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P.C. Goebel et al. 2010. How important are riparian forests to aquatic foodwebs in agricultural watersheds
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How important are riparian forests to aquatic foodwebs in agricultural
watersheds of north-central Ohio, USA
P. Charles Goebel 1* , Charles W. Goss 1 , Virginie Bouchard 2 & Lance R. Williams
3
1
School of Environment and Natural Resources, Ohio Agricultural Research and
Development Center, The Ohio State University, 1680 Madison Ave., Wooster, OH
44691, USA
2 School of Environment and Natural Resources, The Ohio State University, 2021
Coffey Rd., Columbus, OH 43210-1085, USA
3
Department of Biology, University of Texas at Tyler, 3900 University Blvd., Tyler,
TX 75799, USA
Abstract
In agricultural landscapes restoring riparian forest patches along streams is a watershed
management priority. There are questions, however, as to the degree to which aquatic food
webs are supported by inputs from small and often isolated forested riparian patches in
agricultural landscapes. To examine these contributions we compared the plant communities
and stream food webs between forested and non-forested riparian patches in an agricultural
landscape and used stable isotope analyses to determine whether the primary source of energy
for different levels of aquatic food webs were derived from terrestrial or aquatic sources. We
observed no differences in the δ 13 C signatures of consumers between forested and non-forested
riparian areas. Similarly, we also observed few differences in δ 15 N signatures between forested
and non-forested sites for different trophic levels. This suggests that there may be other
mechanisms driving the structure of aquatic food webs than basal resources alone.
Keywords: riparian forests, stable isotope analysis, food webs, ecosystem structure
1. Introduction
Riparian forests are dynamic components of the landscape that promote many ecosystem
functions vital to the sustainability and productivity of watersheds through their influence on
stream water quality, in-stream habitat, food web structure, and ecosystem function (Gregory et
al. 1991; Naiman et al. 1993; Wallace et al. 1997). Although riparian areas are subjected to a
variety of natural disturbances (e.g., flooding, drought, landslides, and wildfire) that alter habitat
structure and biodiversity (Ilhardt et al. 2000), human disturbances (including agricultural
practices) can alter riparian forests in complex and often synergistic ways (Gregory et al. 1991).
In many agricultural landscapes, riparian forests have been removed or greatly modified. As a
result and because of the importance of riparian areas to watersheds, riparian corridors are often
protected around streams, and they are a major component of most watershed management and
restoration initiatives.
Under ideal conditions, headwater streams are heterotrophic systems where allochthonous
(carbon) inputs from riparian forest vegetation provides energy and nutrients for aquatic food
* Corresponding author. Tel: +1 330-263-2789 – Fax: +1 330-263-3658
Email address: goebel.11@osu.edu
Forest Landscapes and Global Change -New Frontiers in Management, Conservation and Restoration. Proceedings of the IUFRO Landscape Ecology
Working Group International Conference, September 21-27, 2010, Bragança, Portugal. J.C. Azevedo, M. Feliciano, J. Castro & M.A. Pinto (eds.)
2010, Instituto Politécnico de Bragança, Bragança, Portugal.