Document: DEB-3-59-36

Assessing the spatial and temporal variation in belowground carbon allocation in an old-growth neotropical rain forest.

CLARK, D.A.* ¹, E.VELDKAMP ², L.SCHWENDENMANN ², T.BRENES ³, J.MACKENSEN ² and S.F.OBERBAUER ⁴

University of Missouri-St. Louis, St. Louis, MO 63121, U.S.A. ¹
University of Goettingen, Goettingen, GERMANY ²
La Selva Biological Station, Puerto Viejo de Sarapiqui, COSTA RICA ³
Florida International University, Miami, FL 33199, U.S.A. ⁴

Abstract:
Since April 1998, we have estimated belowground carbon allocation as part of a cross-scale analysis of the carbon stocks and fluxes in a lowland tropical rain forest (La Selva Biological Station, N.E. Costa Rica). To evaluate landscape-scale edaphic variation of the carbon cycle, replicated 0.5 ha plots were established in old growth on the dominant soil types: Inceptisols (old alluvial terraces), and the less fertile Ultisols (highly weathered residual soils). In three plots per soil type, fine litterfall and soil respiration have been measured concurrently. Biweekly, fine litterfall is collected in nine 0.25 m² traps per plot and soil CO₂ efflux is measured with an infrared gas analyzer in 8 permanent soil chambers per plot. We used the C-balance method to estimate the total belowground carbon allocation by the vegetation in the plots (TBCA). Over the first complete measurement year, estimated TBCA was substantial on all plots (5.7-10.8 Mg C/ha/yr). Mean estimated TBCA was 41% higher on the poorer soils (9.2 Mg C/ha/yr for the Ultisols, compared to 6.6 Mg/ha/yr on the Inceptisols), in line with the higher fine root stocks we have found on these soils. Estimated TBCA substantially varied between years for most plots (mean inter-year change of 24% for the 6-month period April-September in the first two years). These data indicate considerable spatio-temporal variation in carbon dynamics within terra firme tropical rain forest.

Keywords: tropical rain forest,carbon cycling, belowground NPP, soil respiration, litterfall, Costa Rica, La Selva

This abstract is being presented at: 10:45 AM in session:
Oral Session #25: Organic Matter Dynamics in Ecosystems.