Mid and late Holocene forest fires and deforestation in the subalpine belt of the Iberian range,northern Spain

The conversion of subalpine forests into grasslands for pastoral use is a well-knownphenomenon, although for most mountain areas the timing of deforestation has not been determined. The presence of charcoal fragments in soil profiles affected by shallow landsliding enabled us to date the occurrence of fires and the periods of conversion ofsubalpine forest into grasslands in the Urbión Mountains, Iberian Range, Spain. We found that the treeline in the highest parts of the northwestern massifs of the Iberian Range(the Urbión, Demanda, Neila, and Cebollera massifs) is currently between 1500 and 1600 m a.s.l., probably because of pastoral use of the subalpine belt, whereas in the past it would have reached almost the highest divides(at approximately 2100–2200 m a.s.l.). The radiocarbon dates obtained indicate that the transformation of the subalpine belt occurred during the Late Neolithic, Chalcolithic, Bronze Age, Iron Age, and Middle Ages. Forest clearing was probably moderate during fires prior to the Middle Ages, as the small size of the sheep herds and the local character of the markets only required small clearings, and therefore more limited fires. Thus, it is likely that the forest recovered burnt areas in a few decades; this suggests the management of the forest and grasslands following a slash-andburn system. During the Middle and Modern Ages deforestation and grassland expansion affected most of the subalpine belt and coincided with the increasing prevalence of transhumance, as occurred in other mountains in the Iberian Peninsula(particularly the Pyrenees). Although the occurrence of shallow landslides following deforestation between the Neolithic and the Roman Period cannot be ruled out, the most extensive shallow landsliding processes would have occurred from the Middle Ages until recent times.

Effects of cropland abandonment and afforestation on soil redistribution in a small Mediterranean mountain catchment

In slopes of Mediterranean mid-mountain areas,land use and land cover changes linked to the aban-donment of cropland activity affect soil quality and degradation and soil redistribution;however,limited attention has been paid to this issue at catchment scale.This paper evaluates the effects of cropland abandonment and post-land abandonment management(through natural revegetation and afforesta-tion)on soil redistribution rates using fallout ^(137)Cs measurements in the Araguás catchment(0.45 km^(2),Central Spanish Pyrenees).A total of 52 soil core samples,distributed in a regular grid,from the first 30-40 cm and 9 sectioned reference samples were collected across the catchment and soil properties were analysed.Fallout ^(137)Cs was measured in a 5 cm sectioned references samples and in bulk grid samples.^(137)Cs inventories were used to estimate soil erosion and deposition rates across the catchment.Results show that the highest erosion rates were recorded under sparsely vegetated sites in the badland area,while the lowest rates were found in the afforested area,but no significant differences were observed between the different uses and covers in soil redistribution rates likely due to a long history of human intervention through cultivation in steep slopes and afforestation practices.However,the recovery of the soil organic matter in afforested areas suggest that afforestation can reduce soil degradation at long-term scale.The information gained achieve a better understanding of soil redistribution dynamics and provide knowledge for effective land management after cropland abandonment of agroecosystems in Mediter-ranean mountain areas.