Sagebrush Seedling Recruitment Following Tebuthiuron Application
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Sagebrush Seedling Recruitment Following Tebuthiuron Application
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Sagebrush Seedling Recruitment Following Tebuthiuron Application
- 1. Sagebrush seedling recruitment following tebuthiuron application Sara Germain, Rebecca Mann, Kari Veblen, Tom Monaco Dept. of Wildland Resources, SURCO, NRCS CIG, Utah Agricultural Experiment Station, USDA-ARS Forage and Range Research Lab.
- 2. Ecological Site-Based Management Goals 1.Work with ranchers to increase forage for livestock. 2. Determine amount of shrub reduction in response to treatments 3. Evaluate how these responses vary with Ecological Site
- 3. Cedar Fort: Snakeweed Gutierrezia sarothrae Bear Lake: Sagebrush Artemisia spp. Birdseye: Rubber Rabbitbrush Ericameria nauseosus Park Valley: Greasewood Sarcobatus vermiculatus Study Area Two Ecological Sites per ranch
- 4. Bear Lake Site Specifics Ecological Site: Upland Stony Loam Soils: Lonjon Silt Loam Elevation: 2225m Temperature: 6 C Precipitation: 305-406mm Shrubs Wyoming Big Sagebrush Black Sagebrush Rubber Rabbitbrush Green Rabbitbrush Bitterbrush Saskatoon Serviceberry Grasses/Forbs Wheatgrass Needle + Thread Prairie Junegrass Lupine Buckwheat Arrowleaf Balsamroot Aster
- 5. Tebuthiuron and Sagebrush What is tebuthiuron? Soil active herbicide used to kill mature shrubs How was it applied? Flew on pellets in fall 2012 – tebuthiuron 20P (2.5 lbs/ac) Research Questions 1. How does tebuthiuron affect young Sagebrush? 2. Does tebuthiuron affect Sagebrush seedling emergence?
- 6. Transect Map
- 7. Sampling Sagebrush density by age class: dead, mature, young • 1 Summer after treatment July 2013 • 2 Summers after treatment July 2014 Seed rain trap – capture seed from this year • Autumn October – Nov 2013 • Winter/Spring December – May 2014 Seed bank samples – capture seed from previous years
- 8. Grow-out trials Grew 200 sub-samples per trial (3 trials) in USDA greenhouse, counted and identified seedlings as they emerged (n=40 per trial) • 2 Seed rain – sagebrush only • 1 Seed bank – sagebrush, shrubs, forbs, grasses
- 9. Results – Density At the ranch... • Mature sagebrush decreased • Young sagebrush increased Why? • Mature sagebrush is killed, opening new niches for young sagebrush to grow • Application rate may be too low to kill young plants 40 35 30 25 20 15 10 5 0 Sagebrush Density after Tebuthiuron Treatment 2013 2014 Mean Number of Sagebrush Year Young Mature
- 10. Results - Seed Rain In the greenhouse... • Fewer Sagebrush seedlings emerged from treated samples than control samples Why? • Higher mortality of mature sagebrush means fewer reproducing plants • Is tebuthiuron reducing the viability of seeds from plants in treated areas?
- 11. Results - Seed Bank In the greenhouse... • No differences in seedling emergence (sagebrush, forbs, or grasses). Why? • Viability of seed bank doesn’t seem to be affected by treatment.
- 12. Tebuthiuron and Sagebrush Management On an Upland Stony Loam E.S: • Initial reduction of mature Sagebrush is effective • Success may be offset by the failure to target reestablishment mechanisms • Repeated applications, or use with other management tools, likely necessary to keep sagebrush densities low over time: this may be more costly
- 13. Acknowledgements Monty Weston Property Owner Justin Williams Field Assistance Rebecca Mann Graduate Student Advisor Kari Veblen Faculty Advisor Tom Monaco Experimental Design
Notes de l'éditeur
- Ranch owners aim to reduce dominance of the shrub on their property; we worked with each to select an herbicide appropriate for their situation. All four ranches were treated as of this summer... Work with ranchers to improve range by decreasing dominant shrub, in turn releasing grasses/forbs from competition to increase forage for livestock. Determine the magnitude of shrub reduction in response to treatments and rate of recovery of target shrubs. The key for us, is that underlying each of these shrub dominated sites are two differing soil types & associated ecological sites. This allows us to study how ecological sites will differ in their response to our given management actions over the course of the four year project. Evaluate how outcomes of shrub management tactics vary due to Ecological Site, eight total Ecological Sites in study area.
- Stars are the locations of the four ranches that we have partnered with and where we are performing field experiments. At each of these ranches, one target shrub species dominates the overstory… These shrubs are over abundant at these ranches due to site responses to past management.
- Set the stage – (western , slender, intermediate, bluebunch) Shrubby/sulfur buckwheat not much cheatgrass, snakeweed problem Grazing throughout the study
- Otherwise known as spike Commonly used , but Tends to reestablish within 1-2 decades Young = not yet of reproductive age Seedling emergence = production from treated plants and seed bank
- After we flew on pellets, we walked out and visually confirmed control areas. The clumping of control is because there was significant drift of pellets and it was difficult to find clear areas.
- Sagebrush density 2013 and 2014 by age class to compare treat/control in years directly following application Seed rain – capture this year’s seeds Seed bank – capture previous year’s seeds
- 1) We confirmed the efficacy of tebuthiuron at decreasing mature sagebrush 2) Young sagebrush increased in density following treatment – treated areas now more dense than control
- We observed fewer seedlings emerge from treated areas – while this is most likely an artifact of fewer reproducing mature plants after treatment, I would like to know what the direct effects are on seed viability. Never counted seeds – could be same amount of seeds but lower viability in treated areas.
- When mature shrubs die back, these seeds are free to germinate and grow in newly opened niches.
- When aiming to control sagebrush, important to calculate costs based on necessity of future applications. Of course this is going to depend on the site, area being treated, and the optimal sagebrush density you’re aiming for.