RECENT POLLEN SPECTRA FROM FOREST AND STEPPE OF SOUTH ARGENTINA - A COMPARISON WITH VEGETATION AND CLIMATE DATA

This is one of the first research projects in Patagonia, Argentina (Santa Cruz Province), that attempts to characterise modern vegetation in terms of contemporary pollen spectra so as to interpret pollen spectra from Late Pleistocene and Holocene deposits. The most common vegetation type is semi-desert (with 200 mm precipitation) associated with shrub-steppe. In the range of 300-500 mm precipitation a rather dense grass-steppe predominates; with precipitation greater than 500 mm deciduous forest prevails. In the grass-steppe zone there are clear disturbance indicators, such as Rumex acetosella, mainly due to sheep overgrazing. Recent pollen samples were obtained from semi-desert, grass-steppe, shrub-steppe, and forest. A total of 35 superficial soil samples taken from south Santa Cruz Province was used. Eleven vegetation plots were made, between 50 and 52-degrees-S at representative sites within the main vegetation units of the region. To assist in the interpretation of the pollen and vegetation data, two multivariate statistical techniques were used: cluster analysis and principal components analysis. These techniques showed groupings that coincide with the main phytogeographical units and correspond with the precipitation gradient. This analysis provides a recent vegetation-palynological model that can be used in the reconstruction of the past environments by means of the modern analogue method.