Cynthia Susan Brown

• Ph.D.
• Professor at Colorado State University

Local adaptation may facilitate range expansion during invasions, but the mechanisms promoting destructive invasions remain unclear. Cheatgrass ( Bromus tectorum ), native to Eurasia and Africa, has invaded globally, with particularly severe impacts in western North America. We sequenced 307 genotypes and conducted controlled experiments. We found...

Purpose The sensitivity of wildland plants to temperature can be directly measured using experimental manipulations of temperature in situ. We show that soil surface temperature and plant density (per square meter) have a significant impact on the germination, growth, and phenology of Bromus tectorum L., cheatgrass, a short-statured invasive winter...

Sustainable ecosystem management relies on our ability to predict changes in plant diversity and to understand the underlying mechanisms. Empirical evidence demonstrates that abundance‐ and functional‐based processes simultaneously explain the loss of plant diversity in response to human activities. Recently, a novel indicator based on percent cove...

Ecological models predict that the effects of mammalian herbivore exclusion on plant diversity depend on resource availability and plant exposure to ungulate grazing over evolutionary time. Using an experiment replicated in 57 grasslands on six continents, with contrasting evolutionary history of grazing, we tested how resources (mean annual precip...

Significance Predicting the effects of anthropogenic nutrient enrichment on plant communities is critical for managing implications for biodiversity and ecosystem services. Plant functional types that fix atmospheric nitrogen (e.g., legumes) may be at particular risk of nutrient-driven global decline, yet global-scale evidence is lacking. Using an...

Numerous functional traits have been identified as key contributors to plant performance under drought. However, many of these traits, specifically root traits, are rarely considered in the development of native plant cultivars. In this study we assessed whether cultivars of the perennial grass, Elymus trachycaulus (Slender wheatgrass) developed fo...

Abstract Understanding the combined effects of drought and invasive species on plant community development and soil moisture could provide valuable insight into the mechanisms hindering successful native plant establishment in dryland restoration projects. We implemented a re‐vegetation experiment at two sites in Colorado, USA (one each in the West...

Aims Although leaf and root traits may change considerably throughout plant development, ontogenetic variation is rarely considered in trait-based ecology. Studies focused on how morphological root traits change throughout ontogeny are especially rare. Our objectives were to determine how ontogeny influences seedling traits to inform trait selectio...

A foundational goal of trait‐based ecology, including trait‐based restoration, is to link specific traits to community assembly, biodiversity, and ecosystem function. Despite a growing awareness of the importance of belowground traits for ecological processes, a synthesis of how root traits can inform restoration of terrestrial plant communities is...

Soil nitrogen (N) availability is critical for grassland functioning. However, human activities have increased the supply of biologically‐limiting nutrients, and changed the density and identity of mammalian herbivores. These anthropogenic changes may alter net soil N mineralization (soil net Nmin), i.e., the net balance between N mineralization an...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Microbial processing of aggregate‐unprotected organic matter inputs is key for soil fertility, long‐term ecosystem carbon and nutrient sequestration and sustainable agriculture. We investigated the effects of adding multiple nutrients (nitrogen, phosphorus and potassium plus nine essential macro‐ and micro‐nutrients) on decomposition and biochemica...

Water‐holding soil amendments such as super‐absorbent polymer (SAP) may improve native species establishment in restoration but may also interact with precipitation or invasive species such as Bromus tectorum L. (cheatgrass or downy brome) to influence re‐vegetation outcomes. We implemented an experiment at two sites in Colorado, USA in which we in...

Anthropogenic activities are increasing nutrient inputs to ecosystems worldwide, with consequences for global carbon and nutrient cycles. Recent meta-analyses show that aboveground primary production is often co-limited by multiple nutrients; however, little is known about how root production responds to changes in nutrient availability. At twenty-...

Soil nitrogen mineralisation (Nmin), the conversion of organic into inorganic N, is important for productivity and nutrient cycling. The balance between mineralisation and immobilisation (net Nmin) varies with soil properties and climate. However, because most global-scale assessments of net Nmin are laboratory-based, its regulation under field-con...

Predicting changes in plant diversity in response to human activities represents one of the major challenges facing ecologists and land managers striving for sustainable ecosystem management. Classical field studies have emphasized the importance of community primary productivity in regulating changes in plant species richness. However, experimenta...

Leaf traits are frequently measured in ecology to provide a ‘common currency’ for predicting how anthropogenic pressures impact ecosystem function. Here, we test whether leaf traits consistently respond to experimental treatments across 27 globally distributed grassland sites across 4 continents. We find that specific leaf area (leaf area per unit...

Investments in urban agriculture (UA) initiatives have been increasing in the United States, but the costs and benefits to society are poorly understood. Urban agriculture can link socioeconomic and health systems, support education and societal engagement, and contribute to a range of conservation goals, including nutrient recycling and biodiversi...

Evaluating the conditions where a species can persist is an important question in ecology both to understand tolerances of organisms and to predict distributions across landscapes. Presence data combined with background or pseudo-absence locations are commonly used with species distribution modeling to develop these relationships. However, there is...

Given the high cost of restoration and the underlying assumption that reducing annual grass abundance is a necessary precursor to rangeland restoration in the Intermountain West, United States, we sought to identify limitations and strengths of annual grass control methods and refine future management strategies. We systematically reviewed all publ...

Accurate and reliable predictions of invasive species distributions are urgently needed by land managers for developing management plans and monitoring new potential areas of establishment. Presence-only species distribution models are commonly used in these evaluations, however they are rarely tested with independent data over time or compared wit...

Within a species, the distance travelled by a particular diaspore depends on its morphology. In Poaceae, the presence of terminal sterile florets can lead to diaspore heteromorphism, which may influence dispersal. We tested the hypothesis that the presence of sterile florets favored dispersal in Bromus tectorum L., an invasive grass in the Western...

Directing plant establishment after disturbance by manipulation of C:N ratios in the topsoil with compost, mulch, and synthetic polymers. Treatments were applied in all pairwise combinations, with compost+mulch most clearly resulting in highest native species density and cover. Forb cover was higher in compost and bare ground treatments. Invasive c...

Aboveground net primary production (ANPP) is a key integrator of C uptake and energy flow in many terrestrial ecosystems. As such, ecologists have long sought to understand the factors driving variation in this important ecosystem process. Although total annual precipitation has been shown to be a strong predictor of ANPP in grasslands across broad...

Fraser et al. (Reports, 17 July 2015, p. 302) report a unimodal relationship between productivity and species richness at regional and global scales, which they contrast with the results of Adler et al. (Reports, 23 September 2011, p. 1750). However, both data sets, when analyzed correctly, show clearly and consistently that productivity is a poor...

Exotic annual Bromus species are widely recognized for their potential to invade, dominate, and alter the structure and function of ecosystems. In this chapter, we summarize the invasion potential, ecosystem threats, and management strategies for different Bromus species within each of five ecoregions of the western United States. We characterize i...

The factors that determine plant community resistance to exotic annual Bromus species ( Bromus hereafter) are diverse and context specific. They are influenced by the environmental characteristics and attributes of the community, the traits of Bromus species, and the direct and indirect interactions of Bromus with the plant community. Environmental...

Invasive annual grass research and management in arid and semiarid ecosystems of the Western United States (USA) have historically focused on reducing weed abundance as opposed to ecosystem restoration, which addresses the underlying processes responsible for their persistence. Given the current impact of invasive annual grasses and their continued...

The spread and impacts of exotic species are unambiguous, global threats to many ecosystems. A prominent example is the suite of annual grasses in the Bromus genus (Bromus hereafter) that originate from Europe and Eurasia but have invaded or are invading large areas of the Western USA. This book brings a diverse, multidisciplinary group of authors...

Bromus (L.) species are cool-season grasses of temperate regions and tropical high elevations. Some species in the genus Bromus have been widely introduced into new areas of the globe and are invasive in the Western United States, while others occur only in their native ranges. We developed a database with information about traits of Bromus species...

Invasions by exotic grasses, particularly annuals, rank among the most extensive and intensive ways that humans are contributing to the transformation of the earth’s surface. The problem is particularly notable with a suite of exotic grasses in the Bromus genus in the arid and semiarid regions that dominate the western United States, which extend f...

The spread and impacts of exotic species are unambiguous, global threats to many ecosystems. A prominent example is the suite of annual grasses in the Bromus genus ( Bromus hereafter) that originate from Europe and Eurasia but have invaded or are invading large areas of the Western USA. This book brings a diverse, multidisciplinary group of authors...

Exotic species dominate many communities; however the functional significance of species’ biogeographic origin remains highly contentious. This debate is fuelled in part by the lack of globally replicated, systematic data assessing the relationship between species provenance, function and response to perturbations. We examined the abundance of nati...

This report characterizes ecological management impacts on species diversity over time by the National Park Service in montane ecosystems. There are restoration, invasive, and species-specific studies conducted mostly on a 3-5 year timeline. Some studies included soil sampling but most were focused on above-ground biodiversity. All work was advised...

National Parks are hallmarks of ecosystem preservation in the United States. The introduction of alien invasive plant species threatens protection of these areas. Bromus tectorum L. (commonly called downy brome or cheatgrass), which is found in Rocky Mountain National Park (hereafter, the Park), Colorado, USA, has been implicated in early spring co...

To meet the sustainability challenges of the future, we need leaders who are trained to work well in diverse, multidisciplinary teams and a populace that understands the biophysical and socioeconomic challenges facing humanity and how to meet the needs of its diverse stakeholders. With a goal of increasing climate literacy amongst college students,...

Background/Question/Methods Disturbance along roadsides leads to changes in resource availability, which alters native and exotic plant germination and establishment. In Rocky Mountain National Park (RMNP), 23 acres of roadsides were hydro-seeded with native grasses and forbs after road realignment and widening. We monitored post-construction pla...

Normal seed germination of native herbaceous species can be reduced by high concentrations of deicer products and their constituent salts. Chloride salts are commonly used during the winter months in temperate climates to remove ice and snow. Although these products greatly improve driving conditions, they can have detrimental effects on the vegeta...

Human alterations to nutrient cycles1, 2 and herbivore communities3, 4, 5, 6, 7 are affecting global biodiversity dramatically2. Ecological theory predicts these changes should be strongly counteractive: nutrient addition drives plant species loss through intensified competition for light, whereas herbivores prevent competitive exclusion by increas...

The success of invasive species has been explained by two contrasting but non-exclusive views: (i) intrinsic factors make some species inherently good invaders; (ii) species become invasive as a result of extrinsic eco-logical and genetic influences such as release from natural enemies, hybridization or other novel ecological and evolutionary inter...

Alien grass invasions in arid and semi-arid ecosystems are resulting in grass–fire cycles and ecosystem-level transformations that severely diminish ecosystem services. Our capacity to address the rapid and complex changes occurring in these ecosystems can be enhanced by developing an understanding of the environmental factors and ecosystem attribu...

Successful management of downy brome (also known as cheatgrass) requires understanding land managers' perceptions and decisions about whether to invest in its control. We investigated ranchers' and natural resource professionals' (NRPs) perceptions and knowledge about downy brome ecology and its impacts, their current downy brome management practic...

Background / Purpose: We developed a database, populated it with data for over 150 species of Bromus grasses and and used the data to search for patterns of invasiveness. We defined invasiveness as wide distribution outside of the native range combined with listing as a crop weed, ruderal weed, or weed in natural habitats. Main conclusion: Tax...

Invasions have increased the size of regional species pools, but are typically assumed to reduce native diversity. However, global-scale tests of this assumption have been elusive because of the focus on exotic species richness, rather than relative abundance. This is problematic because low invader richness can indicate invasion resistance by the...

Background/Question/Methods Cheatgrass (Bromus tectorum) is an invasive annual grass in the western United States that is most problematic in the Great Basin and Columbia Plateau. The species invades perennial sagebrush shrublands and increases fire frequency. Recent research highlighting the difficulty in modeling this generalist species suggest...

Background/Question/Methods National parks are the hallmarks of ecosystem preservation in the United States. The introduction of non-native invasive species into these areas threatens natural ecosystems, altering their structure and functioning. Species distribution models (SDMs) are commonly used for evaluating the potential spread of invasive s...

Background/Question/Methods Bromus tectorum L. (hereafter Bromus) is a widespread, invasive annual grass that has greatly impacted ecosystems of the western U.S., especially in the Great Basin. Bromus has been well-studied in this winter-wet area, but less is known about its ecology in the summer-wet Southern Rocky Mountain region, where it is an...

Background/Question/Methods Climate and grazing are both strong drivers of grassland community structure and function. We know that plant communities can be very sensitive to temporal changes in precipitation and temperature, but little is known about how seasonality interacts with grazing. In light of climate models that predict seasonal changes...

Cheatgrass Management, noxious weed management

Background/Question/Methods Bromus tectorum L. (common names downy brome or cheatgrass) is a winter annual grass that was introduced into the United States from Eurasia in the late 19th century, and has since altered the structure and function of native and agro- ecosystems throughout the western United States. In Rocky Mountain National Park (RM...

Background/Question/Methods Cheatgrass (Bromus tectorum), a winter annual grass introduced from Eurasia, has invaded much of the Western United States over the last century. More recently, cheatgrass has become a threat to the montane and subalpine plant communities and ecosystems of Rocky Mountain National Park (RMNP). Cheatgrass aggressively in...

Russian olive (Elaeagnus angustifolia L.), a Eurasian tree now abundant along rivers in western North America, has an apparent southern distribution limit running through southern California, Arizona, New Mexico and Texas. We used field observations to precisely define this limit in relation to temperature variables. We then investigated whether la...

Particularly well-known among the many impacts of the invasive annual grass downy brome (Bromus tectorum, Poaceae) is its ability to alter fire cycles and increase in abundance after fire. However, little is known about how fire influences B. tectorum dispersal. We quantified fire effects on B. tectorum dispersal using three recently burned areas i...

Pan et al. claim that our results actually support a strong linear positive relationship between productivity and richness, whereas Fridley et al. contend that the data support a strong humped relationship. These responses illustrate how preoccupation with bivariate patterns distracts from a deeper understanding of the multivariate mechanisms that...

For more than 30 years, the relationship between net primary productivity and species richness has generated intense debate in ecology about the processes regulating local diversity. The original view, which is still widely accepted, holds that the relationship is hump-shaped, with richness first rising and then declining with increasing productivi...

Downy brome (Bromus tectorum L.), an invasive winter annual grass, may be increasing in extent and abundance at high elevations in the western United States. This would pose a great threat to high-elevation plant communities and resources. However, data to track this species in high-elevation environments are limited. To address changes in the dist...

Many ecosystems worldwide are dominated by introduced plant species, leading to loss of biodiversity and ecosystem function. A common but rarely tested assumption is that these plants are more abundant in introduced vs. native communities, because ecological or evolutionary-based shifts in populations underlie invasion success. Here, data for 26 he...

In temperate grasslands, spatial and intra-annual variability in the activity of plants and microbes are structured by patterns in the precipitation regime. While the effects of total annual precipitation have been well-explored, the ecological dynamics associated with individual precipitation events have not. Rainfall events induce a short-term pu...

Dispersal is a critically important process in the spread of invasive plants. Although knowledge of dispersal will be crucial to preventing the spread of invasive plants, little research has been performed within this context. Many important invasive or agricultural weeds disperse their seeds via tumbling, yet only one previously published paper in...

Background/Question/Methods Primary production in herbaceous systems is influenced by soil nutrient availability. Generally primary production increases with nutrient additions across many herbaceous systems. However the strength of this response can vary greatly across systems and the mechanisms driving this response remain unclear. We examined...

Background/Question/Methods Bromus tectorum (cheatgrass) is one of the most widespread invasive species in the western United States. In sagebrush steppe rangeland it alters fire frequency, soil moisture, and nutrient dynamics, decreasing the value of rangeland for wildlife and livestock and increasing costs associated with fire remediation and h...

Background/Question/Methods The introduced riparian tree Russian-olive (Eleagnus angustifolia L.) is abundant throughout the interior western United States, except in the extreme south. Russian-olive seeds generally exhibit embryonic dormancy and require a period of cold stratification. We hypothesized that insufficient cold stratification limits...

Background/Question/Methods For decades, the science of restoring damaged ecosystems has been progressing as our understanding of post-disturbance succession has improved. Many studies of natural and man-made disturbances and the stages of their recovery have been conducted in grassland ecosystems. Incorporating what has been learned from these pa...

At two field sites that differed in fertility, we investigated how species richness, functional group diversity, and species composition of constructed plant communities influenced invasion. Grassland communities were constructed to be either functionally diverse or functionally simple based on belowground resource use patterns of constituent speci...

High-impact biological invasions often involve establishment and spread in disturbed, high-resource patches followed by establishment and spread in biotically or abiotically stressful areas. Evolutionary change may be required for the second phase of invasion (establishment and spread in stressful areas) to occur. When species have low genetic dive...

In recent decades, a growing number of studies have addressed connections between ecological and evolutionary concepts in biologic invasions. These connections may be crucial for understanding the processes underlying invaders’ success. However, the extent to which scientists have worked on the integration of the ecology and evolution of invasive p...

The United States National Park Service was created to protect and make accessible to the public the nation’s most precious natural resources and cultural features for present and future generations. However, this heritage is threatened by the invasion of non-native plants, animals, and pathogens. To evaluate the scope of invasions, the USNPS has i...

Cheatgrass (Bromus tectorum L.) is an exotic annual grass that has invaded approximately 40,000,000 ha of rangelands in the United States, including montane ecosystems that are important habitats for wildlife and livestock. In addition to well-understood mechanisms by which Cheatgrass gains competitive advantage, recent studies have shown that Chea...

Background/Question/Methods The most pressing issues facing the world stem from complex interactions between humans and the environment. How will we address these multifaceted challenges in ways that will sustainably maintain ecological integrity, economic well-being and social justice at local, regional and global scales? Resolution of these chal...

Background/Question/Methods Cheatgrass (Bromus tectorum L.), an invasive winter annual grass, may be increasing in extent and abundance at high elevations in the western United States. However, data to track this species in high elevation environments are limited. To address changes in the distribution and abundance of cheatgrass, we used traditio...

Background/Question/Methods Cheatgrass (Bromus tectorum) is one of the most prolific invaders of western rangelands, increasing fire frequency, decreasing wildlife and livestock habitat value and limiting the use of prescribed fire as a management tool. Once cheatgrass becomes established, it modifies the environment to create an ecologically sta...

Categorizing species according to their functional traits, such as spatial and temporal patterns of resource use, effects on ecosystems, and responses to environmental perturbations, can facilitate successful restoration of plant communities. Functional guilds condense species lists by grouping species according to similarities in characteristics w...

It is essential that we improve our ability to predict which nonnative species will become invasive in order to prevent their introduction and spread. Past attempts to foresee invasions have met with limited success, but increased computing power, increased availability of information about exotic species, and comprehensive evaluations of invasion...

The invasive grass Bromus tectorum (cheatgrass, downy brome) has extensive ecological breadth in its introduced range, and is increasing in abundance at high elevations. As a predominantly selfing species with high potential population growth rates, it is a likely candidate for having general-purpose genotypes that facilitate its invasion into high...

Invasive plants are a common problem in the management and restoration of degraded lands in the semiarid western United States, but are often not the primary focus of restoration ecologists. Likewise, restoring native vegetation has not been a major concern of weed scientists. But trends in the literature demonstrate increasing overlap of these fie...

The invasion of 40 million hectares Of the American West by cheatgrass (Bromus tectorum L.) has caused widespread modifications in the vegetation of semi-arid ecosystems and increased the frequency of fires. In addition to well-understood mechanisms by which cheatgrass gains competitive advantage, it has been implicated in reducing arbuscular mycor...

Current invasion ecology theory predicts that disturbance will stimulate invasion by exotic plant species. Cheatgrass or Downy brome (Bromus tectorum) was surveyed in three sites near Florence, Colorado, U.S.A., immediately following Tamarisk or Saltcedar (Tamarix spp.) control and restoration activities that caused disturbance. Despite predictions...

Fire is a natural part of most forest ecosystems in the western United States, but its effects on nonnative plant invasion have only recently been studied. Also, forest managers are engaging in fuel reduction projects to lessen fire severity, often without considering potential negative ecological consequences such as nonnative plant species introd...

Reestablishing native perennial plants and reducing invasive species are pivotal for many ecological restoration projects. The interactions among plant species, arbuscular mycorrhizal fungi, and soil P availability may be critical determinants of the success of native and non-native plants in restoration and species invasions. Here we assessed myco...

A species-addition experiment showed that prairie grasslands have a structured, nonneutral assembly process in which resident species inhibit, via resource consumption, the establishment and growth of species with similar resource use patterns and in which the success of invaders decreases as diversity increases. In our experiment, species in each...

Prairie restoration is not complete without the establishment of both grasses and forbs. However, if desirable forbs and grasses are seeded simultaneously, control of broadleaf weeds is problematic. If possible, a two-step process of introducing forbs after establishing grasses would allow use of broadleaf-specific herbicides at the critical early...

Native perennial grasses were once common in Cali-fornia prairies that are now dominated by annual grasses introduced from Europe. Competition from exotics may be a principal impediment to reestablish-ment of native perennial grasses. Introduced annual grasses, such as Vulpia myuros (zorro fescue), are of-ten included with native perennial species...

Along rural roadsides of the Sacramento Valley of California, we seeded native and non-native perennial grasses to gauge their potential value in roadside vegetation management programs. In trial I (polycultures), three seeded complexes and a control (resident vegetation only) were tested. Each seeded plant complex included a different mix of peren...

It is estimated that 40,000,000 ha of rangelands in the United States, once dominated by perennial bunchgrasses and shrubs, are now infested with cheatgrass (Bromus tectorum). Its early life cycle enables cheatgrass to dominate plant communities by depleting nutrients and water in the winter and early spring months when natives are dormant, and end...

LS Means across all samples (+/-standard error). F-statistics from natural log transformation of data. Figure 3. UPGMA tree; data analyzed as subpopulations (habitats) within populations (geographic region). Low N High N Average Total Biomass (g) 0 1 2 3 4 5 6 7 High H20 Low H20 Figure 1. Interaction of Nitrogen and Water on total biomass. (p=0.022...