Chemistry And Decomposition Of Litter From Populus Tremuloides Michaux Grown At Elevated Atmospheric Co2 And Varying N Availability

Summary

It has been hypothesized that greater production of total nonstructural carbohydrates (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 nutrient cycling in forest ecosystems of the future. To evaluate the effects of elevated atmospheric CO2on litter chemistry and decomposition, we performed a 111 day laboratory incubation with leaf litter of trembling aspen (Populus tremuloidesMichaux) produced at 36￢ﾀﾃPa and 56￢ﾀﾃPa CO2and two levels of soil nitrogen (N) availability. Decomposition was quantified as microbially respired CO2and 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 CO2did not significantly affect initial litter concentrations of TNC, N, or condensed tannins. Rates of decomposition, measured as both microbially respired CO2and DOC did not differ between litter produced under ambient and elevated CO2. Total C lost from the samples was 38￢ﾀﾃmg￢ﾀﾃg￢ﾈﾒ1litter as respired CO2and 138￢ﾀﾃmg￢ﾀﾃg￢ﾈﾒ1litter as DOC, suggesting short￢ﾀﾐ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 CO2.