Reconstructed vegetation of the past 400 years at Laguna Carse, Costa Rica

Authors: Taber Friedel*, Florida Atlantic University, Erik N. Johanson , Florida Atlantic University, Sally P. Horn, University of Tennessee
Topics: Paleoenvironmental Change, Human-Environment Geography, Latin America
Keywords: Palynology, lake sediments, neotropics, fire history
Session Type: Virtual Poster
Day: 4/8/2021
Start / End Time: 8:00 AM / 9:15 AM
Room: Virtual 51
Presentation File: No File Uploaded

Laguna Carse is a 1.5 ha landslide-formed lake with a maximum depth of 5 m located in the southern Pacific lowlands of Costa Rica. The lake is within the Grito Alto formation of the Fila Costeña mountain range. The site is classified as a tropical moist forest life zone, but the modern vegetation consists of pastures and agricultural fields. In 2016 a sediment core, 7 m long, was taken from the lake for paleoecological analyses. The basal radiocarbon date of 350 cal yr BP is recent for a core this long, but means that the record provides very high temporal resolution. Prior analyses of macroscopic charcoal and stable carbon isotopes (d13COM) showed patterns of positive d13COM shifts and inferred increases in maize agriculture preceded by increased forest clearance and agricultural burning. This study assesses changes in vegetation through pollen analysis from the recovered Laguna Carse sediments. These changes may be related to climate stress from the LIA or to the earlier arrival of the Spanish. A relative increase of disturbance-type vegetation (grasses and herbaceous types) is seen from 225 – 200 cal yr BP. This is followed by a relative increase in tree and shrub pollen, with a peak around 170 cal yr BP. This aligns with a peak in the d13COM curve at 160 cal yr BP. A smaller shift showing a relative increase in disturbance-type vegetation is seen at 50 cal yr BP.

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