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Title: The influence of chemistry, production and community composition on leaf litter decompositon under elevated atmospheric CO2 and tropospheric O3 in a northern hardwood ecosystem

Author
item LINGLI LUI
item KING, JOHN
item GIARDINA, CHRISTIAN
item Booker, Fitzgerald

Submitted to: Ecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2009
Publication Date: 3/25/2009
Citation: Lingli Lui, King, J., Giardina, C., Booker, F.L. 2009. The influence of chemistry, production and community composition on leaf litter decompositon under elevated atmospheric CO2 and tropospheric O3 in a northern hardwood ecosystem. Ecosystems. 12:401-416.

Interpretive Summary: Rising concentrations of atmospheric carbon dioxide and air pollutant ozone have the potential to alter leaf production and chemistry. In turn, these changes may alter decomposition processes, forest productivity and soil quality. In this study, we examined the effects of elevated carbon dioxide and ozone and their interaction on leaf litter chemistry and decomposition in an aspen and birch-aspen ecosystem. We performed a 935-day field incubation study at the Aspen-FACE experiment in Rhinelander, WI with naturally-fallen leaf litter using in situ litter bags. Decomposing litter was sampled seven times during the incubation period and was analyzed for biomass loss, and concentrations of soluble sugars, soluble phenolics, condensed tannins, lipids, hemicellulose, and lignin. We found that decomposition of litter from the elevated carbon dioxide treatments was significantly reduced (-10%) in the first year, but increased (+ 46%) in the second year. Elevated ozone reduced litter decomposition (-13%) in the first year, and had no effect in the second year. Most soluble components (94% of soluble sugars, 99% of condensed tannins and 91% of soluble phenolics) and any treatment effects on initial concentrations disappeared rapidly. Most lignin loss occurred in the second year and elevated carbon dioxide accelerated its decomposition. The mean residence time of litter from the birch/aspen community (3.1 years) was significantly lower than that of pure aspen (4.8 years). Our results indicate that elevated carbon dioxide and ozone are likely to alter short-term litter decomposition dynamics while longer-term trends depend more on forest community composition.

Technical Abstract: Rising concentrations of atmospheric carbon dioxide and tropospheric ozone have the potential to alter leaf litter production and chemistry. In turn, these changes may alter the decomposition of labile and recalcitrant carbon compounds, as well as forest productivity and sequestration of soil carbon. In this study, we examined the effects of elevated carbon dioxide and ozone and their interaction on leaf litter chemistry and decomposition in an aspen (Populus tremuloides Michx) and birch (Betula papyrifera Marsh)-aspen ecosystem. We performed a 935-day field incubation study at the Aspen-FACE experiment in Rhinelander, WI with naturally senesced leaf litter using in situ litter bags. Decomposing litter was sampled seven times during the incubation period and was analyzed for biomass loss, and concentrations of soluble sugars, soluble phenolics, condensed tannins, lipids, hemicellulose, and lignin. We found that mass loss of litter from the elevated carbon dioxide treatments was significantly reduced (-10%) in the first year, but increased (+ 46%) in the second year. Elevated ozone reduced litter mass loss (-13%) in the first year, and had no effect on mass loss in the second year. Most soluble components (94% of soluble sugars, 99% of condensed tannins and 91% of soluble phenolics) and any treatment effects on initial concentrations disappeared rapidly. Most lignin loss occurred in the second year and elevated carbon dioxide accelerated its decomposition. The mean residence time of litter from the birch/aspen community (3.1 years) was significantly lower than that of pure aspen (4.8 years). Our results indicate that elevated carbon dioxide and ozone are likely to alter short-term litter decomposition dynamics while longer-term trends depend more on forest community composition.