Nature Notes

Volume XXV - 1994

Hiking in a Montane Mire
By Jean Danielson and Steve Mark

Sphagnum Bog is one of many charming areas in Crater Lake National Park. It is four miles west of the lake, but an easy hike from the Rogue River National Forest. The trail to Sphagnum Bog can be reached by taking state highway 230 and turning east at the sign for National Creek Falls. Use forest road no. 6536 to go east, then spur road 660 to find the trailhead. It is only about one quarter mile to the park boundary once you are on the trail.

On the way into Sphagnum Bog, you may be lucky enough to see a number of rare and interesting plants. One with a small purple-blue flower is Mount Mazama collomia, Collomia mazama. If you see one, note its location and report your find on the observation cards available at park visitor centers. Remember, as with all flowers in the park, do not pick or allow anything to harm it.

In roughly a mile and a half, the access trail intersects with the so-called Bald Crater Loop. Go south to Crater Springs and cross the creek once to reach the bog. The total distance to the bog is 2 1/4 miles. Upon finding the wetland area, a deep sense of the primordial can be felt. Amid the bog's hollows and mounds of vegetation, you should find that sphagnum becomes more obvious. This genus is represented by two species in the bog, S. squarrosum and S. subsecundum Sphagnum has large open cells which make it seem like a sponge to the touch. This is because most members of the genus have the ability to hold 20 or more times their dry weight in water.

Sphagnum is a moss which grows only in water and has the ability to acidify its surroundings. Although it grows continually upward, Sphagnum is balanced by decay at the bottom of the plant. Its partial decomposition in water forms peat. Varying in consistency from turf to a slime, peat further decomposes to a dark brown or black and can impart a tea color to standing water.

Boggy peatlands characterize much of the British Isles, northern Canada, and other places in the upper latitudes. Sphagnum bogs in those areas usually have relatively few nutrients and harbor acid-tolerant vegetation such as pitcher plants, sundew, or heaths. The park's sphagnum bog is somewhat different than the boggy peatlands, though it is a peat producing ecosystem. It is classified as a montane mire, which are relatively common in subalpine regions of the Cascade Range where moisture accumulates in small basins or in poorly-drained slopes.

Sphagnum Bog is an area that is saturated most of the year. The trail will bring you to the headwaters of Crater Creek, which is fed by two large springs. This part of the Crater Creek basin is relatively flat and poorly drained in comparison to other spring areas on the park's western boundary. Along with sedges and shrubs, Sphagnum forms a carpet of vegetation in many wet areas of this bog. Water beneath this carpet can be deep, so be careful or you may be struggling to free yourself from the mud. Most of the wet areas can be avoided by staying to the forest or shrub communities which surround the bog.

Spaghnum Bog pool
One of Spaghnum Bog's pools
Photo by Roger Brandt.

bog blueberry
bog blueberry
Hickman, pp. 569 & 543.

These plant communities also illustrate the slow process of plant succession in the mire. In contrast to the boggy peatlands, the park's sphagnum bog is not dominated by Sphagnum. Being relatively high in nutrients, this montane mire is characterized instead by brown mosses, shrubs, and sedges. Plant succession began with sedge communities establishing themselves on gentle slopes where seepage from the two springs drainage accumulated. Thickets of boa blueberry, Vaccinium occidentale, followed at the basin's edge. Conifer invasion of the mire, however, has been somewhat retarded. A limiting factor is probably the prevalence of peat.

The peat in Sphagnum Bog averages six feet deep and is underlain by pumice. Mount Mazama's eruptions produced the pumice, though formation of the mire presumably began when a cool, wet trend in the region's climate developed about 4000 years ago. At that time, sedges and herbs began invading shallow pools which had formed over poorly drained areas.

Hickman, pp. 569 & 543.

What eventually developed at Sphagnum Bog is a fascinating mosaic of vegetation highlighted by the wetland's deep pools and insectivorous plants. The pools are sometimes called kettle holes, though this is a misnomer because Sphagnum Bog is not glacially-carved. They are five feet or more in depth and located in the lower portion of Sphagnum Bog's eastern arm. Two species of sundew, Drosera anglica and Drosera rotundifolia, and three bladderworts, Utricularia, feed on insects. The sundew trap bugs with sticky hairs that bend over once the prey is caught. When the insect dies, the hairs secrete a digestive juice that breaks down the soft parts of the insect's body. The soluable products are then absorbed and used by the plant.

Despite some wet footwear and pant legs, a day spent at Sphagnum Bog will provide an experience with a rich variety of plant habitats in a fairly small area. If you are fortunate, a large number of birds and mammals may also be seen. Like other wetlands, Sphagnum Bog is a place that provides a memorable contrast to drier forest areas in the park. But keep your eyes open for Sphagnum so that you will avoid an unexpected encounter with the bog's deep pools!

Further Information

Susan Seyer, Vegetative Ecology of a Montane Mire, Crater Lake National Park, Oregon. M. S. Thesis, Oregon State University, Corvallis, 1979.

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