PARENT SESSION
Poster Session 30: Soil Ecology.

Wednesday, August 4 Presentations from 5:00 PM to 6:30 PM, Exhibit Hall A 1.

Collembolan population responses to Liquidambar styraciflua leaf litter produced under ambient and elevated carbon dioxide.

Bell, Stephanie¹, Bairdsen, Randi¹, Lincoln, David^*,1, ¹ University of South Carolina, Columbia, SC, USA

ABSTRACT- The objective of this study was to assess the population responses of two species of decomposer fauna to leaf litters produced under ambient or elevated carbon dioxide regimes. Colonies of two native collembolan species (Isotoma trispinata and Folsomia highlandia) were established from the litter beneath Liquidambar styraciflua trees growing at the Forest FACE (Free Air Carbon Dioxide Enrichment) Facility at Oak Ridge National Laboratory (ORNL) under ambient and elevated ( +200ppm) CO₂. Mesocosms (50 x 50 cm) were filled with 20 cm of fumigated mineral soil from sites adjacent to the field fumigation treatments, inoculated litter added (502 g m^-2 for elevated CO₂ grown litter and 425 g m^-2 for ambient grown litter mesocosms, collected in Fall 1999), and housed in a controlled environment chamber. Each treatment was replicated five times to provide a total of 30 mesocosms (2 species x 2 litter types x 5 replicates plus five control mesocosms of each litter type without collembolans). The collembolans were separately inoculated into the mesocosms at approximate field density (51.5 individuals/100 cm²), sampled every two weeks, and isolated from the sampled litter using Burlese-Tulgren extractors. Both F. highlandia and I. trispinata exhibited higher maximum population abundances in elevated rather than in ambient carbon dioxide produced litter. Overall, population growth was negatively correlated with abundance, suggesting density dependent population growth for both species, perhaps related to litter availability. Two-way ANOVA revealed that neither litter treatment nor species nor their interaction were significant sources of litter mass loss variation at the end of the experiment. In addition, decomposition in the presence of the collembolans did not significantly differ from the controls. The lack of differences in decomposition suggest that the results can be accounted for by the increased amount of litter produced under elevated carbon dioxide (16% at ORNL), without necessarily including possible changes in litter quality.

Key words: leaf litter, population growth, elevated carbon dioxide, collembola