The Black Hills Ecosystem

 

(more photos coming soon!)

The Black Hills are an emerald-green oasis towering above the endless sea of high-plains prairie that surrounds them.  The Lakota Nation refers to this area as “paha sapa,” which literally means “hills that are black.”  Ponderosa pine dominates these forests, although Black Hills spruce (South Dakota’s State Tree), trembling aspen, paper birch, and other bottomland hardwood trees are present on moist sites.  Elevations reach as high as 7300 feet, and while the geography and terrain is tremendously varied, it is invariably breathtaking.  Wildlife is diverse and abundant, ranging from impressive trout fisheries to big game species like elk, bison, whitetail and mule deer, and bighorn sheep.  In many ways, the Black Hills are a mixing ground of east and west, of mountains and plains, and of moist and arid climates.

Authors and scientists Wayne Shepperd and Michael Battaglia1 describe the Black Hills ecosystem this way:

    “The Black Hills is a forested refuge on the Missouri Plateau of the Great Plains Province2.  This refuge spans 125 miles from north to south and 60 miles from east to west3.  The total land base is nearly 6,000 square miles, with two-thirds of the area in southwest South Dakota and one third in northeast Wyoming4.  

The Black Hills and neighboring Bear Lodge Mountains to the west were formed by a regional uplift of the Earth’s surface during the Laramide mountain-building episodes that produced most of the ranges of the Rocky Mountains several million years ago.  Granites pushing up beneath overlying sedimentary formations formed this maturely dissected domed uplift5.  The uplift is elliptical in shape, with a crystalline (granite) core, which occupies about 20 percent of the Black Hills area.  The core is encircled by steeply dipping sedimentary deposits.  As a general rule, the closer a (rock) formation is to the center of the Black Hills, the older its age6.  These distinct differences in geology across the Black Hills affect vegetation distribution and growth.”

The resilient, bountiful forests of this land and the promise of rare mineral exploration moved the political leaders of the time to commission George Armstrong Custer on an expedition here in 1874.  Custer’s expedition paved the way for rapid European settlement, so the Black Hills have experienced forest management in some form or another for over 100 years.  Bear in mind, as you drive through our oasis of the high plains, that the beauty of the Black Hills has in part been shaped by the hand of forest managers - long have we lived in harmony with the forest, and with the support of people like you, we will continue to do so long after today.

In the many eons before we got here, however, three discrete forces of nature were chiefly responsible for how the Black Hills’ forests developed: climate, wildfire, and insects. 

Climate:  The Black Hills are a mixing ground of mountain and high plains climate.  Winters are cold and windy no matter where you are in the ‘Hills, but snowfall and overall precipitation varies widely with elevation and latitude.  Summers are relatively dry and temperatures are moderate, especially at higher elevations.  Spring is when the real magic happens in the Black Hills, at least as far as the ponderosa pines are concerned.  In every other portion of its range, ponderosa pine have a tough time regenerating themselves successfully.  Much of the southwest, for example, is prime “pondo” country, but because their spring moisture is scanty, these forests may go more than ten years between vigorous seed crops.  This disparity is both a blessing and a curse for the Black Hills.  On the one hand, we typically get ample spring moisture, which lends itself to both new generations of seedlings almost every year, and vigorous tree growth in established, large trees every year.  On the other, all those little trees sprouting up year after year, and all those big trees growing larger and larger every year, tend to clog themselves into very dense conditions unless foresters step in and thin them out.  If left to their own devices, these sorts of dense forest conditions can present a high risk for very intense wildfire events.

Wildfire: The historic fire regime of the Black Hills is thought to have been two-tiered.  One component consisted of frequent (as often as once a year), low-intensity ground fires which served to thin the forest of seedlings, saplings and woody debris.  These fires were prevalent in the more arid portions of the forest, and served to generate and maintain sparse, open, park-like forest conditions with mature ‘yellow-bark’ or ‘yellow-bellied’ pines.  The second fire regime component was considerably less subtle; it was characterized by relatively large fire events that burned down entire stands of trees at a time.  This type of fire is thought to have been common in areas with higher annual precipitation, but burned much with less frequency, perhaps occurring on one hundred-year intervals or more.  These events generated continuous patches of younger trees, growing up in dense conditions from the ashes of the forest that preceded them.  As a result of these to very different wildfire scenarios, the Black Hills were characterized by widely varying forest conditions.  Over time, and as a result of fire suppression policies, this system seems to have skewed toward the latter component, and the fires of today are larger, more frequent, and more destructive than those of days past. 

Forest insects: Insects are ever-present catalysts of change in every forest system.  In the Black Hills, a small native insect called the mountain pine beetle serves this role.  Mountain pine beetles prey on trees growing under stressed conditions, such as the intense competition for light, nutrients, and water that develops when trees are allowed to grow too closely together.  Historically, mountain pine beetles in the Black Hills have oscillated between small, confined, or ‘endemic’ populations and large outbreaks, or ‘epidemics’.  General Land Office and Forest Service accounts dating back to the late 1800s tell us of large mountain pine beetle events in several parts of the Black Hills, and on what appears to be a recurring ten-year cycle, beetles have reared their head to devour several thousand acres at a time.  Since this time, science has learned much about managing the negative effects that large beetle outbreaks can incur upon the forest.  Through years of rigorous study, it was determined that keeping beetles at low levels is as simple as thinning the forest to more open conditions.  This open forest condition creates unfavorable “habitat” for the beetles, mostly because the trees are growing vigorously and can defend themselves against attack.

It should be noted that the Black Hills are in the midst of a terribly serious beetle outbreak, but something is different this time than in years past - the bugs aren’t stopping their march at several thousand acres.  Current data on mountain pine beetle activity shows that something more like tens of thousands of acres could be affected, if forest managers cannot step in soon.  Insect experts on the forest have described the situation as having the potential to turn into ‘Beetle-geddon’, largely due to the presence of very contiguous, over-dense stands of trees that are prime “food” for mountain pine beetles.  For more about mountain pine beetles, see our article later in this section.

References:

1. RMRS-GTR-97, 2002

2. Hoffman, G.R.; Alexander, R. R. 1987. Forest vegetation of the Black Hills National Forest of South Dakota and Wyoming: a habitat type classification. Res. Pap. RM-276. Ft. Collins, CO: USDA Forest Service, Rocky Mt. Research Station. 48p.

3. Fenneman, N. M.; 1931. Physiography of Western United States.  New York: McGraw-Hill book company, Inc. 534p.

4. Froiland, S. G. 1990.  Natural History of the Black Hills and Badlands.  Sioux Falls, SD: Center for Western Studies, Augustana College.  225p.

5. Orr, H. K.  1975.  Watershed management in the Black Hills: the status of our knowledge. Res. Pap. RM-141. Ft. Collins, COL USDA Forest Service, Rocky Mt. Research Station. 7p.

6. Raventon, E.  1994.  Island in the plains: a Black Hills natural history.  Boulder, CO: Johnson Books, 272p.