Big Blue: A Grass for the Times?

Last fall I had an email from a botanist friend: What’s going on with big bluestem? After he pointed it out, I noticed that, sure enough, this species, one of the dominant grasses in the tallgrass prairie (as in the source of the original Kansas sods that once housed the homesteaders), was bustin’ out all over the foothills!

Above: Fall color in "turkeyfoot," Big Bluestem grass (Andropogon gerardii), looking across Section 16 and Boulder's Jewell Mountain Open Space. (You can even see the turkey feet in this photo!)

Normally, Big Bluestem does occur on the slopes of our mountain front in sporadic patches, but has been expanding in recent years. In 2010, this warm-season grass had an extraordinary year. Its abundance first drew attention at Lookout Mountain, on the slopes of Windy Saddle Park and adjacent areas, where patches of last fall's russet color could still be spotted in January, even from a distance, as long as the ground was free of snow. Big bluestem and its cousins in the grass family provide great winter color in the landscape.

[This post is a revised version of an article that appeared in the March edition of the Plan Jeffco newsletter, and is therefore oriented toward local open space parks.]

Tallgrass prairie, whether here or in the East, is a tattered remnant of what it was in its glory days. We’re lucky to have sizable patches in Jefferson County; efforts to protect some have been underway for more than 20 years. It’s been years since we talked tallgrass prairie here at FF, but we have continued to monitor developments in the Rocky Flats area, where our best examples of this rare ecosystem survive, including the Ranson/ Edwards property and Jewell Mountain, where Boulder conveniently protected several hundred acres. Patches of big bluestem on the foothills slopes are fine, but limited, reminders of the more extensive remnant prairie that once rolled out across the county but now have retreated to a fringe along the mountain front. Most of what you see west of Highway 93 and north of Hwy 72 is tallgrass prairie.

Big Bluestem (grass)
Andropogon gerardii

• Warm-season sod-forming grass.
  
• Height: 4-5 feet in Colorado; to 8 ft in prairie states.
  
• Range: All but the five westernmost of the lower 48 states, as well as the central provinces of Canada.
  
• Dominant and characteristic grass of the tallgrass prairie ecosystem.
  
• Flowering heads are 4-5 inches long, with 3 (sometimes more) spreading branches, suggesting its other common name: turkeyfoot
  
• Links: At USDA Plants database; at Illinois Wildflowers.
  

Don't Confuse Big Bluestem with:
Smooth Brome (Bromus inermis; Bromopsis inermis) is a ubiquitous pasture grass that was introduced in the late 1800s for livestock forage and erosion control. A sod-former, it tends to grow in extensive monocultures, unlike the patch effect of bluestem, although it is a similarly robust grass that turns color in the fall (more brownish than reddish, however). Smooth brome has leaves on the stem, not just at the base, and lacks the characteristic "turkey foot" seedhead. It is invasive in prairies, and some states consider it a weed. According to the USDA, Smooth Brome now occurs in every state except Hawaii, Alabama, and Florida.

Big Bluestem in Jeffco’s Landscape
Look for these foothills patches primarily on unforested south- and east-facing slopes: on Mt. Morrison, most central-county slopes visible west of Highway 93, and on the north slopes of our canyons, from Bear Creek to Golden Gate. In Mt. Galbraith Park, you can see the colorful auburn patches across the canyon opposite as you make your way up the trail. Driving west on I-70, look for it to the north as you enter the foothills, on the slopes in Matthews-Winters Park.

In the southwest part of Red Rocks Park, bluestem occurs on more prairie-like level sites, because that area has been long protected and contains isolated spots where the Rocky Flats alluvium persists on lands that would otherwise have been cultivated or developed. In fall, Big Bluestem blends perfectly with the outcrops of the Fountain Formation that define Red Rocks.

Lack of development, and a somewhat inhospitable climate, have also protected the Rocky Flats area. The extremely cobbly soils, beloved of gravel companies, hampered agricultural attempts on much of the area, and enhanced the available moisture content for the growth of these taller species. These soils are considered among the oldest in Colorado, in part because the area is unplowed, with some estimates placing their age at 2 million years. But Big Bluestem’s visibility in the landscape of any given year reflects how we’re doing on overall precipitation and temperature.

The Water Year and Other Influences
Based on the 30-yr average precipitation, our wettest month of the year should be May. When it is, that’s about perfect for big bluestem and other warm-season grasses (including blue grama, sideoats grama, little bluestem, and switchgrass), which are just getting started as the weather warms toward summer. By June, the cool-season grasses (such as the common lawn grasses, including Kentucky bluegrass, which take advantage of early season moisture to start growth) will be ready to flower and set seed, but you’ll still have to hunt around on the ground to find evidence that big bluestem is even alive. Large clumps of hairy, velvety blue-green leaves will be your hint.

In July, those spreading clumps send up tall flowering shoots, which produce the “turkey-foot” seedheads by August. When cool-season grasses are giving it up and their seed has scattered, Big Bluestem ripens into the terra cotta masses that reveal its presence even from a distance.

This seasonal habit represents an entirely different metabolism (called “C4”) in these warm-season plants, which use carbon along different pathways than many familiar plants. According to some researchers, this may give them an advantage under conditions of elevated carbon dioxide (think global climate change), especially during drought.

Interestingly, although it seemed, until February snows, that it’s been droughty for several months, 2010 was a good moisture year during its first half, giving Big Bluestem the start it needed. In fact, rainfall in this part of the county has been at or above normal every month from April 2009 through last June. (Later records have not yet been posted online; I’d guess July stayed high as well.) Average temperatures have also hovered a degree or two above normal since late in 2008. Both conditions have supported growth of Big Bluestem, a species that prefers it a little more moist and warm than is the rule in Colorado. If we go too dry and warm, we’re apt to see more of its cousin, little bluestem, but as long as it finds a moist spot, Big Bluestem will remain a part of the county’s natural prospect.

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Further Reading
Many more references—bison grazing effects, mycorhizal associations, fire, etc.—can be found via Google Scholar; here are a few to get you started. If you've been following our Indian Gulch fire, some of the articles on fire may be of interest; parts of Mt. Galbraith Park, mentioned above, burned. Note that most articles are in Jstor, and only abstracts are available to those of us without university connections.

Biomass production and species composition change in a tallgrass prairie ecosystem after long-term exposure to elevated atmospheric CO2
Clenton E. Owensby, Jay. M. Ham, Alan. K. Knapp, Lisa. M. Auen, 2001, Wiley Online Library.

Photosynthetic and water relations responses to elevated CO 2 in the C 4 grass Andropogon gerardii
AK Knapp, EP Hamerlynck, CE Owensby, International Journal of Plant Sciences, V 154,#4, pp 459-466, 1993.

In absence of water stress, such systems don’t respond to elevated C, but in water-limited envts, levels of leaf phi, leaf-level ps rates, and stomatal conductance are all likely to be affected by elevated atmos CO2, with the net result being inc in biomass productn.

Growth and Gas Exchange of Andropogon gerardii as Influenced by Burning
Tony J. Svejcar and James A. Browning, Journal of Range Management, Vol. 41, No. 3 (May, 1988), pp. 239-244

Long-Term Effects of Annual Burning at Different Dates in Ungrazed Kansas Tallgrass Prairie
Gene Towne and Clenton Owensby, Journal of Range Management, Vol. 37, No. 5 (Sep., 1984), pp. 392-397

Mentor, verb

The dictionary insists it's a noun, but we often use it these days as a verb. This post is a little tribute to a mentor who made a huge difference in my life by inspiring, at a relatively early stage, an enthusiasm for field ecology: Dr. Paul D. Kilburn. I was a biology major in an upstate New York college when a friend suggested a summer field excursion to Colorado. We went, and four weeks later, though I didn't know it at the time, I was bound to become a Coloradoan.

Three of those weeks were spent learning the Colorado flora, with Paul as instructor: identification, montane ecology, and alpine ecology at one week each. In Rocky Mountain National Park! That foundation formed my career in the 1970s and '80s, and my passion in these later decades, though sometimes rarely exercised.

But this isn't a nostalgia trip, this is to tell you what Paul has accomplished now! After ten or twelve years of struggle (through the 1990s), I got busy and abandoned our joint attempt to save an important chunk of native tallgrass prairie in the northern part of our county. But the foundation was laid, and Paul persisted. Last week he made some significant headway, almost 10 million dollars worth, toward protecting and restoring what's left of an important grassland ecosystem. Here's Paul, right, with Dave Buckner, ten years ago today, in a nice chunk of prairie that was purchased by City of Boulder Open Space and is now protected. Dave's a consultant with whom we launched a 5-year grassland study—paid for by the aggregate interests—of the native warm-season grasslands at Rocky Flats.

This photo shows the Chemist, left, and Paul, right, in July 1999 with the Developer who knows his chunk of this well preserved prairie is going to be very remunerative for him, as it is situated at the intersection of two important highways, soon to be a major beltway bringing traffic to his door—if development interests prevail. (Here we bless the economic "downturn" for breathing space.)

In 2001, Paul (far right) led this field trip to the site of a proposed oil well within the boundaries of a portion of the grassland that had been placed in a "Stewardship Trust" by the State of Colorado (which owns Section 16, a state school section). One of the uses for the $10 million will be to purchase certain mineral rights in the Rocky Flats area so that other parts of this grassland won't be turned upside down in a quest for... gravel, bluestone aggregate. Happily, most of Rocky Flats, once a weapons plant, is now a wildlife refuge, so areas inside the fence are protected from pretty much everything except mineral owners and weeds.

Paul's been fighting the good fight, as well as leading groups to collect native seeds for revegetation and pull invading weeds, ever since those early days. Why does he do it? I think it's so his grand-children—and yours—can enjoy sights like this! (Tallgrass prairie in fall, looking toward the foothills.)

Fall color in "turkeyfoot," big bluestem grass (Andropogon gerardii), looking across Section 16 and Boulder's Jewell Mountain Open Space.

Intersections of Interest

The Husband and I are reading, each in our own separate book. We are so intrigued by these two books that we even read passages out loud to each other, a virtually unprecedented move. This morning I was struck by a sudden intersection between the diverse ideas that landed us squarely in the realm of human (and especially American) psychology.

He's reading Michael Pollan's book In Defense of Food. Pollan illuminates the fat phobia that has driven a massive experiment on the American diet in the last thirty years. In fact, we have changed our diets, and (he explains) not for the better: after adopting the claims of nutritionists, we are no more healthy today than we ever were. Across the pond, James Lovelock argues that we have a similar phobia centered on nuclear power, a phobia he considers unfounded and harmful. In The Revenge of Gaia, he demolishes the claims of "renewable" energy sources and postulates that only by adopting nuclear power can we avert imminent climate catastrophe.

So, it would seem, here we are: our environments, internal and external, are now threatened by habits and beliefs we have been persuaded to adopt only in the last three to five decades. Yes, indeed, most interesting, especially perhaps to a generation that grew up protesting having someone else's ideas shoved down its throat.

Food is our most personal and intimate interaction with our external environments, and no one would question that our food decisions can wreak havoc on the planet. But I particularly appreciated Lovelock's perspective on our fears of nuclear waste:

Wild plants and animals do not perceive radiation as dangerous, and any slight reduction it may cause in their lifespans is far less a hazard than is the presence of people and their pets. It is easy to forget that now we are so numerous, almost anything extra we do in the way of farming, forestry and home building is harmful to wildlife and to Gaia. The preference of wildlife for nuclear waste sites suggests that the best sites for its disposal are the tropical forests and other habitats in need of a reliable guardian against their destruction by hungry farmers and developers.

Now that, friends, is delightfully perverse. That is, it seems to contradict our intuitive understanding—until we somehow learn that Lovelock is right. Fear, even irrational fear, provides great protection for natural areas.

I wasn't involved in 1992 when the Rocky Mountain Arsenal, a Superfund site, became a wildlife refuge here in Colorado, so my enlightenment came later, in the struggle to prevent the commercial development of Rocky Flats. The Cold War was over, and the market for plutonium triggers was crashing. The Rocky Flats weapons plant was situated between Denver and Boulder, high on a rocky plateau. Post-war (II) wisdom suggested it be surrounded by a large "buffer zone" to protect neighboring communities, thus the plant site itself occupied less than 10% of the 6,240-acre (2,525 ha) site. Almost ten square miles of mostly undeveloped land was, and is, a rarity in this part of the Front Range. Developers were eager, to say the least.

In the 1990s, the buffer zone and adjoining properties also became the focus of local efforts to preserve a pretty significant ecosystem, the tallgrass prairie. Encroaching development on the east and mountain uplift to the west pinched this plant community into a narrow zone along the foothills, in front of what we call the "mountain backdrop." Thanks to the rocks, the area had never been plowed (it remains, however, too vulnerable to gravel mining). Chronic, sometimes vicious, winds kept it from being overly attractive to settlement or development. This land surface, the Rocky Flats Alluvium, is the oldest undisturbed surface in Colorado.

We made many field trips, most to a spot outside the official buffer zone, but sometimes we signed documents, gave up our cameras, donned dosimeter badges, and toured the inside as well. What made it a special treat was long views across the expanse of prairie, the opportunity to find new and unusual plants, and, above all, the absence of people and cows. This was grass that hadn't been grazed by domestic stock for more than 30 years! The sense of solitude, and tall waving grasses around us, gave us the illusion of traveling back in time. The guards in the towers with rifles didn't make much difference: they watched us just as closely when we were outside the fence.

By June 2004, access had become easier, and teams of scientists and volunteers conducted a 24-hour Bioblitz in the Rocky Flats area, recording almost 1,400 species of living beings in this 10-sq-mile sample of mixed grassland. Click on "All the Species" at the above-linked page for a list of the results. Don't you wonder what we'd find if we looked at other places this closely!

Soon it became clear that hundreds of acres of native tallgrass prairie, unusual plants, and healthy wildlife populations would not be enough to save this area from development—but public fears of radioactivity could help. In 2005, despite protests, the area was designated Colorado's newest National Wildlife Refuge, with the Dept of Energy retaining management of a central core to mitigate safety concerns. Although people can visit to hike and view wildlife, many of those who commented on the refuge proposal during the years of negotiation will continue to avoid the area because of health concerns. And that's just fine with 1,396 species of plants, lichens, fungi, insects, spiders, other arthropods, birds, mammals, and one fish!