Spruce Gulch Wildlife and Research Reserve
The Spruce Gulch Wildlife and Research Reserve is a 476-acre natural area in the foothills of the Rocky Mountains just outside Boulder, managed by the Institute of Arctic and Alpine Research (INSTAAR). The reserve is home to a pristine foothills watershed, making it a unique site for ecological and hydrological research. Its natural beauty and close location to CU Boulder campus also make it an excellent site for experiential learning in the humanities, social sciences, architecture and the arts. Our mission is to provide research and educational opportunities for scientists, students, K-12 educators and nonprofit groups.
Although Spruce Gulch is not open to the public, it is available for research, education and conservation initiatives from both CU-affiliates and other local organizations. If you would like to inquire further, you can reach out to reserve director Tim Seastedt at timothy.seastedt@colorado.edu.
We are setting up the reserve to be a transformative program. It will benefit research, teaching, and outreach as well as advance environmental sustainability initiatives for our community.
Director of the Spruce Gulch Wildlife and Research Reserve
Professor Emeritus, EBIO and INSTAAR, CU Boulder
A dynamic landscape
Over the years, Spruce Gulch has been sculpted by extreme events and steady stressors.
FIRE
The 2020 Calwood Fire burned over 10,000 acres in Boulder County, but only portions of upper Spruce Gulch.
Spruce Gulch was severely impacted by fires in 1988 and 2003 and moderately impacted by fires in 2011 and 2020.
The burned area above shows a post-fire increase in trees and shrubs between 2005 (left) and 2025. Unburned areas are also showing increases.
FLOOD
BEFORE: The old mining road in 2011, the last remaining road on the property at that time. The others were abandoned decades earlier and have been colonized by trees, shrubs, and grasses.
AFTER: The old mining road was destroyed by a large flood in 2013. An extreme rainfall event over multiple days led to flooding, erosion, and landslides in the reserve and along the Front Range.
INVASIVE PLANTS
Spotted knapweed (Centaurea stoebe, purple flower) drives out native plants and destroys rangeland. Introduction of a knapweed-eating weevil to Spruce Gulch has helped reduce its impact locally.
Myrtle spurge (Euphorbia myrsinites, yellow-green mats) is another ‘to be eradicated’ plant species in the reserve. It's known for its toxic, milky sap that can cause skin irritation and is poisonous if ingested.
Cheatgrass (Bromus tectorum), an introduced annual plant, is a major wildfire concern. In one of the reserve's meadows, it declined by about 50% over 13 years when there was no grazing or burning.
GRAZING
BEFORE: Grazed area in 2006.
AFTER: Same area in 2019, 13 years after ranching and grazing ended.
Wildlife & conservation
This reserve, in conjunction with adjacent U.S. Forest Service land and Heil Ranch Open Space property, creates a major wildlife corridor. We yield the trails to a number of occupants, including:
Mountain lion (spotted on a trail cam)
Black bear (spotted on a trail cam)
Rattlesnake (photo by Timothy Seastedt)
The lack of active roads and infrastructure at Spruce Gulch allows wildlife to move freely.
Research program
Spruce Gulch hosts interdisciplinary research efforts in the natural sciences. The site is also open to researchers and collaborators from the social sciences, humanities and arts.
Knapweed at the start
The first research project at Spruce Gulch began in 2001, when the former owner of the site asked for INSTAAR ecologist Tim Seastedt’s help removing spotted knapweed (Centaurea stoebe), an invasive plant species, on the property. At the time, the Seastedt lab was involved in research on a relatively new experimental method for knapweed control. Instead of spraying herbicide, the scientists released innocuous knapweed-eating insects called flower weevils (Larinus species). The intervention was highly effective on the Spruce Gulch property. In 2021, the team published a 20-year review in the journal Biological Control.
Wide-ranging topics
Since 2001, Spruce Gulch has hosted numerous research projects and CU Boulder classes. The site has aided CU faculty and students in producing more than 40 journal articles, doctoral dissertations, master's theses and undergraduate honors studies.
Example topics
Publications
A Colorado Front Range grassland exhibits decreasing dominance of cheatgrass (Bromus tectorum) over time.
Janet S. Prevéy and Timothy R. Seastedt. Ecosphere. 2025.
Phenology forecasting models for detection and management of invasive annual grasses.
Janet S. Prevéy et al. Ecosphere. 2024.
Invasive annual cheatgrass enhances the abundance of native microbe and microinvertebrate eukaryotes but reduces invasive earthworms.
Dorota L. Porazinska et al. Plant and Soil. 2022.
Empirical test of increasing genetic variation via inter-population crossing for native plant restoration in variable environments.
April M. Goebl et al. Restoration Ecology. 2022.
A 20-year evaluation of successes with biological control of spotted knapweed (Centaurea stoebe) Colorado.
David G. Knochel and Timothy R. Seastedt. Biological Control. 2021.
Changing edaphic conditions and exploitation of an expanded phenological niche allows for increased exotic (introduced) species dominance.
Amy L. Concilio et al. Plant and Soil. 2017.
Limited conifer regeneration following wildfires in dry ponderosa pine forests of the Colorado Front Range.
Monica T. Rother and Thomas T. Veblen. Ecosphere. 2016.
Imposing antecedent global change conditions rapidly alters plant community composition in a mixed-grass prairie.
Amy L. Concilio et al. Oecologia. 2016.
Effects of short-term soil conditioning by cheatgrass and western wheatgrass.
James J. O’Connor et al. The Prairie Naturalist. 2015.
Effects of precipitation change and neighboring plants on population dynamics of Bromus techtorum.
Janet S. Prevéy and Timothy R. Seastedt. Oecologia. 2015.
Response of a mixed grass prairie to an extreme precipitation event: Introduced species, soil nitrogen and previous precipitation patterns influence responses.
Amy L. Concilio et al. Ecosphere. 2015.
Increased winter precipitation benefits the native plant pathogen Ustilago bullata that infects an invasive grass.
Janet S. Prevéy and Timothy R. Seastedt. Biological Invasions. 2015.
Biological control of invasive plant species: A reassessment for the Anthropocene.
Timothy R. Seastedt. New Phytologist. 2015.
Seasonality of precipitation interacts with invasive species to alter composition and phenology of a semi-arid grassland.
Janet S. Prevéy and Timothy R. Seastedt. Journal of Ecology. 2014.
Mowing reduces exotic annual grasses but increases exotic forbs in a semi-arid grassland.
Janet S. Prevéy et al. Restoration Ecology. 2014.
Factors affecting seedling establishment rates of spotted knapweed (Centaurea stoebe).
Anastasia P. Maines et al. Invasive Plant Science and Management. 2013.
Biological control and precipitation effects on spotted knapweed (Centaurea stoebe): Empirical and modeling results.
Anastasia P. Maines et al. Ecosphere. 2013.
The lesser of two weevils: physiological responses of spotted knapweed (Centaurea stoebe) to above and belowground herbivory by Larinus minutus and Cyphocleonus achates.
Stuart C. Wooley et al. Biological Science and Technology. 2011.
Additive effects of above- and belowground herbivores on the dominance of spotted knapweed (Centaurea stoebe).
David G. Knochel et al. Oecologia. 2010.
Effects of plant competition, seed predation, and nutrient limitation on seedling survivorship of spotted knapweed (Centaurea stoebe).
David G. Knochel et al. Biological Invasions. 2010.
Reconciling contradictory findings of herbivore impacts on spotted knapweed (Centaurea stoebe) growth and reproduction.
David G. Knochel and Timothy R. Seastedt. Ecological Applications. 2010.
Interactions and effects of multiple biological control insects on diffuse and spotted knapweed in the Front Range of Colorado.
Timothy R. Seastedt et al. Biological Control. 2007.
Post-release evaluation of Mecinus janthinus host specificity, a biological control for invasive toadflax (Linaria spp.).
Nehalem C. Breiter and Timothy R. Seastedt. Weed Science, 2007.
Barr, K.; 2025 (in progress). Effects of neighbor species identity on the growth of cheatgrass. Undergraduate Honors Thesis, CU Boulder
Garfinkel, C.F.; 2023. Thermal physiology and ecology of montane carrion beetle communities (one chapter). PhD. Dissertation, CU Boulder.
Goebl, A.M.; 2020. Factors affecting establishment, adaptation, and persistence of small populations in variable environments (only chpt 2: Empirical test of increasing genetic variation via inter-population crossing for native plant restoration in variable environments). PhD. Dissertation, CU Boulder.
Lyon, H.; 2019. Effects of soil conditioning by Bromus tectorum on decomposition rates of plant litter and soil properties. Undergraduate Honors Thesis, CU Boulder.
Sechler, B.; 2018. Biochar as a soil amendment for willow and cottonwood plantings in a riparian restoration. MS Thesis, CU Boulder.
Amir, Z.; 2016. Assessing collateral damage: interactions among native thistles and the introduced biological control agent, Rhinocyllus conicus in the Colorado Front Range. Undergraduate Honors Thesis, CU Boulder.
Reibold, R.H.; 2015. Precipitation and the interaction of seedhead biological control insects for spotted knapweed in the Rocky Mountain Front Range. Undergraduate Honors Thesis, CU Boulder.
Rother, M.T.; 2015. Conifer regeneration after wildfire in low-elevation forests of the Colorado Front Range: Implications of a warmer, drier climate. PhD. Dissertation, CU Boulder. (Spruce Gulch was one of multiple research sites.)
Prevéy, J.S.; 2014. Precipitation change in a semi-arid grassland: Plant community responses and management strategies. PhD. Dissertation, CU Boulder.
Maines, A.P.; 2013. Effects of biological control and precipitation on spotted knapweed (Centaurea stoebe) population dynamics. MS Thesis, CU Boulder.
O’Connor, J.; 2011. Bromus tectorum soil conditioning. Undergraduate Honors Thesis, CU Boulder.
Jamieson, M.A.; 2010. Chemical ecology of an invasive plant, Dalmatian toadflax (Linaria dalmatica), and two specialist herbivores, Calophasia lunula and Mecinus janthinus. PhD. Dissertation, CU Boulder (one chapter of dissertation).
Knochel, D.C.; 2009. Interactions among herbivory, soil resources, and plant competition govern the recruitment and dominance of spotted knapweed (Centaurea stoebe) in North America. PhD. Dissertation, CU Boulder.
Breiter, N. C.; 2005. How selective are biological controls? Evaluating the potential for nontarget herbivory by Mecinus janthinus Germar [Coleoptera: Curculionidae], a biological control agent for Dalmatian (Linaria dalmatica L. P. Mill.) and yellow toadflax (Linaria vulgaris P. Mill.) [Scrophulariaceae]. MS Thesis, CU Boulder.
Varied study sites
The reserve's location in the foothills provides many research opportunities across a range of landscapes and habitats.
Example areas
Click to zoom and see captions
Foothills grassland
Ponderosa savanna
Hillslope ecosystem
Riparian zone
Fire recovery research
Flood recovery research
Precipitation manipulation
Cheatgrass research
Modest management
The reserve is managed using low impact, science-based methods that preserve or enhance site conditions. For example, weeds and pests are managed using hand tools and cautiously introduced biological controls. No herbicides or pesticides may be used.
A growing team of researchers
More than 30 faculty and students have participated in research at Spruce Gulch so far, mostly from CU Boulder and the U.S. Geological Survey (USGS).
Participating CU Boulder units
A special thanks goes to Dr. Janet Prevéy of USGS for all her efforts.
Advisory committee
- Nancy Emery (EBIO + INSTAAR)
- Christy McCain (EBIO + MUSM)
- Keith Musselman (INSTAAR + GEOG)
- Irina Overeem (INSTAAR + GEOL)
- Julian Resasco (EBIO)
- Katie Suding (INSTAAR + EBIO)
- William Taylor (ANTH + MUSM)
Thank you, volunteers
Our volunteers have contributed thousands of hours of research and restoration help, including removing invasive plant species by hand. More volunteers are needed. If you are interested, contact reserve director Tim Seastedt.
Boulder community impact
Spruce Gulch's impact extends beyond INSTAAR and CU Boulder. We partner with local leaders and organizations to identify and solve environmental sustainability issues that impact local communities.
An AmeriCorps team removes myrtle spurge from a hillside that was severely burned in the Overland Fire of 2003.
An upcoming BERC workshop
The research team at Spruce Gulch recently helped form the Boulder Ecosystem Resilience Collaborative (BERC) and is busy planning a kickoff workshop for the group. The meeting will bring together academics, managers, policy makers and stakeholders to identify pressing applied research questions important to the Boulder community. Example actions that can be undertaken at Spruce Gulch include:
- Evaluating biotic responses to climate change and nature-based solutions.
- Improving ecological resilience to extreme events.
- Assessing invasive species and grassland sustainability.
- Empowering land stewards and enhancing cultural values.
Partnering with the city
CU’s acquisition of the Spruce Gulch Wildlife and Research Reserve has enormous potential benefits for our community. As we face the growing impacts of climate change on our local environment, we have an urgent need for places where we can monitor these changes and identify land stewardship strategies that can reduce these impacts. We look forward to working closely with CU and its remarkable faculty and students in using this site to help explore strategies for enhancing our social and environmental resilience to these changes.
Brett Kencairn
Sr Policy Advisor for Climate & Resilience,
City of Boulder
History & ecology timeline
Today, Spruce Gulch is a mosaic of ponderosa pine savanna, meadow and riparian areas. The site provides excellent habitat for invertebrates, mammals and birds. Overall, Spruce Gulch is home to a large percentage of the plant and animal species found in Boulder County.
Over the years, the landscape, flora and fauna of Spruce Gulch have been shaped, in part, by human impacts and extreme weather. The following timeline documents some of these events. Some dates are estimates based on limited assessment of artifacts found at the Spruce Gulch Wildlife and Research Reserve.
STEP 1
Pre 1850
Archaeological evidence indicates that Indigenous peoples occupied the land at the Spruce Gulch Wildlife and Research Reserve for thousands of years before European settlers arrived in the American West. The Arapaho peoples are likely the last Native American inhabitants of the land. Before the 1850's, native flora and fauna flourish.
STEP 2
1880s
During the late 1800s, a number of prospectors file mining claims on the site. Primitive roads are cut through the rugged hillside, small mines are excavated and loggers clearcut the forest. One prospector establishes a homestead at the southern end of Spruce Gulch. Roads, mines and logging operations heavily impact plant communities and wildlife, and grazing livestock are introduced.
STEP 3
1910s
By the early 1900s, mining and logging operations give way to small-scale ranching and farming. In the absence of industry, the ecosystem bounces back — wildflowers spring up in the meadows, ponderosa pines grow on the hillsides and riparian vegetation creeps up along the creek. With the plants, comes wildlife habitat. Birds, grazers and predators return to the land, which is now a sanctuary for mountain lions, mule deer and songbirds.
STEP 4
1927
Before CU Boulder acquires the Spruce Gulch Wildlife and Research Reserve in 2025, the site had been owned by the same family for almost a century. In 1927, Irma Freudenberg buys 500 acres of land in Lefthand Canyon. Together with her children, she establishes what the family calls Red Rock Ranch. They keep a small herd of cattle, several horses and chickens on the property. They also grow alfalfa, wheat and apples.
STEP 5
1959
After Irma's death in 1959, her daughter, Alice Holubar, inherits Red Rock Ranch along with 174 acres of land. Then, in 1962, Alice’s husband, LeRoy Holubar, purchases an adjacent 320 acres. The land immediately around Red Rock Ranch still remains in the family today. The rest of Alice and LeRoy’s combined acreage is now the Spruce Gulch Wildlife and Research Reserve.
STEP 6
1980s
Spotted knapweed spreads across Colorado’s front range. The invasive forb arrives at Spruce Gulch after the U.S. Forest Service distributes contaminated grass seed to reestablish vegetation destroyed by a wildfire.
STEP 7
1988
Unnamed wildfire, unknown extent.
STEP 8
1994
LeRoy Holubar’s daughter, Linda Holubar Sanabria, inherits the Spruce Gulch property after her father’s death. For the next seven years, she works passionately to eradicate knapweed from the land.
STEP 9
1998
Lefthand Reservoir Fire (small)
STEP 10
2000
2000 Lefthand Canyon Fire (small)
STEP 11
2001
Holubar's mission to fight knapweed encroachment leads her to recruit help from INSTAAR ecologist Timothy Seastedt. Seastedt’s lab releases knapweed-eating weevils at the site as part of a biocontrol experiment. Over the next 24 years, Seastedt brings collaborators and students to the site, which becomes a hub for ecological research and education.
STEP 12
2003
Overland Fire (large)
STEP 13
2006
The end of ranching and grazing on the property.
STEP 14
2008
Volunteers begin removing invasive plant species by hand under the direction of the Seastedt lab.
STEP 15
2011
2011 Lefthand Canyon Fire (small)
STEP 16
2013
An extreme rainfall event over multiple days causes flooding and landslides. Both native and invasive species are reseeded from adjacent land.
STEP 17
2020
Calwood Fire (large)
STEP 18
2025
Holubar donates the property to CU, along with an endowment to support ongoing research and education opportunities on the reserve. INSTAAR now leads research efforts at the Spruce Gulch Wildlife and Research Reserve and Seastedt is the reserve director.