Date of Award
12-1-2013
Degree Name
Master of Science
Department
Zoology
First Advisor
Whiles, Matt
Abstract
Conversion to agriculture, land fragmentation, and removal of native grazers have made tallgrass prairies and the streams that drain them one of the most imperiled systems on earth. Patch-burn grazing (PBG), an increasingly common management practice on remaining prairie parcels, has been shown to benefit cattle and grassland birds. However, potential influences of this practice on streams are unknown. To address this, we sampled stream macroinvertebrates and benthic organic matter two years before and three years during PBG on two watersheds with riparian fencing (fenced), two grazed watersheds without riparian fencing (unfenced), and two ungrazed (control) watersheds. Very fine benthic organic matter increased 51% in unfenced watersheds after implementation of PBG, accompanied by a threefold increase in fine organic sediments in the same watersheds. Contribution of fine inorganic sediments to total substrata increased 28% in unfenced watersheds during PBG, while fine inorganic sediments decreased in both the control (18%) and fenced (16%) watersheds. Increases in the contribution of Chironomidae to total macroinvertebrate abundance (18% before, 49% during PBG) and biomass (10% before, 19% during PBG) were evident in unfenced streams. In contrast, abundance of sensitive EPT taxa decreased an order of magnitude from 7,635 to 687 individuals m-2 in unfenced streams, but did not change in fenced and control streams. Increases in tolerant taxa and fine organic and inorganic sediments, along with reductions in metrics of biotic integrity, suggest PBG adversely impacts prairie streams. However, the absence of negative responses in fenced watersheds indicates that riparian fencing can mitigate these impacts by serving as a buffer to prevent excess sedimentation. In order to properly manage remaining tallgrass prairie parcels, it is important to consider both the aquatic and terrestrial components of these systems, as they are tightly linked. Results from this study provide a basis for management and policy decisions regarding remaining grassland watersheds.
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