HR: 14:45h
AN: B33A-04    [Abstracts]
TI: Response of leaf litter decomposition to rises in atmospheric CO₂ and temperature
AU: * Hammrich, A
EM: arne.hammrich@eawag.ch
AF: Eawag/ETH, Kastanienbaum, Seestr. 79, Kastanienbaum, LU 6047, Switzerland
AU: Flury, S
AF: Eawag/ETH, Kastanienbaum, Seestr. 79, Kastanienbaum, LU 6047, Switzerland
AU: Gessner, M O
AF: Eawag/ETH, Kastanienbaum, Seestr. 79, Kastanienbaum, LU 6047, Switzerland
AB: Atmospheric concentrations of CO₂ have considerably increased in the last century and are expected to rise further. Elevated CO₂ concentrations not only increase global temperature but also have potential to change plant litter quality, for example by increasing lignin content, changing C:N ratios and altering tannin contents. These chemical changes may interact with increased temperature to alter litter decomposition. To test whether changes in litter quality and warming affect decomposition, we conducted a field experiment with leaf litter collected from six species of mature deciduous trees exposed to either ambient or elevated CO₂ levels. We used a set of 16 enclosures installed in four blocks in a freshwater marsh in a prealpine lake to test for the effects of CO₂-mediated litter quality and temperature and the interaction of both factors. We measured leaf mass loss of the twelve litter types in control and heated enclosures (4 °C above ambient) and also in the open marsh. In contrast to expectations, species decomposing at low (oak and beech) and medium (hornbeam and maple) rates showed faster mass loss when leaves were grown under elevated CO₂ conditions, whereas fast-decomposing species (cherry and basswood) showed no clear response. The accelerated decomposition of CO₂-enriched litter could be due to higher amounts of nonstructural carbohydrates, which may have been either leached or readily degraded. Warming had a surprisingly small influence on mass loss of the tested litter species, and interactive effects were weak. These results suggest that direct and indirect effects of elevated CO₂ levels on litter decomposition may not be readily predictable from first principles.
DE: 1630 Impacts of global change (1225)
SC: Biogeosciences [B]
MN: 2007 Joint Assembly