Modern proxy-calibration studies are a powerful tool for paleoecological interpretation. This paper analyzes the relationships among modern pollen rain, vegetation and altitude in the central Pyrenees, where several paleo-palynological studies have been developed, but a modern analog survey is still unavailable. The work analyzes the pollen content of moss polsters from different vegetation communities along an altitudinal transect, as well as the flora and vegetation using the Braun-Blanquet system. DCCA showed that altitude satisfactorily explains both vegetation ( r2 = 0.988) and pollen ( r 2 = 0.841) gradients. Besides the complexity of pollen—vegetation relationships, some regularities were found to be useful for paleoecological and paleoenvironmental interpretation. In general, altitudinal vegetation and pollen patterns show similarities, but pollen belts and boundaries are less well defined, likely because of the homogenizing effect of upward wind transport. Palynological differentiation of montane from subalpine/alpine belts is straightforward from the trends of the more significant pollen types, mainly the low-altitude deciduous trees and the high-mountain herbs. Palynological differences between subalpine and alpine belts, which boundary coincides with the treeline, are more subtle and need quantitative criteria and complementary proxies. From an individual point of view, four main groups of pollen were distinguished, in relation to their usefulness as vegetation and altitudinal indicators: (1) very good indicators, (2) good indicators, (3) non indicators, and (4) allochthonous pollen types. The first two groups resulted to be useful as indicator taxa for modern analogs for paleovegetational and paleoaltitudinal reconstruction, while the latter two groups should be interpreted with caution in paleoenvironmental studies.

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Dediquem aquest treball al professor Salvador Rivas-Martínez, pal de paller i animador incansable de la fitocenologia ibèrica Abstract. We present a review of the main trends of vegetation zonation in the entire Pyrenean mountain system, including previous overviews and a great many papers on flora and vegetation. The main floristic territories are roughly set as parallel zones along the main axis. The high mountain zone forms a central core, characterized by the dominant Boreo-Alpine element. The Atlantic mid altitudes and lowlands (mainly on the north face of the chain) and the mid altitudes of the Iberian side bear Medioeuropean flora as their dominant element, but include a good representation of the transitional Submediterranean element. Lower down, the Iberian lowlands harbour dominant Mediterranean flora. This landscape zonation may be understood in terms of the Alpine model, by which high mountains include three belts (subnival, alpine, subalpine), the mid altitudes show one belt on the Atlantic face (montane) and two on the Iberian face (montane, submontane), and the low altitudes form a basal belt with two contrasting faces (Atlantic and Mediterranean). The vegetation belts are briefly defined in terms of the main potential communities, since these are the most closely related to bioclimate. Thus, the boundaries between belts mostly coincide with boundaries of potential domains, but a few vegetation domains occur in two neighbouring belts. Then, substrata properties and regional climatic variation within the same belt produce noticeable shifts in the potential domains. This makes the basal and montane belts more diverse throughout the Pyrenean range than the high mountain belts. The boundaries between belts run a bit higher on south-facing slopes than on north-facing slopes, reflecting the effect played by topographic thermal and hydric drivers on vegetation. Also, the somewhat higher location of the boundaries in the central sector than towards the edges of the chain is connected with the continental character of the inner Pyrenean area.

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