Chemistry and decomposition of litter from Populus tremuloides Michaux grown at elevated atmospheric CO 2 and varying N availability

It has been hypothesized that greater production of total nonstructural carbohydrates (TNC) in foliage grown under elevated atmospheric carbon dioxide (CO 2 ) will result in higher concentrations of defensive compounds in tree leaf litter, possibly leading to reduced rates of decomposition and nutrient cycling in forest ecosystems of the future. To evaluate the effects of elevated atmospheric CO 2 on litter chemistry and decomposition, we performed a 111 day laboratory incubation with leaf litter of trembling aspen ( Populus tremuloides Michaux) produced at 36 Pa and 56 Pa CO 2 and two levels of soil nitrogen (N) availability. Decomposition was quantified as microbially respired CO 2 and dissolved organic carbon (DOC) in soil solution, and concentrations of nonstructural carbohydrates, N, carbon (C), and condensed tannins were monitored throughout the incubation. Growth under elevated atmospheric CO 2 did not significantly affect initial litter concentrations of TNC, N, or condensed tannins. Rates of decomposition, measured as both microbially respired CO 2 and DOC did not differ between litter produced under ambient and elevated CO 2 . Total C lost from the samples was 38 mg g −1 litter as respired CO 2 and 138 mg g −1 litter as DOC, suggesting short-term pulses of dissolved C in soil solution are important components of the terrestrial C cycle. We conclude that litter chemistry and decomposition in trembling aspen are minimally affected by growth under higher concentrations of CO 2 .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75335/1/j.1365-2486.2001.00388.x.pd