Abstract:
By means of palinological studies realized in the pet bog Lagunas Natosas, at páramo de Jimbura, 73 taxa of pollen and spores were identified, of which 24 are the most frequent and important. Four different zones (LNT I to IV) were differentiated through cluster analysis of terrestrial pollen taxa. These data allowed the reconstruction of vegetation, including fire and climate history in the last 15,000 years BP. During the Late Pleistocene (ca. 15,000 12,000 years BP) the percentage of montane forest pollen recorded was higher in relation to the páramo, reflecting a gradual shift of this type of vegetation. This event indicates an increase in temperature during that period, causing a retreat of glaciers allowing the expansion of montane forest. In the early Holocene (ca. 12,000 – 4,800 years BP) the timberline rose, a higher percentage of Podocarpaceae, Polylepis Acaena and Hedyosmum are registered at this stage, to even greater heights than at present and, páramo vegetation was limited to 3,300–3,500 m. The climate became much warmer and wetter. Mean while the Late Holocene, about 4,800 years BP until the present, was characterized by a higher percentage of Poaceae and Cyperaceae, which are representatives of páramo vegetation. During that time, the timberline decreased, giving way to the current location of the páramo. On the other hand, the sediment record (LNT) showed that despite the fires, caused by anthropogenic activity, were much more frequent in the beginning of the Holocene, these did not affect drastically the vegetation composition at Lagunas Natosas, páramo de Jimbura.
