação De Análise Multicriterial Para Determinação De Áreas Prioritárias À Recomposição Florestal

“…Os recursos hídricos no Brasil e em diversas regiões no mundo são constantemente comprometidos por atividades agrícolas, quando realizadas sem manejo adequado do solo, uso excessivo de fertilizantes e defensivos (Ashok et al, 2007), além do desmatamento e a expansão urbana (Benito et al, 2003). Os cursos d'água frequentemente transportam solo, muitas vezes provenientes de áreas agrícolas adubadas ou corrigidas a altos custos financeiros, contaminando águas superficiais e subterrâneas, comprometendo seu uso para o abastecimento público e na irrigação (Assad et al, 1998).…”