Improving Grazing Management Increases Terrestrial Invertebrate Inputs that Feed Trout in Wyoming Rangeland Streams
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Authors: W. C. Saunders, and K. D. Fausch
Date: 2007
Journal: Transactions of the American Fisheries Society
Volume: 136
Number: 5
Pages: 1216-1230
Summary of Methods: The effects of season long (SL) and high-density short-duration (HDSD) grazing on terrestrial invertebrates populations and the importance of these invertebrates in rangeland stream systems in western Wyoming were examined. Stream reaches within larger pastures where contrasting grazing systems are used were chosen, ten sites near Lander, WY, in 7 streams on North Platte and Wind River drainages, supporting salmonid populations. Season long grazing occurred from early spring to fall often exceeding 120 days; while in the HDSD system cattle were rotated through riparian pastures in intervals of 14 days or less. Aboveground vegetation biomass, species composition, and percent cover were measured at each site. Dominant vegetation types (graminoid, forb, or shrub) were also recorded. Terrestrial invertebrates were collected at each reach with individuals using water at any stage of life classified as aquatic. Fish abundance and biomass were estimated. Trout were collected by electrofishing; collections ended when 10 trout were collect or the reach was electrofished twice. Captured fish were measured and weighted. Reaches were also measured for large woody debris, substrate composition and embeddedness, bankful width, gradient, discharge, number pools, and temperature.
Article Summary / Main Points: There was greater ground cover and vegetative biomass on HDSD sites than on SL sites. While trout densities were similar on both sites, trout biomass on HDSD sites was on average more than twice that on SL sites. HDSD sites had greater streamside vegetation (3x greater aboveground biomass, ~2x greater overhead cover, and generally a greater number of species), input of terrestrial invertebrates and biomass of both terrestrial and aquatic invertebrates than SD sites. Study results suggest HDSD grazing management increases trout population through several food web pathways.
Vegetation Types: California Grasslands (including all annual grasslands)
MLRA Ecoregions: 34A Cool Central Desertic Basins and Plateaus
Agrovoc Control Words: Riparian Zones Trout Invertebrate
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: riparian zone, high density short duration (hdsd) grazing system, season long (sl) grazing system, terrestrial invertebrate biomass, rangeland streams
Annotation: This article offers a perspective on the effects of grazing in riparian areas on other animal species including invertebrates and trout.
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