Environmental changes in biodiversity hotspot ecosystems of
South Ecuador: RESPonse and feedback effECTs (FOR2730)

Abstract:

We reconstructed the palaeoenvironmental conditions of the last ca. 8000 years in the Tres Lagunas region of the Quimsacocha volcanic basin (ca. 3800 m a.s.l.) in the southwestern Ecuadorian Andes by means of a pollen and charcoal record. Sediment deposits and pollen taxa reflect warm and possibly drier conditions in the early to mid-Holocene. The late Holocene undergoes several warm and cold-phases of which the most prominent one was the Little Ice-Age which is characterised by a marked increase of taxa that correspond to cold and moist conditions. As charcoal can be recorded since the early to mid-Holocene and Polylepis underwent several phases of degradation and re-establishment in the region, the presence of human influence might be dated back to this time.

Abstract:

The vegetation,climate and fire history of high mountain ecosystemsin the southern Ecuadorian Andes are documented in a continuous pollen and charcoal record,from Lagunas Natosas Forest bog,at 3495 m a.s.l. spanning the late Pleistocene and Holocene periods since 15,930 cal yr BP.The chronology of this record is based on four radiocarbon dates.Páramo vegetation with abundant Poaceae and Plantago rigida characterized the Late Glacial(LG)period, implying cold and wet conditions. Slight expansions of mountain forests suggest warming during the LG. The upper foresl line was lower than today and fire events were rare during the Pleistocene. During the early and mid-Holocene until 4300 cal yr BP, the area of páramo was markedly smaller and the subpáramo with woody vegetation (Melastomataceae) was larger. The upper mountain forest dominated and the upper forest line shifted to higher elevations. The pollen record provides the first evidence of the development of Polylepis forests in the southern part of the so-called Andean Depression reflecting warmer and drier climatic conditions during early and mid-Holocene. The late Holocene after about 4300 cal yr BP is characterized by larger areas of páramo and subpáramo promoted by moister conditions. These moister conditions and frequent fires may have been the cause of the very rare occurrence or even extinction of Polylepis populations in the Jimbura region. Since ca. 1000 cal yr BP human occupation has altered the landscape by frequent burning, woodcutting, grazing and cultivation.

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.

Abstract:

We reconstructed the palaeoenvironmental conditions of the last ca. 8000 years in the Tres Lagunas region of the Quimsacocha volcanic basin (ca. 3800 m a.s.l.) in the southwestern Ecuadorian Andes. By means of a pollen and charcoal record, we analysed vegetation, fire, and climate history of this area, which is sensitive to climatic changes of both the Pacific as well as of the eastern Andes and Amazon region. Sediment deposits, pronounced increase of pollen and charcoal concentrations, and pollen taxa reflect warmer and drier conditions in the early to mid-Holocene (~8000 to 3900 cal B.P.). During the late Holocene (2250 to -57 cal B.P.), 5 warm and cold-phases occurred at Quimsacocha. The most prominent cold phase possibly corresponds to the globally recognized Little Ice-Age (LIA; ~600 to 100 cal B.P.). The cold phase signal at Quimsacocha was characterized by a higher abundance of Poaceae, Isoëtes and Gentianella, which favour cold and moist conditions. Frequent charcoal particles can be recorded since the early to mid-Holocene (~7600 B.P.). The high Andean tree species Polylepis underwent several phases of degradation and re-establishment in the basin, which can indicate the use of fire by pre-Columbian settlers to enhance the growth of preferred herb species. The Tres Lagunas record suggests that human populations have been influencing the environment around Quimsacocha since the last ca. 8,000 years.