PARENT SESSION
Poster Session #42: Carbon Storage.
Thursday, August 9, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall

Increased carbon accumulation in a Chesapeake Bay wetland due to increased C3 plant species abundance.

SAUNDERS, COLIN¹, REYNOLDS, JAMES¹, MEGONIGAL, J², DRAKE, BERT³, ^{1 2 3}

ABSTRACT- We developed an ecosystem model predicting carbon accumulation in a Chesapeake Bay marsh impacted by recent increases in C₃ abundance (Scirpus olneyi) over C₄ species (Spartina patens). The model simulates vegetation changes and concomitant changes in production, root depth, and litter quality. Flooding, reconstructed from historic records, was used to drive the soil environment, and the observed increase in C₃ abundance was used to drive changes in plant community. Model simulations suggest there has been an increase in root depth and substantial increases in bulk density (g soil/cm3) and soil carbon density (gC/cm3). Such increases are most discernible in soil depths below 20 cm (>75% increase), but absent in the top 15 cm. Increased labile litter from C₃ plants did not alter total carbon but did increase the proportion of labile carbon. The model results agree with observations at our site of a positive association between C₃ abundance, deep roots and labile litter. Simulated soil carbon and bulk density agree with observations at our site; measured soil ¹³C shows, in general, that bulk density and soil carbon correlate positively with increased C₃ abundance. Also consistent with model predictions, correlation of these trends increases with depth, ranging from no correlation from 0-10 cm to an R² of 0.82 at 30-40 cm (p<0.0005). Our results suggest coastal wetlands in the Chesapeake Bay will experience substantial changes in carbon stocks as vegetation changes.

KEY WORDS: carbon, modeling, salt, marsh