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Posts Tagged ‘Forest’

A Douglas’s Squirrel sitting on a branch. Photo: National Park Service

In his “Wilderness Essays,” John Muir said that the Douglas’s Squirrel “…is the most influential of the Sierra animals, quick mountain vigor and valor condensed, purely wild…”

And a couple of weeks ago, while my family and I camped in Kings Canyon National Park, I got to see how some of this influence is wielded.

In the early morning, I spent a bit of time wandering through the forest around the campground. As I was exploring, and watching Mountain Chickadees and Brown Creepers and Williamson’s Sapsuckers and White-headed Woodpeckers, I heard a thud of something hitting the ground close to me. I paused and then heard another thud. I looked up and high above my head I saw a Douglas’s Squirrel (Tamiasciurus douglasii) moving through the branches of a pine tree.

The forests of Kings Canyon National Park are filled with Douglas’s Squirrels! Photo: Aaron N.K. Haiman

The squirrel was moving from branch to branch checking the various cones. It would climb out to the tips of the branches where the cones grow and carefully and quickly assess each cone to come to a decision on whether or not it was ready to be harvested. If it was ripe enough, the squirrel nibbled away any pine needles blocking the base of the cone, and would then chew through the stem of the cone.

Once it had the cone off the branch, the cone would fall from the squirrel’s mouth and plummet to the ground. At first, I thought that the squirrel had accidently dropped the cone. However, after watching this process repeat a couple of times, I realized the squirrel was intentionally dropping the cones, and attentively watching where they fell. After observing the fall of a cone, the squirrel would scamper to the next cone.

I watched this process repeat again and again for over forty-five minutes. The squirrel was very strategic in how it went about its harvest. It was clearly working its way down the tree from highest branch to lowest. It would run out a branch to check the cones on it, harvest the cones that it wanted, then run back towards the trunk. Then it would jump to the next lowest branch and repeat the check-and-harvest process. In this way, it systematically checked every branch on the tree.

In the time I spent watching it, this squirrel must have harvested and dropped at least twenty cones. In that time, it also took a break for a few minutes to stretch out on a branch and rest, it took a few shorter breaks to groom its fur, and it spent a bit of time calling out into the forest. I figured that once the squirrel had enough food down on the ground, it would come down and feast, but it never did. I had to carry on with my day, so I left the Douglas’s Squirrel to it’s.

When I returned home, I read up a bit on this harvesting behavior, and it turns out that my assumption that the squirrel would eat the fallen cones was wrong. Douglas’s Squirrels do harvest large numbers of cones, but they are for winter storage! Once the squirrel I was watching was done harvesting cones, it was probably going to come down to ground level and begin hiding all those cones away in various locations so that the squirrel can come back and dig them out once the snow is covering the ground and other food sources are scare.

Forests filled with, and shaped by, Douglas’s Squirrels. Photo: Aaron N.K. Haiman

And this is where a big chunk of that influence comes in because the squirrels never make it back to eat every cone that they stash. These uneaten cones, and the seeds they contain, are where new trees sprout, so by hiding cones and then leaving them, these squirrels are shaping the forest of the future! That is some serious influence!

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Fire suppression has been the standard policy for the U.S. Forest Service since the 1950s.  It was based on the idea that fire was a bad thing that destroyed habitat and commercially harvestable trees, and should therefore be excluded from forests as much as possible.  This has resulted in major changes to the forests of California, and other habitats as well.

Before the 1900s fires in California burned an average of 2.5 million acres each year.  These were largely ignited by lightening strikes and they burned uninhibited by humans.  In the  middle of the century, active fire suppression began and the annual average area that burned dropped to about 250,000 acres.  However, since the 1980s, the amount of area that burns each year has been increasing to the point where today about 7 million acres burn each year.  Further, most of these 7 million acres burn in very large fires.  This indicates that fire suppression was initially able to stop fires from burning, but the absents of fire resulted in the accumulation of fuels to the point where now fuel loads are so heavy that when a fire does start it is so large that it cannot be controlled.  This lack of control ability has not stopped the U.S. Forest Service from continuing to attempt to control them.  Today, the majority of the U.S. Forest Service budget goes not to habitat conservation or managing timber harvesting practices or to researching how forests work, but to firefighting.

Another effect of fire suppression is in tree mortality and germination.  Before 1900, many small fires that burned at low to moderate severity resulted in the trees within an area that were of a wide range of ages.  This was because many trees could survive the fires and get older, but a few trees would be killed.  The gap that resulted from these scattered moralities provided sites for seeds to germinate and young trees to grow.  However, since 1900, the large catastrophic, stand-replacing fires tend to kill all the trees in a large area.  this whole area is then covered with young trees that germinate from seeds that were already in the soil.  The forest that grows up in these areas are comprised of trees that are all the same age.  This homogeneity reduces the diversity of habitats and the the number of niches for species to occupy.

The forests that we can all go out and see today have not had their natural fire regimes for as much as a hundred years.  This absents have had profound and dangerous effects.  To counter act these effects, more prescribed fires are strongly recommended.  By introducing fire back into California’s ecosystems, more natural habitats can be restored.  This is a long and labor intensive process, but one that most assuredly needs to be pursued.

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