Category Archives: Open Space

Weber Clouds

Weber: Clouds form on horizons, but what follows?
By William A. Weber Sunday, October 21, 2007

Chris Brown Photography
Chris Brown Photography

Cloud formations are one of Boulder’s most interesting and beautiful environmental features. When the clouds come down below the summits of Eldorado Mountain, Green Mountain and Bear Peak and cover the upper half of the Flatirons, we know it will soon rain in town. When a smooth-capped mass of clouds forms on the western horizon, we know that Chinook winds will blow soon.

In 1961, I helped a university Natural Areas Committee to explain the scientific values and need for preservation in its natural state of the Flatirons-Mesa trail area. Many folks have forgotten what these values were. It is time for us to remember.

The abruptness of the outer foothills creates locally moist microclimates on the east-facing mountainsides partly because of the deep shade afforded by the cliffs and the steep ravines that face northeast. In addition, however, the great height and steep faces of the Flatirons have the frequent effect of stimulating the formation of a cloud veil just in this area, when warm moist air from the southeast meets with colder air from the west.

To the west of the Flatirons-Mesa Trail area, this cloud veil is usually absent. The localized effect of the cloud veil is to raise the relative humidity on the slopes of the Flatirons. This in combination with the more shaded, steep slopes provides localized relatively moist microclimatic conditions.

These more moist conditions provide unique habitats on which many plants not ordinarily suited to our dry climate can survive and reproduce. The effects of this moist situation are reflected even on the back side of Green Mountain and Eldorado Mountain.

The steep gradient of this area has caused a telescoping of the flora and fauna belonging to a great range of habitats, altitudes and temperature tolerances into a relatively small area where they live side-by-side. Because of the steep north and south slopes, this actually results in some of the higher-altitude life forms occurring lower on the north-facing slopes than the low-altitude forms on the south facing slopes. This situation provides unique settings of extraordinary aesthetic and scientific values.

One curious and unique fact about the flora of this strip is that a number of plants typical of the Deciduous Forest Region of Eastern North America occur in very small and scattered stands. On the back of the Flatirons is the only stand of paper birch in Colorado (and the southernmost one in the United States). This is true also of plants such as the hazelnut, wild sarsaparilla, carrion flower, bird-foot violet, wood lily, rattlesnake fern, dwarf creeping raspberry, yellow lady-slipper and several extremely rare orchids.

Other plants in the Flatirons-Mesa Trail area seem to be “living fossils,” relics of the time long ago when the redwood forests were present over all this region. Some relic species are the Oregon-grape and several of the yellow-flowered parsleys common in the lower foothills and largely restricted to this area.

It is the many spots of unusually moist microclimatic conditions that certainly account for the presence of these outpost or relic species of plants in the Flatirons-Mesa Trail area. During the Pleistocene ice ages, when the local climate here was probably cooler and moister, there was apparently a westward movement of the eastern flora along the moist drainage systems as well as an eastward movement of Rocky Mountain species out onto the plains, resulting in the meeting and mixing of these elements along the base of the Front Range.

This wild mixture of unusual geographic vegetation types has all but disappeared in Colorado except for a few moist sites along the Front Range, of which the one represented by the Flatirons-Mesa Trail group is probably the best still remaining.

It would be a real tragedy if these last remnants were destroyed through our ignorance. Filling in the details of their climatic origins and potential for survival in an urban setting would enhance appreciation by the Boulder community of these unique gifts of nature to our open spaces

William A. Weber is a professor emeritus at the University of Colorado at Boulder.

Boulder County Flora

The Flora of Boulder County, Tim M Hogan, University of Colorado Herbarium

Chris Brown Photography
Chris Brown Photography

Extending from the short grass prairie of the Great Plains to the alpine tundra of the Continental Divide, Boulder County enjoys a wealth of landscape types. The county covers approximately 750 square miles, rising from 5,000 feet on the eastern plains to 14,000 feet along its western boundary. A variety of natural habitats including grasslands, riparian zones, woodlands, forests, and alpine tundra represent an assemblage of communities that is matched by a diversity of plants and animals that make the county their home.

One thousand five hundred thirty eight (1,538) species of vascular plants found in 135 families and 667 genera are documented for Boulder County. These species account for nearly one half of the flowering plants known from the state of Colorado, and is only slightly less than the entire flora of Alaska.

One reason so many species are known from the county is because Boulder has been well studied by botanists over the years. But the more important reasons are ecological. The easternmost extension of the Continental Divide in North America is along the Indian Peaks. Within a short horizontal distance one can experience a range of floristic regions that would be found on a walk from Mexico to the Arctic. Precipitation ranges from 12 inches on the plains to over 40 inches in the moist forests of the subalpine zone. Substrates include geologically young glacial deposits, shales and sandstones deposited by ancient seas and winds, and some of the oldest granites on the continent. Sheltered foothill canyons where the plains meet the mountains at lower treeline offer refugia for a number of eastern woodland and prairie plants. Many of the broad alpine ridges along the Divide escaped the most recent glacial scouring and serve as another type of refugia for rare alpine species. Boulder County’s rich floristic heritage is harbored in prairie wetlands and pockets of native grasslands on the plains; in open meadows and forest of ponderosa pine in the middle mountains; among old-growth spruce/fir forests near treeline; and upon expanses of windswept tundra where the mountains meet the sky.

Our flora is not only quantitatively abundant, it is also qualitatively rich. A number of rare, threatened, and endangered species occur here. The lady’s tresses orchid (Spiranthes diluvialis) and Bell’s twinpod (Physaria bellii) are federally listed, while many other plants are of special concern. Some plants that are common in the Boulder area such as the Front Range beardtongue (Penstemon virens) and bracted alumroot (Heuchera bracteata) are found nowhere else in the world beyond the southern Rockies – they are endemic. Other species found in Boulder County are at the edge of their range and therefore represent an important element of that species’ genetic diversity. The northernmost occurrence of mountain tail-leaf (Pericome caudata), a southwestern species, is on screes in the Boulder Mountain Park. Also found in the Mountain Park is one of the southernmost localities for paper birch (Betula papyrifera). Other denizens of our local flora reach back into deep time. There is fossil evidence of Oregon grape (Mahonia repens) and waxflower (Jamesia americana) that documents their occurrence in our area from 50 million years ago.

We are fortunate to live amongst such a rich and varied flora – a flora with roots in the Tertiary and with branches that reach across continents. The protection of natural areas serves to preserve the evolutionary lineages and the ecological habitats upon which our native plants and animals depend.[A Checklist of Vascular Plants of Boulder County, Colorado by Curator Emeritus William A. Weber has been published by the University of Colorado Museum of Natural History and is #16 in the Natural History Inventory of Colorado series. Along with a complete list of the Boulder flora, the publication includes a discussion on principal habitats, floristic zonation, weeds, historical plant geography, special floristic patterns, and the significance of anthropogenic change on the flora. It can be purchased at the museum for $5.00.]

Bartlett Open Space

Professor Al Bartlett on the start of the city’s space program
by Al Bartlett

Al Bartlett

Remarks prepared by Albert A. Bartlett for presentation at the celebration on the Pearl Street Mall (Boulder, Colorado, November 17, 2007) of the 40th anniversary of the November 1967 election in which Boulder voters approved the establishment of a sales tax to support Boulder’s Greenbelt – Open Space program.

And now it is time for me to say “thank you.” To a long list of people who have contributed so much to the initiation and continuing success of Boulder’s Greenbelt – Open Space program.

First, to Bob and Mavis McKelvey. I had the good fortune to work with them when they got this whole thing started with the Blue Line back in 1959.

Next, to Ruth Wright who was chair of PLAN—Boulder County. Forty years ago Ruth guided the massive campaign effort made by PLAN—Boulder County to urge voters to support the Greenbelt – Open Space sales tax ballot proposal.

Her leadership in the election campaign was effective, inspiring and wonderfully successful.

Next, to Oakleigh Thorne whose lifelong devotion to the understanding and preservation of ecosystems knows no bounds. The long-term protection of ecosystems was a central theme of Oak’s extraordinary participation in the Greenbelt–Open Space election campaign. His efforts to educate people about ecosystems continues undiminished to this day.

An unsung hero in the Greenbelt–Open space election effort of 1967 was the late Harold Malde whose photograph of the McKelvey and Gerstle children playing in a meadow Below the flatirons has become the iconic image for all that the Greenbelt–Open Space program represents.

Next, thanks to several leaders in the Boulder business community who supported our campaign. They had the vision to see that the Greenbelt–Open Space program was essential to a great community.

Next, we all need to thank Ted Tedesco, who, in 1967, was the new city manager. He saw that the Blue Line was only a short-term protection of Boulder’s mountain backdrop and that if boulder was to preserve the mountain backdrop for the long-term, it was necessary that the city own the mountain backdrop.

He saw what had to be done, and did it. He convinced a reluctant city council to put the Greenbelt–Open Space sales tax issue on the ballot.

At an informal meeting in the parking lot west of city hall, he then turned to a small group of us from PLAN—Boulder County and said, “you guys have got to win the election.”

We must thank an informal group of about a hundred volunteers from PLAN—Boulder County and others from the community, who recognized that this was a once-in-a-lifetime opportunity. Their tireless efforts through the entire fall of 1967 carried the Greenbelt–Open Space message to hundreds of boulder voters.

The great work of these volunteers was crucial to the passage of the Greenbelt–Open Space sales tax measure.

barlett_speechAnd now, we all want to thank the wonderful people of the staff of the Open Space and Mountain Parks Department of the City of Boulder. Today, and throughout the last 40 years, with dedication and devotion, they have done a magnificent job in the judicious purchase, acquisition and preservation of open space lands for the long-term protection of many ecosystems and recreation areas around Boulder.

While we are here on the grounds of the Boulder County Courthouse we should note that the voters of Boulder County followed the lead set by the voters of the City of Boulder. Some years after the city’s program was started, voters in Boulder County initiated an independent county open space land acquisition program.

The county’s program can only be characterized as absolutely outstanding, and for that we need to thank the dedicated staff of the Boulder County open space program. Most of all, we all need to thank you, the voters of Boulder, who have steadfastly supported the Greenbelt–Open Space program.A major manifestation of your support occurred with the Greenbelt–Open Space sales tax election 40 years ago.

We thank you for your continuing support in subsequent elections in which you have authorized the continuation and extension of this vital program.

To all the voters, past and present, we express our sincere gratitude.

Without this Greenbelt–Open Space program Boulder today would be just another dreary, suburban city, unsustainable and indistinguishable in the smog, pollution, sprawl and congestion of a giant and spreading urbanization that is engulfing and destroying the unique ecology of the entire Colorado Front Range.

The Greenbelt–Open Space program has made Boulder a special place.

Our task as citizens, now and throughout the future, is to work with the public and with the staff of Boulder’s Open Space and Mountain Parks Department, to continue the program of acquisition of more open space lands. Continuation of the vigorous program of open space land acquisition is made necessary by the continuing population growth in and around Boulder. Equally important, and as was envisaged 40 years ago, we must exert great diligence in protecting our open space lands from degradation and destruction by things such as circuses, carnivals and contests, and even from benign over-use.

We have the responsibility to manage our open space lands and their unique ecosystems so that they can be passed on, ecologically undiminished, to our children, to their children, to their children, … Ad infinitum.

My sincere thanks to all of you.