Influence of herbaceous riparian buffers on physical habitat, water chemistry, and stream communities within channelized agricultural headwater streams

Authors: Smiley, Peter - Rocky; King, Kevin; Fausey, Norman

Submitted to: Ecological Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2011
Publication Date: 7/2/2011
Citation: Smiley, P.C., King, K.W., Fausey, N.R. 2011. Influence of herbaceous riparian buffers on physical habitat, water chemistry, and stream communities within channelized agricultural headwater streams. Ecological Engineering. 37:1314-1323.

Interpretive Summary: Many agricultural conservation programs in the midwestern United States incorporate herbaceous riparian buffers (i.e., grass filter strips, vegetative filter strips, grass riparian buffers, conservation buffers) to assist with reducing nutrients, pesticides, and sediments within agricultural watersheds. Yet, the ecological effects of this agricultural conservation practice on agricultural streams have not been evaluated. We evaluated the effect of herbaceous riparian buffers on the physical habitat, water chemistry, and stream communities within channelized agricultural headwater streams (i.e., agricultural drainage ditches). These streams are common throughout the midwestern United States and there is much need to identify ways of managing them to reduce the impacts of agriculture. Installation of herbaceous riparian buffers adjacent to channelized agricultural headwater streams in central Ohio only leads to the widening of riparian zones. Installation of herbaceous riparian buffers did not influence vegetative structure, vegetative type, channel form, instream habitat, water chemistry, or the stream biota. Our comprehensive evaluation of this conservation practice suggest that installation of herbaceous riparian buffers adjacent to channelized agricultural headwater streams in the midwestern United States may only provide limited ecological benefits, if any. Our results also suggest that future conservation strategies for channelized agricultural headwater streams in the midwestern United States will need to use a combination of conservation practices in conjunction with herbaceous riparian buffers that will either increase the filtration ability of the buffers, reduce nutrient and pesticide loads, and/or address physical habitat degradation caused by stream channelization. These results will be useful for state, federal, and private agencies involved managing agricultural watersheds to assist them meeting their conservation and restoration goals.

Technical Abstract: Herbaceous riparian buffers are a widely used agricultural conservation practice in the United States for reducing nutrient, pesticide, and sediment loadings in agricultural streams. The ecological impacts of herbaceous riparian buffers on the channelized agricultural headwater streams that are common throughout the midwestern United States have not been evaluated. We sampled riparian habitat, geomorphology, instream habitat, water chemistry, fishes, and amphibians for four years from three channelized agricultural headwater streams without herbaceous riparian buffers and three channelized streams with herbaceous riparian buffers in central Ohio. Only seven of 55 response variables exhibited differences between buffer types. Riparian widths were greater in channelized headwater streams with herbaceous riparian buffers than streams without buffers. Percent insectivores and minnows were greater in channelized streams without herbaceous riparian buffers than streams with buffers. Percent clay, turbidity, specific conductance, and pH differed between buffer types only during one sampling period. No differences in geomorphology and amphibian communities occurred between buffer types. Our results suggest channelized agricultural headwater streams with and without herbaceous riparian buffers are similar physically, chemically, and biologically. Installation of herbaceous riparian buffers alone adjacent to channelized agricultural headwater streams in central Ohio and other parts of the midwestern United States may only provide limited environmental benefits. Alternative conservation and restoration strategies are needed that combine the use of herbaceous riparian buffers with other conservation practices capable of increasing the filtration ability of the buffers, reducing nutrient and pesticide loads, and/or addressing physical habitat degradation caused by stream channelization.