Relict Tallgrass Prairie of the Upper Black Squirrel Creek Drainage, El Paso County, Colorado: Change Since the 1940’S

RELICT TALLGRASS PRAIRIE OF THE UPPER BLACK SQUIRREL CREEK DRAINAGE, EL PASO COUNTY, COLORADO: CHANGE SINCE THE 1940’S

A THESIS

Presented to the Faculty of the Environmental Program

Colorado College

In Partial Fulfillment of the Requirements for the Degree

Bachelor of Arts in Environmental Science

Sebastian A. E. Tsocanos

May 2012

______Sylvia Tass Kelso, PhD. Miroslav Kummel, PhD. First Reader Second Reader

CONTENTS

ABSTRACT………………………………………………………………………………………. 2

INTRODUCTION………………………….…………………….………………………………. 3

THE STUDY SITE………………………….…………………………………………....7

LOCAL GEOLOGY……………………………………………………..………………11

LOCAL CLIMATE…………………….………………………………………………..14

METHODS

CLIMATE ANALYSIS………………………….……………………………………...15

LOCATING HISTORIC & CURRENT TALLGRASS PRAIRIE REMNANTS….…...16

INVENTORY OF FLORAL DIVERSITY………………….…………………………..17

VEGETATION TRANSECTS: COMMUNITY STRUCTURE & COMPOSITION…..18

RESULTS

CLIMATE ANALYSIS RESULTS………………….……………………………….... 22

EXTENT OF THE REMAINING TALLGRASS PRAIRIE.…………….……………..29

FLORAL DIVERSITY INVENTORY RESULTS……………………………………..30

VEGETATION TRANSECT RESULTS…....………………………………………….30

DISCUSSION…………………………………………………………………………………....43

ACKNOWLEDGEMENTS……………………………………………………………………..50

APPENDICES

APPENDIX A…..………………………………………………………………………..51

APPENDIX B………...……………...…………………………………………………..57

APPENDIX C...………………...………………………………………………………..59

BIBLIOGARPHY……...…………………………………………………………………………68

ABSTRACT

In the mid 1940s remnant tallgrass prairie near Colorado Springs was recognized in vegetation studies on the plains. Tallgrass prairie is unusual in the arid Great Plains, and is of significant conservation value, particularly given the past and present pressures of urban expansion, intense grazing, and water development. Our study examined the question of whether this community type still exists in the region, if the extent of the community type has changed since then, and whether the species composition has changed. We found that while true tallgrass prairie vegetation is no longer dominant at many of the sites used in the original studies, patches of true tallgrass prairie still occur in the area. The extent of tallgrass prairie in the vicinity has clearly declined over the past 70 years. The vegetation of remaining patches is composed of very similar species to those originally documented. We found that the dominant vegetation is still characteristic of true tallgrass prairie. Among the important grasses were prairie dropseed, indian grass, little bluestem), and big bluestem. Important widespread forbs indicative of true tallgrass prairie included american licorice (Glycyrrhiza lepidota), stiff goldenrod (Oligoneuron rigidum), white heath aster (Symphyotrichum ericoides), and purple prairie clover (Dalea purpurea) among many others. We determined that overall precipitation and temperature in the locality has not changed dramatically since the 1940’s. The alluvial aquifer across much of the area is evidently little changed, but hydrology on a site-by-site basis is poorly understood. While the continued existence of some true tallgrass prairie communities here is reassuring, their diminished extent is cause for concern, especially given increasing pressure from urban expansion, livestock grazing, invasive species, and water development. The uncertain status of future temperature and precipitation, as well as the maintenance of critical surface and subsurface hydrologic regimes is also of concern.

INTRODUCTION

Tallgrass prairie is among North America’s most threatened ecological communities, today occupying less than 0.01% of its historic distribution (Samson and

Knopf 1994). Valued for its diverse flora and fauna, the genetic diversity it contains, its productivity, agricultural importance, carbon sequestering capacity, and its aesthetic and recreational value, tallgrass prairie preservation and restoration is increasingly being recognized as one of the most important goals of North American conservation today (Samson and

Knopf 1994; Packard and Mutel 1997;

Samson et al 2004). In Colorado, where small pockets of tallgrass prairie have historically occurred and a declining number of remnant Fig. 1. This map outlines the historically dominant types of communities continue to persist, the grassland of the North American Great Plains. Note that isolated occurrences of relict tallgrass prairie along the need for tallgrass prairie conservation western edge of the plains are not shown. Also absent is the thin strip of mixed-grass prairie in the foothills of the Rocky Mountains. American Grasslands: Discovery Earth. is of critical concern (Bock and Bock 2012.

1998; Colorado Natural Heritage Program (CNHP) 2011: www.cnhp.colostate.edu/download/list/communities.asp))

The grasslands of eastern Colorado represent the western extent of North

America’s Great Plains (Shantz 1923; Shaw 2008). Broadly speaking, shortgrass prairie/dry steppe vegetation dominates the western Great Plains, mixed-grass prairie vegetation occupies the central Great Plains, and tallgrass prairie (a.k.a. Midwestern tallgrass prairie or simply true prairie) is restricted to the eastern portion of the continent’s grasslands where the dynamics of moderate precipitation coupled with frequent episodes of drought, heavy but irregular grazing, and regular fires create a patchwork of highly productive prairie, forest and savanna landcapes (Shelford 1963;

Weaver 1954; Knapp et al 1998) (See Fig. 1).

While the majority of the Colorado's eastern grasslands consist of dry steppe/shortgrass prairie vegetation (Shaw 2008) dominated by aridity tolerant species of grass such as blue grama (Bouteloua gracilis (Kunth) Lag.), disparate occurrences of tallgrass prairie vegetation, dominated by signature tallgrass species such as big bluestem

(Andropogon gerardii Vitman), prairie dropseed (Sporobolus heterolepis (Gray) A.

Gray), switchgrass (Panicum virgatum L.) and indiangrass (Sorghastrum nutans (L.)

Nash) have been recognized since the early twentieth century (not shown in Fig. 1)

(Shantz 1906; Dodds et al 1908; Vestal 1914; James 1930; Livingston 1947; Branson et al 1965; Moir 1972).

Moir (1972) and Livingston (1941, 1947, 1952) documented these true prairie communities as occurring mainly within Boulder and El Paso Counties (near the towns of

Boulder and Falcon, respectively). Their research, as well as recent analysis (Bock and

Bock 1998), have suggests that these communities are relicts from a past geological period of glaciation when higher precipitation supported tallgrass prairie throughout the plains. When the plains became more arid as the rain shadow of the Rocky Mountains

pushed east, the bulk of true prairie retreated before it. Right along the base of the mountains, however, intact communities have persisted for thousands of years in places where particular soils, underlying geology, topography, and local precipitation patterns have maintained pockets of consistent, perennial, a-zonal soil moisture (Livingston 1952;

Branson et al. 1965; Bock and Bock 1998). The widespread disappearance of even these remnant communities over the past century, due mainly to intensive livestock grazing and urban expansion, has made them of considerable conservation concern (Moir 1972; Bock and Bock 1998; Colorado Natural Heritage Program (CNHP) 2011: www.cnhp.colostate.edu/download/list/communities.asp).

While certain individual species within the tallgrass community type are of conservation concern (CNHP 2011: http://www.cnhp.colostate.edu/download/list/vascular.asp), the potential elimination of the assemblage or community as a whole, (as defined by dominant grass species in association with particular herbaceous species) is also of great concern at this time.

Today, two types of mesic tallgrass prairie and two types of xeric tallgrass prairie are fully tracked by the Colorado Natural Heritage Program (CNHP 2011: www.cnhp.colostate.edu/download/list/communities.asp) and are considered to be imperiled or critically imperiled natural plant communities within the state and imperiled plant communities globally. These communities are defined by the dominance of

1) Big bluestem and prairie sandreed (Calamovilfa longifolia (Hook.)

Scribn.) along with associated herbaceous vegetation (a mesic tallgrass

prairie)

2) Big bluestem and little bluestem (Schizachyrium scoparium (Michx.)

Nash) with associated western Great Plains herbaceous vegetation (a

xeric tallgrass prairie)

3) Big bluestem and indiangrass with associated western Great Plains

herbaceous vegetation (a mesic tallgrass prairie)

4) Big bluestem and prairie dropseed, with associated western foothills

herbaceous vegetation (a xeric tallgrass prairie).

Each community type is listed as imperiled throughout the state, while the latter two communities may be critically imperiled in the state. The first, third, and fourth community types are imperiled globally. The global status of the second community type is unknown. While these are currently the only assemblages that CNHP officially tracks, we considered a broader range of assemblages (made up of other characteristic tallgrass prairie grass species associated with forbs and shrubs typical of Midwestern tallgrass prairie) to be true tallgrass prairie as well and of similar conservation concern.

While the true prairie remnants in the vicinity of Boulder have been thoroughly studied in recent decades (Baker 1985; Santanachote 1992; Bock and Bock 1998; Craig

1999; Collinge 2003) there have been no follow-up studies or monitoring efforts of the remnant prairie communities in El Paso County since Livingston’s original 1947 thesis.

The broad objective of this study is to follow-up on Livingston’s seminal works and to assess the current extent and floristic quality of the tallgrass prairie in this area. The focus of the present study is to reexamine the grassland communities in the Black

Squirrel Creek drainage and to compare their extent, their floristic composition, and the general vegetation patterns that exist now with the patterns that Livingston found more than sixty years ago. We asked the following questions:

1) Has the extent or distribution of tallgrass prairie in the upper Black

Squirrel Creek drainage changes since Livingston recorded it in 1940’s?

2) Are the dominant species of grass the same today as they were 60 years

ago; that is, do they still represent those dominant in the Midwest

prairie?

3) Is the relative rank of each grass species the same as measured by total

basal cover and as by frequency of occurrence within transects?

4) Are there still a large number of forb species that are typically

associated with Midwestern true prairie?

5) Is the degree of species evenness similar to what it was: i.e. are the

ranked abundance curves for each community a similar shape to those

sampled by Livingston in 1947?

The Study Site

Where the plains meet the mountains along the Colorado Front Range, the vegetation transitions into both mixed-grass and montane communities as shrubland and ponderosa pine forest intermix with open grasslands (Vestal 1917; Williams and Holch

1946; Kelso 2008). In the Pikes Peak region, between Colorado Springs and Denver, an extension of this foothills/montane vegetation locally known as the Black Forest extends eastward along the Palmer Divide, a ridge of moderately elevated topography (~ 7500 ft,

2286 m) that separates the Arkansas and South Platte River watersheds (Shaddle 1930;

Williams and Holch 1946; Livingston 1949; Maley 1994). Studies by Livingston (1941,

1947, 1949, 1952) documented the unusual vegetation patterns in this area; including small pockets of grassland communities characterized by tallgrass-dominated species-

assemblages usually restricted to the true prairie of the Midwestern states. He documented occurrences both within the matrix of the Black Forest ponderosa pine community and within the adjacent matrix of mixed and shortgrass-dominated plains of the Black Squirrel Creek drainage. In addition to describing their extent, Livingston

(1947, 1952) examined the floristic composition and community structure of each meadow in considerable detail. He called attention to the community type’s unique contribution to the region’s ecology and highlighted its significant conservation value.

Our study focused on the northernmost portion of the upper Black Squirrel Creek drainage, between the municipalities of Falcon and Peyton, CO. This drainage basin lies within the larger Arkansas River watershed. The stream system begins near the Black

Forest of the Palmer Divide and flows in a southeastern direction onto the plains (Fig. 2) eventually joining the Arkansas River. The upper portion of the basin is at approximately

7,150 ft (2,179 m), the land gently sloping down to 6940 ft (2,115 m) in elevation at its southern boundary (Fugere 2012). The Black Squirrel drainage lies to the southeast of the

Black Forest and consists of gently rolling uplands of dry loam soils, separated by lowland drainages and swales containing mesic soils of generally high organic content, wetlands, seeps, streams and ponds, as well as sandy soils where sparsely vegetated seeps, cut banks, dry streambeds and sandbars occur (Fugere 2012). Summer rainstorms are often very local in extent and usually track the elevated topography of the Palmer

Divide closely (personal observations). Precipitation decreases substantially at lower elevations just a few miles from the northwestern end of the watershed (Topper 2008).

The main stem of the Black Squirrel Creek and its tributaries are perennial towards the upper elevations of the watershed (Tracy Lee 2011, personal communications) but by the

time the creek passes Judge Orr Rd. to the southeast, it is ephemeral and dry for most of the year (Topper 2008). Wetlands, seeps and ponds are abundant in the north

Area of Study

Fig. 2. The area of our study, outlined in light blue, is also roughly congruent with extent of the northern half of the upper Black Squirrel Creek drainage. Four Way Ranch is outlined in yellow. Our primary study area is outlined in red, in the northwest corner of the ranch and our larger study area. Livingston studied relict prairie communities both within the Black Forest, which can be seen easily to the northwest of our study area, and on the plains, within the upper Black Squirrel Creek drainage. His plains field station were generally southeast of our primary study site.

Fig. 3. Four-Way Ranch (ca. 7,700 acres in extent) is outlined in yellow. Colorado highway Route 24, a major artery connecting eastern Colorado to the Front Range, forms the southeastern boarder of the ranch, running between Peyton in the upper right

(northeast) of the map to Falcon in the lower left (southwest) of the map. The encroaching suburban development is visible along the southeastern and western boarders of the ranch, as Falcon continues to expand rapidly. The edge of the Black Forest is just visible in the upper left (northwestern) corner of this map. The sandy bed of the Black

Squirrel Creek is visible running perpendicular to CO Rt. 24.

Local Geology

Livingston (1952) and Branson et al. (1965) both noted the tight relationship between soils of perennially high moisture content, and the persistence of true prairie communities in Colorado, variously attributed to special soil types, water table dynamic, and local climate. In the area of our study there are two aquifers that play dynamic roles in the hydrology of the region, an alluvial aquifer and an underlying bedrock aquifer

(Bittinger 1976; Topper 2008). The watershed overlies the southern-most extent of the

Denver Basin, an extensive bedrock aquifer of moderately well lithified sandstones that are exposed in the Palmer Divide (Colorado Division of Water Resources Geology of the

Denver Basin Aquifers. 1985). The formations’ subsurface topography, shaped by the ancestral Black Squirrel Creek, slopes steeply south of the divide, covered now by subsequently deposited glacial alluvium. The Black Squirrel Creek Aquifer consists of these widespread alluvial deposits (0-215 m thick) of gravels and course sands containing thin prisms of siltstone, clays and mudstones. The depth of this alluvium generally increases further from the divide. In addition to these glacial deposits, modern streams have deposited alluvial material along their courses, such as the Piney Creek alluvium.

In the central and lower Black Squirrel Creek basin, the alluvial aquifer is a significant source of well water for domestic, agricultural, and municipal uses (Topper

2008). In the northern portion of the basin, however, where our study is concerned, the glacial alluvium is thin (<20 m) or completely absent, and water is likely developed from the bedrock aquifer (Topper 2008, personal communication). The stream, wet meadows, seeps and springs in this area may be directly connected to the bedrock aquifer, probably in connection with modern stream alluvial deposits.

In our primary study area, the Dawson Formation is exposed, except where the

Piney Creek alluvium, deposited by present day streams, makes up current floodplains and recent terraces (Topper 2008). In this area the water table is ca. 3 m below the surface on average and likely meets the surface in certain places (Topper, personal communication). While the alluvial aquifer of the central Black Squirrel basin has receded in past decades, namely in the 1960s and 1970’s (ca. 7 m) due to agricultural and municipal development, the water table at the northwestern edge of the alluvial aquifer receded far less (ca. 0.7 m) (Topper, personal communication). Where the alluvial deposits end and the bedrock formations are exposed, there is no water table data available. Even where data exists in the northern part of the alluvial aquifer, monitoring wells are so dispersed that inferences of micro-hydrological changes in specific wet meadows and prairies are difficult to make. The anthropogenic influence on the bedrock aquifer in in this part of the basin has not been calculated.

In addition to return flows from irrigation and wastewater, the entire basin receives 90% of its recharge from precipitation (Topper 2008). Because of the high permeability of the eolian and alluvial deposits, and the moderate permeability of the exposed bedrock formations, infiltration is high and runoff is low across the basin.

Streams across most of the basin only have surface flow during very large local rainstorms or because of high snowmelt.

As with many dryland streams (Zeedyk and Clothier 2009), flow events may lose substantial amounts of water to the dry alluvium of the streambed and unsaturated alluvial deposits bellow the active streambed. Because of this transmission loss, flow events upstream due to local precipitation or bedrock features may not result in surface

flow events downstream, counter to the regional curve concept (Zeedyk and Clothier

2009). In our primary study area the streams are perennial, which is unusual for this region. This is likely due to both the higher precipitation associated with its elevation, an absence of thick alluvial deposits, and the dynamics of the exposed Dawson Formation.

This formation allows for moderate infiltration, but the high water table allows for discharge into seeps, springs, and streams where they have down-cut through the surrounding topography.

Fig. 4. Looking north northwest along the main stem of the upper Black Squirrel Creek.

In the center left of the photograph the abandoned stream terraces where transects 1 and 2 are located is just visible, on the west side of the stream. Photo by Tass Kelso,

September, 2010.

Local Climate

Like much of the Great Plains, our study area receives most of its annual precipitation during a monsoonal period of frequent summer rainstorms between May and September.

Winters usually experience little precipitation, typically in the form of snow (Livingston

1942, 1947, 1952; Shantz 1906; Shaddle 1939). Unlike much of the Great Plains, the locality consistently experiences mid-monsoonal droughts during July (Livingston 1942,

1947; Kelso personal communications). Annually, precipitation averages 10-12 inches per year, but inter-annual variation in precipitation can be extreme (Topper, 2008).

Approximately 80% of annual precipitation occurs between April and September of each year, and the remaining 20% occurs between October and March (Topper 2008,

Livingston 1947; 1952). Because rainstorms often closely track the elevated topography of the Palmer Divide, the northern portion of the Black Squirrel Creek basin receives considerably more precipitation than do the central and southern portions (Topper 2008).

Even within our general survey area, precipitation varied considerably, decreasing noticeably even short distances away from the divide.

METHODS

Climate Analysis

The main climatic factors that can maintain or disrupt the soil moisture balance

(essential for the persistence of tallgrass prairie in Colorado) are precipitation and temperature. We examine both here, looking at both long-term regional trends and relatively recent local patterns.

In order to see long-term patterns of precipitation change in the region, we used a regional dataset of annual cumulative precipitation extending back to 1985 and current through 2011 from Eads, CO, made available by the United States Historical Climatology

Network (USHCN) (Menne et al. 2012: http://cdiac.ornl.gov/epubs/ndp/ushcn/access.html). Having such an extensive and complete dataset is useful for observing overall regional trends, but, because of the distance between Eads and our study site, precise spatial resolution is compromised in that analysis. To compensate for this, data available from the Western Regional Climate

Center (WRCC 2012: http://www.wrcc.dri.edu/CLIMATEDATA.html) for Eastonville,

CO were used to examine local precipitation trends over the past fifty years (1959-2010).

Eastonville is situated immediately to the northwest of our study area. We used this data to examine local patterns of annual rainfall, as well as local shifts in the seasonal distribution of precipitation. We analyzed precipitation within the early growing season

(defined here as April-June), the late growing season (July-Sept), the full growing season

(April-Sept) and the non-growing season (October-March).

For our analysis of annual and seasonal temperature change, we used temperature data from Colorado Springs beginning in the 1940’s (WRCC 2012: http://www.wrcc.dri.edu/CLIMATEDATA.html). Colorado Springs is sufficiently close

(<20 miles) to our study area that temperature trends should be substantially similar. As with our analysis of cumulative precipitation trends, we examined mean temperature on an annual basis, by growing and non-growing seasons, and by further subdividing the growing season into early and late growing seasons. For a look at long-term regional trends in temperature, again we used data from USHCN for mean annual temperature, annual mean of monthly minimum temperature, and annual mean of monthly maximum temperature from Eads, CO between 1895 and 2011 (Menne et al. 2012: http://cdiac.ornl.gov/epubs/ndp/ushcn/access.html).

Locating Historic and Current Tallgrass Prairie Remnants: Surveys of Regional Grassland Communities

We conducted field surveys throughout the upper Black Squirrel Creek drainage in the vicinity of Livingston’s original 1947 and 1952 field stations in order to determine the current location and extent of tallgrass prairie in the region. We conducted visual surveys along and adjacent to the Black Squirrel Creek from Eastonville Rd. in the northwest to just below Judge Orr Rd. in the southeast. In the southern portion of this area, east of Elbert Rd. the survey was restricted to the floodplains and abandoned terraces of the main-stem Black Squirrel Creek. In the northern portion of the area

(between Elbert Rd. on the east, Eastonville Rd on the west, Latigo Blvd. to the south and

Murphy Rd. to the north) we thoroughly surveyed all of the land, including side drainages

of the Black Squirrel Creek and upland areas. We identified meadows, seeps, swales, stream terraces, and gentle slopes that contained elements typical of tallgrass prairie, and returned to those locations most often to observe their development. We sought out

Livingston’s (1947, 1952) field stations based on his written descriptions and simple maps, but also looked for potential new communities. Because of the number of small wet meadows, terraces and hillsides evidently dominated by tallgrass species in the northwestern corner of the basin, that became our primary study area.

This primary study area was located within Four-Way Ranch, a largely intact, ca.

7,700 acre, cattle ranch located north of CO highway 24, extending between the communities of Falcon, Peyton, and Eastonville, CO. All quantitative data of vegetation cover and species composition were taken from transects located within this area. While none of the exact transect sites used by Livingston were able to be assessed due to inexact information, restricted landownership, or obvious extreme disturbance, our sites were located between, and very close to, several of his sites, and within the same local climatic, hydrological, geological and ecological systems.

Inventory of Floral Diversity

In order to record as much of the floral diversity within the primary study area as possible, the area was visually surveyed repeatedly throughout the growing season between early may and late August of 2011. Because of the relatively high diversity and the high spatial and temporal variability of reproductive cycles in mesic lowland drainages (characterized by seeps, moist slopes, intermittent and perennial streams, ponds, and wetlands), they were surveyed systematically, returning to each feature

approximately every two weeks. The xeric uplands, because of their general spatial uniformity, were treated as a single large unit (not separate features). We covered the uplands thoroughly throughout the growing season but visited specific upland locations only sporadically.

Vegetation Transects: Community Structure and Composition

In order to analyze the grassland vegetation quantitatively, we used the same quadrat method of Livingston (1947, 1952), who determined that it gave comparable results to a line intercept method, and was significantly more efficient. He established that a set of 10 quadrats, each 1 m x 0.5 m, along a 100 meter transect was sufficient to sample of each community, giving a satisfactory species area curve (Livingston 1947,

1952). We modified this design slightly, using 20 quadrats of the same dimensions along four 105 m transects, because the small scale spatial heterogeneity and patchiness we observed suggested a higher resolution for each community would be informative. In late

August, each transect was laid out where characteristic elements of tallgrass prairie had been observed; all parallel to lowland drainages (see Fig. 5). Quadrats were spaced 5 m apart, with their shorter dimension parallel to the transect line. Coordinates of the starting and ending points of each transect are listed in Table 1 below.

Fig. 5. Our primary study area is outlined in red. Transects 1(dark red) and 2 (light red). Are visible in the southeast corner, along the main stem of the Black Squirrel Creek, which runs generally west to east here. Transect 2 (blue) is located in a upland swale/side drainage of the main creek. Transect 4 (yellow) is in the northwest corner of the study area, along another side drainage of the main creek. Each transect is 105 m in length, for reference.

Table 1. Geospatial coordinates of transect starting and ending points.

Longitude (UTM) Latitude (UTM)

Transect 1 Start 0173332 4462156

End 0173250 4462213

Transect 2 Start 0173303 4462195

End 0173207 4462238

Transect 3 Start 0172904 4462403

End 0172819 4462455

Transect 4 Start 0171782 4464513

End 0171690 4464565

Within each quadrat, visual estimates of several parameters were made and recorded. We documented the combined total vegetative basal cover of all plants as a percentage of the total area of each quadrat, and the percent of the total area not covered by vegetation or leaf litter (i.e. bare ground). We documented the combined total basal cover of all graminoids (grasses, sedges, and rushes) present as a percent of the total vegetative basal cover, and we recorded the percentage of the vegetative basal cover attributable to each identifiable graminoid species. In addition to quantifying the relative abundance of the graminoids, we noted the presence or absence of all identifiable forb, shrub and semi-woody plant species within each quadrat. Basal cover was interpreted as either stem cross sectional area, or, if grasses or forbs were so dense as to effectively exclude other plants, the total area dominated at ground level, was considered basal area.

Similarly, most bunch-grass growth forms were considered as cumulative basal cover of

a single plant. This may have resulted in absolute percentages of basal cover being higher than other similar studies, including Livingston (1947; 1952), and closer to measures of canopy cover, but the relative abundance of each of the specific groups and species is comparable to similar studies. The measure of basal cover is less sensitive to environmental fluctuations such as precipitation than other measures of species composition (such as canopy cover) and more consistent throughout the growing season.

The use of this measure allowed us to make a closer comparison to the earlier regional studies.

We analyze the transect data both within individual transects and across all transects. Most transects vary considerably from one another, in terms of species composition, ranked abundance, ranked frequency, and ranked relative importance values, as well as by their exact forb composition and the proportion of the community made up of Sedges (Family Cyperaceae) and Rushes (Family Juncaceae). While transects one and two are physically in proximity to one another, even their vegetation profiles are not identical. The other two strips of prairie, captured by transects three and four, are discontinuous with transects one and two, and each other. Both reflect that in their distinct community structure. On the other hand, there are broad similarities among the communities as well. For example, most transects share the same main dominant grasses, most transects have similar overall grass species diversity, and many of the dominant forbs are ubiquitous across the community type. These observations seem to justify treating each small discontinuous patch as an aspect of a larger community type, and see what characteristics this community type currently exhibits across the region. This treatment of the data follows Livingston (1947, 1952).

RESULTS

Results: Climate Analysis

Both precipitation and temperature have increased slightly since the late 1800s, and more dramatically in recent decades. Temperature on Colorado’s eastern plains have increased substantially since 1985. This is true of the mean of monthly maximum temperatures (Fig

7.) mean of monthly minimum temperatures (Fig. 8) as well as the overall annual mean temperature (Fig. 6). Temperatures closer to our study site, measure in Colorado Springs, have followed this trend as well, increasing slightly over the past fifty years (Fig. 9 and

Fig. 10).

Fig. 6. Annual mean of monthly mean temperature for Eads, Colorado. Note the long- term increase in mean annual temperature, as well as the wide inter-annual fluctuations. The y-axis is in Degrees F, and the x-axis is time by year, from 1890-2020. Chart produced at http://cdiac.ornl.gov/epubs/ndp/ushcn/access.html (Menne et al 2012)

Fig. 7. Annual mean of monthly mean maximum temperature for Eads, Colorado. Note the long-term increase in mean annual maximum temperature, as well as the wide inter- annual fluctuations. The y-axis is in Degrees F, and the x-axis is time by year, from 1890- 2020. Chart produced at http://cdiac.ornl.gov/epubs/ndp/ushcn/access.html (Menne et al 2012)

Fig. 8. Annual mean of monthly mean minimum temperature for Eads, Colorado. Note the long-term increase in mean annual minimum temperature, as well as the wide inter- annual fluctuations. The y-axis is in Degrees F, and the x-axis is time by year, from 1890- 2020. Chart produced at http://cdiac.ornl.gov/epubs/ndp/ushcn/access.html (Menne et al 2012)

Mean Annual Temperature, Colorado Springs, CO 52

51 y = 0.0128x + 23.484 50 R² = 0.0441 49 Annual 48 Linear (Annual) Temperature Temperature (f) 47

46 1950 1970 1990 2010 Year

Fig. 9. Mean annual temperature for Colorado Springs, CO. Note the gradual increase in temperature. R-Squared = 0.044. Data is from the Western Regional Climate Center (WRCC. 2011: )

Mean Growing Season Temperature, Colorado Springs, CO

66 y = 0.0131x + 35.324

64 R² = 0.0272 62 60 Series1

58 Linear (Series1) Temperature Temperature (f) 56 1950 1970 1990 2010 Year

Fig. 10. Mean Growing Season temperature for Colorado Springs, CO. Note the slightly increase in temperature. R-Squared = 0.027. The Same trend is observed for the Early Growing Season, Late Growing Season, and Non-Growing Season. Data from the Western Regional Climate Center (WRCC. 2011: )

There have been several periods of severe drought since the 1940s, (in the late

1970’s and early 2000’s, for example) but, if anything, overall precipitation has increased slightly (Fig.11). The significance of this change is unknown, but likely minimal.

Increased are seen in cumulative annual precipitation and for seasonal precipitation, including the early growing season from April through June, for the late growing season from July through September, for the whole growing season, and for the non growing season (Fig. 12). Overall, the non-growing season precipitation is relatively consistent, but because it contributes relatively little to the overall precipitation totals (Fig. 13), annual precipitation fluctuates widely (Fig. 11) due to variations in growing season precipitation.

Annual Cumualative Precipitation: Eads, CO. 35

30 25 20 15 10 Precipitation Precipitation (in) 5 y = 0.0157x + 13.663 R² = 0.0184

1951 1895 1899 1903 1907 1911 1915 1919 1923 1927 1931 1935 1939 1943 1947 1955 1959 1963 1967 1971 1975 1979 1983 1987 1991 1995 1999 2003 2007 2011 Year

Fig. 11. Annual cumulative precipitation for Eads, CO, between 1895 and 2010. Eads is to the southeast of our study sit, at a lower elevation (1285 m) on the plains. Note the yearly variability (with fluctuations between 5 and 30 inches) but long term stability. Although there is not a dramatic increase in mean annual precipitation, the trend is upward. (Menne et al 2012: http://cdiac.ornl.gov/epubs/ndp/ushcn/access.html)

Mean Cumulative Precipitation, Annual and Seasonal: Eastonville, CO 30

20 Annual 15 Growing

10 Late Growing Early Growing Precipitation (in) Precipitation 5 Dormant 0 1960's 1970's 1980's 1990's 2000's Decade

Fig. 12. Mean cumulative precipitation for Eastonville, CO since the 1960’s, by decade. Every season is shown. Note the substantial rise in precipitation over the last 50 years. Slightly greater gains have been made for Growing Season Precipitation, (evenly split between the first and second half of the growing season) than we see in the dormant season, but the dormant season precipitation has increased as well. (WRCC. 2011: )

Percent Annual Precipitation During Growing Season: Eastonville, CO

Percent Percent Annual Precip. (%) 1960's 1970's 1980's 1990's 2000's Decade

Fig. 13. This graph shows the proportion of annual precipitation that arrives during the growing season, averaged over each decade, for Eastonville, CO. The proportions do not vary greatly, fluctuating around a long-term mean of 75%. The seasonality of precipitation events has remained substantially the same. The same is true of early and late growing seasons. (WRCC. 2011:

What is of most importance to our study is the combined effect of precipitation and temperature on the soil moisture balance, as that is what likely allows tallgrass prairie to persist in this arid environment. Increased temperature causes increases in evapotranspiration rates, thereby reducing soil moisture. Increased precipitation increases recharge, thereby increasing soil moisture. The dynamics of these interacting forces, as well as complicating factors such as infiltration and runoff rates, soil type and humidity, means that the net effect of changing precipitation and changing temperatures are not readily apparent. A study by Dai et al. (2004), however, suggest that, at least on a large scale, much of Colorado became more dry (in terms of the soil moisture balance) between 1900 and 1949, and then became more wet between 1950 and 2002 (Fig. 14).

Fig. 14. “Maps of linear trends of PDSI (Palmer Drought Severity Index) [change (50 yr) calculated with both precipitation and temperature changes] during (top) 1900–49 and

(middle) 1950–2002. (bottom) The trends of PDSI calculated without temperature changes. Red (blue) areas indicate drying (wetting)” Reproduced from Dai et al (2004). their analysis of Colorado’s long-term soil moisture balance seems to agree with our data. Although temperatures have increased over the past fifty years, precipitation has trended upwards as well, compensating, thus far, for increases in evapotranspiration rates, and actual causing an overall positive soil moisture balance. That is true on a very long timescale, at least, and a large scale for Colorado. Smaller fluctuations in space and time could potentially have impacted tallgrass prairie in El Paso County over the past half a century.

Results: Regional Surveys of Grassland Communities

Our qualitative surveys of the upper Black Squirrel Creek drainage area indicated that only a few grassland communities comparable to those that Livingston described

(1947, 1952) still occur. These are all small in extent, only a few acres at most, and much smaller than the ~40 acre communities described by Livingston. Several of the communities we observed throughout the summer, encouraged by early identification of certain tallgrass species, never developed into what we would describe as true tallgrass prairie. While elements such as prairie dropseed are present in limited amounts, they are not abundant now, and the extensive communities described as extant in 1952 are clearly no longer intact. Some of the areas are developed with housing tracts, and most appear heavily grazed. Most of the plains study sites utilized in the earlier studies are no longer dominated by the grass species previously noted and have changed to more xeric communities representing the typical short to mid-grass prairie steppe dominated by grama,

Results: Inventory of Floral Diversity

Fugere (2012) reported the results of these surveys. She compiled a comprehensive species list for the upper Black Squirrel Creek Drainage, documenting the floral diversity captured in our surveys as well as those species previously recorded in the area, reproduced here in. list of graminiod, forb, shrub, and semi-woody species found primarily in the drainages is given in Appendix B, and the entire species list for the area is given in Appendix C, both reproduced from Fugere (2012). For a full discussion of the overall floristic diversity captured by these surveys, see Fugere (2012).

Results: Vegetation Transects

Before looking more closely at each transect and prairie community as a unique species assemblage in its own right, we will examine the community type as a whole, across the entire primary study area, looking at the mean values of relative cover/abundance and relative frequency across all four transect, combined as one sample of a single community type.

ALL TRANSECTS (GRAMINOIDS: GRASSES, SEDGES, AND RUSHES)

Across all transects, the mean vegetative basal cover accounted for 53.2% of the total area (Fig. 15). On average, graminoids made up 41.9% of the total basal cover and

79.8% of the vegetative basal cover. Non-graminoid cover made up 11.3% of the total area and 20.2% of the vegetative basal cover. Organic Litter, on average, covered 39% of the total area, leaving an average of 7.8% of the total area bare.

Ground Cover 100% 90% 80% 70% 60% % Graminiod Cover 50% % Forb Cover 40% %Litter Cover 30% % Bare Ground

Percent Percent Total Area (%) 20% 10% 0% T1 T2 T3 T4 Mean Transect

Fig. 15. The proportionate ground cover of graminoids, forbs, litter, and bare ground, within each transect and between all four transects (Because each transect samples the same size area, and contains the same number of quadrats, each is weighted evenly, and a simple mean of the four quadrats summarizes them well). Forb cover and litter cover are calculated values. Note the dominance of the graminoids, the relatively small amount of bare ground, and the large amount of litter present.

Overall, the grassland communities we studied are currently dominated by the grasses S. heterolepis (15.1% of total vegetation basal cover), M. montana (13.2%), S. scoparum (11.0%), S. nutans(10.7%) and C. longifolia (7.8%). Of these, S. heterolepis,

S. scoparum, and S. nutans, are characteristic dominants of Midwestern tallgrass prairie.

Associated grasses were A. gerardii (2.8%), H. spartea (1.2%) and P. virgatum (0.8%), all of which are also important elements of Midwestern tallgrass prairie. A species of Poa

(probably pratensis based on that species’ observed widespread presence earlier in the

season) (0.3%) and K. macrantha, (0.2%) although not numerically abundant, also represent typical components of Midwestern tallgrass prairie.

Where small seeps of completely saturated soils exist within these communities,

Juncus arcticus (3.1%), other rushes (2.4%) and several sedges (4.3%) were prevalent.

Grass species such as Bouteloua gracilis (2.4%), B. hirsuta (hairy grama) (1.3%), and

Nassella viridula (0.2%) represented the intergrading of short and mixed grass prairie elements with the tallgrass prairie elements that are dominant.

Graminoids Ranked by Relative Abundance Across All Transects

18.000 16.000 14.000 12.000 10.000 8.000 6.000 4.000

2.000

0.000

…

… …

✜ ✜ ✜ ★ ✜ ✜ ✜

Poa sp.

Elymussp.

Relative Relative Cover/Abundance (% VBC)

Stipa viridula

Muhlenbergia…

Schizachyrium Schizachyrium

Juncusarcticus

Agrostisscabra

Stipa spartea

Bouteloua hirsuta

Bouteloua gracilis

Hordeumjubatum

Phleum Phleum pratense

Calomogrostisstricta…

Panicum Panicum virgatum Sporobolus Sporobolus heterolepis

Species Koeleria macrantha

Sorghastrum nutans

Muhlenbergiamontana

Andropogon Andropogon gerardii Calomovilfa Calomovilfa longifolia

Fig. 16. Mean ranked abundance/relative cover of grasses, rushes and sedges, identified at least to genus, across all four transects. Relative cover is the contribution of a specie’s basal cover to the total vegetative basal cover (VBC) of all plant species. Mean values for each transect were averaged, as each transect has equal weight in describing the general composition of the community type throughout the area. indicates species characteristic of Midwestern tallgrass prairie (Weaver and Fitzpatrick 1934; Weaver 1954; Livingston 1952).  denotes species that the Colorado Natural Heritage Program (2012) lists as rare within Colorado. indicates regionally uncommon or locally endemic species of the Pike’s Peak region (Kelso 2008).

Across all of the grassland communities studied, the highest frequency graminoids, were M. montana (42.5% frequency), S. scoparium (37.5%), S. nutans

(36.25%), C. longifolia (35%), S. heterolepis (33.75%), and J. arcticus (32.5%)

(Appendix A). Of these, S. scoparium, S. nutans, S. heterolepis represent elements of tallgrass prairie. Species of secondary importance as ranked by frequency were H. spartea (16.25%), B. gracilis (15%), A. gerardii (8.75%) and species of Poa (8.75%).

Cyperaceae (sedge) species were present across 25% of all quadrats.

Graminoids Ranked by Relative Frequency Across All Transects

60.000

50.000

40.000

30.000

20.000

10.000

0.000

Series1

✜ ★ ✜

✜

✜ ✪ ✜ ★

✜

Relative Relative Frequency (% occurance)

Poa sp.

Elymussp.

Stipaviridula

Juncusarcticus

Agrostisscabra

Stipa Stipa spartea

Boutelouahirsuta

Boutelouagracilis

Hordeumjubatum

Phleum pratense Phleum pratense

Panicum virgatum

Koeleria Koeleria macrantha

Muhlenbergiamontana

Andropogon Andropogon gerardii

Calomovilfalongifolia Sorghastrum Sorghastrum nutans

Species Calomogrostisstricta (ssp.…

Muhlenbergiaminutissima

Schizachyrium scoparium Sporobolus Sporobolus heterolepis

Fig. 17. Mean ranked relative frequencies of grasses, rushes and sedges, identified at least to genus, across all four transects. Relative frequency is a measure of the spatial distribution of a species throughout or between sample areas. The relative frequency of a species is the proportion of all quadrats in which members of a given species are

identified, expressed as a percent rather than a fraction here. This graph shows frequencies of species among the quadrats of all transects, grouped together. Mean values for each transect were averaged, as each transect has equal weight in describing the general composition of the community type throughout the area. See Fig. 16 for an explanation of the symbols used next to species names.

In order to integrate our data on each graminoid species’ relative abundance and relative frequency, we calculated Relative Importance Values (RIVs) for each of those species.

RIVs are calculated as the product of the relative abundance and relative frequency of a species, divided by two (Master 1997). The resulting ranked order, as expected, is similar overall to those produced by both the relative abundance and relative frequency (Fig. 18).

Graminoids Ranked by Relative Importance Across All Transects

0.1 0.1 0.1 0.1 0.1 0.1 0.0 0.0 0.0 0.0

0.0 Relative Relative Importance Value

Species

Fig. 18 Ranked relative importance of graminoid species across all transects. Relative importance values are calculated as the product of a species relative frequency and its relative abundance (both expressed as decimal fractions). This helps integrate information on a species distribution contribution to vegetative cover. Note that mountain muhly (Muhlenbergia montana), generally a mountain and mixed grass prairie species, appears to dominate the community type. This is largely due to it’s dominant role in a

single transect (Transect Four, see Fig. 23) which will be discussed further in the paper. See Fig. 16 for an explanation of the symbols used.

ALL TRANSECTS Combined (FORBS, SHRUBS, AND SEMI-WOODY PLANTS)

In this analysis of all non-graminiod plant species, we continue to treat all transect data as a single unit describing a single community type. When considering all plant species, the community type as a whole is characterized by both the abundant graminoids listed above and by the presence of a few widely distributed forbs, shrubs, and semi- woody species. Nine of the ten most widely distributed forbs and shrubs across all four transects are representative of true prairie (Fig 19). This include Glycyrrhiza lepidota

Pursh (american licorice), a tallgrass prairie element (TPE) is in 47.5% of all quadrats, making it more frequent than any of the grass species. Oligoneuron rigidum (L.) Small

(stiff goldenrod) TPE (38.75% frequency) is less frequent than M. Montana, but more frequent than the rest of the grasses. Other species that are widely distributed are

Artemisia ludoviciana Nutt. (white sagebrush) TPE (26.25%) Symphyotrichum ericoides(L.) A. Löve& D. Löve (white heath aster) TPE (25%), Rosa arkansana Porter

TPE (Arkansas rose) (23.75%), Helenium autumnale (L.) (common sneezeweed) TPE

(21.25%), Equisetum arvense L. (field horsetail) TPE (21.25%), Comandra umbellata L.

Nutt. (bastard toadflax)(20%), and Dalea purpurea Vent. TPE (purple prairie clover)

(20%). Also of note are Symphotrichum laeve(L.) A. Löve and D. Löve TPE (smooth blue aster) (18.75%), other species of Asteraceae (13.75%), Geranium atropurpureum

Jones (western purple cranesbill), Iris missouriensis Nutt. (rocky mountain iris),

Pedicularis canadensis L. (Canadian lousewort), and Thermopsis montana Nutt.

Non-Graminoids: Ranked by Relative Frequency Across All Transects. Includes Species if f > 7.5 % 50 45 40 35 30 25 20 15

Relative Relative Frequency (% occurance) 10

… … …

…

✜ ✜

✜

Fragariasp.

Heterothecasp.

Achillea lanulosa

Symphyotrichum

Iris Iris missouriensis

DaleaPurpurea

Rudbeckia hirta

Rosaarkansana

Packera pseudaurea

Monarda fistulosa

Comandraumbellata

Oligoneuron Oligoneuron rigidum

Thermopsis montana

Symphotrichum Symphotrichum laeve

Artemisia Artemisia ludoviciana

Equisetum Equisetum arvense

Pediculariscanadensis

Glycyrrhiza lepidota

Antennaria microphylla Helenium autumnale Species

Fig. 19 All Forbs, Shrubs and semi-woody species present in at least 7.5 percent of all 80 quadrats in the four transects, ranked by relative frequency. Note that nine of the 10 most widely distributed (relatively frequent) species are typical components of Midwestern tallgrass prairie, indicated by this symbol: .

TRANSECT ONE

Transect 1 was along a second tier terrace of the Black Squirrel Creek and was the most mesic site observed, with abundant subsurface water, and a small seep dominated by Juncus arcticus Willd. (arctic rush). This transect had the highest total basal cover

(63.8%) of the four transects and the highest proportion of forbs, although graminoids still clearly dominated the community with rushes, sedges, and grasses together making up 69.5% of the total vegetation cover. Organic litter material covered an additional

32.8% of the area, leaving only 3.4% as bare ground.

The meadow community was dominated by Sorghastrum nutans (L.) Nash

(indiangrass), Sporobolus heterolepis (A.Gray) A. Gray (prairie dropseed), and

Schizachyrium scoparum (Michx.) Nash, (little bluestem). These three species made up

26.5 % of the total vegetative cover, by basal area, contributing 12.3% 9.0% and 7.5% respectively. Juncaceae and Cyperaceae made up another 23.1% of total cover, largely due to the isolated seep within this transect. Associated grasses in transect 1 were

Bouteloua hirsuta Lag. (hairy grama)(4.5%), Muhlenbergia montana (Nutt.) Hitch.

(mountain muhly) (4.2%), Calamovilfa longifolia (Hook.) Scribn. (prairie sandreed)

(3.2%), Panicum virgatum L. (switchgrass) (2.8%), Koeleria macrantha (Ledeb.) Schult.

(prairie junegrass) (0.7%) and Poa sp. (0.2%). Three of these associated grasses, C. longifolia, P. virgatum and K. macrantha, are important elements of Midwestern tallgrass prairie.

While S. heterolepis was among the two most abundant grasses in the transect, its distribution was limited to 25% frequency, less than half the frequency of S. nutans

(55%). Both S. scoparium and J. arcticus were also more widespread than S. heterolepsis, both found throughout 30% of the transect.

Transect 1: Graminoid Relative Abundance

14.0 12.0 10.0 8.0 6.0 4.0 2.0

0.0 Relative Cover (%VBC)

Secies

Fig. 20. Grasses, sedges and rushes ranked by percent vegetative basal cover, a.k.a. relative abundance or relative cover. Note that for all graphs of ranked species abundance, genus phylum are included, but undifferentiated family groups, such as the sedges (Cyperaceae) and rushes (Juncaceae) are not included, as each represent multiple unidentified species. It would be inappropriate to compare their abundance with the abundance of individual grass species.

TRANSECT TWO

Transect 2 was located in the same vicinity as Transect 1 on an adjacent 1st order terrace. Despite their close proximity, the community structures captured by each transect were distinct (Fig. 21). The complex micro topography of the terraces contributed to highly variable soil moisture, soil type, and aspect characteristics within a small scale, and may have contributed to the variable species distributions observed.

Transect 2 had 58.8% total vegetative basal cover. Of this, 77.7% was composed of graminoids, dominated by the grasses S. nutans (25.3% of the total vegetative cover) and S. scoparium (20.2 % of the total vegetative cover). Along with the associated M. montana (8.9%), C. longifolia (7.4%), and S. heterolepsis (7.2%), these grasses made up

69% of the total vegetative cover. In addition to these, Bouteloua gracilis (willd. Ex

Kunth) Lag. ex Griffiths (blue grama) (1.3%), Hesperostipa spartea (Trin.) Barkworth

(porcupine grass) (1.2%), Nassella viridula (Trin.) Barkworth (green needle grass)

(1.0%), and Poa sp. (0.2%) were other species of note. Nassella viridula is a typical element of tallgrass prairie. The dominant and associated grasses as measured by basal cover were similarly of primary and secondary importance as measured by frequency within this transect (See Appendix 1).

Transect 2: Graminoid Relative Abundance

30.0 25.0 20.0 15.0 10.0 5.0

0.0 Relative Relative Cover (%VBC)

Species

Fig 21. Grasses, sedges and rushes ranked by percent Vegetative Basal Cover (VBC) within Transect Two. See Fig. 16 for an explanation of the symbols used.

TRANSECT THREE

Transect three was located along the edge of a side drainage to the south of Black

Squirrel Creek. A shallow depression in the surrounding xeric uplands, this drainage supported seeps, wetlands, and hummock formations as well communities of tallgrass in the transition zone between the B. gracilis, N. viridula, and M. Montana dominated uplands and the extensive Carex nebrascensis Dewey (Nebraska Sedge) dominated wetlands along the bottom of the drainage.

Along this 1-10 m wide belt, which extends along the entire length of the drainage, the grassland community had 46.5% total vegetative basal cover, of which graminoids comprised 86.45% (Fig. 22). Organic litter cover was abundant, leaving only

1.1% of the area as exposed, bare soil. The community was dominated by S. heterolepis,

C. longifolia and Andropogongerardii Vitman (big bluestem). These made up 27.1, 20.0, and 12.0 percent of the vegetative cover respectively, collectively accounting for 59.1% of the total cover. Other grass species in this community include the tallgrass S. scoparium (0.9%) as well as B. gracilis (8.9%) and M. Montana (4.9%) representing the short grass and mixed grass-dominated uplands, and arctic rush (2.1%) and sedges

(4.4%), representing the wetlands of the drainage bottom. While arctic rush comprised only 2.1% of the vegetative basal cover, it had the highest frequency (55%) of any graminoid within the community. Otherwise the most abundant grasses were also the most widespread.

Transect 3: Graminoid Relative Abundance

30.0 25.0 20.0 15.0 10.0 5.0

0.0 Relative Relative Cover (%VBC)

Species

Fig 22. Grasses, sedges and rushes ranked by percent Vegetative Basal Cover (VBC) within Transect Three. See Fig. 16 for an explanation of the symbols used.

TRANSECT FOUR

Transect 4 was along a similar transition zone belt running parallel with another side drainage of the Black Squirrel Creek. In the northwest quadrant of our primary study area, this drainage was substantial. A perennial stream ran through wetlands dominated by nebraska sedge, cattail, and bulrush and the topographic relief created significant aspect variation along the sides of the drainage. The transect was along the southern side of the drainage, on a slope with a northeastern aspect.

Transect 4 had the lowest vegetative cover among the four transects at 43.8%. Of this vegetation, graminoids made up 85.7% by basal cover. Despite the low vegetation cover, only 5.8% of the ground was bare, with litter cover high at 50.5%. This grassland community was dominated by M. montana, S. heterolepis, and S. scoparium (Fig. 23).

These made up 73.0% of the community collectively, each contributing 36.8, 18.7, and

17.5 percent respectively. The rare species H. sparteaand S. nutans also made up 3.9 % and 3.0 % of the total vegetative cover, respectively. Poa sp. was found in this community as well, comprising 1% of the vegetative cover. Despite its limited abundance, H. spartea was among the most widespread grasses in the community, present in 50% of the area. Muhlenbergia montana and S. scoparium were also widespread, with frequencies of 80% and 50% respectively.

Transect 4: Graminoid Relative Abundance 40.0

35.0 30.0 25.0 20.0 15.0 10.0

Relative Relative Cover VBC) (% 5.0 0.0

Species

Fig. 23. Grasses, sedges and rushes ranked by percent Vegetative Basal Cover (VBC) within Transect Four. See Fig. 16 for an explanation of the symbols used.

DISCUSSION

Our results indicate that within the upper Black Squirrel Creek drainage, vegetation communities still occur that may be correctly classified as true tallgrass prairie, comparable to those described by Livingston 60 years ago (1947, 1949, 1952).

Unfortunately, the number of remnants in the region, as well as the average remnant size, is much reduced. Instead of finding forty-acre meadows of tallgrass prairie, we found thin strips of prairie, generally in transitional zones between the mesic drainage bottoms and xeric uplands of the plains. On the other hand, the composition of the prairie communities observed today is remarkably similar to the composition documented in those earlier studies. The true prairie communities today are still clearly dominated by grasses, the majority of which are still those species characteristic of Midwest tallgrass prairie.

Similarly, these communities still contain many forb, shrub, and semi-woody species that are also important components of tallgrass prairie. The overall floristic species richness of the drainage is nearly identical to what it was in the 1940’s (Fugere 2012), and the diversity within transects is comparable.

Today the relative abundance and frequency of individual grass species within transects are not identical to what Livingston observed, but the overall dominant species are highly similar (Appendix A), and the dominant grasses today are characteristic of true tallgrass prairie. All of the grass species that were dominant components of the plains relict communities during the 1940s are still dominant components today. These include

S. heterolepis, S. nutans, S. scoparium, as well as B. gracilis. In comparison to the earlier studies, however, today we find A. gerardii, C. longifolia, and M. montana to be

dominant components of individual transects as well. Andropogon gerardii is the signature species of tallgrass prairie, and may have been missed in the early studies due to its patchy occurrence; the other two species are common components of the regional mixed grass prairie now, and may have increased in abundance and ecological profile.

Livingston had four stations in or near the Black Forest, and three stations, comprised of five transects, on the plains (Livingston 1947, 1952). Our study sites are located on the plains, midway between Livingston’s plains and forest stations. Thus, while our sites are more comparable to Livingston’s plains stations, their relative proximity to the forest is evidenced by the species composition we encountered, which included many species that Livingston found in his forest study sites but not in his plains sites (Appendix A).

As closely as it was possible to determine, we found that the specific sites studied by Livingston appear to have been degraded significantly. Although too heavily grazed to be thoroughly assessed at the species level, it is clear that they can no longer be considered true prairie in their current form. There are several factors which may have contributed to the their decline, including local climate change, altered soil hydrology, development, and overgrazing. Whatever the cause, these were among the largest patches of relict true prairie described by Livingston, upwards of 40 acres in one case, and so their loss is a significant loss for the region. Although we were able to locate other small patches of true prairie in the drainage, the communities are limited in size. Many are long, thin strips occupying a narrow zone of adequate moisture between the xeric uplands and mesic wetlands at the bottom the lowland depressions, intermixing on one side with short-grass steppe and on the other with Nebraska sedge (Carex nebrascensis) dominated

wetlands.

Tallgrass prairie is particularly sensitive to heavy grazing (Weaver, 1954). This is largely due to livestock’s strong preference of many of true prairies signature species, even when other forage is abundant (Weaver 1954). Thus, grazing pressure can have a significant impact on grassland species composition. Stock density, timing of grazing within the growing season, duration of grazing periods, and time for plant recovery between grazing periods are also important factors. Tallgrass prairie is not well adapted to heavy, continuous grazing, and may be replaced by communities of grazing-tolerant and xeric-adapted species such as blue grama.

In Colorado, livestock may also disproportionately graze in small tallgrass prairie remnants where consistently available soil moisture, creates oases of palatable forage even in times of drought. Because pastures in the region tend to be quite large, livestock can be disproportionately attracted to these patches especially in years of drought. While tallgrass prairie can be remarkably productive, certain grazing regimes can lead to the replacement of the productive tallgrass species by less productive species that are better able to cope with high grazing pressure. Livingston (1947, 1952) hypothesized that the tallgrass prairie communities he found had survived because they were managed as fall hay fields and winter pasture, rather than summer pasture. This schedule might give the tallgrass species time to grow, to reproduce sexually and a-sexually, and to replenish their energy reserves for the following growing season. Similarly, the intact prairie communities that we studied are currently managed primarily for fall and winter pasture with low stock densities, meaning the majority of plants are grazed only after reproduction and while dormant. While noting the abundance of relict prairie in the Black

Squirrel Creek drainages around Falcon and Peyton, Livingston also noted that even then,

“there is evidence to indicate that overgrazing may have destroyed extensive former relicts in this locality” (Livingston 1952, p.81)

Our analysis of the local climate suggests that, while both precipitation and temperature have trended upward over the past century, there have not been sufficiently substantial long-term climatic changes to adequately account for the decline in extent of this moisture-dependent type of prairie. On the other hand, idividual periods of drought, likely in combination with other factors such as overgrazing, may have contributed to the degradation or loss of individual patches and the overall regional decline of tallgrass prairie. Because the tallgrass prairie communities in this region are typically supported by local hydrology that historically maintained consistently high soil moisture, likely through periods of prolonged drought, the precipitation patterns per se may only play a supporting role rather than a critical one in their persistence. It is unclear whether changes in the local hydrology have caused the reduction of tallgrass prairie, as little data are available to assess changes in subsurface moisture or aquifer levels in northern portion of the basin. Any changes in the local hydrology that may have occurred, however, are not likely due to local climate over the past century, but rather due to anthropogenic influences.

The factors that have negatively impacted the tallgrass prairie to this point will continue to influence the health and extent of the remaining tallgrass prairie. Water development in the area, as well as other drilling activities, are a concern in relation to potential drop in the level of the alluvial aquifer. While net extraction is probably the most likely course in the area, intentional or unintentional recharge of the alluvial aquifer

with water imported from outside of the drainage may also be a possibility, potentially helping to reverse the dropping water table in some locations, but perhaps not uniformly, nor necessarily in the areas that currently support prairie fragments.

Besides inappropriate grazing regimes, the most immediate threat to the areas tallgrass prairie is probably from suburban and exurban development. Further expansion of Colorado Springs metropolitan area continues to expand rapidly, as it has for the past several decades. The population of Falcon, CO has been growing rapidly as well.

Housing developments and ex-urban “ranchettes” now nearly surround Four-Way Ranch.

Such development is not only an issue because prairie may be directly destroyed under houses, driveways, and access roads, but also because gardens, lawns, roadways, trails, horse paddocks, hobby livestock husbandry, etc., all act as vectors for invasive weedy species. Weaver (1954) discusses the stability of tallgrass prairie except where overgrazing occurs and where human development creates conditions that are conducive to invasion. Both purple loosestrife (Lythrum salicaria) and canada thistle (Circium arvense) are already present in the study area, and are becoming more abundant. The potential for future introductions and harboring by adjacent developed sites is a significant threat. Cooperation between landowners will be a key part of successful conservation in the future.

Tallgrass prairie is of significant conservation value in Colorado, and is one of the tracked community types with conservation concerns by the Colorado Natural Heritage

Program. It has notable aesthetic and recreation value (Moir, 1972, Bock and Bock1998) with high floral diversity that may have adaptations unique to the state’s environment.

Increasingly fragmented and disjunct, these populations may also harbor a

disproportionate degree of genetic variation within populations (Bock and Bock1998

(Keeler and Kwankin 1989; Norrmann et al 1997)). The floral diversity supported by healthily functioning tallgrass prairie also supports faunal diversity, providing irreplaceable habitat for certain animal species including amphibians (Mierzwa 1997), insects (Taron 1997; Craig et al 1999; Collinge et al. 2003), large mammals such as bison

(Steuter 1997), and Birds (Byre 1997) (for lists of tracked animal species in Colorado, see

CNHP 2011: www.cnhp.colostate.edu).

When managed well, true prairie has very high productivity and thus economic importance as livestock pasture, for hay production and as forage for game animals

(Weaver and Fitzpatrick 1934; Weaver 1954; Packard and Mulet 1997). The tallgrass prairie of Colorado also has historical value as a legacy of the past, worth preserving in honor of its historical significance (Bock & Bock).

Restoring true prairie to sites where it existed historically but has been degraded is notoriously difficult (Weaver, 1954, Packard and Mulet 1997, Samson et al 2004). If the causal factors at play can be more clearly determined, perhaps those true prairie communities documented by Livingston, and subsequently lost, may be restored. In the meantime, it is far easier to protect what remains than to restore what has been lost.

In summary, The remaining tallgrass prairie communities of the upper Black

Squirrel Creek drainage are substantially similar in composition to those remnants studied by Livingston in the 1940’s, but since that time the extent of tallgrass prairie in the region has decreased dramatically. The communities examined can legitimately be classified as true tallgrass prairie for two primary reasons: they consist of an assemblage of grasses that are characteristic of true tallgrass prairie in the Midwest, and many forbs

typical of true prairie are widespread throughout the communities. These remaining patches of relict tallgrass prairie are of high conservation value and of high conservation concern.

ACKNOWLEDGEMENTS

I would like to express my deep gratitude to both Professor Tass Kelso and Miro

Kummel who have both served as invaluable advisors throughout out this project.

Particular thanks are due to Tass Kelso, who taught me everything I know botanically and provided me with such an enjoyable research question. I would like to thank Tracy

Lee, owner of Four-Way Ranch, for allowing us to conduct our research on his beautiful property, and for being such a good steward of that land. Special thanks to my field partner Leah Fugere, with whom all of the surveys were conducted, and many of the plants identified, joyfully. Thanks to Adam Freierman, for assisting with transect data collection, and to George Maentz, Dan Fosha, Boyce Drummond, and Mike Siddoway for lending their eyes and expertise to the research and sharing their excitement for the prairie.

APPENDICES

Appendix A. Data from current study, and data from Livingston's 1947 and 1952 papers. Nomenclature follows USDA, NRCS PLANTS Database (2012). Names of species identified by Livingston have been changed to reflect the same nomenclature. Data from Livingston on Forb abundance and frequency are not included here. Station numbers reflect those given in Livingston, 1947.  indicates that the species is an important element of true tallgrass prairie (Weaver and Fitzpatrick, 1934).  indicates that the species is rare (Colorado Natural Heritage Program, 2011) indicates that the species is regionally uncommon (Kelso, 2008) * Cover refers to basal cover in all cases where applicable.

Relict Tallgrass Prairie Communities of the Upper Black Squirrel Creek Drainage 2011 Data - Tsocanos 1942 Data - Livingston Transects Forest Stations Plains Stations Community 17 Structure 1 1 1 2 3 4 11 14 15 16 2 3 U Mi Lo p d w Vegetation 16 17 19 18. 18. 63.8 58.8 46.5 43.8 20.5 23.5 21.5 19.8 Cover (% .5 .1 .5 8 7 total area) Graminoid 70 90 45 47. 24. 69.5 77.7 86.4 85.8 87.8 89.3 88.5 66.2 Cover (% of .7 .6 .8 8 8 veg. cover) Graminoid 11 15 8. 44.3 45.7 40.2 37.5 18.0 21.0 19.0 13.1 9.0 4.6 Cover (% .7 .5 9 total area) Litter Cover (% total 32.8 20.4 52.4 50.5 area)* Bare Ground (% total 3.5 20.8 1.1 5.8 area) 2011 Data - Tsocanos 1942 Data - Livingston Transects Forest Stations Plains Stations Species 17 Composition 1 1 1 2 3 4 11 14 15 16 2 3 U Mi Lo p d w % % % % % % % % % % % % ve ve ve ve ve ve ve ve ve ve ve ve % A. Dominant g g g g g g g g g g g g veg ba f ba f ba f ba f ba f ba ba ba f ba f ba f ba ba Grasses, bas s s s s s s s s s s s s 2011 cov co co co co co co co co co co co co v v v v v v v v v v v v

Andropogon 12 3 5. 1 0. 6. 5. gerardii  .0 5 2 0 4 10 5 70 2 30

Bouteloua 1. 2 8. 3 0. 1 14 6. 19 10 1. 31 15. gracilis 3 0 9 0 1 0 .2 8 .8 0 1 30 .0 4.9 0

Calomovilfa 3. 2 7. 5 20 5 1. 2 8. 0. 10 longifolia  2 0 4 0 .0 0 4 0 1 90 9 30 .6 0.8

Muhlenbergi 4. 1 8. 4 4. 3 36 8 4. 8 5. 9. 0. 3. a montana 2 5 9 0 9 5 .8 0 9 0 6 3 4 20 1

Schizachyriu m scoparium 5. 3 20 6 0. 1 17 5 2. 1 2. 3. 28  2 0 .2 0 9 0 .5 0 1 0 3 7 .2

Sorghastrum 12 5 25 8 3. 1 4. 7. 0. 30. nutans  .3 5 .3 0 0 0 1 10 6 30 3 7 2.1 Sporobolus heterolepis 9. 2 7. 2 27 5 18 3 29 7 10 33 73 10 12 30 10 2.  0 5 2 5 .1 0 .7 5 .1 0 .1 .9 .4 0 .5 40 .7 0 9 9.5 1.5 33 70 73 77 41 32 53 74 82 45 44 45. 19. Totals: .9 .3 .8 .5 .3 .2 .7 .2 .3 .5 .8 1 4 B. Subdominant Grasses; Dominant and Subdominent Sedges and Rushes, 2011

Agrostis 0. 0. 1 scabra 9 5 2 5

Bouteloua 4. 1 0. hirsuta 5 5 1 5 Calomogrosti s stricta (ssp. 0. inexpansa) 3 5 tr 10 8. 2 3. 2 4. 4 0. 1 Cyperaceae 5 5 1 5 4 0 3 0 0. 1 Elymus sp. 5 5

Hordeum 0. jubatum 2 5 tr 8. 2 Juncaceae 3 0

Juncus 6. 3 1. 1 2. 5 1. 3 0. 0. 0. arcticus 3 0 7 5 1 5 6 0 2 90 8 60 8 40 tr 0.1 1.2

Koeleria 0. 1 0. 1 2. 1. 0. 2. macrantha  7 5 1 0 8 3 4 50 8 Muhlenbergi a 0. 0. minutissima 0 5 6 5

Panicum 2. 0. 1. virgatum  8 5 1 5 3

Phleum 0. 0. 2. 0. pratense  0 5 4 0 3 30 0. 0. 1 1. 2 Poa sp. 2 5 2 0 0 0 Stipa spartea 1. 1 3. 5 7. 4 2. 5.  2 5 9 0 0 0 9 4 tr 10 1. Stipa viridula 0 5 tr tr

Unknown 3. grass 1 2 5

Unknown 0. grass 2 0 5

Unknown 0. grass 3 2 5

Unknown 0. 1 grass 4 4 0

Unknown 3. 1 0. 2. 1 grass 5 1 5 1 5 2 0 32 5. 7. 3. 0. 3. 3. 0. 4. 1. 0. Totals: .5 1 2 8 1 2 3 6 9 1 0 0.1 1.2 C. Grasses, Sedges and Rushes,

Absent in 2011 (of the Plains) Andropogon 0.9

hallii

Carex aurea tr 10 Carex filifolia tr 1.5 Carex nebraskensis tr 10 Carex praegracilis tr 10 Hesperostipa comata 0.9

Juncus 0. 0. longistyslis 2 20 4 0.1

Juncus 0. Torreyi 1 Muhlenbergi a asperifolia tr 10

Poa 0. fendleriana 4 10

Spartina 4. pectinata 1 50 Sporobolus cryptandrus 0.2 0. 0. 0. 0. 0. 0. 0. 0. 0. 4. 0. Totals: 0 0 0 0 0 0 0 0 0 7 5 0.1 3.5 D. Grasses, Sedges and Rushes, Absent in 2011 (of the Plains and Forest)

Agrostis 0. 4. gigantea 5 20 1 50

Agrostis 0. 2 0. 0. 1. hyemalis 1 0 tr 4 tr 10 4 10 0 10 5. Carex brevior 3 20 tr 30 Carex inopsis ssp. 2. 6 3. 0. 0. Heliophila 9 0 7 8 tr 10 3 10

Carex 1. 0. oreocharis tr 8 2 10 tr 0.2 0.7 Eleocharis palustris tr 10 tr 10 Elymus trachycaulus ssp 1 0. 8. trachycaulus tr 0 1 10 0 50 tr Elymus trachycaulus ssp. 2 0. 0. 0. subsecundus tr 0 8 8 5 20 tr 10 Muhlenbergi a 0. 1. richardsonii tr 5 10 8 20 1.8

Pascopyrum 0. 0. 0. smithii 4 tr 10 4 10 5 0.2 Poa Pratensis 31 8 6. 6. 4.  .4 0 6 4 6 40 0.3 0. 0. 0. 0. 34 11 10 11 1. 14 0. Totals: 0 0 0 0 .4 .1 .6 .5 3 .9 5 2.5 0.7 E. Grasses, Sedges and Rushes,

Absent in 2011 (in the Forest only)

Achnatherum 0. nelsonii ssp. 7 Dorei

Blepharoneur 1 2. 3. on tricholepis tr 0 5 7

Bromus 0. inermis 4 1. Carex pellita 3 20

Danthonia 4. 2 5. 9. 0. spicata 9 0 6 3 4 20

Elymus 0. canadensis  5

Elymus 0. 4 0. Elymoides 1 0 7

Muhlenbergi 2. a wrightii 3

Poa 10 2. 1. compressa .5 3 3 20

Vulpia 0. octoflora 4 0. 0. 0. 0. 5. 21 17 3. 0. 0. 0. Totals: 0 0 0 0 0 .3 .6 0 0 0 0 0.0 0.0

2011 Data - Tsocanos 1942 Data - Livingston Transects Forest Stations Plains Stations F. Forbs, Shrubs, and Semi-woody 17 1 1 Plants of 1 2 3 4 11 14 15 16 2 3 2011 U Mi Lo p d w

Glycyrrhiza 2 5 8 3 lepidota  5 0 0 5 DATA AVAILABLE IN LIVINGSTON, 1947, 1952

Oligoneuron 4 5 5 rigidum  5 0 5 5

Artemisia 4 3 2 ludoviciana  5 0 5 5 Symphyotrich um ericoides 2 7  0 5 5

Rosa 2 6 1 arkansana  0 0 0 5

Helenium 1 6 1 autumnale  0 0 5

Equisetum 1 2 1 3 arvense  0 5 5 5

Comandra 4 3 umbellata 5 5

Dalea 1 3 3 Purpurea  5 5 0

Symphotrich 3 2 1 um laeve  5 0 5 5 1 2 1 Asteraceae 5 5 5 0 Geranium atropurpureu 2 1 1 m 5 5 0 5

Iris 2 3 missouriensis 0 5

Pedicularis 2 3 canadensis 0 5

Thermopsis 2 2 1 montana 0 0 5

Heterotheca 1 2 1 sp. 0 5 5

Antennaria 2 1 microphylla 5 0 0 1 1 Fragaria sp. 0 5 5

Monarda 1 2 fistulosa  0 5 0

Packera 3 pseudaurea 0 5

Achillea 1 1 lanulosa 5 5 0

Rudbeckia 1 1 hirta  5 5 2 Unamia alba 0 5

Arenaria 2 hookeri 0

Artemisia 1 frigida 5 0 5

Prunella 1 vulgaris 5 5 1 Salix exigua 5 5

Allium 1 cernuum 0 5

Calylophus 1 serrulatus 5 Campanula rotundifolia 5 5 5

Circium 1 arvense 5 0

Drymocallis 1 arguta 5 Gentianopsis procera ssp. 1 Crinita 5

Hypericum 1 formosum 5 Liatris ligulistylis 1  5 0 Symphoricar pos 1 occidentalis 5 0 1 Bryophyta 0

Dodecatheon 1 pulchellum 0 Galium septentrional 1 e 0

Liatris 1 punctata 0

Lobelia 1 siphilitica  0

Lycopus 1 americanus  0 Nyctaginacea e 5 5

Sisyrinchium 1 idahoense 0

Trifolium 1 pratense 0 Agromonia striata 5 Ambrosia psilostachia 5 Circium sp. 5 Geum sp. 5 Parnassia sp. 5 Platanthera aquilonis 5 Prunus pumila var. besseyi 5 Triglochin sp. 5 Valeriana edulis 5

Unknown 1 forb 1 0 Unknown forb 2 5 Unknown forb 3 5 5 Unknown forb 4 5

Unknown 3 forb 5 0 Unknown forb 6 5 Unknown forb 7 5 Unknown forb 8 5

Unknown 2 forb 9 0 Unknown forb 10 5

Unknown 3 forb 11 0 Unknown forb 12 5 Unknown forb 13 5 Unknown forb 14 5

Appendix B. This is partial a reproduction of the list of significant species occurring in the upper Black Squirrel Creek drainage compiled by Fugere in 2012. This particular adaptation highlights the species closely associated with Midwestern tallgrass prairie, not all of which were positively identified or captured by the transects of this study.

Midwest Species Foothills/Montane Uncommon Rare Prairie Agropyron X cristatum Andropogon X gerardii Anemone X X canadensis Anemone cylindrica X X Artemisia X ludoviciana Astragalus X X canadensis Bouteloua X curtipendula Calamovilfa X longifolia Cicuta douglasii X Dalea candida X Dalea purpurea X Elymus canadensis X Equisetum arvense X Gentianopsis X virgata Glycyrrhiza X lepidota Helenium X X autumnale Helianthus rigidus X Hypoxis hirsuta X X Juncus X X brachycephalus Koeleria macrantha X Liatris ligulistylis X X Lilium X X X philadelphicum Lobelia siphilitica X Lycopus americanus X

Lysimachia ciliate X X

Monarda fistulosa X Oligoneuron album X X Oligoneuron X rigidum Panicum virgatum X Penstemon gracilis X X Poa pratensis X Rosa arkansana X Rudbeckia hirta X X Schizachyrium X scoparium Solidago X missouriensis Sorghastrum nutans X X Sporobolus X X heterolepis Symphotrichum X ericoides Symphotrichum X X laeve Toxicodendron X X rydbergii Viola sororia X X

Appendix C. This list is reproduced from Fugere (2012). While some upland species are omitted, the flora of the tallgrass prairie remnants is represented in its entirety.

Vascular Flora of Upper Black Squirrel Creek Drainages, El Paso Co., Colorado

Species list for vascular flora occurring in the drainage areas associated with Black Squirrel Creek; list encompasses some upland species occurring sporadically in the drainage systems that are more typically found in the drier surrounding grassland matrix. Additional species found only in the drier grasslands are not included. Nomenclature follows NRCS database (www. Plants.USDA.gov; accessed 11/02/2011) and Flora of North America (Oxford University Press); Poaceae follows Shaw (2008). Nomenclature commonly used in Colorado (e.g. Weber and Wittmann, 2001) is given in parentheses. Voucher specimens are at COCO. Common local species observed but not collected are in italics. Significant species are coded as follows:

(LN) Species noted by Livingston (1941; 1947; 1952). FM Species more common locally at in Foothills/Montane zone (Weber and Wittman 2001; Kelso 2008) MWP Species characteristic of Midwest Prairie Grasslands as noted by Weaver and Fitzpatrick (1934) and Livingston (1952) R Rare species listed by Colorado Natural Heritage Program (2011) U Regionally uncommon or local endemic

Amaranthaceae Froelichia gracilis (Hook.)Moq.

Alismataceae Sagittaria cuneata Sheldon Sagittaria latifolia Willd. Alisma triviale Pursh

Alliaceae Allium cernuum Roth (LN)

Anacardiaceae (Toxicodendron rydbergii (Small)Greene) M, MWP

Apiaceae Cicuta douglasii (D.C.) J.M. Coulter & Rose MWP Berula erecta (Hudson) Coville

Apocynaceae Apocynum cannabinum L.

Asclepiadaceae

Asclepias hallii A. Gray R, M Asclepias speciosa Torr.

Asteraceae Achillea millefolium L. (LN) Agoseris glauca (Pursh) Raf. Antennaria microphylla Rydb. (LN as A. parviflora) Artemisia frigida Willd. (LN) Artemisia ludoviciana Nutt. (LN as A. gnaphalodes)MWP Bahia dissecta (A.Gray)Britton Bidens tenuisecta A.Gray Carduus nutans L. Cirsium arvense (L.)Scop. Cirsium flodmanii (Rydb.)Arthur Cosmos parviflorus Jacq. U Erigeron bellidiastrum Nutt. Erigeron compositus Pursh Erigeron divergens Torr. & A. Gray Erigeron flagellaris A. Gray Erigeron glabellus Nutt. Erigeron lonchophyllus Hook. (Trimorpha lonchophylla) M Erigeron subtrinervis Rydb. ex Porter & Britton Erigeron vetensis Rydb. Grindelia squarrosa Dunal Helenium autumnale L. M, MWP (LN) Helianthus annuus L. Helianthus nuttallii Torr. & A. Gray Helianthus petiolaris Nutt. (LN) Helianthus pumilus Nutt. Helianthus rigidus (Cassini)Desfontaines (LN), MWP Heterotheca canescens (D.C.) Shinners ( LN ? as Chrysopsis villosa) Lactuca tatarica (L.)Meyer Liatris ligulistylis (A. Nelson) K. Schum. (LN), R, MWP Liatris punctata Hook. (LN) Lygodesmia juncea (Pursh)D. Don ex Hook. Oligoneuron album (Nutt.)G.L. Nesom (Unamia alba) R, MWP Oligoneuron rigidum (L.)Small MWP as Solidago rigidum Packera pseudaurea (Rydb.)W.A. Weber & A. Löve M Packera tridenticulata (Rydb.)W.A. Weber & A. Löve Pseudognaphalium canescens (D.C.) W.A. Weber Ratibida columnifera (Nutt.)Woot. & Standl. Ratibida columnifera X tagetes Rudbeckia hirta L. (LN) M, MWP Senecio spartioides Torr. & A. Gray Solidago gigantea Aiton Solidago missouriensis Nutt. (LN), MWP

Solidago nana Nutt. M Solidago velutina D.C. Symphotrichum ericoides (L.)A. Löve and D. Löve (Aster ericoides) MWP Symphotrichum laeve (L.) A. Löve and D. Löve (Aster laevis) M, MWP Symphotrichum lanceolatum (Willd.) G.L. Nesom (Aster lanceolatus) Tetraneuris acaulis (Pursh)Greene Thelesperma megapotamicum (Spreng.) Kuntze Tripleurospermum perforatum (Merat)M. Lainz (Matricaria perforata) M

Boraginaceae Mertensia lanceolata (Pursh)D.C. Cryptantha cinerea (Greene)Cronquist (Cryptantha jamesii) Onosmodium bejariense DC var. occidentale (Mack.)B.L. Turner (Onosmodium molle subsp. occidentale) Plagiobothrys scouleri (Hook. & Arnott) I. M. Johnst.

Brassicaceae Boechera retrofracta (Graham) A. Löve & D. Löve (Arabis holboelii) M Barbarea orthocera Ledeb. Draba nemorosa L. Sisymbrium loeselii L.

Cactaceae Pediocactus simpsonii (Engelmann) Britton & Rose M (Opuntia polyacantha Haworth)

Campanulaceae Campanula rotundifolia L. M Lobelia siphilitica L. (LN) MWP

Caprifoliaceae Symphoricarpos occidentalis Hook.

Caryophyllaceae Eremogone hookeri (Nuttall)W.A. Weber (Arenaria hookeri) Stellaria longifolia Muhlenberg M Paronychia jamesii Torr. & A. Gray

Chenopodiaceae Chenopodium graveololens Willd. (Teloxis graveolens) Chenopodium leptophyllum (Moq.)Nuttall (LN) Cycloloma atriplicifolium (Spreng.) J.M. Coulter Suaeda calceoliformis (Hook.) Moq. (Suaeda depressa)

Commelinaceae Tradescantia occidentalis (Britton) Smythe

Crassulaceae Sedum lanceolatum Torr.

Cyperaceae Carex aurea Nutt. (LN) M, U Carex brevior (Dewey) Mack. (LN) Carex crawei (Dewey) R, M Carex disperma Dewey M Carex douglasii Boot Carex echinata Murray (Carex angustior) M, U Carex pellita Muhl. (Carex lanuginosa) (Carex nebrascensis Dewey) (LN) *Carex parryana Dewey ssp. hallii (Olney) D. Murray [specimen coll. R.B. Livingston 1430; @COCO] Carex simulata Mack. Carex xerantica L.H. Bailey Eleocharis acicularis (L.) Roemer & Schultes Mariscus schweinitzii (Torr.)Koyama Schoenoplectus acutus (Muhl.) A. Löve & D. Löve (Scirpus acutus) Scirpus microcarpus Presl. & C. Presl

Equisetaceae Equisetum arvense L. (LN) MWP

Euphorbiaceae Euphorbia brachycera Engelm.

Fabaceae Amorpha fruticosa L. var. angustifolia Pursh Astragalus canadensis L. U, MWP Dalea candida Michx. ex Willd. MWP Dalea purpurea Vent. (LN as Petalostemon purpureus) MWP Thermopsis montana Nutt. Trifolium hybridum L. Gleditsia triacanthos L. Glycyrrhiza lepidota Pursh (LN) MWP Lathyrus polymorphus Nutt. Lupinus pusillus Pursh Oxytropis multiceps Nutt. Robinia neomexicana A. Gray

Gentianaceae Gentianella amarella (L.)Borner ssp. acuta (Michx.) Gillette [Gentianella strictiflora (LN as Gentiana strictiflora). As noted by Weber and Wittmann (2001), the densely white flowered form with a stiffly erect

inflorescence is very distinctive in this region and recognized as separate from the amarella/acuta form) Gentianopsis virgata (Raf.) Holub (Gentianopsis procera ssp. crinita; G. crinita) MWP

Geraniaceae (Geranium atropurpureum Jones) (G. caespitosum ssp. atropurpureum)

Haloragaceae Myriophyllum sibiricum Kom.

Hippuridaceae Hippuris vulgaris L. M

Hypericaceae Hypericum scouleri Hook. (Hypericum formosum) M

Hypoxidaceae Hypoxis hirsuta (L.)Coville R, MWP

Iridaceae Sisyrinchium idahoense E. P. Bicknell Sisyrinchium montanum Greene

Juncaceae Juncus alpinoarticulatus Chaix (Juncus arcticus Willd. ssp. balticus (Willd.) Hyl.) (LN as J. balticus) Juncus brachycephalus (Engelm.)Buchenar R, MWP Juncus bufonius L. Juncus dudleyi Wieg. Juncus interior Wieg. Juncus longistylis Torr. Juncus marginatus Rostk. Juncus nodosus L. Juncus saximontanus A. Nelson Juncus torreyi Coville (LN)

Juncaginaceae Triglochin maritima (LN) Triglochin palustris L. M

Lamiaceae Lycopus americanus Muhl. ex Bartram MWP Mentha arvensis L. Monarda fistulosa L. MWP Prunella vulgaris L. (LN) Scutellaria galericulata L. U

Stachys palustris L.

Lentibulariaceae Utricularia minor L. R, M

Liliaceae Calochortus gunnisonii S. Watson Lilium philadelphicum L. R, M, MWP

Lythraceae Lythrum salicaria L.

Malvaceae Sidalcea neomexicana A. Gray U, M

Najadaceae Najas guadalupensis (Spreng.)Magnus

Nyctaginaceae Abronia fragrans Nuttall ex Hook. Mirabilis linearis (Pursh)Heimerl (Oxybaphus lanceolatus)

Oleaceae Forestiera pubescens Nuttall (Forestiera neomexicana)

Onagraceae Calylophus serrulatus (Nuttall) P. H. Raven Epilobium ciliatum Raf. ssp. glandulosum (Lehm.) Hoch & P. H. Raven Epilobium leptophyllum Raf. Gaura coccinea Nuttall ex Pursh Gayophytum diffusum Torr. & A. Gray M Oenothera coronopifolia Torr. & A. Gray Oenothera flava (A. Nelson)Garrett U Oenothera nuttallii Sweet Oenothera villosa Thun. (LN as Anogra strigosa) (Oenothera strigosa)

Orchidaceae Platanthera aquilonis Sheviak (Limnorchis hyperborea, Platanthera hyperborea) M Spiranthes romanzoffiana Cham. M, U

Plantaginaceae (s. str.) Plantago elongata Pursh Plantago patagonica Jacq. (LN as P. purshii)

Poaceae Achnatherum nelsonii (Scribn.)Barkworth Agropyron cristatum (L.)Gaertn. MWP Agrostis gigantea Roth. Agrostis scabra Willd. M Alopecurus aequalis Sobol M Andropogon gerardii Vitman (LN as A. furcatus) MWP Beckmannia syzigachne (Steud.)Fernald (Bouteloua curtipendula (Michx.)Torr.) MWP Bromopsis inermis (Leyss.)Holub (Bromus inermis) Calamagrostis stricta (Timm.)Koeler M Calamovilfa longifolia (Hook.)Scribn. (LN) MWP Ceratochloa carinata (Hook. & Arnott)Tutin (Bromus carinatus) Chondrosum gracile Kunth (Bouteloua gracilis) Chondrosum hirsutum (Lag.)Sw. (Bouteloua hirsuta) Critesion jubatum (L.)Nevski (Hordeum jubatum) (LN) Critesion brachyantherum (Nevski)Barkworth & D.R. Dewey (Hordeum brachyantherum) Distichlis spicata (L.) Greene Elymus canadensis L. MWP Elymus lanceolatus (Scribner & J.G. Sm.)Gould Elymus trachycaulus (Link)Gould ex Shinners (LN as A. pauciflorum) Glyceria elata (Nash ex Rydb.)M.E. Jones M Glyceria striata (Lam.)Hitchc. M Hesperostipa comata (Trin. & Rupr.)Barkworth (Stipa comata) (LN) Hesperostipa spartea (Trin.)Barkworth (Stipa spartea) (LN) Nassella viridula (Trin.)Barkworth (Stipa viridula) Koeleria macrantha (Ledeb.)Schult. (LN as Koeleria cristata) MWP Muhlenbergia asperifolia (Nees & Meyer) Parodi (LN) Muhlenbergia minutissima (Steud.)Swallen Muhlenbergia montana (Nutt.)Hitchc. M Nassella viridula (Trin.)Barkworth (Stipa viridula) Panicum virgatum L. (LN) MWP Pascopyrum smithii (Rydb.)Barkworth & D.R. Dewey (LN as Agropyron smithii) (Agropyron smithii, Elytrigia smithii) Phleum pratense L. (LN) Poa annua L. Poa fendleriana (Steud.)Vasey (LN) M Poa interior Rydb. M Poa leptocoma Trin. Poa pratensis L. (LN) MWP Schizachyrium scoparium (Michx.)Nash (LN as Andropogon scoparius) MWP Sorghastrum nutans (L.)Nash (LN)U, MWP Spartina pectinata Link (LN) Sporobolus airoides (Torr.)Torr. Sporobolus heterolepis (A.Gray)A. Gray (LN) R, MWP

Thinopyrum ponticum (Podp.)Z.W. Liu & R.C. Wang (Elytrigia elongata)

Polemoniaceae Collomia linearis Nutt.

Polygonaceae Eriogonum alatum Torr. (Pterogonum alatum) Eriogonum annuum Nutt. (LN) Polygonum amphibium L. (Persicaria amphibia) MWP Polygonum convolvulus L. (Fallopia convolvulus) Polygonum douglasii Greene Polygonum pensylvanicum L. (Persicaria bicornis) Polygonum lapathifolium L. (Persicaria lapathifolia) Polygonum punctatum Elliott (Persicaria punctata) Rumex crispus L. Rumex vulgaris L. (Acetocella vulgaris)

Portulacaceae Phemeranthus calycinus (Engelm.)Kiger (Talinum parviflorum) (LN)

Potamogetonaceae Potamogeton natans L.

Primulaceae Dodecatheon pulchellum (Raf.)Merr. M Lysimachia ciliata L. U, MWP (as Steironema ciliata)

Ranunculaceae Anemone canadensis L. M, MWP Anemone cylindrica A. Gray M, MWP Myosurus minimus L. Ranunculus trichophyllus Chaix

Rosaceae Agrimonia striata Michx. U, M (Fragaria virginiana Miller) MWP Geum aleppicum Jacq. M Potentilla arguta Pursh (Drymocallis arguta) M Potentilla hippiana Lehm. Potentilla norvegica L. Potentilla plattensis Nutt. Prunus pumila L. var. besseyi (L.H. Bailey) Gleason (Prunus besseyi; Cerasus pumila) Rosa arkansana Porter MWP

Rubiaceae Galium boreale L. (Galium septentrionale) M

Galium trifidum L. M

Salicaceae Populus angustifolia James M (Populus deltoides Bartram ex Marsh) Salix exigua Nutt. Salix irrorata Anderss. M Salix ligulifolia (C.R. Ball)C.R. Ball Salix lucida Muhlenb. ssp. caudata (Nuttall)Argus

Santalaceae (Comandra umbellata (L. Nutt.) (LN as C. pallida)

Saxifragaceae Parnassia palustris L. var. parviflora (DC)Boivin (Parnassia parviflora )

Selaginellaceae Selaginella densa Rydb. M

Scrophulariaceae (s. lat.) Mimulus glabratus Kunth Nuttallanthus canadensis (L.)D.A. Sutton (Linaria canadensis) U Orthocarpus luteus Nutt. (LN) Pedicularis canadensis L. M Penstemon auriberbis Pennell Penstemon glaber Pursh M Penstemon gracilis Nutt. U, MWP (Scrophularia lanceolata Pursh) Veronica anagallis-aquatica L. (Veronica catenata) Veronica peregrina L. (LN) Veronica serpyllifolia L. ssp. humifusa (Dicks.)Syme M

Solanaceae Physalis virginiana Mill.

Sparganiaceae Sparganium angustifolium Michx. M

Valerianaceae Valeriana edulis Nutt. ex Torr. & Gray

Verbenaceae Verbena bracteata (NEED)

Violaceae Viola sororia Willd. M, MWP as V. papilionacea

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