Vegetation and environmental dynamics in the Paramo of Jimbura region in the southeastern Ecuadorian Andes during the late Quaternary

摘要

The last 15,000 years of vegetation, fire and climate history were reconstructed from the Laguna Natosa Peat bog core (3600 m elevation) in the Paramo of Jimbura region in the Cordillera Real, close to the Peruvian border of southern Ecuador in the southernmost part of the Andean depression. The pollen record, dated by 5 radiocarbon dates, indicates that during the late Glacial (ca. 15,000 -12,000 cal yr BP) a gradual expansion of mountain forest, restricting the paramo vegetation to small patches, and a shift of the forest line to higher elevation took place; reflecting an increase in temperature. However, a clear signal of the warmer Etalling/Allered interstadial and the cooler Younger Dryas period, are not reflected in the record. During the transition from the late Glacial to the early/mid-Holocene (ca. 12,000-4800 cal yr BP), tree taxa such as Hedyostnum and Podocarpaceae are well represented, suggesting that the upper forest line, especially in the mid-Holocene, reached slightly higher elevations than at present. Hence, paramo vegetation was limited, indicating warmer climatic conditions for the early to mid-Holocene period than today. The late Holocene from 4800 cal yr BP until the present is characterized by higher occurrences of paramo taxa. During this period, the upper forest line shifted downwards giving room to the expansion of the paramo vegetation to its current size. Fire was rare during the late Glacial period but became more frequent after about 8000 cal yr BP, probably due to the dry event during the mid-Holocene and increased human activity.