Tuesday, June 5, 2007 - 11:15 AM
159

The contribution of corn detritus to metabolism and carbon cycling in Midwestern agricultural streams

Natalie A. Griffiths1, Jennifer L. Tank, PhD1, Thomas J. Warrner2, Todd V. Royer2, Therese C. Frauendorf1, Catherine P. Chambers3, Jillian D. Pokelsek4, Michelle A. Evans-White, PhD5, Emma J. Rosi-Marshall4, and Matt R. Whiles3. (1) Biological Sciences, University of Notre Dame, Department of Biological Sciences, Galvin Life Science Center, Notre Dame, IN 46556, (2) School of Public and Environmental Affairs, Indiana University, 1315 East Tenth Street, Bloomington, IN 47405, (3) Department of Zoology and Center for Ecology, Southern Illinois University, Life Science II, Carbondale, IL 62901, (4) Biology, Loyola University Chicago, Chicago, IL 60626, (5) Biology, Kansas State University, Division of Biology, Manhattan, KS 66506

In the Midwestern US, agricultural practices have reduced deciduous riparian vegetation and replaced native prairie and forest vegetation with crops.  We investigated the effect of these alterations on organic carbon dynamics in 6 headwater streams draining corn fields in central Indiana.  Agricultural streams are typically considered to be autochthonous; however, corn harvest byproducts (leaves, stalks and cobs) may represent an overlooked allochthonous carbon source to these streams.  In this study, we quantified the input of corn byproducts and examined whether these inputs affected stream metabolism and carbon cycling by measuring reaeration-corrected whole-stream metabolism before and after corn harvest.  Prior to harvest, net ecosystem production (NEP) varied across streams (range: -4.7 to 3.6 gO2/m2/day), with 50% exhibiting positive NEP.  After corn harvest, all streams had negative NEP (range: -0.6 to -8.9 gO2/m2/day), indicating that these streams were net heterotrophic.  The conversion from autotrophy to heterotrophy was influenced by seasonal changes in temperature and sunlight.  Variation in gross primary production was predicted by photosynthetically active radiation (r2=0.42, P=0.001) while variation in community respiration was partially explained by water temperature (r2=0.32, P=0.004).  Future research examining the shift to heterotrophy attributable to corn byproducts will be examined using pre- and post-harvest carbon budgets.

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