Edited by Tom Schweich  

Ecological Systems of Colorado

Notes:

1. ^[R3C3] Stipa comata grassland of 30-60 acres near western rim of mountain, may be partly due to effects of the 1988 fire.

Ecological Systems Recognized by the Colorado Natural Heritage System

Ecological systems are dynamic assemblages or complexes of plant and/or animal communities that 1) occur together on the landscape; 2) are tied together by similar ecological processes, underlying abiotic environmental factors or gradients; and 3) form a readily identifiable unit on the ground. These systems provide a coarser level unit than plant associations and alliances as defined under the International Vegetation Classification standard, and are more easily identified on the ground.

The descriptions and summarized viability guidelines presented here are intended to serve as a tool for conservation and management planning by providing a context for conservation and management (i.e., what systems do we have in Colorado), and by providing easy access to ranking and evaluation criteria for key ecological attributes of each system (i.e., what is the condition of our systems).

System descriptions and viability guidelines are based on materials compiled by NatureServe or developed by the Colorado Natural Heritage Program. Funding for the development of these documents was provided in part by the Bureau of Land Management, The Nature Conservancy, and the USDA Forest Service (CNHP, 2005).

Southwest Regional Gap Analysis Project (SWReGAP)

USNVC -- United States National Vegetation Classification

EcoVeg

Studies of Prairie or Foothill Ecosystems

Restoration and Effects of Attempts Thereof

Wilson, Scott D., 1989. The suppression of native prairie by alien species introduced for revegetation. Landscape and Urban Planning. 17(2), april 1989, pp. 113-119.

Abstract Natural prairie has become uncommon in North America, making the revegetation of disturbed areas by native species a desirable goal. Alien species are often introduced for revegetation because of their abilities to stabilize and nitrify soil. The objective of this study was to test whether these attributes of introduced species would allow them to promote the recovery of native vegetation. Seven treatments (six commercially-available mixtures of introduced species and an unseeded control) were applied to a randomized field experiment in disturbed mixed-grass prairie in south-west Manitoba, Canada. Sampling eight years later revealed that introduced species suppressed native vegetation. Introduced species did not aid revegetation: plots seeded with introduced species did not produce significantly higher standing crop or below-ground biomass than did unseeded plots. Unseeded plots had the lowest frequency of bare ground. Allowing prairie to revegetate without sowing introduced species produced both the highest cover of bare ground and the greatest abundance of native species.

Wilson, Scott D., and Joyce W. Belcher, 1989. Plant and Bird Communities of Native Prairie and Intoduced Eurasian Vegetation in Manitoba, Canada. Conservation Biology. 3(1), pp. 39-44, March 1989.

“… introduction of Eurasian plant species to North American prairie not only replaces the native plant community, but also produces significant changes in the species composition of a higher trophic level … ”

Abstract: Large areas of North American prairie are dominated by Eurasian plant species introduced either for range improvement or accidentally as weeds. We examined the impact of introduced plants on both native vegetation and bird communities in a mosaic of North American mixed-grass prairie and Eurasian vegetation. We established ten transects five in areas of native prairie and five in areas dominated by introduced plant species. Each transect comprised five sampling stations separated by 100 m. Vegetation was sampled in four 0.5m2 quadrats at each station. The cooers of eight of the ten most common plant species varied significantly (p < 0.05) between native and introduced vegetation. One common native plans Andropogon scoparius, was absent in introduced vegetation Singing birds were identified to species at each station on three occasions during the breeding season All bird species found were native to prairie. The total number of birds did not vary between vegetation types Two out of eight bird species, upland sandpiper and Sprague's pipit were signifcantly more abundant in native prairie than in introduced vegetation No bird species were significantly more common in introduced vegetation. A correlation matrix calculated for all bird species and the ten most abundant plant species divided the bird community into two groups. The first group (western meadow lark, upland sandpiper, Sprague's pipit, Baird's sparrow and savannah sparrow) was positively correlated with native plant species and negatively with introduced plants, while the second (vesper sparrow, clay-colored sparrow, and grasshopper sparrow) was negatively correlated with native species and positively correlated with introduced Discriminant analysis separated transects from native and Eurasian vegetation on the basis of their respective bird communities. The results illustrate that the introduction of Eurasian plant species to North American prairie not only replaces the native plant community, but also produces significant changes in the species composition of a higher trophic level.

Heidinga, Lawrence, and Scott D. Wilson, 2002. The Impact of an Invading Alien Grass (Agropyron cristatum) on Species Turnover in Native Prairie. Diversity and Distributions. 8(5), September 2002, pp 249-258.

Abstract Alien invasions typically reduce species richness of habitats, but few studies have examined their effects on species turnover, the difference in species composition between localities. Agropyron cristatum (L.) Gaertn. (crested wheat grass) has been planted on 6-10 million ha of North American prairie, and is invading native prairie. We studied the invasion of A. cristatum into native prairie by measuring species composition along a gradient from maximum to minimum A. cristatum abundance. As A. cristatum increased, the abundance of most common native species decreased, but one appeared to be unaffected (Bouteloua gracilis (H.B.K.) Lag.), and another (Poa sandbergii Vasey) increased. The effect of A. cristatum on species turnover was investigated by examining species-area curves for areas from 0.5 m2 to 8.0 m2. Species diversity was reduced by 35% at high A. cristatum abundances at all areas. A. cristatum reduced the intercept of the species-area curve, but not the slope, suggesting that A. cristatum affected species turnover proportionally in all areas and habitats. This unusual result may indicate a homogeneous environment where species are distributed randomly. A. cristatum produced almost twice as many seeds as all native grasses combined. The number of seeds collected of native grasses and A. cristatum was highly correlated with the number of seed heads immediately nearby, but not with transect position. This suggests most seeds were dispersed over distances less than 5 m. In sum, the invasion of native prairie by A. cristatum might be related to high rates of seed production, and has the effect of decreasing species turnover by reducing the intercept of the species-area curve.

Salesman, Jessica Bolwahn, and Meredith Thomsen, 2011. Smooth Brome (Bromus inermis) in Tallgrass Prairies: A Review of Control Methods and Future Research Directions. Ecological Restoration. 29(4), December 2011, pp. 374-381.

Abstract. Smooth brome (Bromus inermis) is a cool-season rhizomatous grass of Eurasian origin that has escaped intentional plantings and spread widely in natural areas. A large body of work exists regarding smooth brome's biology and response to conservation management strategies designed to reduce its competitive effects on native prairie species, particularly for the tallgrass prairies of North America. Here we summarize that literature to improve restoration practice. In tallgrass prairie, smooth brome benefits from the early start of its growing season and its rhizomatous growth form, making it a strong competitor against native warm-season grasses. Late-spring burns timed to target smooth brome when root reserves are at their lowest have shown promise as a control strategy. Uncertainty remains, however, about the relative efficacy of fire, herbicide, mowing, or grazing to accomplish late-spring defoliation, the effect of repeated treatments, and the potential benefits of treatment combinations. The responses of resident or seeded natives to brome control treatments and/or the resulting decreases in brome cover also remain largely unexamined. Research focused on the questions we highlight would reduce costs associated with the control of smooth brome and increase confidence in the outcomes of restoration efforts.

Grant, Todd A., Bridgette Flanders-Wanner, Terry L. Shaffer, Robert K. Murphy, and Gregg A. Knutsen, 2009. An Emerging Crisis across Northern Prairie Refuges: Prevalence of Invasive Plants and a Plan for Adaptive Management. Ecological Restoration. 27(1), March 2009, pp. 58-65.

Abstract In the northern Great Plains, native prairies managed by the U.S. Fish and Wildlife Service (Service) can be pivotal in conservation of North America's biological diversity. From 2002 to 2006, we surveyed 7,338 belt transects to assess the general composition of mixed-grass and tallgrass prairie vegetation across five "complexes" (i.e., administrative groupings) of national wildlife refuges managed by the Service in North Dakota and South Dakota. Native grasses and forbs were common (mean frequency of occurrence 47%-54%) on two complexes but uncommon (4%-13%) on two others. Conversely, an introduced species of grass, smooth brome (Bromus inermis), accounted for 45% to 49% of vegetation on two complexes and another species, Kentucky bluegrass (Poa pratensis) accounted for 27% to 36% of the vegetation on three of the complexes. Our data confirm prior suspicions of widespread invasion by introduced species of plants on Service-owned tracts of native prairie, changes that likely stem in part from a common management history of little or no disturbance (e.g., defoliation by grazing or fire). However, variability in the degree and type of invasion among prairie tracts suggests that knowledge of underlying causes (e.g., edaphic or climatic factors, management histories) could help managers more effectively restore prairies. We describe an adaptive management approach to acquire such knowledge while progressing with restoration. More specifically, we propose to use data from inventories of plant communities on Service-owned prairies to design and implement, as experiments, optimal restoration strategies. We will then monitor these experiments and use the results to refine future strategies. This comprehensive, process-oriented approach should yield reliable and robust recommendations for restoration and maintenance of native prairies in the northern Great Plains.

Recreation in Foothill and Prairie Ecosystems