Cedar Grove Botanical Area | Aldrich Mountains, Oregon
Just below Aldrich Mountain Lookout, in a wet north-facing canyon which drains to the John Day River, Alaska yellow-cedars have endured an arid climate since the end of the Pleistocene.
After a night watching the Perseids meteor shower atop Aldrich Mountain we headed to the trailhead and downward into the canyon that holds these relict trees. I was expecting trees similar to what is found in the Siskiyou Mountains. I assumed they would be growing in an open forest along a rocky, cirque like drainage in the absence of competition from other conifers. I also expected the trees to be diminutive in size compared to what is found in the northern part of the range. What I did not consider was how the arid climate would affect the population in the Aldrich Mountains. In the Siskiyous trees enjoy upwards of 80 inches of precipitation each year—which is also true of the trees further north. In this region of Oregon I cannot imagine the mountains receive much more than 40 inches of precipitation each year—this is why these outliers were different from those in the Siskiyous. In the Aldrich I would find they grew tall and in the presence of dense forest competition.
After descending from the ridge for about a mile through thick forest of lodgepole pine (Pinus contorta), western larch (Larix occidentalis), Douglas-fir (Pseudotsuga menziesii), and white fir (Abies concolor) we eventually broke out onto a sunny hillside which fostered ponderosa pine (Pinus ponderosa) and western juniper (Juniperus occidentalis). I had a hard time believing we were about to see a grove of Alaska-cedar adjacent to these high desert species.Within minutes we rounded into the headwaters of Buck Cabin Creek and found the cedars. However, upon entering the grove, we discovered that most of the trees were dead. After touring the creekside we estimated a 90% mortality for the Alaska yellow-cedars while the other conifer species were faring just fine.
The mortality we witnessed was disturbing. This—the quintessential outlier population—offered a relict habitat from an ancient era finely balanced but now seemingly on the edge of extinction. This population is one that should be monitored and understood as climate change effects microsites across the West, and in fact it is being well watched. Joseph Rausch, a botanist with the Malheur National Forest, explained that in 2006 a fire was sweeping across the range and the decision was made to set a low intensity backburn through the botanical area to 'save' the 26 acre population. The fire moved through the understory but has since had a negative effect on the cedars. Alaska cedars have thin bark which makes them generally intolerant of fire and it appears this backburn led to their current demise.
Mortality near 90% was witnessed within the grove—no other species seemed to be as affected by the understory fire of 2006.
On a positive note,seedling recruitment is being witnessed—especially creekside. However, it is concerning that since the other conifers were not effected by the fire the canopy may ultimately close over—shading the cedar seedlings out. Only time will tell. In the Klamath Mountains, at the southern end of the cedar's range, a minimum of 9 individual populations persist. These are spread out over 50+ air miles. The scattered distribution coupled with the wetter climate virtually ensures their survival—at least in our lifetimes. But, we need to watch and understand these microsites change as we change our climate. Watching and understanding how these outlying species are affected is for our well being as well as theirs.