A Mosaic Forest

The following blog entry was submitted to the Arizona Daily Sun by the
National Forest Service with my permission. It ran about ten days later.

Yesterday, I described the impact of the Warm Fire in summary terms.  If you read that post, you'll find a description that sounds rather worse than what I saw on the ground when I visited the scene.  In order to see what the reality behind the statistics might be, I drove and walked many miles through the burn area, and was surprised at how varied and hopeful the landscape appeared.  Areas of total destruction bordered others of modest, or even no impact, and in many areas the scene changed from one state to the other rapidly and repeatedly. 

The principal reasons, I expect, are because the terrain is very varied (rolling, and often steep), and because some areas affected had previously been burned.  For example, a slope fifty feet high might be utterly destroyed where the wind swept flames and burning embers uphill, and yet green grass and trees would have survived right up to the break of the slope on top. In other situations, groves of aspen bore witness to the fires of not long ago.  In contrast, the Yellowstone National Park burn areas seemed vastly and uniformly devastated when I visited them several years after their destruction.


On the Kaibab, the result has been the creation of what is called a "mosaic" landscape: a desirable, natural state that comprises many patches of different types of growth simultaneously existing at various stages of maturity.  How that state is achieved once fire offers the opportunity makes for an interesting story, and the tale of the aspen features prominently in that process.

At times of prior fires, an area might have lost individual trees, allowing aspen seeds to blow in.  Aspens, like many marine animals, utilize a broadcast strategy of propagation that relies on spreading millions of offspring upon the currents (of air, in this case), banking on the occasional random seed alighting in favorable circumstances.  The strategy has a risk, however, because a seed that is minute enough to travel great distances can carry scarcely any food at all.  In consequence, an aspen seed that cannot find light, nutrients and water immediately upon sprouting is doomed to die.

The best places to find such conditions are in burn and blowdown areas.  In each, the soil is disturbed, the canopy is open, and there is no competition for resources.  In burn areas, conditions are even more fortuitous, as the nutrients previously locked into existing growth have been released back into the soils.  If even one aspen seed succeeds in reaching modest size, the next step in the aspen’s survival strategy enters into play: like sumac and beech trees, aspens also propagate by sending out roots from which sprout clone trees.  When you see clumps of similarly-aged aspens (recall some of Ansel Adams’ most memorable pictures), what you are seeing is a single tree multiplied.


Only at maturity does the Aspen’s strategy break down, because aspens have sparse crowns when full grown.  This vegetation is sufficient to provide the shade that ponderosa and other pine species need to flourish when young, but not thick enough, or high enough, to prevent those other species from over-topping the aspens that nurtured them, and eventually crowding them out.  Were I to return here in a few years time, much of today’s burn area would be colonized by new groves of aspen, just as many of the unburned, and partially burned areas I see today show all stages of progression from aspen grove, to mixed pine and aspen, to climax pine, spruce and other species.


While the impact of the fire was uneven, it was compelling where it was extreme.  It is hard not to think that the aftermath of a high intensity fire in an area of thin soils such as this resembles what a post-nuclear landscape would look like.  Where once there was a forest, only the trunks of the largest trees remain.  Even the stumps of trees harvested in years gone by have disappeared.  Instead, the negative images of their forms remain in the earth, with tunnels twisting away that mark where once large roots had run.  As at Hiroshima, shadows of living things sometimes remain, reminding where trunks had burned away into nothing.


The ground in such an area appears totally naked.  All organic matter has been vaporized, leaving only broken stones resembling the cinders of old fashioned coal furnaces behind.  Around stumps that have partially survived, the surface is burned away, and also down, six, or eight or twelve inches from where the charred stump itself.  What little soil that remains has collected in shallow depressions as small puddles of brown.  Over all, a pungent smell of burnt pine prevails.


Of course, as in all things natural, there is beauty as well as destruction.  Along the main road, I occasionally saw tall, untouched aspens standing unicorn-white against the blackened spires of ponderosa pines.  In areas of high heat, the bark of ponderosa pines was carbonized into an intense, shining black, reminiscent of high tech furniture.  On some of these trees, drips of still-oozing pine pitch sparkled like diamonds or citrines as they captured and gave back the light of the sun. 


Not surprisingly, the surfaces of the sinkholes that dot this limestone plateau and fill with runoff water were coal black after collecting the soot and ash washed down by recent rains.  Burnt trees stand in small sinkholes, creating a perfect negative image of a kettle hole pond in winter back east, its surface frozen white.


Incredibly, only weeks after the fires were quelled, the landscape is already recovering.  Lupines bloom on the barest ground, sprung as if by magic from a surface that seems otherwise to have been sterilized by the heat.  The dark green of rye grass springs up wherever running rainwater collected, in stump holes and sinkholes and depressions.  Pine needles blow in from adjacent areas, and pinecones rain down from the branches of the charred remains of trees, all beginning the process of creating humus anew.


To me, the burn area was a hopeful scene.  Whatever the political fallout or the most accurate characterization of the Warm Fire might be, clearly a step has been taken back towards a more natural state for the Kaibab.  If the powers that be are able to withstand the criticism and stay the course, the plateau will eventually return to the state of nature in which all that lives and grows here originally evolved to best succeed.

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