Carlton Ridge Research Natural Area (RNA): A Refresher

The 920-acre Carlton Ridge RNA is located atop and somewhat on the north-facing side of Carlton Ridge, about 7 air miles southeast of Lolo, MT.  It extends from middle elevations to the ridge crest (from 5600 – 8300 feet elevation).  Average annual precipitation at the lower elevations is about 30 inches; at the top end is about 45 inches.  Rocks are mostly schist and gneiss, but the ridge top is overlain by a well-developed mantle of volcanic ash.  A nearly pure park-like stand of alpine larch dominates the ridge top, with a significant association of white bark pine and alpine fir.

This very unusual RNA was established in the 1970’s to protect the unique old-growth alpine larch stand that occupies the ridge top and other features associated with alpine larch ecology.  This protection would assure future options for research area.  The mature alpine larch are 500 years and older; there are numerous areas of younger larch too.  The older trees present opportunity to study global climate change because natural disturbance to this stand has been rare, indeed.  Western larch is found on the lower reaches of the RNA, up to about 7000 ft.  Pockets of alpine larch are found on exposed rocky areas down to about 6000 ft; thus there is a band where western and alpine larch grow in close proximity to each other. In these areas, natural hybrids of the two species exist and provide important clues to their genetic similarities, as well as to the evolution of North American larch species.

Besides the importance of the RNA to research on alpine larch ecology, Carlton Ridge RNA is simply beautiful to behold.  The large open-grown alpine larch, in association with a ground cover of mountain heather, woodrush, dwarf huckleberry and other species, defines the meaning of “park-like.” During late-September of any year, when alpine larch needles turn brilliant orange and the shrubs are turning to eye-catching purples and reds, one stands in awe of this unique resource and ponders their own relation to the natural environment.  The long-standing RNA designation protects this opportunity not only for scientists, but for people from all walks of life.

When the Bitterroot Resort (BR) originally proposed that a major ski area be developed that would seriously impact the RNA on Carlton Ridge, Friends of Lolo Peak and others strongly urged the U. S. Forest Service to deny BR any access to or through the RNA.  We have been successful at that – so far! The Forest Service decreed that the RNA must not be impacted, even in the smallest way.  But there are no absolute guarantees for the future. 

We need to be continually vigilant as we monitor the activities of the BR – and any other activities which might jeopardize the RNA. In the meantime, do yourself a favor and visit the Carlton Ridge RNA and convince yourself that it’s worth saving for posterity, and for research.

Clint Carlson, Forest Research Scientist and Project Leader, Retired