Managing Grassland Vegetation with Winter-Patch Grazing: Potential Benefits to Livestock and Wildlife

Managing Grassland Vegetation with Winter-Patch Grazing: Potential Benefits to Livestock and Wildlife

Summary

This study was implemented in winter 2015-16 with heavy winter patch grazing (WPG) of research station and cooperator ranch pastures followed by summer grazing of all research and cooperator pastures. Data on livestock, vegetation, and wildlife attributes were collected according to protocol and are being analyzed.

Two events have altered the trajectory of this project. The first was a severe hailstorm in July 2016 that destroyed all standing vegetation in a large area, including the pastures of one of our cooperators. Lack of sufficient vegetation growth and recovery precludes us from including that cooperator ranch in Year 2 of the study. The second event was a large wildfire in October 2016 that burned substantial portions of 4 of the 8 pastures at the Cottonwood Research Station that were included in this study. We have modified the study to include both WPG and the burn in Year 2.

Year 2 research plans:

1. A new WPG patch was created in winter 2016-17 on the remaining cooperator pastures and 2 of the unburned research station pastures. Grazing and data collection will be conducted as in Year 1.
2. The 6 remaining research station pastures were recombined to form 3 separate pastures, each having a burned patch, a 2016-17 WPG patch, and a control (not burned, not winter-grazed) area. Each of these 3 pastures will be grazed in summer 2017 by steers having access to all patches in their assigned pasture.  Data collection will be conducted as in Year 1.

Objectives/Performance Targets

Attachment

Objectives of this research are to evaluate winter-patch grazing (WPG) on 1) heterogeneity in vegetation structure/composition, 2) cattle performance, and 3) habitat and use of pastures by grassland birds. The research is occurring at 2 scales/intensities: 1) intensive, statistically rigorous data collection on small-scale research station pastures and 2) extensive data collection on production-scale pastures on 2 ranches.

Objectives and Performance Targets for Year 1 (2015-16) that were met include:

1. Winter-patch grazing was accomplished on a 20% patch of the 4 study pastures at the Cottonwood Research Station and the 2 producer pastures.
2. Summer grazing occurred on all study pastures.
3. All data collection was accomplished on the Cottonwood Station and one cooperator’s ranch, but was suspended on the 2^nd cooperator ranch (see below for explanation).

Accomplishments/Milestones

All pastures were grazed according to the study protocol. This included 1) heavy winter grazing of 20% patches on the 4 study WPG pastures at the Cottonwood Research Station and the 2 producer WPG pastures, and 2) summer grazing on all research and producer pastures (see below for exception). Data collected on research station and producer pastures included: livestock production (weights); livestock spatial use patterns (GPS collars); vegetation structure, composition, and utilization (plant height, biomass, forage removal); quality of bird habitat (height-density); and use by bird species (bird species identification, bird counts, nesting, and nest success). In addition, satellite imagery was collected and converted into an NDVI image for all study pastures to aid in evaluation of structural differences and vegetation greenness between winter-grazed patches and control areas of pastures. Data from all of these aspects of the study are currently being analyzed.

Two events have affected this study:

1. The first was a very large, severe hailstorm that occurred in the area of one of our producer ranches in July 2016. All of that cooperator’s pastures (several thousand ac.) were affected; vegetation both inside and outside of grazing exclosures was reduced to a 2 inch stubble by hailstones up to 3” in diameter. Cattle were seriously injured and wildlife were killed in the storm. Sampling of vegetation, livestock, and birds was immediately suspended on that ranch. The rancher was forced to rent pasture elsewhere for the remainder of the summer, fall, and winter grazing seasons, thus no further data collection on his pastures was possible. Vegetation recovery did not occur as expected; this storm occurred at the end of the growing season for this region, and subsequent drought conditions were not favorable for plant growth. As a result, we were unable to implement the winter patch grazing protocol on that rancher’s pastures in winter 2016-17. Because we could not include this rancher’s pastures in Year 2 of the study, we considered including another ranch as a substitute. Two major issues ultimately precluded us from adding a new ranch to the study: 1) limited time for initiation of the study on a new ranch and 2) lack of a 2016 WPG patch on a new ranch pasture which limited its comparability with our remaining collaborator’s pastures. Thus we have only one producer cooperator ranch involved in the project in Year 2 (2017).
2. The second was a 41,000 ac wildfire, the “Cottonwood Fire”, that occurred in the area of the Cottonwood Research Station on October 16, 2016. The Cottonwood Station was on the north edge of the fire, however over 1100 ac of pasture were burned on the station, including substantial portions of 4 of the 8 pastures involved in this study (Pastures 3b, 5a, 5b, and 6b; see Attachment). The fire burned 3 of the 4 patch pastures (Pastures 3b, 5b, and 6b; see Attachment) completely to nearly so, including the 2016 WPG patches in each. One control pasture (Pasture 5a) also lost substantial acreage to the fire. The burn occurred so late in the year that vegetation recovery did not occur prior to onset of winter. Vegetation growth on the burned areas is not expected to appear until spring 2017. As a result, no winter-patch grazing was possible on those 3 patch pastures.

After considerable thought and discussion, we have determined that our best option going forward is to implement the following modifications of the study in Year 2:

1. We will repeat the study in the remaining cooperator pastures. Winter-patch grazing of a new patch has been completed there as of this report. Grazing and data collection will be conducted as in Year 1.
2. One pasture pair remains at the Cottonwood Research Station for which both the control (pasture 2a) and patch (pasture 2b) pastures were not affected by the fire. We plan to repeat the study as previously planned in those pastures. Winter-patch grazing of a new patch has been completed as of this report (see Attachment). Grazing and data collection will be conducted as in Year 1.
3. The study for the remaining pasture pairs for which one or both subpastures were substantially burned will be modified to incorporate the burn into the study design. The pastures will be recombined to form 3 pastures (Pasture 3=3a+3b, Pasture 5=5a+5b, and Pasture 6=6a+6b); each pasture will have a control patch (not burned or heavily grazed in winter), a burned patch, and a heavy winter-grazed patch (Control, PBG, and WPG, respectively; see Attachment). These 3 pastures will be grazed by separate herds of cattle in summer 2017. Data will be collected on all 3 pastures on all components of the study (livestock production; livestock spatial use patterns; vegetation structure, composition, and utilization; quality of bird habitat; and use by bird species as was done in Year 1 (2016). 
4. Satellite imagery will be collected and converted into an NDVI image for the research station study pastures in May 2017 to aid in evaluation of structural differences between WPG, PBG and control patches of the pastures.

Impacts and Contributions/Outcomes

Interest in this study is high and has increased since the Cottonwood Fire in October 2016. Prior to that fire, several ranchers in the area surrounding the research station had expressed concerns regarding plans for controlled burns on US Forest Service allotments; they were very interested in the results of this study as it may provide an alternative strategy for managing rangelands on the National Grasslands. Their interest has increased since the wildfire.

This study was featured in an episode in a weekly, half hour television series, “Out On The Land”. Reed Cammack, one of our cooperators, was interviewed by the host of the series, Dr. Larry Butler, in summer 2016, prior to the hailstorm that decimated the Cammack Ranch pastures. This NCR-SARE study was one component of the Cammack Ranch operation that was featured in the episode, and included video of the pastures, cattle, and heifers wearing the GPS collars collecting data for this study. The episode (Season 8, Episode 96) can be accessed at http://www.outontheland.com/#!season-8-episodes/ja3rk.

Collaborators: