Research Project: Development of Management Strategies for Livestock Grazing, Disturbance and Climate Variation for the Northern Plains

Location: Livestock and Range Research Laboratory

2023 Annual Report

Objectives
Objective 1: Develop management strategies to improve rangeland cattle production and ecological stability through effective use of rangeland forage and supplementation. Subobjective 1A: Determine effects of dormant rangeland forage utilization on heifer development, young cow productivity, plant productivity, and species composition. Subobjective 1B: Determine effects of seasonal rangeland forage utilization by steers and heifers during backgrounding on estimates of respiration gas. Subobjective 1C: Determine timing of grazing season and grazing intensity effects on plant productivity, community composition and cattle diet quality. Subobjective 1D: Enhance the accuracy of DNA metabarcoding to assess diet composition. Subobjective 1E: Evaluate factors regulating calf growth on rangelands. Subobjective 1F: Use precision management technologies (global positioning of livestock, sensor networks, virtual fencing, remote sensing of landscape and others) to enhance livestock producer capability for optimum management of pastures and rangelands, allowing balance between production and ecosystem services. Objective 2: Develop management techniques to improve stock water quality in reservoirs by manipulating plant and microbiota abundance. Objective 3: Develop management strategies to restore degraded rangelands and prevent weed invasions. Subobjective 3A: Develop bacterial management strategies to reduce invasive bromes. Subobjective 3B: Improve vegetation outcomes on Conservation Reserve Program lands. Subobjective 3C: Design seed mixes to more consistently meet plant establishment goals during rangeland restoration. Subobjective 3D: Identify seasonal grazing effects on revegetation following Russian olive removal. Objective 4: Identify cool-season perennial grass seed rates that are high enough to prevent weed invasions and low enough to allow establishment of diverse plant communities on disturbed rangelands. Subobjective 4A: Identify cool-season grass seed rates needed to prevent weed invasions and allow seeded shrub establishment during rangeland restoration. Objective 5: Determine the effect of subsurface soil calcium carbonate on available phosphorus, plant biomass, root traits, and mycorrhizal responsiveness. Objective 6: Develop fire management strategies to maintain and improve rangeland stability and livestock production. Subobjective 6A: Determine perennial grass response to timing of fire relative to plant phenology. Subobjective 6B: Quantify drought and post-drought fire effects on plant community composition and productivity. Subobjective 6C: Determine how seasonal timing of fire affects forage quality and cattle grazing preference.

Approach
Sustainability of rangeland production hinges on the ability of plant communities to resist change and quickly recover from disturbance (stability) because changes in species composition, forage production, and forage quality fundamentally affect the animal community. Primary forces of change in rangelands are weather, grazing, alien plants, fire and their interactions. This project is designed to improve ecological sustainability and rangeland production by addressing opportunities for increased efficiency of livestock nutrient conversion, mechanisms affecting restoration success and weed control, and interacting effects of management with weather. Improved efficiency of nutrient conversion from dormant rangeland forages is among the most viable options for increasing animal production and minimizing effects on plant communities. We will address this proposition through a series of experiments evaluating plant and animal responses to dormant-season utilization and supplementation strategies. Rangeland restoration methods will be evaluated for direct weed control and mechanisms controlling successful establishment of desirable species. Water manipulations and historical weather data will be included in experiments to determine weather and long-term climate effects on plants and livestock because precipitation is the primary controlling factor for plant productivity and community composition. Fire research will focus on timing of fire (seasonal and phenological) to facilitate development of fire prescriptions that reduce weedy species, promote desirable species, and increase availability of quality forage. Scientists will be integrated across objectives to determine interacting effects of precipitation, grazing, weeds, and fire on soil and plant communities (production, species composition, diversity, propagation, survival) and cattle (weight gain, reproductive performance, diet quality, diet selection). Understanding mechanisms that control rangeland stability and animal responses to alterations in plant communities will assist land managers and livestock producers in improving rangeland integrity (diverse communities dominated by native species) and efficiency of livestock production. Results will also provide scientists greater understanding of the complex interacting forces on rangelands.

Progress Report
Objective 1A: Laboratory analysis is completed, and data are currently being statistically analyzed and a manuscript is being prepared for refereed journal. Objective 1C: Prescribed grazing treatments were applied and vegetation sampling was completed. Plans were made to sample soil carbon next year. Objective 1D: Checked 1) the temperature certificates and readiness of our 10 thermocyclers and 2) sample and supply inventories. Objective 1F: Unpiloted Aerial Vehicle (UAV) imagery collected at fall/winter and spring/summer grazing areas along with herbaceous biomass samples for pairing with imagery. Statistical analysis initiated on image and biomass data for developing predictive equations. Data collection on spectral signatures of rangeland vegetation initiated. Forage samples were scanned with spectrometer and data prepared for chemometric equation development. Objective 3B: The project was completed and a manuscript was published. Objective 3C: The project was completed and a manuscript is in review. Objective 3D: Seedlings survived a flood but were subsequently defoliated and killed by grasshoppers. New seedlings were generated by collaborators in Sidney, Montana and have been planted to continue the study. Objective 4A: Preliminary analyses were completed and the need for additional data was determined. Data collection will continue for 2023 and 2024. Objective 5: Started data analysis. Analysis progress was delayed by the collection of additional response variables for our completed greenhouse experiment, which has further limited our collaborator’s ability to fully complete collection of planned data. We recently measured several additional response variables including three foliar nutrients (i.e. manganese, nitrogen, & phosphorus), plant available phosphorus with anion exchange resins, and determined levels of additional soil nutrients of experimental soil treatments. A collaborator will describe the mycorrhizal fungal community composition of root samples and determine root length colonized by mycorrhizal fungi. Objective 6A: The collaborator that was to grow the plants was unable to do so. We germinated all test species and successfully transplanted all species but one from the field as well and grew them in our new growth chambers. Environmental variables are being manipulated to determine conditions required to synchronize plant developmental stages across species. Objective 6B: Data have been analyzed. A short-term study including treatments from this objective was conducted and data matching our treatments will be added to the dataset due to experimentally desirable precipitation received this year. Objective 6C: Final data have been collected and will be analyzed this fall for publication.

Accomplishments
1. Grazing intensity and seasonality manipulate invasive annual grasses and native vegetation. Simultaneous desires for greater livestock production and reduced purchased feed inputs are further complicated by potential for rangeland degradation and weed invasion. Grazing management that emphasizes greater use of dormant rangeland forages may provide solutions. ARS researchers in Miles City, Montana, tested grazing season (summer or fall) and intensity (moderate or heavy) combination effects on plant community composition and productivity for 5 years to determine whether rangelands can sustain heavy dormant-season use without reducing native perennials. Total plant productivity was greatest with moderate fall grazing (1350 kg/ha) and similar among heavy fall, heavy summer and moderate summer grazing (1206 kg/ha). Heavy summer grazing had the lightest native species standing crop. Heavy summer grazing reduced perennial cool-season grass standing crop 22%, primarily through effects on needle-and-thread and threadleaf sedge. Moderate dormant fall grazing increased perennial cool-season grass standing crop 15%, but also increased the invasive annual, Japanese brome. Heavy dormant fall grazing effects did not differ from that of moderate summer grazing for perennial cool-season grass or total native species standing crop, but heavy fall grazing reduced cheatgrass 51%. Where Japanese brome and cheatgrass co-occur, moderate growing season grazing combined with heavy dormant fall grazing may be needed to affect both species. Diversity and native species standing crop were similar between heavy fall and moderate summer grazing, but heavy fall grazing caused the least non-native species standing crop. Heavy fall use is recommended as potential treatment to be rotated among pastures over time or focused on pastures that could benefit from effects observed. Effects likely vary with differences in climate or species composition.

2. Lessons from a next generation carbon ranching experiment. Managing grasslands to sequester carbon is of global importance and groups are contracting with land managers to do so, but effects of grazing on soil organic carbon (SOC) stocks remain uncertain. In other words, the existing research base is not adequate to reliably predict where/how to manage livestock to sequester the maximum amount of SOC. ARS researchers in Miles City, Montana, performed a next generation carbon ranching experiment. After five-years, no grazing and severe summer and fall grazing accrued 0.85 to 1.22 kg/m2 (0-60 cm soil depth) more SOC than conventional moderate summer grazing and represent appreciable increases in SOC stocks. Unclear is whether these grazing treatments can accrue SOC over longer periods (>5 years) and reduce atmospheric carbon. While severe grazing may have positive effects on SOC accrual in the short-term (~5 years), severe grazing may negatively impact plant species composition, soil structure, and other ecosystem services.

3. Prefire vegetation structure of high severity wildfires in western rangelands. In the last 30 years, the land area burned by large wildfires has increased in the western United States, with many of these fires being classified as high severity. These high severity fires can impact trees, shrubs, and grasses, which in turn, can affect water quality, carbon storage, and the atmosphere. In addition, high severity fires can affect human safety and infrastructure. In order to better understand the vegetation conditions that resulted in historical high severity fires, ARS researchers in Miles City, Montana, used historical remote sensing data that identified high severity fires (Monitoring Trends in Burn Severity), as well as a new product derived from remote sensing data that identifies the amount of plant cover on rangelands over time (Rangeland Analysis Platform Cover 2.0). Using these datasets, statistics were used to identify groups of fires having similar rangeland cover characteristics. Nine groups were identified. Five of these groups accounted for 76% of the total land area having high severity wildfires. These 5 groups were characterized as having high tree and shrub cover (approximately 50%) prior to the fires. Another two of these 9 groups, accounted for 13% of the land area with high severity wildfires, and had high cover of perennial forbs and grasses (40%) and moderately high tree and shrub cover (25%) prior to the wildfires. Management strategies, such as prescribed burning, that could decrease tree and shrub cover, reduce standing dead vegetation, and break up continuous fuel loads could be effective in reducing the risk and extent of high severity wildfires on rangelands in the western United States.

4. Fire reduces Russian olive seed germination and seedling survival with increasing fuel load. Russian olive is an aggressive invasive tree species that establishes within riparian areas in the western United States, reducing native species and forage production. It is very hard to control once established and control methods can be expensive. Studies have been conducted to examine scarification and cold treatment effects on germination and establishment of Russian olive seeds. However, to date, fire effects on seeds and newly emerged seedlings have not been documented. ARS researchers in Miles City, Montana, sought to address this information gap by subjecting Russian olive seeds and seedlings to three different fuel loads (1500, 3000, and 4500 kg/ha) and a non-burned control. Our results indicated that with no fire, 40% of Russian olive seeds germinated. However, fire at any of the three fuel loads reduced germination (80-100%). For new seedlings (< 10 weeks old), fire killed all but one of the 250 seedlings tested, indicating the susceptibility of young seedlings to fire-induced mortality. Results from our study indicate that fire reduces seed viability rather than increasing germination through seed scarification. In addition, fire could potentially be used as a management practice to reduce numbers of Russian olive seedlings less than one year old.

5. Establishing forbs for pollinators in agricultural landscapes of the Great Plains. Pollinator insects are declining, partly because grasslands containing forbs that pollinators feed on have been converted to cropland. This conversion is prevalent in the Great Plains, home to several imperiled pollinators and 40% of U.S. honeybees. Over 1.0 million ha of former cropland have been seeded with forbs that could benefit Great Plains pollinators, but success of these seeding efforts is unclear. ARS researchers in Miles City, Montana, quantified forb abundances and factors regulating these abundances in 120 crop fields seeded to forbs and grasses by managers in the Great Plains (Colorado and Montana). Data indicated a need to improve forb establishment. Two to five growing seasons after seeding, seeded forb cover was <10% in most fields, and no seeded forbs were observed in 23% of fields. Data also indicated ways to benefit forbs. High grass seed rates and high weed densities shortly after seeding reduced forb cover at the end of the study. Managers sometimes applied risky herbicides before seeding that appeared to persist in soil and reduce forb establishment. Seed rates were too low to maximize forb abundances, and much money was wasted on seeds of species that did not establish. Researchers identified several species with relatively high establishment probabilities that will support most pollinators. For now, these species should be seeded at high rates. Lower rates could become sufficient if effective weed control is implemented. This research has been presented in a webinar and two invited presentations to about 120 Conservation Reserve Program planners and researchers.

6. Weather and fuel as modulators of grassland fire behavior in the northern Great Plains. Land managers are realizing the importance of fire as a positive ecological force. Safely and effectively using prescribed fire requires knowledge of how vegetation and weather conditions affect fire behavior, but little such information is available for the Northern Great Plains. ARS researchers in Miles City, Montana, reported temperatures and rates of spread for prescribed burns in grazed pastures in central and southwestern North Dakota. Higher winds caused fires to move more quickly, but not necessarily to burn hotter. Rather, flame temperatures increased with higher fuel loads and lower moisture content.

7. Fire and nitrogen effects on purple threeawn mineral concentrations. Purple threeawn is a perennial bunchgrass native to much of North America that may dominate disturbed or previously overgrazed rangelands and is mostly avoided by herbivores as forage. Management of threeawn using fire and nitrogen addition can increase forage quality and likelihood of selection by livestock. ARS researchers in Miles City, Montana, assessed effects of fire, nitrogen fertilizer addition, and growth stage on purple threeawn mineral concentrations the first growing season after fire on two similar sites in southeastern Montana. Fire (no fire, summer fire, fall fire) and rate of nitrogen fertilizer addition (0, 46, 80 kg N/ha) were assigned to test each unique combination of treatments. Samples were collected at five growth stages throughout each growing season. With no nitrogen addition, summer and fall fire increased calcium from 0.22 to 0.38 and 0.31%, respectively, sulfur from 0.08 to 0.15 and 0.13%, and magnesium from 0.06 to 0.14 and 0.12%, while fall fire decreased iron from 289 to 176 ppm. In the vegetative stage, fire (fall and summer averaged) increased potassium from 0.38 to 1.08%, calcium from 0.22 to 0.35%, phosphorus from 0.10 to 0.23%, sulfur from 0.08 to 0.16%, magnesium from 0.05 to 0.13%, zinc from 19.2 to 35.8 ppm and copper from 2.8 to 6.2 ppm. Increasing rate of nitrogen addition and advancing growth stage had little to no effect on mineral concentrations relative to fire effects. Results indicate prescribed fire can increase mineral concentrations from deficient levels to exceeding requirements for growing cattle, providing more evidence supporting use of prescribed fire to increase forage quality and potential herbivore utilization of purple threeawn within one-year following fire.

8. Estimating rangeland fine fuel using high-resolution imagery and machine learning. Fire spread and intensity on rangelands are greatly influenced by fine fuel biomass. However, the ability to accurately estimate fine fuel biomass is a challenge because of the heterogeneity in plant communities across rangeland landscapes. Machine learning offers opportunities to use remote sensing imagery and limited field data to train models to estimate fine fuel biomass across these heterogenous landscapes. In this study, high spatial resolution (0.23m) images were used by ARS researchers in Miles City, Montana, to classify the landscape into different fuel types (e.g., grass, grass/shrub mix, shrub, etc.) and to predict rangeland fine fuel biomass using a machine learning model. The model performed well for predicting fuel types, having an overall accuracy of 95%. For biomass estimation, the model that considered image texture information (i.e., spatial variation in pixel brightness) performed better than the model that did not include texture (81% vs. 77% of variation explained). The machine learning model was then used to predict biomass at the scale of moderate resolution satellites (Landsat, 30 m resolution) using fuel type cover information derived from the high-resolution imagery and Landsat spectral information. Results of this analysis indicated that the fine fuel biomass accuracy was slightly lower than for the high-resolution biomass estimation (56% vs. 77% of the variability explained). These findings indicate that high spatial resolution images have the potential to effectively estimate rangeland fine fuel biomass and can be helpful for rangeland monitoring and management.

9. Developing wildland fire literacy through hands-on experience with prescribed fire. There is a lack of robust wildland fire science due to a lack of training in essential research methods in the wildland fire profession. ARS researchers in Miles City and Sidney, Montana, worked alongside federal and non-profit partners to collect fuels, fire weather, and fire behavior data during burns at The Nature Conservancy's Dunn Ranch Prairie, a series of burns intended to provide hands-on experience for cooperators while achieving The Nature Conservancy management goals. In addition to increasing knowledge about fuels and fire behavior in the Great Plains, these activities helped develop research and management capacity among cooperators and stakeholders in the region.

Review Publications
Clark, A., McGranahan, D.A., Geaumont, B.A., Wonkka, C.L., Ott, J.P., Kreuter, U. 2022. Barriers to prescribed fire in the US Great Plains, Part I: Systematic review of socio-ecological research. Land. 11(9). Article 1521. https://doi.org/10.3390/land11091521.
Clark, A., McGranahan, D.A., Geaumont, B.A., Wonkka, C.L., Ott, J.P., Kreuter, U. 2022. Barriers to prescribed fire in the US Great Plains, Part II: Critical review of presently used and potentially expandable solutions. Land. 11(9). Article 1524. https://doi.org/10.3390/land11091524.
Copeland, S.M., Hoover, D.L., Augustine, D.J., Bates, J.D., Boyd, C.S., Davies, K.W., Derner, J.D., Duniway, M.C., Porensky, L.M., Vermeire, L.T. 2023. Variable effects of long-term livestock grazing across the western United States suggest diverse approaches are needed to meet global change challenges. Applied Vegetation Science. 26(1). Article e12719. https://doi.org/10.1111/avsc.12719.
Dufek, N.A., Vermeire, L.T., Waterman, R.C., Ganguli, A.C. 2022. Fire and nitrogen effects on Aristida purpurea mineral concentrations. Rangeland Ecology and Management. 86:44-49. https://doi.org/10.1016/j.rama.2022.10.006.
Duquette, C., McGranahan, D.A., Wanchuk, M.R., Hovick, T., Sedivec, K., Limb, R. 2022. Heterogeneity-based management restores diversity and alter vegetation structure without decreasing invasive grasses in working mixed-grass prairie. Land. 11. Article 1135. https://doi.org/10.3390/land11081135.
Frost, M.D., Komatsu, K.J., Porensky, L.M., Reinhart, K.O., Wilcox, K.R., Koerner, S.E. 2023. Consequences of rainfall manipulations for invasive annual grasses vary across grazed northern mixed-grass prairie sites. Rangeland Ecology and Management. 90:1-12. https://doi.org/10.1016/j.rama.2023.05.007.
Li, Z., Angerer, J.P., Jaime, X., Yang, C., Wu, X. 2022. Estimating rangeland fine fuel biomass in western Texas using high-resolution imagery and machine learning. Remote Sensing. 14(17). Article 4360. https://doi.org/10.3390/rs14174360.
Li, Z., Angerer, J.P., Wu, X. 2022. Prefire vegetation structure of high severity wildfires in nonherbaceous-dominated rangelands in the western United States. Earth's Future. 10(10). Article e2021EF002624. https://doi.org/10.1029/2021EF002624.
Majumdar, S., Kaur, H., Rinella, M.J., Erbilgin, N., Callaway, R.M., Cadotte, M., Singh, I. 2023. Synergistic effects of canopy chemistry and autogenic soil biota on a global invader. Journal of Ecology. 111:1497-1513. https://doi.org/10.1111/1365-2745.14113.
Mcgranahan, D.A., Maier, C.M., Gauger, R.P., Woodson, C.A., Wonkka, C.L. 2022. The Dunn Ranch Academy: Developing wildland fire literacy through hands-on experience with prescribed fire science and management. Fire. 5(4). Article 121. https://doi.org/10.3390/fire5040121.
McGranahan, D.A., Zopfi, M.E., Yurkonis, K.A. 2022. Weather and fuel as modulators of grassland fire behavior in the northern Great Plains. Environmental Management. 71:940-949. https://doi.org/10.1007/s00267-022-01767-9.
Meki, M.N., Osorio-Leyton, J., Steglich, E.M., Kiniry, J.R., Propato, M., Winchell, M., Rathjens, H., Angerer, J.P., Norfleet, L.M. 2023. Plant parameterization and APEXgraze model calibration and validation for U.S. land resource region H grazing lands. Agricultural Systems. 207. Article 103631. https://doi.org/10.1016/j.agsy.2023.103631.
Muscha, J.M., Vermeire, L.T., Angerer, J.P. 2023. Fire reduces Russian olive seed germination and seedling survival with increasing fuel load. Restoration Ecology. 11. Article e13904. https://doi.org/10.1111/rec.13904.
Muscha, J.M., Vermeire, L.T., Haferkamp, M.R. 2023. Clipping height and frequency effects on Japanese brome seed production and viability. Rangeland Ecology and Management. 90:290-293. https://doi.org/10.1016/j.rama.2023.04.003.
Reinhart, K.O., Komatsu, K., Vermeire, L.T. 2022. Effects of mowing, spring precipitation, soil nutrients and enzymes on grassland productivity. Agrosystems, Geosciences & Environment. 5(4). Article e20320. https://doi.org/10.1002/agg2.20320.
Rhodes, E.C., Perotto-Baldivieso, H.L., Tanner, E.P., Angerer, J.P., Fox, W.E. 2023. The declining Ogallala Aquifer and the future role of rangeland science on the North American High Plains. Rangeland Ecology and Management. 87:83-96. https://doi.org/10.1016/j.rama.2022.12.002.
Rhodes, E.C., Tolleson, D.R., Angerer, J.P. 2022. Modeling herbaceous biomass for grazing and fine fuels management in central Arizona. Land. 11(10). Article 1769. https://doi.org/10.3390/land11101769.
Rinella, M.J., Porensky, L.M., Bellows, S.E., Knox, J.M., Metier, E.P. 2022. Establishing forbs for pollinators in agricultural landscapes of the Great Plains. Restoration Ecology. 31(4). Article e13846. https://doi.org/10.1111/rec.13846.
Vermeire, L.T., Waterman, R.C., Reinhart, K.O., Rinella, M.J. 2023. Grazing intensity and seasonality manipulate invasive annual grasses and native vegetation. Rangeland Ecology and Management. 90:308-313. https://doi.org/10.1016/j.rama.2023.04.001.
Wilmer, H.N., McGranahan, D.A., Moffet, C., Taylor, J.B. 2023. Effect of burn season and grazing deferment on mountain big sagebrush plant communities. Plant Ecology. 224:501-512. https://doi.org/10.1007/s11258-023-01317-1.
Young, S.L., Archer, D.W., Blumenthal, D.M., Boyd, C.S., Clark, P., Clements, D.D., Davies, K.W., Derner, J.D., Gaskin, J.F., Hamerlynck, E.P., Hardegree, S.P., Jensen, K.B., Monaco, T.A., Newingham, B.A., Pierson Jr, F.B., Rector, B.G., Sheley, R.L., Toledo, D.N., Vermeire, L.T., Wonkka, C.L. 2023. Invasive annual grasses: re-envisioning approaches in a changing climate. Journal of Soil and Water Conservation. 78(2):95-103. https://doi.org/10.2489/jswc.2023.00074.