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 during Year 1 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 Update:
Cottonwood Research Station: As a result of the fire that burned substantial portions of several pastures at the Cottonwood Station, 6 of our 8 pastures were recombined into 3 pastures; the remaining 2 pastures were maintained in their original configuration (1 WPG and 1 control). Each of the recombined pastures includes a WPG patch, a burned (PBG) patch, and a control (no burn, no winter grazing). A new patch in the remaining WPG pasture and the WPG areas of the recombined pastures were heavily grazed in winter 2016/2017. Yearling steers grazed each of the study pastures in summer 2017. Due to extreme drought conditions in the area, grazing animals were removed from pastures in mid-July rather than the planned mid-August removal date. Data on livestock, vegetation, and wildlife attributes were collected according to protocol during Year 2 and are being analyzed.
Cooperator Pastures: A new patch was grazed during winter 2016/2017 in the WPG pasture of the remaining cooperator ranch. Cow/calf pairs grazed the WPG and control pastures according to protocol for the entire summer (drought conditions were much less severe compared to Cottonwood). Data on livestock, vegetation, and wildlife attributes were collected according to protocol during Year 2 and are being analyzed.
Year 2 research plans:
- A new WPG patch was created in winter 2016-17 on the remaining cooperator pastures and on the unburned WPG research station pasture. Grazing and data collection will be conducted as in Year 1.
- 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.
Year 3 research plans:
- Field data collection for the project is complete.
- Data collected in Years 1 and 2 will be summarized and analyzed, and reports and manuscripts will be developed and submitted.
Original 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.
A new objective of this research was added in year 2 as a result of the wildfire that burned several of the research pastures at Cottonwood. That objective is to compare WPG, patch burn grazing (PBG), and control (no burning, no winter grazing) on 1) heterogeneity in vegetation structure/composition, 2) cattle vegetation/site selection, and 3) habitat and use of pastures by grassland birds. The original objectives were maintained for the non-burned pasture pair at Cottonwood and the remaining cooperator ranch pastures.
Objectives and Performance Targets for Year 1 (2015-16) that were met include:
- Winter-patch grazing was accomplished on a 20% patch of the 4 study pastures at the Cottonwood Research Station and the 2 producer pastures.
- Summer grazing occurred on all study pastures.
- All data collection was accomplished on the Cottonwood Station and one cooperator’s ranch, but was suspended on the 2nd cooperator ranch (see below for explanation).
Objectives and Performance Targets for Year 2 (2016-17) that were met include:
- Winter-patch grazing was accomplished on a 20% patch of the remaining original WPG pasture at Cottonwood and on the cooperator WPG pasture.
- Six of the study pastures at Cottonwood were recombined into 3 pastures, each having a burned and non-burned area. Half of each non-burned area of each pasture was grazed heavily in winter 2016/2017 to form a WPG patch.
- Summer grazing occurred on all study pastures. Grazing was suspended in mid-July at Cottonwood due to extreme drought conditions; grazing continued as planned at the cooperator ranch due to much milder drought conditions there.
- All data collection was accomplished on the Cottonwood Station and the remaining cooperator ranch.
Hypotheses for this study include:
- We expect that winter-patch grazing (WPG), as compared to control, will:
- Increase plant structural heterogeneity
- Alter livestock use patterns, with concentrations of cattle use on patches; attraction to winter grazed patches should decline over the summer
- Maintain or increase livestock weight gains
- Increase bird species richness and numbers
- (Added after fire burned several study pastures at Cottonwood Station) WPG and patch burn grazing (PBG) will
- Increase plant structural heterogeneity similarly
- Alter livestock use patterns, with cattle attracted to WPG and PBG patches similarly for grazing; attraction to WPG and PBG patches will decline similarly over summer.
- Bird species richness and density will be similar on WPG and PBG patches
Data collection at Cottonwood and on cooperator pastures included:
- Vegetation height, height density (Robel Pole), species composition (% based on weight), and utilization were measured in winter-grazed patches and control areas of all pastures in the study, and on the burned patches in each of the burned study pastures.
- Cattle were weighed onto and off of patches during winter grazing. Cattle were weighed onto and off of study pastures during summer grazing. A subset of cattle in each study pasture was fitted with GPS collars that recorded location and grazing activity of cattle throughout the summer grazing season. GPS data are being evaluated using ArcGIS to determine cattle preferences for winter-grazed patches, burned patches, and control areas.
- Habitat suitability for bird nesting was evaluated using height-density measures (Robel Pole) in winter-patch and control areas of all pastures in the study, and on the burned patches in each of the burned study pastures. Bird surveys to identify bird use of pastures were conducted. Bird nest dragging was performed to find nests; success/failure of each nest was followed throughout each summer.
- Species richness and biodiversity were measured for vegetation on permanent plots and for birds from nest and bird surveys.
Data analysis for both years of the study are currently being conducted. Some preliminary results from our analyses include:
- Vegetation production was highest in control areas, lowest in burned patches, and intermediate in winter-grazed patches. The low production in burned areas is likely due, in part, to lower soil moisture resulting from lack of snow capture on burned areas.
- Average daily gains (ADG; kg/hd/d) of steers were similar (P>0.05) across all treatments.
- Cattle preferred (in terms of time spent) burned and winter-grazed patches over control patches in 2 of the 3 study pastures. Data are being further analyzed to determine which areas they prefer specifically for grazing.
- Bird abundance (total # birds) and density (birds/ha) are generally higher on pastures with burned and/or winter-grazed patches than on pastures with no patches.
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. The project director was invited to present information about this study and to provide some preliminary results at the annual meeting of the Association of National Grasslands in October 2017.
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.
Year 1 Accomplishments:
All pastures were grazed according to the study protocol in Year 1. 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:
- 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).
- 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:
- 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.
- 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.
- 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).
- 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.
Year 2 Accomplishments
All pastures were grazed according to the modified study protocol in Year 2 (see above). This included 1) heavy winter grazing of a 20% patch on the one remaining WPG pasture at the Cottonwood Research Station and the 1 remaining producer WPG pasture, 2) heavy winter grazing of the WPG patch in each of the three recombined pastures at the Cottonwood Station, and 3) summer grazing on all research pastures at the Cottonwood Station and on the pastures of the remaining cooperator ranch. 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, burned patches, and control areas of pastures. Data from all of these aspects of the study are currently being analyzed.
Educational & Outreach Activities
- Importance of heterogeneity for sustainable livestock production