Submitted to: Agriculture, Ecosystems and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/23/2016
Publication Date: 6/9/2016
Publication URL: https://handle.nal.usda.gov/10113/5254794
Citation: Jordan, M.A., Casteneda, A., Smiley, P.C., Gillespie, R.B., Smith, D.R., King, K.W. 2016. Influence of instream habitat and water chemistry on amphibians within channelized agricultural headwater streams. Agriculture, Ecosystems and Environment. 230:87-97.

Interpretive Summary: Agricultural drainage has led to the development of numerous channelized agricultural headwater streams (agricultural drainage ditches) in North America and Europe. Channelized agricultural headwater streams have been documented to serve as habitat for amphibians, a vertebrate group exhibiting population declines as a result of habitat loss and degradation due to agriculture and other anthropogenic watershed alterations. Currently, stakeholders lack critical information on amphibian habitat relationships within these small streams that is needed for developing effective conservation and restoration strategies. We sampled instream habitat variables (i.e., hydrologic, substrate, and physicochemical variables) nutrients, herbicides, and amphibians in channelized streams in CEAP watersheds in Indiana and Ohio over a two year period. We documented that amphibians were most strongly influenced by nutrient and herbicide concentrations. Our results suggest conservation and restoration strategies that lead to reductions of nutrients and herbicides within channelized agricultural headwater streams will provide the greatest benefits for amphibians within these degraded streams. These results will assist state agencies, federal agencies, non-profit groups, and consulting agencies involved with conservation and management of amphibians as well as those involved with managing agricultural watersheds. Our results also provide information that will assist with climate change adaptation as it indicates what types of conservation and restoration practices will be most likely to assist with mitigating the effects of agriculture in the face of climate change.

Technical Abstract: The widespread use of stream channelization and subsurface tile drainage for draining agricultural fields has led to the development of numerous channelized agricultural headwater streams within agricultural watersheds of the Midwestern United States, Canada, and Europe. Channelized agricultural headwater streams have been documented to serve as habitat for amphibians, but information on amphibian habitat relationships is lacking and needed for developing effective conservation strategies. We sampled instream habitat, water chemistry, and amphibians from seven channelized streams in Cedar Creek, Indiana in 2008 and 2009 and five channelized stream sites in Upper Big Walnut Creek, Ohio in 2009. We conducted an indirect gradient analysis involving the use of Principal Component Analysis and Generalized Linear Mixed Effect Model Analysis to determine which variables had the greatest influence on amphibian community and population structure. Overall, amphibian community and population structure was most strongly correlated with water chemistry rather than instream habitat within channelized agricultural headwater streams in Indiana and Ohio. Ten of 12 amphibian response variables were most strongly correlated with either a water chemistry gradient of nitrate+nitrite and acetochlor or total nitrogen and ammonia. Only two amphibian response variables were most strongly correlated with an instream habitat gradient of dissolved oxygen and water depth. Our results suggest conservation strategies that target reductions of nutrients and herbicides will provide the greatest benefits for amphibians within channelized agricultural headwater streams.