Chemistry and decomposition of litter from Populus tremuloides Michaux grown at elevated atmospheric CO2 and varying N availability

It has been hypothesized that greater production of total nonstructural car bohydrates (TNC) in foliage grown under elevated atmospheric carbon dioxide (CO2) will result in higher concentrations of defensive compounds in tree leaf litter, possibly leading to reduced rates of decomposition and nutrien t cycling in forest ecosystems of the future. To evaluate the effects of el evated atmospheric CO2 on litter chemistry and decomposition, we performed a 111 day laboratory incubation with leaf litter of trembling aspen (Populu s tremuloides Michaux) produced at 36 Pa and 56 Pa CO2 and two levels of so il nitrogen (N) availability. Decomposition was quantified as microbially r espired CO2 and dissolved organic carbon (DOC) in soil solution, and concen trations of non-structural carbohydrates, N, carbon (C), and condensed tann ins were monitored throughout the incubation. Growth under elevated atmosph eric CO2 did not significantly affect initial litter concentrations of TNC, N, or condensed tannins. Rates of decomposition, measured as both microbia lly respired CO2 and DOC did trot differ between litter produced under ambi ent and elevated CO2. Total C lost from the samples was 38 mg g(-1) litter as respired CO2 and 138 mg g(-1) litter as DOC, suggesting short-term pulse s of dissolved C in soil solution are important components of the terrestri al C cycle. We conclude that litter chemistry and decomposition in tremblin g aspen are minimally affected by growth under higher concentrations of CO2 .