Long-term perspectives on climate-and human-induced shifts in plant communities and tree line in mountains are often inferred from fossil pollen records. However, various factors, such as complex patterns of orographic wind fields and abundant insect-pollinated plants in higher altitudes, make pollen-based reconstruction in mountain regions difficult. Over the last decade the Landscape Reconstruction Algorithm (LRA)-a model-based approach in reconstruction of vegetation-has been successfully applied in various parts of the globe. However, evaluation of its effectiveness in mountain ranges is still limited. The present study assesses the extent to which the LRA approach helps quantify the local changes in vegetation cover at Vicdessos valley in northern French Pyrenees as a case study. In the study area well-dated sediment cores are available from eight bogs and ponds, 6-113 m in radius, located above the current tree line. We first use a simple simulation experiment to evaluate the way how pollen records from "landscape islands" (mountain tops and plateaus) would represent local vegetation and to clarify important factors affecting the LRA-based reconstruction in a mountainous region. This study then uses pollen records from these sites and vegetation and land-cover data both within a 50-km radius around the Vicdessos valley and within a 2-km radius from each site for evaluation of the REVEALSand LOVE-based reconstruction of the regional and local plant cover, respectively, in the LRA approach. The land-cover data are complied for coniferous trees, broadleaved trees and non-forested areas from the CORINE and historical maps in three time windows:

Fir (Abies alba Mill.) occupies an important place in the Pyrenean context, where the species finds its optimal conditions in this mountain zone (800e1800 m a.s.l.). In the Pyrenees, the fir woods of Volvestre (Ari ege, France) are of particular interest because of two peculiarities of its location: its northern latitude with respect to the usual location of fir in the Pyrenean axis, and its lower altitude (330e440 m a.s.l.). This has given rise to various theories, some considering the silver fir forests as a glacial relic and others pointing to anthropogenic interference and possible plantings during the Middle Ages. Pedoanthracological and palynological studies have been performed to establish the origin and history of this ancient forest, and both approaches show an ancient anthropized landscape with a continuous presence of Abies alba throughout the mid-and late-Holocene. The fir woodlands of Volvestre are testimonies to the ancient and significant presence of fir on the northeast slope of the Pyrenees and the current suitability of this species for lowland areas. Pedoanthracological sampling inside the forest has shown differences in vegetation dynamics at different valley points (north slope, south slope, and valley bottom).

The term agroforestry covers practices that are promoted to maintain or even enhance biodiversity. However, the relationship between agroforestry and invasive species is rarely addressed, even though the spread of such species is an important issue, not only ecologically but also economically and socially. Over the past few decades, humans have greatly accelerated the process of biological invasions, to such an extent that they are now recognized as the second cause of rapid decline in biodiversity. In France (as in other parts in Europe) abandonment of agricultural land in remote areas is a major problem having socio-economic, landscape and environmental implications. The objective of the research presented here was to find a method for studying the relationship between traditional agroforestry systems and invasive species, despite a lack of available data. We investigated the evolution of a traditional agroforestry system in the Pyrenean foothills, where invasive species are abundant, by implementing two complementary methods: i/ interviews highlighting the local stakeholders' perception of landscape evolution, invasive species and the challenges they represent for the local traditional agroforestry landscapes, and ii/ detailed mapping of an area occupied by invasive plants, by means of very high resolution spatial technologies using UAV's and aerial photography. The results show that invasive species have spread in relation with the abandonment of agricultural land, which has also led to "landscape closure" by the encroachment of natural afforestation. They also underline the difficulty of assessing the spread of invasive species. This situation is of major importance in terms of land-use planning, as the various stakeholders have different perceptions of the problem, and it raises questions about the sustainability of practices and territories.

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