PARENT SESSION
Oral Session #58: Elevated CO2. Presiding: A. Finzi.
Thursday, August 9, 2001. 8:00 AM to 12:00 PM. Madison Ballroom C.
Fine root biomass and fluxes of soil carbon in young stands of paper birch and trembling aspen as affected by elevated atmospheric CO2 and tropospheric O3.
King, John1, Pregitzer, Kurt1, Zak, Donald2, Sober, Jaak1, Isebrands, Jud3, Dickson, Richard 3, Hendrey, George4, Karnosky, David1, 1 2 3 4
ABSTRACT- Rising atmospheric carbon dioxide may stimulate forest productivity, possibly increasing carbon (C) storage in terrestrial ecosystems, but how tropospheric ozone will modify this response is unknown. Because of the importance of fine roots to the belowground C cycle, we monitored fine root biomass and associated C fluxes in regenerating stands of trembling aspen, and mixed stands of trembling aspen and paper birch at FACTS-II, the Aspen FACE project in Rhinelander, WI. Free air CO2 enrichment was used to elevate concentrations of CO2 (average enrichment concentration 535 ml/L) and O3 (53 nl/L) in developing forest stands in 1998 and 1999. Soil respiration, soil pCO2, and dissolved organic carbon in soil solution (DOC) were monitored biweekly. Fine root biomass averaged 266 g C/m2 in control plots and increased 96 % under elevated CO2. The increased root biomass was accompanied by a 39 % increase in soil respiration and a 27% increase in soil pCO2, although DOC was unaffected. Ozone decreased the above responses to elevated CO2, but effects to date were rarely statistically significant. We conclude that regenerating stands of northern hardwoods have the potential for substantially greater C input to soil due to greater fine root production under elevated CO2. Greater fine root biomass will be accompanied by greater soil C efflux as soil respiration, but leaching losses of C will probably be unaffected.
KEY WORDS: global change, northern hardwoods