DOI: 10.5061/dryad.m905qfv1g
title: Mitigating ecosystem service tradeoffs in rangelands by using grazing duration and timing to manage water quality

description: 1. Mitigating ecosystem service (ES) tradeoffs is a key management goal in
 locations where stakeholders value different and potentially conflicting
 ecosystem services (ESs). However, studies are not often designed to
 examine how local management actions address ES tradeoffs, and therefore
 do not provide options that can alleviate conflict. 2. In semi-arid
 rangelands, we examined the potential for managers to mitigate tradeoffs
 between livestock production and water quality. To move away from
 solutions that offer cattle removal as a singular management strategy, we
 examined how cattle presence, plus two elements of rotational grazing -
 the length of time cattle spend on rangeland (i.e., duration), and the
 season grazed (i.e., timing), affected stream Escherichia coli (E. coli
 concentrations). We also modeled how grazing duration and timing affected
 the ability to meet regulatory benchmarks for water quality throughout a
 grazing season. 3. Grazing duration controlled the length of time E. coli
 concentrations were high in streams. In short- and medium-duration
 systems, E. coli concentrations were high for shorter periods of time than
 in long-duration systems, resulting in fewer violations of national and
 state water quality standards. 4. Stream E. coli concentrations showed a
 consistent seasonal pattern, starting low in spring, peaking in summer,
 and declining towards fall. Thus, grazing during spring or fall, rather
 than in summer, reduced the number of days that E. coli levels exceeded
 water quality standards. 5. Our results suggest that reducing the grazing
 duration and shifting its timing are complementary strategies that can
 mitigate the tradeoffs between livestock grazing and water quality without
 fencing-off riparian areas or removing cattle from pastures with streams.
 6. Synthesis and applications. In this study, we found grazing duration
 and timing can be used as tools to mitigate ES tradeoffs between cattle
 production and water quality in rangeland streams. Shorter grazing
 durations reduced the number of days E. coli levels were above regulatory
 limits, as did grazing that occurred either early or late in the season.
 These results support the idea that rotational grazing can be an effective
 strategy to manage water quality in semi-arid rangelands. They also
 highlight the need for more grazing studies that incorporate gradients of
 duration and timing into study designs.
description: We measured stream <i>E. coli</i> levels over three
 years in rangelands employing target grazing treatments. Grazing
 treatments included: <b>continuous-turnout</b> (long-duration,
 no rotation), <b>deferred-rotation</b> (medium-duration, with
 rotation), and <b>time-controlled rotation</b>
 (short-duration, frequent rotation). The first two of these are common in
 this region, the third is used less often. All were in-use across our
 sampling sites prior to this study. Long durations ranged from 82-138
 days, medium durations from 31-81 days, and short durations from 1-30
 days. Timing for continuous-turnout spanned the entire grazing season
 (mid-May through mid- September). For deferred-rotation, grazing began
 across a range of timings including mid-May, mid-June, early July, and
 mid-July. For time-controlled rotation, grazing timing ranged anywhere
 from spring through fall. All sites were grazed with beef cattle cow-calf
 pairs. Stocking densities were 1.03 - 1.78 pairs ·
 ha<sup>-1</sup> in time-controlled areas, 0.11 – 0.28 in
 deferred-rotation, and 0.02 - 0.09 pairs· ha<sup>-1</sup> in
 continuous-turnout areas. These equated to stocking rates of ~0.7 pairs ·
 ha<sup>-1 </sup>· month<sup>-1</sup> in
 time-controlled areas, and ~0.3 pairs · ha<sup>-1 </sup>·
 month<sup>-1</sup> in deferred-rotation and continuous-turnout
 areas. We sampled every two to three weeks from May
 through October/early November, a timeframe that encompasses the grazing
 and recreation season in this area of Utah. By sampling twice per month,
 we captured fluctuating <i>E. coli</i> levels as cattle moved
 in and out of pastures. We collected water grab samples according to UT
 Division of Water Quality’s Standard Operating Procedures for collection,
 handling, and quantification of <i>E. coli</i> samples. At
 each site, we collected 100 mL grab samples from flowing stream channels
 in sterile jars, which we stored on ice. We analyzed samples within eight
 hours of collection using the Idexx <i>E. coli</i> Quanti-Tray
 2000 System (Westborook, MA), adding pre-packaged Colilert reagent to
 jars, sealing mixture into analysis trays, and incubating samples at 35ºC
 for 18 - 28 hours. <i>E. coli</i> concentrations were
 identified as most probable number (MPN) of colony forming units per 100
 ml via florescence under a UV light. The Quanti-Tray System can detect
 <i>E. coli</i> concentrations to a maximum of 2419.6 MPN
 without dilution. We did not dilute samples because this value is above
 all regulatory benchmark values.