Pedoclimatic and Landscape Conditions of the Spanish Olive Groves

Due to its eco-physiological characteristics, the olive tree is well adapted to Mediterranean-type climates, mainly by its ability to compensate the summer water deficit through effective regulation of its transpiration. Thus, avoiding only the Atlantic climate zones with rainfall >800–900 mm, the olive tree is widely distributed by the Mediterranean Spain. Despite this, olive groves define fairly heterogeneous landscape units, with very different features in terms of relief and soils. Many olive groves are sited in plateaus (e.g. La Mancha) or river valleys (e.g. Guadalquivir basin) with gentle to moderate slopes (2–15%), while up to a third of Spanish olive groves are settled in mountainous areas with average slopes >15%. The altitude is also highly variable; it is possible to find olive orchards from the sea level to altitudes above 1500 m (e.g. Sierra Nevada); however, the average range could be established around 500 m. Up to 84% of the Spanish olive orchard soil is included in map units with predominance of five taxonomic groups: Calcic Cambisols, Chromic Luvisols, Chromic Vertisols, Eutric Regosols, and Dystric Regosols. Broadly, soils tend to be fine grained and relatively stony, being remarkable for the low content of organic carbon of the topsoil (< 2%). All the representative profiles of olive grove soils analyzed were marginally suitable (S3 class) in the FAO Land Evaluation systems. The main pedological constraints that have been detected derive from steepness, heavy texture, and organic carbon depletion and, in some soils, the acid pH and low base saturation (Dystric Regosols) or, on the contrary, high pH and CaCO3 content (Calcic Cambisols). Moreover, some climatic constraints can also be found: Some olive groves in mountain areas and high plateaus showed mean annual temperatures close to the lower limit of suitability (13 °C). In general, the Spanish olive grove is well adapted to the biophysical possibilities of the land, although it has intrinsic limitations for sustainable use that reduce profitability and increase the required inputs and degradation risks.