DOI: 10.5061/dryad.w6m905qmb
title: Influences of patch-burn grazing on headwater prairie streams and subsequent recovery

description: 1. Patch-burn grazing (PBG) can promote terrestrial heterogeneity and
 biodiversity, but can temporarily increase stream nutrients, ecosystem
 metabolism, and alter macroinvertebrate assemblages. The impacts of
 grazing on stream channel morphology and post-PBG recovery patterns are
 unclear. 2. We assessed the influence of grazing in PBG managed grassland
 streams in Missouri, USA, and subsequent recovery when grazing ceased for
 two years. We hypothesized that grazing would degrade water quality,
 stream biotic integrity, and channel morphology, but that riparian fencing
 would mitigate these effects. We predicted that biological and chemical
 variables in unfenced streams would return to pre-PBG levels within two
 years after grazing ceased, but channel morphology would not. 3. Six small
 headwater streams (two in ungrazed control watersheds, two in PBG
 watersheds with 10 m fenced riparian zones, and two in unfenced PBG) were
 sampled over seven years; 2 years before PBG, 3 years during PBG, and 2
 years post-PBG. We sampled macroinvertebrates and water chemistry monthly
 when water was present and surveyed channel morphology at least once each
 study period. 4. During grazing, unfenced watersheds showed the greatest
 changes in channel width, depth, and area. During the post-PBG period, one
 of the two unfenced watersheds showed partial recovery of channel
 morphology. Although grazing increased concentrations of nutrients and
 chlorophyll a, concentrations returned to pre-PBG conditions after grazing
 ended, indicating recovery. Very fine organic sediments increased in the
 unfenced watersheds compared to the control during grazing but recovered
 afterwards. Contributions of Chironomidae to total invertebrate abundance
 increased in the unfenced watersheds during grazing, and then decreased
 during the post-PBG period. 5. Riparian fencing mostly mitigated effects
 of grazing on the streams. Unfenced streams were resilient to effects of
 grazing in a PBG managed grassland, with most metrics recovering within
 two years after grazing ceased, except for channel morphology. 6.
 Synthesis and applications: Grazing in a PBG managed grassland coupled
 with riparian fencing could be an effective conservation tool in prairies,
 with relatively modest influences on stream water quality and biotic
 integrity. Persistent changes in stream geomorphology and effects of
 longer periods of grazing deserve further research.
description: <i>Channel
 Morphology</i> Channel morphology (bankfull width,
 depth, width:depth, and channel area) was measured within 5 of 6 study
 streams. The sixth watershed, a control, was not surveyed as it did not
 have a well-defined channel and bankfull stage could not be confidently
 determined. All streams were initially surveyed in the spring of 2011
 prior to cattle grazing to establish baseline conditions. Streams were
 re-surveyed in the spring of 2012 and 2013 to determine annual grazing
 impacts and in the spring of 2016 to assess stream response following
 recovery. Ten permanently marked cross
 sections were established for surveying within each watershed. Cross
 section locations were spaced at approximately even intervals between the
 bottom of each treatment and the upstream channel boundary (where the
 channel turns into hillslope). Average cross section spacing ranged
 between 24 m for the smallest watershed to 81 m for the largest watershed.
 Cross section spacing varied between watersheds due to variability in
 stream length. Within the cattle grazed watersheds, the most upstream
 cross section was placed at the upstream boundary of the electric cattle
 enclosure to ensure that all cross sections were contained within the
 cattle grazed portion of the watershed. We avoided surveying meander bends
 due to accelerated rates of erosion and deposition. Cross section geometry
 was measured with a surveyor’s level and leveling rod at 15.24 cm spatial
 resolution. Bankfull width (m) was defined as the distance from the top of
 the bank that was lower in elevation to the equivalent elevation on the
 opposite bank. Cross sectional depth (m) was calculated by averaging all
 the depth measurements across the bankfull width. Width to depth ratio
 (w:d) was determined by dividing bankfull channel width by average channel
 depth and channel area (m<sup>2</sup>) was determined by
 multiplying the bankfull channel width by the average channel depth
 (Harrelson, Rawlins, & Potyondy 1994). Width to depth ratio was
 included in the analyses as shifts in this parameter may influence habitat
 for biota by altering water temperature and stream bed stability (Blann et
 al. 2002, Jansen & Nanson 2010). If bankfull elevation could not
 be identified, the cross section was excluded from analysis.
 <i>Water Chemistry, Benthic
 Chlorophyll-a, and Macroinvertebrate and Organic Matter Collection and
 Processing</i> Water samples for ammonium
 (NH<sub>4</sub><sup>+</sup>), nitrate
 (NO<sub>3</sub><sup>-</sup>), soluble reactive
 phosphorus (SRP), total nitrogen (TN), total phosphorus (TP), total
 suspended solids (TSS), and benthic samples for chlorophyll were collected
 monthly when flow was present. Samples were analyzed as described in
 Larson et al. (2016). Macroinvertebrate and organic
 matter samples were collected monthly when water was present (study sites
 were dry July to October). Macroinvertebrate biomass, abundance, relative
 abundance and biomass, Ephemeroptera Plecoptera and Trichoptera taxa
 (EPT), functional feeding group and organic matter (benthic organic matter
 (BOM), CPOM, fine particulate organic matter (FPOM), and VFPOM) were
 collected and processed as described in Jackson et al. (2015).
description: Gray boxes in the Osage Geomorphology Data.xlsx file are
 cross-sections that were lost for reasons explained in the
 manuscript.