The use of non-pollen palynomorphs for reconstructing the history of pastoral activities in the Pyrenees : from modern datasets to reconstruction of the past
Non-pollen palynomorphs, microscopic remains produced by a variety of organisms and preserved in peat and lake sediments, are now more widely used in palaeoenvironmental studies. In particular, spores of coprophilous fungi are considered as an adapted tool to reconstruct past land-use such as pastoral activities. However, their ability to reflect the presence and/or the number of cattle is not fully understood yet. Modern analogs from summer pastures in the Basque Mountains and the Ossau valley have been collected. Numerical analysis of modern non pollen-palynomorphs and environmental variables helped to distinguish several pools of microremains associated to distinct environmental conditions in both terrestrial and wet ecosystems. A group of ascospores of dung-related fungi clearly related to grazing activities was isolated. The modern dataset also provided useful information on the spatial scale represented by non-pollen palynomorphs. Fossil non-pollen palynomorphs from four peat records, combined with other palaeoenvironmental data (pollen, fire frequencies), have been studied. They informed on the evolution of the local conditions of the wetlands during Holocene and historical times. The modern data set is used to aid interpretation of the dynamics of past land-use and pastoral activities. The results from both modern and fossil approaches show that other parameters than the grazing pressure can induce variability in the copropilous signals; the indicative value of dung-related ascospores might be broader than expected. The ascospores of dung-related taxa are described and illustrated, alongside with other fungal, algal and unidentified microremains.