PARENT SESSION
Oral Session #10: Elevated CO₂.
Presiding: D. Hileman
Monday, August 5. 8:00 AM to 11:30 AM. Grand Ballroom East, Radisson.

Effects of elevated CO₂ and nutrient supplies on carbon allocation in a pine forest.

MCCARTHY, HEATHER^*,1, PALMROTH, SARI¹, OREN, RAM¹, SCHAFER, KARINA¹, ¹ Duke University, Durham, NC

ABSTRACT- The amount of carbon sequestered through the production of woody biomass in an enriched CO₂ atmosphere has been shown to be controlled by soil fertility. Here we report on the effect of soil fertility on the amount of carbon incorporated into woody versus litter biomass in a free air CO₂ enrichment (FACE) experiment in a 19-year-old Pinus taeda forest. Woody biomass was obtained from allometric equations and litterfall was measured directly. The treatments influenced the dynamics of both wood production and litterfall during the season, with CO₂ slightly delaying the onset of rapid growth at the beginning of the season and of litterfall at the end of the season, condensing most growth and litterfall into a shorter period. Under ambient CO₂ and native nutrition, the forest incorporated 227 g m^-2 y^-1 in woody biomass and lost 228 g m^-2 y^-1 in litter. Fertilization under ambient CO₂ increased each of these components by 22% (P <0.001, P <0.01 ). Under elevated CO₂ and native fertility, C incorporation in these components increased by 18 % and 21 % respectively (P <0.05, P <0.05 ). Combining both resources resulted in C incorporation in wood 56% greater than the additive effect, but the increase in C in litter was only 68% of an additive effect. Thus, increased atmospheric CO₂ under high nutrition increases relative allocation of carbon to pools of greater longevity.

KEY WORDS: elevated CO₂, nutrient supplies, carbon allocation, Pinus taeda