PARENT SESSION
Oral Session # 6: Fire Ecology I: Structure and Demographics
Presiding: R Parmenter
Monday, August 4. 8:00 AM to 11:30 AM, SITCC Meeting Room 105.

Soil charcoal distributions along an elevational gradient in a Costa Rican rainforest.

Titiz, Beyhan^*,1, Sanford, Jr, Robert^*,1, ¹ University of Denver, Denver, CO

ABSTRACT- Fire is an important disturbance in Neotropical rainforests. Here we report a record of ancient fires along an elevational transect that extends through old growth forest from the Continental Divide to the Caribbean lowlands. Soil charcoal amount, depth distribution and age are measured from sixteen 1.5 m deep soil cores, in each 1 ha permanent plot at elevations of 50 m, 300 m, 500 m, 750 m, 1000 m, 1250 m, 1500 m, 1750 m, 2000 m, 2300 m and 2600 m along the Volcan Barva transect in Braulio Carrillo National Park, Costa Rica. The transect crosses four life zones (lowland tropical, premontane, lower montane and montane tropical forests) and extends from 50 m to 2906 m. Charcoal was found at every elevation ranging from as much as 1027 g/m² at 300 m to as little as 20 g/m² at 1750 m. Charcoal samples are radiocarbon dated and the dates range from 23,240 yr B.P. at 110-120 cm soil depth at 1750 m elevation to 140 yr B.P. at 30-40 cm soil depth at 2600 m elevation. Many dates correspond with two intervals of previously studied prehistoric burns of 2430 yr B.P. and 1110 yr B.P. at the lower elevations of the transect. Interestingly, none of the high elevation forest charcoal samples (>2300 m) are older than 170 yr indicating that the forests near the Continental Divide may be relatively young, replacement stands that have come in since the last volcanic eruption. Soil charcoal is a signature of historical land use and is also an indicator of the Holocene fire history. These forests have regenerated multiple times as a consequence of anthropogenic or naturally induced fires and disturbances.

Key words: fire, montane, paleoecology, neotropics