Friday, December 12, 2008

All plants have stories to tell if you pay attention, but trees tend to have the longer narrative. Trees stand out more this time of year, especially in an older stand. We’re lucky to have a patch of protected old-growth nearby which I took to visiting during the deer season.

This stand is notable not only because it nestles against a town but because the land is fairly flat and fertile. A nearby patch of old-growth consists of small but ancient trees growing on a very steep landscape. For most of the land around here, what was farmable was cleared for fields and what resisted farming was still logged. The pattern is certainly not unique to the northwest. Protected land tends to be the more inhospitable land which lacks easily exploited resources. So it’s nice to find gorgeous straight trees which I can barely reach halfway around that were able to escape cutting for hundreds of years.



One of the characteristics of old-growth forest (a somewhat loose term) is a diverse age structure. The elders stand among young and middle-aged individuals, and death is also present. Trees have stories to tell even beyond their death, as well as roles still to play. Only a few species such as maples and hemlock are able to grow under the shade of a complete canopy, albeit slowly. Fire is not a common disturbance in our area, but wind is. Trees falling due to high wind, disease, or age create patches of sunlight which allow shade intolerant species like tuliptrees and black cherries to persist in the stand. Sometimes a tree with a shallow root system will pull up its roots and a part of the ground when it falls (this is called a tipup). The exposed soil provides a substrate for seed germination.



This forest is not untouched by the changes of the last few centuries. Beech trunks wrinkle with imported beech bark disease. Wide-ranging species like the passenger pigeon or gray wolf no longer visit, and in the case of the passenger pigeon no longer exist on earth. Some of the downed wood from the past hundred years is missing. There were two major windstorm events after which the decision was made to salvage log damaged areas. This is unfortunate because the downed wood is important. It provides habitat for such diverse creatures as small mammals, fungi, nematodes, and bacteria. Eventually the wood returns to the soil much of what it took up. Just as a 300-year old hemlock has a long story to tell (which is probably more exciting in its condensed version), nutrients taken up from the dirt and incorporated in the trunk of a long-lived tree have several human lifetimes to persist before returning. So to a human it may seem that if the forest can wait that long, the resources must not be that important. But land that is logged regularly must eventually be fertilized to keep producing. Resource extraction is like having a bank account - you can take the interest but if you dip in too deep you begin to deplete the principal.

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