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United States Department of Agriculture

Agricultural Research Service

Title: Carbon and Nutrient Flow Through Multiple Trophic Levels in Co2-Enriched Plant Communities

Authors
item Rogers Jr, Hugo
item Davis, M - UNIV. OF SO. MISS.

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: November 5, 2002
Publication Date: November 5, 2002
Citation: Rogers Jr, H.H., Davis, M.A. 2002. Carbon and nutrient flow through multiple trophic levels in co2-enriched plant communities [abstract]. In Joint Southeast Regional Center National Institute for Global Environmental Change Annual Conference, Program and Abstracts, November 4-6, 2005, Cape Canaveral, Florida. p. 15.

Technical Abstract: A significant gap exists in our understanding of the mechanisms of energy and material fluxes at the soil-litter interface. Within temperate forests, up to 90% of net primary productivity passes through the food web of the diverse arthropod fauna residing in forest soil and litter. Dietary quality of litter is often reduced by elevated CO2 via changes in leaf chemistry (e.g., increased C:N, increased secondary compound production, and increased lignin content), thus reductions in detritivore-driven decomposition and nutrient cycling are predicted by most models. We are investigating the indirect effects of elevated atmospheric CO2 (i.e., alterations in leaf litter quantity and chemistry) on the soil fauna of southeastern forests. We are currently testing a simple conceptual model that describes environmental controls on leaf litter quality and subsequent effects on arthropod detritivores and predators. Litter collected from at least three CO2 experiments in the southeastern United States is being used to conduct feeding assays to garner information on feeding behavior (consumption rates and selectivity) and detritivore performance (relative growth rate, digestibility of litter) both of which impact nutrient cycling and carbon flow. In addition to feeding trials, intensive macroarthropod surveys are being conducted at the Duke University FACTS-1 site (a loblolly pine plantation), the National Soil Dynamics Laboratory (an agricultural system), and the Oak Ridge FACE site (a sweetgum forest). To date, 488 forest floor samples and 384 pitfall samples have been collected. Both types of samples contribute species richness data and the forest floor samples provide arthropod density data. Preliminary data from the Duke forest samples indicate that the density of predatory mites is greater in CO2-enriched plots, however, overall detritivore species richness is decreased under elevated CO2. Species richness data include arthropods, mollusca and nematodes but are primarily based on insects. Litter from ten different tree species representing different structural and functional guilds was analyzed for C:N, total phenolics, and condensed tannins. Exposure to elevated CO2 did not significantly affect total phenolics condensed tannin contents of litter for most species. Carbon-nitrogen ratios of litter were also unaffected for most species. Initial data indicate that CO2 effects on litter-detritivore interactions will be species specific. Sand post oak (Quercus margaretta) leaf litter derived from plants exposed twice-ambient CO2 for two years had 32% more total phenolic contents than litter from oaks exposed to ambient CO2. When this oak litter was fed to two species of terrestrial isopods, Porcellio sp. performed poorly on a diet of litter from high-CO2 chambers, whereas Armadillidium sp. was unaffected by the CO2 environs of its litter diet. These data provide necessary information for accurately predicting carbon and nutrient flow through the soil-litter interface. Thus, assessing the relative importance of individual plant species that generate litter and detritivore species that consume litter will be critical in evaluating the effects of elevated CO2 on carbon and nutrient fluxes through soil food webs.

Last Modified: 9/10/2014
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