|6/25/2013 12:19:00 PM|
Forest succession in the aftermath of wildfire
By Craig Eisenbeis
|Ten years after the B&B Fire of 2003, the forest is actively regenerating itself.photo by Craig Eisenbeis|
There is no escaping the fact that burned-over forests will be a part of life in Sisters Country for generations to come. The land burned in last year's Pole Creek Fire was only the most recent of thousands upon thousands of local forest acres that have gone up in flames over the last several years.
Fire in the forest has always been a natural part of the greater ecological picture, but recent fires in the second-growth forests of the West are not especially natural. Very few people are living today who have seen our local forests in their truly natural state.
When our local natural, or "climax," forests were logged in the very early years of the 20th century, the forests that grew in their place were very often quite dense and homogenous in terms of size, age, and species. Because of this, the resulting trees were subject to the same mortality factors.
For example, an insect well-suited to infest a particular size and species of tree needed to look no further than the tree next door to find its next victim; and insect infestations exploded. Dense tree populations exacerbated the problem by creating trees weakened by competition that were vulnerable by mere proximity to their neighbors.
The resulting expanses of unhealthy and dead trees became tinderboxes waiting for a spark, and the sparks came. But that is all history. The interesting question at this point is what comes next for the forests.
To a certain extent, each burn has become its own potential classroom or laboratory; and we have several areas now in varying stages of a process called forest succession.
One interesting aspect of the fire cycle is already being observed in the Pole Creek Burn. Scores of mushroom pickers have descended upon the burned areas. Morel mushrooms, in particular, seem to thrive in the ashes and charcoal of recent forest fires. Further, morels seem to grow best at elevations at the 4,000- to 5,000-foot level, which is exactly where most of our burned local forests lie.
Fire morels are in high demand all around the world, with most ending up in restaurants in North America and Europe, where fire morels are considered a delicacy. They are very difficult to grow domestically, and the wild mushrooms bring high prices for pickers. Fire morels continue to grow for years after a wildfire, but the first year after a fire is the most productive for morels.
After the mushrooms come a few grasses, lupine and other wildflowers. Forest communities in early succession are usually dominated by fast-growing and opportunistic species. As succession proceeds, these species will tend to be replaced by other species more suited for the long haul. Although climate change, inadvertent species introduction, and other factors will play a role, if left alone, a new climax forest will eventually result. Eventually. If left alone.
The catch for us short-lived humans is that the process takes centuries, perhaps a millennium. Or more. And who has that kind of time? The process, however, is an interesting one to observe.
Right now, some areas of the Pole Creek Burn look completely barren and sterile. Ten years ago, the situation was much the same in areas scorched by the B&B Fire. But, today, that bleak landscape is changing. True, there is no forest of towering ponderosas or massive firs rising like a green phoenix from the ashes of 2003, but there is plenty of life to be found a decade later. What you see in the forest today is hardly a wasteland, as the land lives out the centuries-long process of regenerating a new forest.
Dense thickets of manzanita and Ceanothus (snowbrush) already cover thousands of acres. The manzanita began blooming in May and is well on its way to producing the small apple-shaped seeds that give the prolific shrub its name - "manzanita," which translates from the Spanish as "little apples."
Manzanita, which has been known to achieve near-tree status at heights approaching 20 feet, is one of the first plants to appear in the wake of fire. The plant's growth typically explodes in post-fire habitat, partly because it thrives in full sun but also because the fire itself helps promote reseeding.
Fast-growing and opportunistic species are the first to take advantage of the clean slate provided by a burn. Among the pioneer trees, the first to colonize many burns is the lodgepole pine. Scientifically, the ability to delay seeding for a more opportune time is described as "serotiny."
The lodgepole pine produces serotinous cones which do not readily open because the cones are sealed shut by a resin. The cones may remain on the tree for many years in that closed state. Temperatures of at least 113 to 140 degrees are required to melt the resin and release the seeds. Forest fires can generate temperatures more than ten times that.
Because of this, a lodgepole forest destroyed by mountain pine beetles, for example, may not immediately regenerate without the catalyst of fire. In some local areas, that was exactly the case. Now, ten years after the B&B Fire, thousands of young lodgepoles have colonized the burn; and some are already taller than head height. The young lodgepoles are not alone, however. Many other species of tree seedlings are present in the burn today, including ponderosa pine, hemlock, spruce, and fir.
The opportunistic pioneer species eventually produce a closed canopy, and the lack of direct sunlight at ground level makes it difficult for their own seedlings to develop. At this point, shade-tolerant species, such as fir and hemlock, begin to take over in the shade established by the pioneers. Eventually, the shade-tolerant species replace the pioneers; and, in a few hundred years - barring another cataclysmic event - a mature climax forest will again dominate.
Fire is a natural ingredient in the forest ecosystem; and, in recent years, much has been learned about forest management that will help minimize catastrophic fires in the future and hasten the development of mature forests.
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