Abstract
Terraces represent one of the most common agricultural landscapes in Mediterranean mountainous regions. However, the demographic and socioeconomic changes occurring in the second half of the last century caused terraces abandonment, leading to the loss of maintenance work required by these agricultural structures, and promoting various erosion processes, in particular the collapse of stone walls and small slides in risers. This paper analyses these mass movements by quantifying their size and frequency and defining the variables involved in their triggering in the upper valleys of Leza, Jubera and Cidacos rivers (Camero Viejo, Iberian Range, Spain), where bench terraces occupied 13,274 hectares (63% of agricultural space). A total amount of 240 small slides were recorded in 53 terraces studied, which means an average of 4.5 slides per plot and 33.1 m3 of material mobilized per 100 m of wall. This study proves that the most decisive causes for slides to start are related to soil infiltration capacity, as well as to the way in which water runs down the hillside.
Highlights
Agricultural spaces in mountainous areas have adapted to rigorous environmental conditions from both a climatic and topographical point of view (Price, 1981)
The extent of agricultural surface was important in some mountainous regions, especially in the Mediterranean area (Lasanta, 1990; Lasanta et al, 2017)
Agricultural land abandonment during the 20th century occurred mainly in the less productive mountainous regions and resulted in loss of landscape heterogeneity and facilitated the disappearance of a cultural landscape built over centuries
Summary
Agricultural spaces in mountainous areas have adapted to rigorous environmental conditions from both a climatic and topographical point of view (Price, 1981). The extent of agricultural surface was important in some mountainous regions, especially in the Mediterranean area (Lasanta, 1990; Lasanta et al, 2017). The lack of maintenance of these fields, in addition to other factors, activated new hydrological and geomorphological dynamics, especially during the early years or decades after abandonment. New research topics have arisen: the intensity and frequency of different geomorphological events (Arnáez et al 1992; Lesschen et al, 2007; Romero-Díaz, et al, 2007; Romero-Díaz, 2016), the estimate of runoff and erosion rates, hydrological functioning of slopes (Gallart, et al., 2002; García-Ruiz and Lana-Renault, 2011; Lana-Renault, et al, 2014; Romero-Díaz et al, 2017), drainage network connectivity (Bellin et al, 2009, Latocha, 2014), carbon redistribution by erosion processes (Boix-Fayos et al, 2017), and plant recolonization and its impact on erosion and soil quality (Benjamin et al, 2005; Pueyo and Beguería, 2007; Van Hall et al, 2017)
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