Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10501259 | Quaternary Research | 2005 | 10 Pages |
Abstract
Pollen analysis of sediments from a high-altitude (4215 m), Neotropical (9°N) Andean lake was conducted in order to reconstruct local and regional vegetation dynamics since deglaciation. Although deglaciation commenced â¼15,500 cal yr B.P., the area around the Laguna Verde Alta (LVA) remained a periglacial desert, practically unvegetated, until about 11,000 cal yr B.P. At this time, a lycopod assemblage bearing no modern analog colonized the superpáramo. Although this community persisted until â¼6000 cal yr B.P., it began to decline somewhat earlier, in synchrony with cooling following the Holocene thermal maximum of the Northern Hemisphere. At this time, the pioneer assemblage was replaced by a low-diversity superpáramo community that became established â¼9000 cal yr B.P. This replacement coincides with regional declines in temperature and/or available moisture. Modern, more diverse superpáramo assemblages were not established until â¼4600 cal yr B.P., and were accompanied by a dramatic decline in Alnus, probably the result of factors associated with climate, humans, or both. Pollen influx from upper Andean forests is remarkably higher than expected during the Late Glacial and early to middle Holocene, especially between 14,000 and 12,600 cal yr B.P., when unparalleled high values are recorded. We propose that intensification of upslope orographic winds transported lower elevation forest pollen to the superpáramo, causing the apparent increase in tree pollen at high altitude. The association between increased forest pollen and summer insolation at this time suggests a causal link; however, further work is needed to clarify this relationship.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geology
Authors
Valentà Rull, Mark B. Abbott, Pratigya J. Polissar, Alexander P. Wolfe, Maximiliano Bezada, Raymond S. Bradley,