Factors explaining the diversity of land cover in abandoned fields in a Mediterranean mountain area

Abstract

Abandoned fields form an integral part of the landscape of Mediterranean mountains. For centuries, very steep slopes with poor soils were cultivated to feed the local population. From the mid-20th century, agriculture on many slopes has been abandoned and secondary succession is taking place with environmental, socioeconomic and landscape implications. This paper investigates the role of physical (climate variability and topography) and human (age of abandonment and field type-flat, sloping, terraced) factors in the process of secondary succession in abandoned fields in a representative Mediterranean mountain area. Aerial photographs from 1956 and 1978 were used to map the space-time process of land abandonment, and field types. Data on vegetation cover in abandoned fields was obtained in the SIOSE, the information system on land use in Spain (2006). The map was incorporated into a GIS and statistical analysis was done with R software (R, version 3.2.3). The results show that altitude and climate variability are the principal factors explaining the distribution of areas of forest and shrub. The slope and solar radiation are less important. Human management, although apparently a lesser determinant, has a strong influence. Management before abandonment conditions the spatial distribution of the seed bank and the extent of soil degradation. Management following abandonment (afforestation of conifers, shrub clearings and livestock grazing) decides where pine forest and pastures are located. The results of our case study suggest, that unlike most of cases in the literature, the age of abandonment is not the main factor explaining the natural succession processes. The knowledge about how natural and anthropogenic factors affect secondary succession should be considered a tool for land management in mountain areas.

Una revisión sobre las tierras abandonadas en España: de los paisajes locales a las estrategias globales de gestión

“…En el valle de Aísa (Pirineo aragonés), por ejemplo, el 54,4% de los campos en pendiente se había abandonado antes de 1956, mientras que la proporción de abandono era menor en los bancales (39,9%), en gran parte debido a que los bancales poseían suelos más fértiles y productivos que los campos en pendiente (Errea Abad et al, 2015). Después de 1956, sin embargo, los bancales se han abandonado de forma masiva, por las dificultades que plantean para la mecanización, tendencia que también se ha puesto de manifiesto en otras montañas mediterráneas (Arnáez et al, 2015;Peña-Angulo et al, 2019), mientras que se mantienen los campos de suave pendiente (Errea Abad et al, 2015).…”

“…La recuperación de la productividad del suelo y el progreso de la sucesión vegetal tienen mucho que ver, además, con las condiciones climáticas (Otto et al, 2006). En un clima húmedo o subhúmedo la sucesión vegetal es rápida, alcanzándose una cubierta de bosque joven en 30-40 años (Pardini et al, 1991;Lasanta et al, 2015;Peña-Angulo et al, 2019), mientras que en ambientes áridos y semiáridos es muy lenta, con un cubrimiento que con frecuencia no alcanza el 60% en campos de elevada edad de abandono (Ries et al, 2000;Lesschen et al, 2008a;Ruiz-Sinoga y Martínez-Murillo, 2009), y donde difícilmente se alcanza el estadio de bosque joven (Bonet y Pausas, 2004;Rey Benayas et al, 2015). Otra diferencia interesante entre áreas con diferentes condiciones climáticas es que en campos sin estrés hídrico la sucesión vegetal progresa de forma uniforme, mientras que en los que sufren estrés hídrico se desarrollan patrones de vegetación donde alternan manchas con cubierta vegetal y otras de suelo desnudo (Cammeraat y Imeson, 1999;Puigdefábregas, 2005).…”

Soil quality and soil organic carbon storage in abandoned agricultural lands: Effects of revegetation processes in a Mediterranean mid‐mountain area

“…The average annual temperature is about 11 C at 600 m a.s.l and 6 C at (Lasanta, 2009). The large area of abandoned fields (11,834 ha), a pasture system that was poorly managed by the herdsmen and based on cattle herds, promoted a natural revegetation process leading to shrubland becoming the main LULC of the landscape, while pastures shrank in size (1,155.7 ha) (Arnáez, Oserin, Ortigosa, & Lasanta, 2008 (Lasanta, Errea, Vicente-Serrano, & Arnáez, 2011;Peña-Angulo et al, 2019). This enabled us to find the main LULCs (Figure 2) in the abandoned fields: Aerial photographs from 1956 and 1981 at a 1:33.000 and 1:25.000 scales, respectively, were used and a GIS was employed to calculate the area occupied by agriculture.…”

Which landscape and abiotic site factors influence vegetation succession across seres at a country scale?

“…Especially the question which environmental factors affect the course of succession have been investigated by many authors (e.g. Řehounková & Prach, 2006;van Breugel et al, 2019;Peña-Angulo et al, 2019;Rohal et al, 2019).…”