| Summary: | International audience The vegetation evolution is analysed on the forefield of two glaciers in Svalbard for a period of 31 years (1975-2006). In 1975, 85 stations were positioned along transects going from the coast line to the glacier fronts; botanical releves were made at each point. The adopted protocol allowed us to carry out a new observation session in 2006 under the same conditions. The collected information is encoded in the proper way to enable a comparison between the two series. Thus, it is possible to make a botanical assessment of species and taxa which have appeared or disappeared, and to see how the releves have evolved in reference to a typology established by coupling correspondence analysis and ascending hierarchical classification. The evolution of the releves is also measured by using vectors positioned in the multidimensional space of correspondence analysis. In this way, the transfers between 7 vegetation types during the period are displayed. These results are shown by the graphs obtained and the changes observed in cartography. On this basis, the evolution of the colonization process is calibrated and dated according to different reference stages, mainly since the end of the Little Ice Age. Moreover, some converging features tend to demonstrate that a drying process related to permafrost melting is affecting soils in this area.
|
|---|