|Rogers jr, Hugo|
|Prior, Stephen - Steve|
Submitted to: Technical Report
Publication Type: Other
Publication Acceptance Date: 12/8/2003
Publication Date: 12/8/2003
Citation: Rogers, H., Davis, M., Pritchard, S., Schlesinger, W., Runion ,B., Prior, S., and Gjerstad, D. 2002. Carbon and Nutrient Flow through Multiple Trophic Levels in a CO2-Enriched Southern Pine Forest Community. Southeastern Regional Center, National Institute for Global Environmental Change, Annual Report for Fiscal Year 2001. The University of Alabama, Tuscaloosa, AL, 10 pp. Interpretive Summary: We are studying the effects of elevated atmospheric CO2, through changes in leaf litter quality, on soil organisms of a southeastern pine forest. Climate driven changes in litter dietary quality and microhabitat may affect soil detritivores and how they influence carbon flow between the litter and soil interface. Early data indicates that litter microhabitat at the Duke forest study area is largely not affected by elevated CO2. Chemical indicators of litter dietary quality also showed little affect of CO2 enrichment. Feeding trials, however, indicate that climate-induced changes in litter chemistry may exist, but mainly for defensive compounds. Detritivore abundance and diversity surveys are being done to describe the effects of CO2-enriched litter on the soil food web. This research focuses on a part of the carbon cycle that has been overlooked.
Technical Abstract: The ability to predict the consequences of global change is predicated on our understanding of controls of energy and material flows through ecosystems. A significant gap in that understanding lies belowground and at the soil-litter interface. The effects of CO2-enriched leaf litter on soil fungi, bacteria, and microarthropods have begun receiving attention in the past decade; however, macroarthropod detritivores-predator interactions have not. Arthropod responses to reduced dietary quality (litter or prey) include reduced fitness, increased consumption, and alterations of dietary preferences, all of which would impact nutrient cycling and carbon flow through forest systems. We are currently testing a simple conceptual model that describes environmental controls on leaf litter quality and subsequent effects on macroarthropod detritivores and predators. For soil/litter arthropod surveys, 192 forest floor samples and 144 pitfall samples have been collected and processing and taxonomic sorting of samples should be complete by May 2003. Both types of samples will contribute species richness data and the forest floor samples will provide arthropod density data. Dry weight of litter samples did not differ between CO2 treatments in September 2001and May 2002. Feeding trials indicated that litter enriched by CO2 did not affect the growth of millipedes over the duration of the feeding experiment, though there was a trend towards decreased weight gain for millipedes fed CO2-enriched Pinus taeda litter. Overall, however, millipedes performed better on a diet of P. taeda litter than on a diet of either Liquidambar styraciflua or Cercis. canadensis litter. Although C. canadensis litter had the highest N content of any other type of litter, detritivores performed poorest on a diet of this litter. Litter from ten different tree species was analyzed for C:N, total phenolics, and condensed tannins; elevated CO2 did not significantly affect total phenolics or condensed tannin contents of litter for any species. Carbon-nitrogen ratios of litter were unaffected for all species except Cornus florida, for C:N was significantly higher in CO2-enriched litter Interspecific differences were present for total phenolics, condensed tannins, and C:N. Of the three species used in the millipede feeding study (P. taeda, L. styraciflua, and C. canadensis), P. taeda litter appeared to be the poorest quality diet based on chemical analysis (high values for phenolics, condensed tannins, and C:N). Yet, as stated previously, millipedes performed better on P. taeda litter than on L. styraciflua or C. canadensis litter. The preliminary findings indicate that assessing the relative importance of plants species that generate litter and detritivore species that consume litter will be critical in evaluating the effects of elevated CO2 on carbon and nutrient flow through soil food webs.