Modern pollen-vegetation relationships in the Champsaur valley (French Alps) and their potential in the interpretation of fossil pollen records of past cultural landscapes

This study is an attempt to evaluate the relationships between the vegetation and the modem pollen rain as a contribution to palaeoecological research. Pollen analysis of surface moss polsters and floristic records has been undertaken for 51 sampling points distributed all over the study area (Champsaur valley, Hautes-Alpes, France), within different vegetation and land-use types and along a west-east altitudinal transect, ranging from 870 to 2200 in a.s.l. The pollen and vegetation data were analysed independently using numerical methods (clustering and correspondence analysis) to investigate how vegetation is reflected in pollen assemblages. There was a good agreement between classifications and ordinations of the two data-sets and a pollen-analytical separation of different types of human activities was found despite the major gradients related to altitude and soil moisture. Both the AP/NAP ratio and the major pollen type percentage ranges given for each vegetation type were however very wide because of the typical fine-scale mosaic of the landscape in this region. Detailed comparisons of the two data-sets showed consistent differences between vegetation and pollen assemblages. Misclassifications of some modem pollen spectra were mainly attributed to differential pollen representation between species, but also to the effect of various land-use practices on flowering and pollination of herbaceous plant taxa. Moreover these differences, as well as discrepancies with earlier published data from lowlands of southern France and other parts of western Europe, are promoted by complex pollen dispersal which characterizes mountain environments. Although an overlap of characteristics thus exists between pollen assemblages, we were able to recognize specific features and indicator pollen taxa have been identified for each natural, semi-natural and human-induced vegetation type. (c) 2005 Elsevier B.V All rights reserved.