Progress report for LNC21-450
Project Information
The Nebraska Sandhills region is one of the largest (20,179 miles2), intact native grasslands remaining in the world. Sandhills grasslands are used primarily for beef cattle production, but these ecosystems also provide important wildlife and plant species habitat, wetlands and water infiltration for recharge of the Great Plains aquifer, and other ecosystem services such as recreation. Vegetation management typically includes a combination of grazing strategies, mechanical and chemical control of invasive plants, and, less frequently, prescribed fire. Tradeoffs that occur among competing ecosystem services (e.g., soil health, cattle weight gain, economic return, wildlife diversity) and disservices (e.g., invasive species, low plant diversity, compromised soils) must be evaluated and quantified when making management decisions that have consequences for sustaining livelihoods.
The collaborative adaptive management (CAM) project at Barta Brothers Ranch evaluates alternative, stakeholder-designed approaches to grassland management in the Sandhills and surrounding north-central Great Plains. Initial meetings with the CAM Project Team (ranchers, land managers, researchers) broadly identified management of invasive species, enhancing livestock performance, and managing for heterogeneity and multifunctionality, or multiple ecosystem services on the same land area, as key uncertainties and primary goals for the research. A patch-burn grazing system was recommended as a management practice that could address these areas of concern.
Utilizing the adaptive management framework, researchers established protocols to monitor monitor and compare outcomes in woody vegetation, herbaceous vegetation, livestock, soil, and social learning among stakeholders before, during, and after a set of four grazing seasons in a patch-burn grazing system and a deferred rotational grazing system. In the springs of 2022, 2023, and 2024, through cooperation among stakeholders in the region, Barta Brothers Ranch completed prescribed burns in a series of 160-acre pastures within a four-pasture system. By opening gates between pastures, cattle were allowed to openly graze all four pastures in the patch-burn system (i.e., season-long continuous grazing), while cattle in the deferred rotational grazing system were rotated among each of the four pastures in each grazing season.
Each year, animals (spayed heifers) were put out to pasture in mid-May and removed in mid-September. Stocking rates (.62 AUMs/acre) reflected real-world conditions and were held constant throughout the grazing seasons despite variable conditions, including periods of above-average precipitation and regional drought. As a control, a similarly stocked four-pasture deferred rotational system was also established at Barta Brothers Ranch. Within each pasture, animals were weighed three times during the grazing season with some heifers (n=8) tracked via GPS collars.
Semi-annual on-ranch meetings, along with phone and email communication, took place each year. This active engagement among stakeholders is foundational to the CAM approach. Through the co-production of science, shared learning and trust are fostered among the participants in the CAM research project at Barta Brothers Ranch.
CAM requires stakeholder involvement from inception to completion. In this project, we: 1) Established a CAM program in the Sandhills to identify management challenges and goals; 2) Established Barta Brothers Ranch (BBR), a University-owned ranch, as a location for “learning-by-management” experiments, where stakeholders voice and test management hypotheses in an environment that does not affect their livelihoods; 3) Are comparing alternative, stakeholder-identified management approaches and evaluating their effects; 4) Are developing monitoring and tradeoff tools for assessing tradeoffs among alternative management approaches and informing decisions that affect the attainment of economic and environmental goals; and 5) Are evaluating progress, success and uptake of the CAM for rangelands.
In 2020, the University of Nebraska-Lincoln launched a collaborative adaptive management (CAM) project at Barta Brothers Ranch to address risks and uncertainties related to grassland management in the Sandhills. This project focuses on evaluating stakeholder-designed management plans in a collaborative research setting. This emphasis on co-producing science ensures CAM reflects real-world ranching conditions of the Sandhills and the north-central Great Plains. This publication highlights preliminary results from years 1 - 3 of management treatment implementation (2022-2024 grazing seasons).
Cooperators
Research
Patch-burn grazing systems can increase livestock performance and rancher profitability while minimizing tradeoffs to other desired functions of the landscape.
Adaptive Management Framework
The foundation of the CAM Project at Barta Brothers Ranch comes from its linkage to the adaptive management framework. Adaptive management is an iterative process with aims to increase understanding of a system through a structured decision-making process. This includes: 1) defining the problem, 2) identifying objectives, 3) formulating evaluation criteria, estimating outcomes, 4) evaluating trade-offs, 5) decide on actions to be taken, 6) implement action plan, 7) monitor system behavior, 8) evaluate management outcomes, 9) adjust management.
Monitoring
The CAM Project Team will continue to refine what and how to monitor, and to develop expectations of responses to stakeholder-implemented management. Since management treatments were first deployed in 2022, CAM members have voted to maintain data collection as described below. Since that time, additional questions regarding rates of eastern redcedar re-encroachment after different treatment were posed by stakeholders and are being addressed through additional monitoring activities and a dissertation (J. Harvey). Similarly, stakeholder questions about differences in post-fire surface temperature between burned and unburned areas are being addressed through additional monitoring activities.
Eastern redcedar mortality
Beginning in the summer of 2024, to quantify the effectiveness of prescribed for managing eastern redcedar in a patch-burn grazing management approach in Sandhills ecosystems, without deferring grazing, we conducted a census of eastern redcedar mortality in Pasture N-8, which as burned in April 2024. To assess tree mortality by size class, each tree was classified as dead or alive and assigned to one of the following height classes: < 1 foot, 1 - 2 ft, 2 - 3 ft, and > 3 ft.
Herbaceous vegetation
Vegetation data has been collected each year, including the year prior to application of treatments, through several different techniques, in pastures managed with patch-burn grazing and deferred rotational grazing. Vegetation variables monitored include plant species composition and aboveground biomass production. Together, these datasets are useful for comparing plant community responses under the alternative management approaches.
From 2021 - 2023, plant community species composition and dry weight rank was assessed using a 40 by 40 cm monitoring frame placed at multiple locations in pastures with different management approaches. Trained technicians located multiple monitoring points based on ecological site, topography, and aspect and recorded all rooted plant species within each monitoring frame placement. These data were used to quantify species richness, species frequency of occurrence and diversity, spatial variability of plant groupings, and relative importance of species across the locations and management alternatives. Methodological details can be found in Nolan Sipe's M.S. Thesis. Plant species composition data was also collected through Catherine Chan's Ph.D. research in 2023 and 2024. Under this approach, plant communities were sampled along 100-m transects in multiple dune complexes and positions within the patch-burn grazing system and deferred rotational grazing system. Transects were sampled twice across the growing season--once at peak C3 plant growth and once at peak C4 plant growth. Catherine's transect-based data is also being compared to remote sensing imagery in Catherine's dissertation.
We also leveraged and adapted long-term on-ranch biomass monitoring to compare plant responses between the patch-burn grazing system and the deferred rotational grazing system. In this approach, multiple grazing exclosures were placed throughout the study pastures and annual net primary plant production was collected at two points during the growing season--C3 (cool season) peak standing crop and C4 (warm season) peak standing crop--by clipping all plant material at ground level, separating by functional plant group, drying to a consistent weight, and recording weights. We also conducted forage nutrient analysis to compare forage quality between the patch-burn system and the deferred rotational grazing system.
Remote sensing and landcover
At broader scales, remote sensing technology is being utilized to evaluate productivity and heterogeneity (i.e., diversity), and thermal responses across Barta Brothers Ranch. In 2022 and 2023, hyperspectral and thermal airborne imagery were collected in mid-July for pastures in the patch-burn grazing system and surrounding areas. In 2024, the same data was collected twice in the growing season--once at peak C3 plant growth in June and once at peak C4 plant growth in August and were aligned with Catherine Chan's field vegetation surveys. At smaller scales, we are using proximal remote sensing (i.e., cell phone camera) the the Canopeo App for real-time biomass sampling through Hannah Allen's M.S. thesis research.
In addition to airborne remote sensing, we are using landcover data--specifically functional percent cover and biomass--from the Rangeland Analysis Platform (rangelands.app) to compare vegetation responses among pastures and between the patch-burn grazing and deferred rotational grazing treatments. Percent cover values are available in an online user interface, for download, and on Google Earth Engine (Gorelick et al. 2017) annually at 30-meter grain, whereas biomass is available annually or over 16-day intervals at 30-meter grain. Additional remote sensing products for early identification and tracking of vegetation state-transitions at multiple scales (state-transition screening, Uden et al. 2019) are being used to monitor woody plant encroachment at larger scales.
Grassland birds
For multiple pastures within both the patch-burn system and deferred rotational grazing system, we established 24 plots in a grid with sampling points spaced 250 m apart. To measure songbird abundance and composition, we conducted 150-m fixed-radius point counts three times at each point in each year from 2021 - 2024. At each point, an observer recorded all birds seen or heard for 6 minutes and the estimated distance from the observer to the bird. Species, sex, and behavior (observed singing, observed calling, heard singing, heard calling, observed only) of the bird were recorded. Additional methodological details are included in Nolan Sipe's M.S. thesis.
Livestock production and behavior
To compare livestock responses between the patch-burn grazing system and deferred rotational grazing system, we monitored cattle weights, movements, and diets. From 2022 - 2024, yearling heifer weights were collected at the beginning (prior to turn out on study pastures), middle, and end (conclusion of the grazing period) of each grazing season. Similarly, GPS tracking collars were placed on a portion of the study animals to evaluate shifts in cattle grazing behavior (i.e., grazing and resting times) and grazing distribution (i.e., where animals are grazing) in the study pastures from 2022 - 2024. Finally, beginning in 2024, animal diets were monitored through two methods that utilize fecal samples to identify plant species in cattle diets--fecal DNA analysis and microhistology--as well as observations of plant species utilization along transects at randomly generated points within pastures under the patch-burn grazing system and deferred rotational grazing system. The fecal DNA, microhistology, and plant species utilization monitoring and analysis is being conducted through Hannah Allen's M.S. thesis research.
Soil erosion and health
To compare soil erosion rates between burned and unburned portions of the patch-burn system, we established grids of erosion pins across (n=38) burned and unburned/control pastures. Initial pin aboveground heights are recorded and periodically remeasured throughout the grazing season. The difference in these measurements is the amount of erosion or deposition that had occurred at that pin location.
To monitor soil health, each year, soil samples are collected across multiple dune complexes and dune positions in burned and unburned (control) pastures before and after prescribed fire. Samples were collected at 0-20 cm depth at 1-m intervals along a 7-m transect on each dune position. Samples of each transect were aggregated, air dried and analyzed for available P (Mehlich III), soil organic matter (loss on ignition), total N, ammonium, and nitrate. Analysis of soil samples will provide data for comparing the patch-burn and deferred rotation systems influences on soil N, C, and P.
Despite several periods of challenging fire weather and drought conditions, the first three years of the CAM project were implemented successfully. Each year, one ~150 acre pasture was burned followed by continuous, open grazing of yearling spayed heifers. In March 2022, Pasture N-5 was burned followed by Pasture N-6 in May 2023 and Pasture N-8 in April 2024. Pasture N-7 is scheduled to be burned in 2025. Heifers were stocked at similar rates (0.6 AUMs/acre) in each year. To monitor outcomes related to key questions and adjust management accordingly, researchers monitored and evaluated a host of vegetation, avian, livestock, and soil variables. Below are preliminary results from years 1 - 3 of the study (2022 - 2024), along with discussions of the research.
Eastern redcedar mortality
Following the 2024 prescribed burn in Pasture N-8, we observed 72% mortality across 1,611 eastern redcedar trees, with the proportion of dead trees decreasing markedly with increasing tree height. This finding echoes those of multiple other studies that report significantly greater eastern redcedar morality at smaller tree size classes. It is notable that the 2024 prescribed fire occurred without deferment of grazing in prior years, indicating a tradeoff between utilization of forage and subsequent control of eastern redcedar trees with prescribed fire, especially trees taller than 2 feet.
Annual plant production
If prescribed fire is to be incorporated into Sandhills grazing systems, vegetation responses to fire in different contexts is paramount. Three years of aboveground plant biomass data at peak C3 (June) and peak C4 (August) plant growth show few differences between burned and unburned portions of the landscape. In other words, we did not observe substantial effects of prescribed fire on plant production. In June and August of 2022-2024, biomass of various plant functional groups was collected in the burned pastures and compared to BBR’s long-term grazing systems data, which contains plant biomass production at the ranch for over 20 years. To date, no differences in the total biomass produced from burned or unburned pastures were found. However, one anticipated difference was detected in the amount of standing dead and litter material. Unsurprisingly, this dry plant matter quickly combusts during a prescribed fire and was significantly lower in burned pastures. In 2023, an additional difference was detected in the production of C3 grasses (cool season). This likely resulted from the timing of the burn, which did not occur until early May as dry and windy conditions persisted throughout the state in March and April. While weather conditions will vary production throughout a given growing season, these two years of data suggest that burning and grazing can occur in the same season with minimal effects on the total plant biomass production.
Forage quality
The fact that total biomass production remained consistent across both burned and unburned pastures at Barta Brothers Ranch does not explain why cattle in the patch-burn grazing system exhibited higher average daily gains (ADG) than animals in a traditional four-pasture deferred rotation. To better understand the nutritional quality of plant biomass, forage quality test were completed in each year. CAM's working hypothesis, that cattle are attracted to graze nutritious regrowth of grasses and forbs following fire, aligns with previous patch-burn grazing research. CAM's forage analysis of crude protein at Barta Brothers Ranch in June of 2022, 2023, and 2024 (1 - 3 months post-burn) found crude protein levels ranging from 11 - 14% in the patch-burn system, compared to a range of 9 - 10% in the deferred rotational system. For context, it is suggested that approximately 9% crude protein is required in forage to achieve a 1.0 lb. ADG, at just over 10% the ADG rises to 1.5lbs. However, when sampled again in August of the 2022, 2023, and 2024 grazing seasons, there were no differences in crude protein between burned and unburned pastures, with each around 7-8%.
Livestock behavior
To quantify the degree to which cattle were attracted to burned areas, we deployed GPS tracking collars on 5-8 animals each year to evaluate shifts in cattle grazing behavior (i.e., grazing and resting times) and grazing distribution (i.e., where animals are grazing) in the patch-burn grazing system study pastures. Results largely align with previous patch-burn grazing research, suggesting cattle are attracted to the flushes of new post-fire growth. For example, in 2022 cattle in the patch burn system were 1.5 – 2.0x as likely to occupy burned patches compared to the unburned patches. This pattern did not hold in 2023, likely due to the timing of the prescribed burn in mid-May and resulting low intensity and patchy fire, but was again apparent in 2024.
Livestock performance
Spayed yearling heifers were weighed three times during the year, pre-turnout in May, mid-season in July, and at pull-off in late September of the 2022-2024 grazing seasons. As a control, heifers in the burned/grazed pastures (pastures N-5 through N-8) were compared to other spayed heifers stocked at a similar rate in a standard four-pasture deferred rotation on the ranch. At the end of the grazing season in 2022, cattle in the patch-burn system were 24% (43 lbs.) heavier than those in the standard deferred system. In 2023, the cattle were 31% (36 lbs.) heavier in the patch-burn system, and in 2024, they were 26% (31 lbs.) heavier. In both years, average daily gains were not consistent throughout the season. In 2022, the cattle tended to gain more weight in June and July but later tracked closely with gains of the animals in the standard deferred rotation. In 2023, average daily gains held throughout the growing season, and in 2024, cattle in the patch-burn system outgained at the end of the growing season. At the sale barn, the greater gains of cattle in the patch-burn system yielded $86.96 more per head in 2022, $138.98 per head in 2023, and $74.90 more per head in 2024.
Soil erosion
Originally formed by windblown sands, soils, and dust, Nebraska’s Sandhills are vulnerable to erosion by their very design. A key stakeholder concern is that by using prescribed fire, an unacceptable amount of risk is created if high winds or dry conditions trigger dune shifts. To monitor this effect, erosion measurements were taken at both burned and unburned pastures before and after the grazing season. On average, the burned/grazed pastures lost .881 cm of soil while the unburned/grazed lost .631 cm. While there was technically more erosion in the burned pasture, these amounts are negligible. This finding aligns with previous research performed in the Sandhills that found 4-5 years of repeated vegetation suppression was required before significant movement of soil occurred.
Soil health
In grassland systems, plant productivity is highly dependent on the availability of nutrients in the soil’s profile. To further document the effects of utilizing prescribed fire, periodic measurements of soil properties such as organic matter, pH, and soil nutrient levels were taken before and after prescribed burning, followed then by monthly sampling through the remainder of the grazing season. These results showed no significant long-term changes in pH levels among burned and unburned pastures; however, there was an expected increase in both pastures one month after the burn (attributed to ash deposition in the pastures). No significant changes in soil organic matter nor any significant biological changes in the soil’s ability to exchange nutrients were detected. Of the major nutrients sampled, nitrate, potassium, and sodium had significant increases following the burn. However, as grazing was introduced, these levels ultimately returned to levels found in the adjacent unburned pastures. These results help support the notion that low-intensity prescribed burning can occur without irrevocably altering the soil’s organic matter, nutrient levels, or production capacity.
Grassland bird diversity
Bird communities are often used as a bellwether of ecosystem health. To further understand how burning affects ecological communities and function, bird species were monitored during the nesting season (May – July) in both burned and unburned pastures in 2022 and 2023. A total of 41 avian species were identified with grasshopper sparrows, western meadowlarks, brown-headed cowbirds, and red-winged blackbirds accounting for 72% of all observations. Findings to date offer preliminary evidence that patch-burn grazing has positive effects on grassland birds by creating a wider array of habitat types. However, due to the relatively small study area, additional evidence will be necessary before stronger conclusions or management recommendations can be provided. 2024 avian survey results are forthcoming.
Landcover monitoring
Field and remotely sensed observations were taken at Barta Brothers Ranch throughout the 2022 (one flight), 2023 (one flight), and 2024 (two flights) grazing seasons. Field sampling was carried out across multiple dune complexes and dune positions in pastures within the patch-burn grazing system and deferred rotational grazing system, and a neutral site formerly used to study biocomplexity in the system (2022 only). In 2022, researchers detected an increase in the burned treatment's reflectance, likely arising from increased albedo affecting the surface energy balance. This team also found decreases in key energy absorption bands, likely resulting from the loss of standing biomass. These two observations may explain a possible surface cooling effect resulting from the use of prescribed fire. Plant species data was collected in 1-m2 quadrats of two dune complexes through Catherine Chan's Ph.D. research.
Comparisons of historical (2006 - 2010) and contemporary (2022 - 2024) hyperspectral flight data is underway. Images from 2006 to 2010 were collected for a grassland destabilization project (these treated areas can be seen in white dots which are more evident in the older images) while 2022, 2023, and 2024 flights were planned to cover a larger area, including CAM fire and grazing treatments. Imagery outlined in yellow (2008 and 2023) had associated ground sampled plant species and hyperspectral data collected along transects on different dune topographic positions (dune top, interdunal north slope, and south slope) in the same summer.
Preliminary results from these studies are shown in boxplots of a) species richness and b) Shannon diversity index derived from transect-level plant species data collected in 2023 along transects at four dune topographic positions (dune top [DT], interdunal [ID], north slope [NS], and south slope [SS]) and c) normalized difference vegetation index (NDVI) and d) spectral diversity (coefficient of variation-CV) derived from the 2022 imagery in Pastures N2 – N8.
From the plots, higher biodiversity may be associated with lower NDVI (greenness), potentially from variation of plant types rather than homogenous green vegetation. Panel d suggests higher variability of spectra for dune tops and interdunes possibly from high variation related to vegetation species, ground types (vegetation, soil, sand), or among transects in different complexes.
Social learning
The CAM approach is a participatory process by which management decisions are made collaboratively. The purpose of this social science research is to chronicle exercises, primarily through a focus on how stakeholders make initial decisions, learn from relevant data, and adapt their thinking about system dynamics. In 2022, a working “cognitive map” was developed to explore the ways knowledge is gained, how learning can be stimulated in collaborative settings, and how differences in understanding the system can be navigated to build consensus. This working model will be revisited with the CAM stakeholders following the 2024 growing season.
The stakeholders of the CAM Project were encouraged by the first three years of results and recommended a continuation of the patch-burn grazing management. These feelings of optimism were also shared by Congressman Adrian Smith (NE-3) who visited BBR in 2023. The fourth year of the CAM Project (2025) will target pasture N-7 for burning, followed once again by season-long grazing across all four pastures. The preliminary results from the first three years of the CAM Project are working to confirm anecdotal observations on the ranch; however, more information is required to determine patch-burn grazing effects on livestock performance, plant production, ranch profitability, and eastern red cedar control. Monitoring of all variables will continue in 2025, along with additions of long-term landcover and eastern redcedar treatment effects.
Project Activities
Educational & Outreach Activities
Participation Summary:
Learning Outcomes
- adaptive management
- patch burn grazing system
- ecosystem services
- management of tradeoffs