Faculty Publications
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Item Open Access Organizational change in the US Forest Service: negotiating organizational boundaries in the collaborative process(Colorado State University. Libraries, 2019-02-27) Orth, Patricia B., author; Cheng, Antony S., authorIn the United States and across the globe, forest governance officials are seeing a rise in the demand from local community members to participate in forest management decision-making. Despite this demand, there have been few studies that seek to describe the impact of community collaborative efforts on the organizational structures and processes of governmental forest management agencies. We empirically examined the boundary negotiations occurring at the field office level of the United States Forest Service in order to understand organizational change with respect to the collaborative process. We employed a qualitative case study approach encompassing the examination of three community collaborative groups. By examining the defining characteristics of organizational boundaries, we found that boundary negotiations are facilitating organizational change through individual-level learning and behavior changes. We present data suggestive of negotiations for boundaries of knowledge, responsibility, and capacity. Understanding the organizational outcomes of community collaboration will help forest managers respond and adapt to changing forest management strategies.Item Open Access An operationally relevant framework for mapping spot fire transmission potential(Colorado State University. Libraries, 2020-11-12) Gannon, Benjamin M., author; Thompson, Matthew P., author; Wei, Yu, authorSpotting is an important fire spread mechanism and cause of fireline breaches, yet current models provide only coarse metrics of spotting behavior that are underutilized in fire operations. We developed a spatial framework to quantify and map potential sources and sinks of spot fire transmission across control lines, based on models of ember production, ember transport, and receiving fuel bed ignition probability. The framework provides several spatially explicit measures of spotting potential (SP), conditional on fire extent and weather, that are designed to inform control line selection and resource allocation to tasks such as line prep, retardant application, and holding operations. We evaluated the utility of SP using two wildfire case studies with growth episodes attributed to spotting. SP captured the general trends in spotting behavior from these wind-driven fires. In its current form, SP may be useful for relative evaluation of control lines, and to help managers think prescriptively about the control tactics necessary on both the source and receiving sides of control lines to avoid spotting breaches. Future research priorities are refining the component models and empirical calibration of SP to spotting probability.Item Open Access Ecological doctors in Maasailand: identifying herding best practices to improve livestock management and reduce carnivore conflict(Colorado State University. Libraries, 2020-08-14) Jablonski, Kevin E., author; Merishi, John, author; Dolrenry, Stephanie, author; Hazzah, Leela, authorIlkisonko Maasai pastoralists in the Amboseli ecosystem of southern Kenya earn livestock-based livelihoods in a difficult environment exacerbated by a range of challenges. In this setting, many stakeholders, including the Maasai themselves, have come to see traditional extensive pastoralism as essential to long-term social–ecological resilience. This includes the maintenance of communal land tenure, which protects both unfragmented landscapes and the cultural practices necessary to thrive therein. This land tenure system has also been well-documented to support diverse wildlife populations, including large carnivores such as the African lion. Lion Guardians is a conservation organization working on the group ranches of the Amboseli ecosystem to reduce human–lion conflict using culturally appropriate strategies, with a 13-year track record of reductions in lion killing as compared to other conflict mitigation approaches. However, in recent years, they have noted a marked increase in the amount of lost livestock. Lion Guardians' data indicate that untended livestock account for >80%of lion attacks, making them a primary driver of human–lion conflict in the ecosystem. In this paper, we present the results of a community-based qualitative study aimed at identifying the causes of lost livestock, in pursuit of win–win solutions for people and lions. Using an iterative multistage research process, we conducted interviews with more than 120 Maasai community members. Finding general agreement that lost livestock are a problem and that poor herding practices are the primary cause, we next sought to identify both herder and herder-mentor best practices. For this, we focused on the knowledge of elders and "master herders," those identified by their communities as especially adept and responsible herders. In creating these lists, we learned that herding best practices relevant to carnivore-conflict prevention are inseparable from those related to pasture management and livestock productivity and largely inseparable from traditional Maasai culture. This means that good herders, who have been called "ecological doctors," can support the vitality of not only plants and pastures but also lions, ecosystems, and entire human cultures.Item Open Access Human ignitions on private lands drive USFS cross-boundary wildfire transmission and community impacts in the western US(Colorado State University. Libraries, 2022) Downing, William M., author; Dunn, Christopher J., author; Thompson, Matthew P., author; Caggiano, Michael D., author; Short, Karen C., authorWildfires in the western United States (US) are increasingly expensive, destructive, and deadly. Reducing wildfire losses is particularly challenging when fires frequently start on one land tenure and damage natural or developed assets on other ownerships. Managing wildfire risk in multijurisdictional landscapes has recently become a centerpiece of wildfire strategic planning, legislation, and risk research. However, important empirical knowledge gaps remain regarding cross-boundary fire activity in the western US. Here, we use lands administered by the US Forest Service as a study system to assess the causes, ignition locations, structure loss, and social and biophysical factors associated with cross-boundary fire activity over the past three decades. Results show that cross-boundary fires were primarily caused by humans on private lands. Cross-boundary ignitions, area burned, and structure losses were concentrated in California. Public lands managed by the US Forest Service were not the primary source of fires that destroyed the most structures. Cross-boundary fire activity peaked in moderately populated landscapes with dense road and jurisdictional boundary networks. Fire transmission is increasing, and evidence suggests it will continue to do so in the future. Effective crossboundary fire risk management will require cross-scale risk co-governance. Focusing on minimizing damages to high-value assets may be more effective than excluding fire from multijurisdictional landscapes.Item Open Access Prescribed fire is associated with increased floral richness and promotes short-term increases in bee biodiversity in the ponderosa pine forest of the southern Rocky Mountains(Colorado State University. Libraries, 2023-02-19) Gelles, Ryleigh V., author; Davis, Thomas S., author; Barrett, Kevin J., author1. Managed low-severity surface fires are frequently implemented in efforts to restore disturbance processes to forests of North America; although the effects of managed fire on forest structure are well-studied, few studies investigate whether these disturbances cascade to impact pollinator communities. 2. We analysed bee-habitat relationships in fire-treated (1- and 3-years post-treatment) and non-treated ponderosa pine stands in Colorado to test wild bee population responses. 3. Observed bee richness and α-diversity were highest in stands 1-year post-fire and had more Anthophora, Bombus, Osmia and Lasioglossum spp. in comparison to 3-year postfire and non-treated stands. Bee functional groups were responsive to treatments, with more below-ground nesting taxa present in stands 3 years post-fire. 4. Floral richness was the highest mid-growing season (June, July) and within 1-year post-fire stands. 5. A model analysing the effects of foraging and nesting habitat variation on bee assemblages indicated positive association between floral richness and bee α-diversity, but negative relationships with stand basal area. Nesting habitat was not associated with variation in bee assemblages. 6. We conclude that managed fire has positive short-term effects on bee biodiversity that are likely mediated by floral richness. However, these effects were not detectable by 3 years post-treatment in the southern Rocky Mountain region.Item Open Access Building loss in WUI disasters: evaluating the core components of the wildland–urban interface definition(Colorado State University. Libraries, 2020-12-20) Caggiano, Michael D., author; Hawbaker, Todd J., author; Gannon, Benjamin M., author; Hoffman, Chad M., authorAccurate maps of the wildland–urban interface (WUI) are critical for the development of effective land management policies, conducting risk assessments, and the mitigation of wildfire risk. Most WUI maps identify areas at risk from wildfire by overlaying coarse-scale housing data with land cover or vegetation data. However, it is unclear how well the current WUI mapping methods capture the patterns of building loss. We quantified the building loss in WUI disasters, and then compared how well census-based and point-based WUI maps captured the building loss. We examined the building loss in both WUI and non-WUI land-use types, and in relation to the core components of the United States Federal Register WUI definition: housing density, vegetation cover, and proximity to large patches of wildland vegetation. We used building location data from 70 large fires in the conterminous United States, which cumulatively destroyed 54,000 buildings from 2000 through to 2018. We found that: (1) 86% and 97% of the building loss occurred in areas designated as WUI using the census-based and point-based methods, respectively; (2) 95% and 100% of all of the losses occurred within 100 m and 850 m of wildland vegetation, respectively; and (3) WUI components were the most predictive of building loss when measured at fine scales.Item Open Access Social outcomes of community-based rangeland management in Mongolian steppe ecosystems(Colorado State University. Libraries, 2016-08) Ulambayar, Tungalag, author; Fernández-Giménez, María E., author; Baival, Batkhishig, author; Batjav, Batbuyan, authorCommunity-based rangeland management (CBRM) has been promoted as a promising option for achieving both rangeland conservation and community well-being. However, research on its effectiveness is limited, and the reported outcomes are mixed, especially with regard to socioeconomic outcomes. We measured social outcomes of CBRM in Mongolia by comparing 77 formally organized pastoral groups with 65 traditional herder neighborhoods across four ecological zones. We used household surveys, focus groups, and interviews to measure livelihoods, social capital, and management behavior. Members of CBRM groups were significantly more proactive in addressing resource management issues and used more traditional and innovative rangeland management practices than non-CBRM herders. However, the group types did not differ in social capital or on most livelihood measures. Our results demonstrate that formal CBRM is strongly associated with herder behavior, but calls for consideration of how to reach livelihood outcomes, a key incentive for community-based conservation.Item Open Access Adaptive grazing management for multiple ecosystem goods and services: does it enhance effective decision-making?(Colorado State University. Libraries, 2016) Wilmer, Hailey, author; Fernandez-Gimenez, Maria E. author; Derner, Justin D., author; Briske, David D., author; Augustine, David J., author; Porensky, Lauren M., author; Tate, Kenneth W., author; Roche, Leslie M., authorItem Open Access Rosa and the pine/Rosa y el pino(Colorado State University. Libraries, 2025) Holmes, Maia, author; Peirce, Erika, illustrator; Fulladolsa, Ana Cristina, translator; Colorado State University, publisherFollow the story of Rosa, the mountain pine beetle, as she goes through her life cycle in the forests of the Rocky Mountains. Readers will learn all about how mountain pine beetles find pine trees to lay their eggs and how they serve as an important part in the ecosystem. Written and illustrated by entomologists (insect scientists) and translated by a plant pathologist (plant disease scientist).Item Open Access Watershed analysis of the Little South Fork of the Cache la Poudre River, Larimer County, Colorado(Colorado State University. Libraries, 1962) Colorado State University. Watershed Management Unit, author; Johnson, Kendall L., editorItem Open Access Height growth in relation to crown size in juvenile lodgepole pine(Colorado State University. Libraries, 1967-10) Mogren, Edwin W., author; Colorado State University, College of Forestry and Range Management, publisherItem Open Access A geospatial framework to assess fireline effectiveness for large wildfires in the western USA(Colorado State University. Libraries, 2020-08-18) Gannon, Benjamin M., author; Thompson, Matthew P., author; Deming, Kira Z., author; Bayham, Jude, author; Wei, Yu, author; O'Connor, Christopher D., authorQuantifying fireline effectiveness (FLE) is essential to evaluate the efficiency of large wildfire management strategies to foster institutional learning and improvement in fire management organizations. FLE performance metrics for incident-level evaluation have been developed and applied to a small set of wildfires, but there is a need to understand how widely they vary across incidents to progress towards targets or standards for performance evaluation. Recent efforts to archive spatially explicit fireline records from large wildfires facilitate the application of these metrics to a broad sample of wildfires in different environments. We evaluated fireline outcomes (burned over, held, not engaged) and analyzed incident-scale FLE for 33 large wildfires in the western USA from the 2017 and 2018 fire seasons. FLE performance metrics varied widely across wildfires and often aligned with factors that influence suppression strategy. We propose a performance evaluation framework based on both the held to engaged fireline ratio and the total fireline to perimeter ratio. These two metrics capture whether fireline was placed in locations with high probability of engaging with the wildfire and holding and the relative level of investment in containment compared to wildfire growth. We also identify future research directions to improve understanding of decision quality in a risk-based framework.Item Open Access Prototyping a geospatial Atlas for wildfire planning and management(Colorado State University. Libraries, 2020-08-20) Thompson, Matthew P., author; Gannon, Benjamin M., author; Caggiano, Michael D., author; O’Connor, Christopher D., author; Brough, April, author; Gilbertson-Day, Julie W., author; Scott, Joe H., author; Forests, publisherWildland fire managers are increasingly embracing risk management principles by being more anticipatory, proactive, and “engaging the fire before it starts”. This entails investing in pre-season, cross-boundary, strategic fire response planning with partners and stakeholders to build a shared understanding of wildfire risks and management opportunities. A key innovation in planning is the development of potential operational delineations (PODs), i.e., spatial management units whose boundaries are relevant to fire containment operations (e.g., roads, ridgetops, and fuel transitions), and within which potential fire consequences, suppression opportunities/challenges, and strategic response objectives can be analyzed to inform fire management decision making. As of the summer of 2020, PODs have been developed on more than forty landscapes encompassing National Forest System lands across the western USA, providing utility for planning, communication, mitigation prioritization, and incident response strategy development. Here, we review development of a decision support tool—a POD Atlas—intended to facilitate cross-boundary, collaborative strategic wildfire planning and management by providing high-resolution information on landscape conditions, values at risk, and fire management resource needs for individual PODs. With the atlas, users can rapidly access and assimilate multiple forms of pre-loaded data and analytics in a customizable manner. We prototyped and operationalized this tool in concert with, and for use by, fire managers on several National Forests in the Southern Rocky Mountains of the USA. We present examples, discuss real-world use cases, and highlight opportunities for continued decision support improvement.Item Open Access Mitigating source water risks with improved wildfire containment(Colorado State University. Libraries, 2020-08-21) Gannon, Benjamin M., author; Wei, Yu, author; Thompson, Matthew P., author; Fire, publisherIn many fire-prone watersheds, wildfire threatens surface drinking water sources with eroded contaminants. We evaluated the potential to mitigate the risk of degraded water quality by limiting fire sizes and contaminant loads with a containment network of manager-developed Potential fire Operational Delineations (PODs) using wildfire risk transmission methods to partition the effects of stochastically simulated wildfires to within and out of POD burning. We assessed water impacts with two metrics—total sediment load and frequency of exceeding turbidity limits for treatment—using a linked fire-erosion-sediment transport model. We found that improved fire containment could reduce wildfire risk to the water source by 13.0 to 55.3% depending on impact measure and post-fire rainfall. Containment based on PODs had greater potential in our study system to reduce total sediment load than it did to avoid degraded water quality. After containment, most turbidity exceedances originated from less than 20% of the PODs, suggesting strategic investments to further compartmentalize these areas could improve the effectiveness of the containment network. Similarly, risk transmission varied across the POD boundaries, indicating that efforts to increase containment probability with fuels reduction would have a disproportionate effect if prioritized along high transmission boundaries.Item Open Access Bark beetle outbreak enhances biodiversity and foraging habitat of native bees in alpine landscapes of the southern Rocky Mountains(Colorado State University. Libraries, 2020-10-02) Davis, Thomas Seth, author; Rhoades, Paul R., author; Mann, Andrew J., author; Griswold, Terry, author; Scientific Reports, publisherLandscape-scale bark beetle outbreaks alter forest structure with direct and indirect effects on plants and animals in forest ecosystems. Using alpine spruce forest and a native bee community as a study system, we tested how tree mortality from bark beetles impacts bee foraging habitats and populations. Bees were collected across the growing season (early-, middle-, and late-season) for two years using passive trapping methods, and collections were used to analyze patterns in species abundances and diversity. Three important findings emerged: (1) forest stands that were post-outbreak had 62% higher floral density and 68% more floral species during peak bloom, respectively, than non-affected stands; (2) bee captures were highest early-season (June) and were not strongly affected by bark beetle outbreak; however, mean number of bee species and Shannon–Weiner diversity were significantly higher in post-outbreak stands and this effect was pronounced early in the growing season. Corresponding analysis of β-diversity indicated higher accumulation of bee biodiversity in post-outbreak stands and a turnover in the ratio of Bombus: Osmia; (3) bee captures were linked to variation in foraging habitat, but number of bee species and diversity were more strongly predicted by forest structure. Our results provide evidence of increased alpine bee biodiversity in post-outbreak stands and increased availability of floral resources. We conclude that large-scale disturbance from bark beetle outbreaks may drive shifts in pollinator community composition through cascading effects on floral resources, mediated via mortality of overstory trees.Item Open Access Relationships between groundwater use, water table, and recovery of willow on Yellowstone's northern range(Colorado State University. Libraries, 2011) Johnston, Danielle B., author; Cooper, David J., author; Hobbs, N. Thompson, author; Ecological Society of America, publisherExcessive levels of herbivory, incision of stream channels, and climate warming are believed to be responsible for the decline of woody deciduous plants in riparian zones in western North America, declines that are likely to be associated with diminished biological diversity. In the northern elk wintering range of Yellowstone National Park, USA, over browsing by elk (Cervus elaphus), lowered water tables resulting from stream incision, and loss of activity by beaver (Castor canadensis) have been implicated in the decline of willow (Salix sp.) communities. Reducing elk browsing appears sufficient for willow recovery in some areas, but where water table changes have been dramatic, recovery may be slow or absent. The importance of water table changes is disputed because experimental results demonstrate water table limitations, but water table depth has failed to explain variation in willow height at landscape scales. One explanation for this apparent discrepancy is that willows that have survived intensive browsing by elk have maintained access to groundwater despite declining water tables. Using stable isotopes of water, we examined the relationships between groundwater use, water table depth, and height of heavily browsed Salix geyeriana. Salix geyeriana groundwater use varied from 30% to 80%, and was higher later in the growing season, when soil water was less available and shoot water potentials were lower. Late season groundwater use explained 26% of the variation in total height of willows (P = 0.002), with taller plants using more groundwater. Water table depth explained only 8% of the variability in total height (P=0.051), with shorter willows having deeper water table depths. Groundwater use and water table depth were uncorrelated. Height recovery following a winter of heavy browsing was related to groundwater use, but not groundwater depth. We suggest that access to deeper water sources alleviates late season water stress, allowing for more rapid height recovery and higher total plant height. Variability in groundwater access may account for variability in height recovery at landscape scales.Item Open Access Hydrologic regime and herbivory stabilize an alternative state in Yellowstone National Park(Colorado State University. Libraries, 2007) Wolf, Evan C., author; Cooper, David J., author; Hobbs, N. Thompson, author; Ecological Society of America, publisherA decline in the stature and abundance of willows during the 20th century occurred throughout the northern range of Yellowstone National Park, where riparian woody-plant communities are key components in multiple-trophic-level interactions. The potential causes of willow decline include climate change, increased elk browsing coincident with the loss of an apex predator, the gray wolf, and an absence of habitat engineering by beavers. The goal of this study was to determine the spatial and temporal patterns of willow establishment through the 20th century and to identify causal processes. Sampled willows established from 1917 to 1999 and contained far fewer young individuals than was predicted from a modeled stable willow population, indicating reduced establishment during recent decades. Two hydrologically distinct willow establishment environments were identified: fine grained beaver pond sediments and coarse-grained alluvium. Willows established on beaver pond sediment earlier in time, higher on floodplain surfaces, and farther from the current stream channel than did willows on alluvial sediment. Significant linear declines from the 1940s to the 1990s in alluvial willow establishment elevation and lateral distance from the stream channel resulted in a much reduced area of alluvial willow establishment. Willow establishment was not well correlated with climate-driven hydrologic variables, but the trends were consistent with the effects of stream channel incision initiated in ca. 1950, 20-30 years after beaver dam abandonment. Radiocarbon dates and floodplain stratigraphy indicate that stream incision of the present magnitude may be unprecedented in the past two millennia. We propose that hydrologic changes, stemming from competitive exclusion of beaver by elk over browsing, caused the landscape to transition from a historical beaver-pond and willow mosaic state to its current alternative stable state where active beaver dams and many willow stands are absent. Because of hydrologic changes in streams, a rapid return to the historical state may not occur by reduction of elk browsing alone. Management intervention to restore the historical hydrologic regime may be necessary to recover willows and beavers across the landscape.Item Open Access Water tables constrain height recovery of willow on Yellowstone's northern range(Colorado State University. Libraries, 2008) Bilyeu, Danielle M., author; Cooper, David J., author; Hobbs, N. Thompson, author; Ecological Society of America, publisherExcessive levels of herbivory may disturb ecosystems in ways that persist even when herbivory is moderated. These persistent changes may complicate efforts to restore ecosystems affected by herbivores. Willow (Salix spp.) communities within the northern range in Yellowstone National Park have been eliminated or degraded in many riparian areas by excessive elk (Cervus elaphus L.) browsing. Elk browsing of riparian willows appears to have diminished following the reintroduction of wolves (Canis lupis L.), but it remains uncertain whether reduced herbivory will restore willow communities. The direct effects of elk browsing on willows have been accompanied by indirect effects from the loss of beaver (Castorcanadensis Kuhl) activity, including incision of stream channels, erosion of fine sediments, and lower water tables near streams historically dammed by beaver. In areas where these changes have occurred, lowered water tables may suppress willow height even in the absence of elk browsing. We conducted a factorial field experiment to understand willow responses to browsing and to height of water tables. After four years of protection from elk browsing, willows with ambient water tables averaged only 106 cm in height, with negligible height gain in two of three study species during the last year of the experiment. Willows that were protected from browsing and had artificially elevated water tables averaged 147 cm in height and gained 19 cm in the last year of the experiment. In browsed plots, elevated water tables doubled height gain during a period of slightly reduced browsing pressure. We conclude that water availability mediates the rate of willow height gain and may determine whether willows grow tall enough to escape the browse zone of elk and gain resistance to future elk browsing. Consequently, in areas where long-term beaver absence has resulted in incised stream channels and low water tables, a reduction in elk browsing alone may not be sufficient for recovery of tall willow stands. Because tall willow stems are important elements of habitat for beaver, mitigating water table decline may be necessary in these areas to promote recovery of historical willow–beaver mutualisms.Item Open Access Carbon dynamics and estimates of primary production by harvest, 14C dilution, and 14C turnover(Colorado State University. Libraries, 1992-04) Lauenroth, W. K., author; Milchunas, D. G., author; Ecological Society of America, publisherLarge plots of native shortgrass steppe were labeled with 14C to assess short-term patterns of carbon allocation and the long-term process of herbivory, death, and decomposition, and to compare estimates of net aboveground, crown, and root primary production using 14C dilution, 14C turnover, and traditional harvest methods. Stabilization of labile 14C via translocation, incorporation into structural tissue, and respiration and exudation required one growing season. Exudation was 17% of plant 14C after stabilization. Estimates of turnover time for leaves, crowns, and roots by 14C turnover were 3, 5, and 8 yr, respectively, yielding estimates of belowground production that were much lower than previously thought. Estimates of aboveground production by 14C turnover were close to those obtained by harvest of peak-standing crop, but lower than reported values obtained by harvest maxima-minima. Estimates of root production by harvest maxima-minima were zero in 2 of 4 yr. 14C turnover appeared to provide reliable estimates of aboveground, crown, and root production. In contrast to reliable estimates by 14C turnover, 14C dilution estimates of root production were anomalous. The anomalous estimates were attributed to a nonuniform labeling of tissue age classes resulting in differential decomposition/herbivory of 14C:12C through time, as well as movement and loss of labile 14C through the first growing season. Isotope-dilution methodologies may be unreliable for any estimate of pool turnover when the labeling period is not as long as pool-turnover time. Problems and biases associated with traditional harvest maxima-minima methods of estimating aboveground primary production are well known, but are greatly exacerbated when the method is used to estimate root production. Estimates of root production by 14C dilution were unrealistic. 14C turnover methodology provided reliable estimates of production in this community.Item Open Access CO2 enhances productivity, alters species composition, and reduces digestibility of Shortgrass Steppe vegetation(Colorado State University. Libraries, 2004-01) Morgan, Jack A., author; Mosier, Arvin R., author; Milchunas, Daniel G., author; LeCain, Daniel R., author; Nelson, Jim A., author; Parton, William J., author; Ecological Society of America, publisherThe impact of increasing atmospheric CO2 concentrations has been studied in a number of field experiments, but little information exists on the response of semiarid rangelands to CO2, or on the consequences for forage quality. This study was initiated to study the CO2 response of the shortgrass steppe, an important semiarid grassland on the western edge of the North American Great Plains, used extensively for livestock grazing. The experiment was conducted for five years on native vegetation at the USDA-ARS Central Plains Experimental Range in northeastern Colorado, USA. Three perennial grasses dominate the study site, Bouteloua gracilis, a C4 grass, and two C3 grasses, Pascopyrum smithii and Stipa comata. The three species comprise 88% of the aboveground phytomass. To evaluate responses to rising atmospheric CO2, we utilized six open-top chambers, three with ambient air and three with air CO2 enriched to 720 mmol/mol, as well as three unchambered controls. We found that elevated CO2 enhanced production of the shortgrass steppe throughout the study, with 41% greater aboveground phytomass harvested annually in elevated compared to ambient plots. The CO2-induced production response was driven by a single species, S. comata, and was due in part to greater seedling recruitment. The result was species movement toward a composition more typical of the mixed-grass prairie. Growth under elevated CO2 reduced the digestibility of all three dominant grass species. Digestibility was also lowest in the only species to exhibit a CO2-induced production enhancement, S. comata. The results suggest that rising atmospheric CO2 may enhance production of lower quality forage and a species composition shift toward a greater C3 component.