There has been an absolute stampede of changes in the plant communities over the past two weeks. I live in the foothills, and every few weeks I make the drive to the next town north of us. There are two routes – one through my town, and one slightly to the east, along the river. I took the river road, through the wide valley between upland sagebrush mesas, that wound and bobbed between hay fields and farms, cresting along the edge of the unending sagebrush before diving back down to the densely vegetated fields of timothy (Phleum spp.) on the valley floor. Adequate precipitation in early spring has greatly contributed to the abundant vegetation along the road sides, and I am likely a danger to myself and others as I drive along, peering intently in the ditches in an attempt to identify plant species at 60 mph. The timothy fields are at least knee high, interseeded with nebulous patches of smooth brome (Bromus inermis) and sometimes agricultural alfalfa (Medicago sativa) interspersed for mixed hay. In the wind it shimmers and ripples, and waves of green, gold, and mauve sway in the gentle breeze – sometimes flattened as they are broadsided by the downdrafts from spring thunderstorms.
The road along the river bisects numerous sagebrush pastures where faded Indian paintbrush (Castilleja wyomingensis) – once vibrant and abundant, like miniature fireworks bursting forth from the silver background of sagebrush – gives way to the bobbing heads of Sego lily(Calochortus nuttallii). Sego lily appears seemingly overnight in a perfectly timed and choreographed emergence of delicate white flowers. Each plant produces one white flower on one slender, silvery-green stalk. The flowers are like upside down bells of white. Three wide petals with narrow points are interconnected at the base – each petal exposing a deep purple spot suspended part way up the petal, with a spray of yellow stamens in the center. Their appearance is even more startling as they protrude above the sagebrush layer in a widely but deliberately spaced sea of heads, bobbing in the wind like fireflies in a pasture at dusk – blinking as the sun catches the translucent white of their petals, and waving to and fro as delicate dancers with their bumbling and stumbling sagebrush partners.
Spring has finally burst forth from the mountains like an awkward fledgling. Snow has been recorded historically in every month of the year, but mercifully not this month. Garden equipment has begun sprouting outside Ace Hardware and True Value, the nursery greenhouses are overflowing with gallon pots, hanging baskets, decorative pots, seedlings in 4″ pots, fruit trees, annuals, perennials, and cement bays spilling top-soil and compost. Gardens are spilling over their fences as white and purple lilac bushes burst forth in an overwhelming display of vivid color and intoxicating scents. Green has come at last to the mountain slopes and an onslaught of wildflowers can be seen ascending the hillsides in an onward marching torrent of yellow as they strive for the snow-capped summits. The red cliffs and canyons around the house contrast sharply with the deep green of the new growth. Near to our house, federal land is leased by livestock ranchers and in mid May we were greeted by the bellows and grumbles of cows as they were turned out onto summer pastures.
The lengthening days provide for extended mountain viewing. Every hour shows a new face to the hillsides – whether shrouded in a cold and hugging rain or blinding flashes of yellow and gold as the contours of the earth are sharply contrasted as the evening sun sets behind the mountains, casting deep shadows along the dip of the smallest hill slope and illuminating the ridges in a highlight of brilliant green. Sunset stretches to infinity and dusk lingers until 10:00 pm as the sun climbs northward toward the summer solstice. The approaching summer brings changes to the valley as well – new birds are frequenting town as well as my bird feeder, vibrant shades of green, yellow, and purple swath the pastures dotted with grazing cows; mares and their young foals. My bird feeder has seen an assortment of new visitors as well – Bullock’s oriole, Baltimore oriole, Lazuli bunting, to name a few. Robins and meadowlarks have begun announcing the rising and setting of the sun, and Mountain bluebirds are nesting in the nest box on our fence.
As the weather warms, the tourists begin to thaw and move about town in increasing numbers. Memorial Day marks the start of the tourism season in the land where snow is sometimes seen on the ground until the middle of the month. To the south of town lie two historic mining towns, founded in the late 1800’s when immigrants traveling the Mormon, Lander, and Oregon Trails settled when gold was discovered along Cottonwood creek. Atlantic City and South Pass City still stand today, though their populations dwindle compared to the once booming metropolis’. South Pass City boasts 40 residents (most are not year round) and many of the houses are renovated cabins from the historic mining days. The town opens its Historic Site from Memorial Day to Labor Day and visitors can tour the historic cabins, mercantile, post office, bar, and jail house before moving up the road to Atlantic City for prime rib at the historic Miner’s Grubstake Restaurant and Saloon. Every other Saturday, the Miner’s Grubstake holds a whiskey and bourbon tasting event, followed by dinner and dancing.
I have been aching to get out in the garden and Memorial Day marked the start of gardening season here in the North. Furtive consultation with knowledgeable nursery staff and experienced neighbors led me to conclude that nothing should be planted outside until after Memorial Day, so May 25 dawned with a trip to the nursery and myself joyfully digging holes all over my garden. Raspberries, strawberries, melons, pumpkins, six varieties of tomatoes, sunflower seeds, hops, and clematis all made an appearance in my garden plot. I struggled with my drip irrigation system which seems to loose pressure after the first 50 feet, so I laid out an odd pattern with a long length and coiled it at the end of one of my beds – secured by stakes – while a second and shorter line of irrigation tubing criss-crossed to water everything the first had missed. Blue flax – a native wild flower – lends a nice back drop to my garden, as does the purple salvia and mint which have established themselves nicely among the rocks. Honey bees and mud daubers have appeared in the past few weeks and what was once a quiet place to sit on the deck is now nearly deafening as bees rummage through the flowers and birdsong echos across the valley.
As the days lengthen and the sun thaws the soil, I look forward to the changes as spring turns to summer. The daily change is imperceptible, but every so often I look at the hills and notice the golden line of wildflowers has advanced another few degrees toward the ridgeline and the cows are making their way higher up the mountain side – their bellows and mumblings floating down the valleys in the evening light as the meadowlarks bid farewell to another day.
This photo, taken at the Oklahoma State University Range Research Station in Stillwater, OK, is a perfect example of a prescribed fire influencing grazing behavior. Pyric herbivory results from the interaction of, and feedbacks between, fire and grazing that occur on landscapes where fire and herds of grazing animals coexist.
First, a little history. The great plains of the United States are a vast and complex series of ecosystems ranging from tall-grass prairie in the plains of Illinois, Kansas, and Oklahoma, to mixed-grass and short-grass prairie in the northern and higher elevations of Texas, New Mexico, Colorado, Wyoming, Montana, and the Dakotas, extending north into Canada. Historians believe that fire events prior to European settlement were primarily anthropogenic (human caused) and more frequent due to the use of fire by native american tribes for hunting, gathering of food, regeneration of natural resources, and warfare. Native herds of bison were thought to follow fire events to take advantage of new growth generated by the removal of decadent (old) plant material, increased sunlight reaching the bud and seed banks of grasses and increasing photosynthesis, and the recycling of nutrients as nitrogen and carbon were released back into the soil from the combustion of plant material.
As European settlers expanded westward across the United States, fire suppression became more common. Crops, livestock, and homesteads dotted the landscape and all fire was suppressed to preserve the livelihood of the settlers. Many areas of the Great Plans, Intermountain West, and Great Basin show encroachment of dense woody shrubs and trees into what was once prairie as a result of suppression of fire.
Both fire and grazing can be used separately to manage landscapes, but it is believed there are certain feedbacks that occur when the two are used in combination. Grazing pressure – or how much time animals spend grazing on a given area of land and how much plant material they remove – can influence fire patterns. If grazing pressure is heavier, there is less plant material to be consumed by the fire. If grazing pressure is lighter or non-existent, there is more fuel for the fire to consume and burn patterns are more continuous and often burn hotter. Additionally, research shows that herbivores (we’ll say cows for the sake of simplicity) are attracted to recently burned areas and their attraction to an area will decrease as time since fire increases (Allred et al. 2011). In other words, animals are more likely to be spending their time grazing on areas more recently burned and – as time increases since the area burned, the animals will spend less time grazing there.
Here’s why: fire removes vegetation. It consumes it – that’s just the nature of the beast. There are plants which resprout following fire (most grasses and forbs [flowering plants] and many species of shrubs which can regenerate by resprouting/asexual reproduction as well as seed/sexual reproduction) and plants that don’t (coniferous trees, shrubs including some species of sagebrush just to name a few – these plants regenerate by seed/sexual reproduction). Plants that resprout are stimulated by different environmental factors including increased solar radiation (photosynthesis), removal of plant material (like when you prune your rose bush and it resprouts), or increased nutrient availability from the soil. Fire provides all these things and immediately stimulates resprouting plants to generate new growth. This new growth is very tender, high in protein, and high in nutrient content and it’s like candy to cows. Think about it – if you had the choice between a huge pile of dried out, bleached out bread or a tiny little cupcake, you’d probably be all over that cupcake. Same applies to cows.
This attraction produces feedbacks in the system. In recently burned areas, cows will concentrate their grazing on the recently burned areas and keep the vegetation grazed short. They will not spend as much time consuming the older vegetation so it will grow and create heavier fuel loading. When the next fire burns through, it will burn more of the ungrazed or lightly grazed areas than the more recently burned area that has been heavily grazed, and a new “recently burned” area will appear. As I mentioned before, the cows will focus their grazing on the areas with the most tender, highest quality vegetation, which is now the new recently burned area. The area which was previously burned will be given more of a rest since the cows won’t be focusing their grazing entirely on it, and the vegetation will continue to grow and become more dense. This process repeats itself, creating large and small mosaic patterns across the landscape as areas are grazed and burned, and as overlap occurs with grazing and burning patterns. What results is a heterogeneous landscape with plant vegetation at varying heights and ages, which is important for sustaining multiple populations of wildlife species with different habitat requirements.
This photo was taken one day after a prescribed burn conducted on my research site for my Masters degree on the Charles M. Russell National Wildlife Refuge in central Montana. It is very evident here that there are situations in which only part of the vegetation will burn and that has to do with – among other things – how continuous the vegetation is. This site was dominated by sagebrush with a club moss and sparse grass understory which didn’t carry the fire very well. Although this wasn’t caused by vegetation removal due to grazing, it illustrates the patchy mosaic that can happen when fine fuel (grasses, etc.) isn’t present in quantities high enough to carry the fire through the plant community.
A juvenile great horned owl utilizing a one year old burned area at the same site in 2011.
How fantastic is all that! Isn’t nature amazing? There are so many processes and feedbacks going on all around us and under our very feet that we may never fully understand. The interaction of fire and grazing is a fairly new concept (last 20 or so years) and the exact and specific interactions are not fully understood. My goal is to continue research looking into the complex relationships fire has with other environmental variables (grazing, climate, other unknown factors) so we as land stewards and managers will have a broader understanding of the ecological processes surrounding us. If you have any questions, please ask. I will check back and try to answer them quickly!
Allred, B.W., Fuhlendorf, S.D., Engle, D.M. & Elmore, R.D. (2011) Ungulate preference for burned patches reveals strength of fire–grazing interaction. Ecology and Evolution, 1,1-13.
Lepofsky, D., E. K. Heyerdahl, K. Lertzman, D. Schaepe, and B. Mierendorf. 2003. Historical meadow dynamics in southwest British Columbia: a multidisciplinary analysis. Conservation Ecology 7(3): 5. [online] URL: http://www.consecol.org/vol7/iss3/art5/