PARENT SESSION
Contributed Oral Session 103: Forest Ecology : Carbon Stocks and Cycling
Wednesday, August 10, 1:30 PM - 5:00 PM, Meeting Room 520 C, Level 5, Palais des congrès de Montréal

Carbon Dynamics of Fire Management in the New Jersey Pinelands.

Clark, Kenneth^*,1, Hom, John¹, Skowronski, Nick¹, Pan, Yude¹, ¹ USDA Forest Service, Newtown Square, PA, USA

ABSTRACT- We studied how fire and fuels management affect carbon dioxide (CO₂) sequestration by oak- and pine-dominated forests in the Pinelands of New Jersey. We used a network of fire weather and eddy covariance towers, extensive biometric measurements, and forest floor measurements pre- and post prescribed fire to quantify forest carbon dynamics. Despite the low nutrient status of sandy, coarse-grained soils in upland forests of the Pinelands, mean maximum net CO₂ exchange during the daytime reached -20 to -25 umol CO₂ m² s^-1 during the growing season, and nighttime net CO₂ exchange was a function of air and soil temperature, averaging 4 to 5 umol CO₂ m² s^-1 during the same period. Both day- and nighttime fluxes were constrained by drought, thus integrated CO₂ exchange was nearly unaffected by soil moisture availability until drought stress became severe. Net CO₂ exchange during the winter averaged 1.5 umol CO₂ m² s^-1 during the day and <1 umol CO₂ m² s^-1 at night, corresponding with minimum LAI and low temperatures. Aboveground production estimated from biometric measurements indicated that ANPP was ca. 450 g m² at all sites, and was dominated by fine litterfall production (ca. 65% of ANPP). The proportion of fine litterfall contributed by the understory increased from 7% to 43% from oak- to pine-dominated stands. When put in the context of annual net CO₂ exchange, prescribed fire treatments released up to twice the amount of CO₂ sequestered annually by these forests, equivalent to 1-3 years of fine litter production. Fire and fuels management may have longer term effects on carbon dynamics, because LAI does not recover to pre-fire levels immediately, and fires apparently exert a memory effect on productivity of the understory. Our study contributes to an understanding of the environmental factors controlling forest productivity, and illustrates how fire and fuels management potentially affects carbon sequestration by forests in the Eastern US.

Key words: carbon sequestration, eddy covariance, prescribed fire, NEE