Your Woods, Part One.

To learn how to manage any woods on your property, or even understand how they got there, it’s helpful to know a little history of Island forests.

All forests develop from a disturbance of some kind, kicking off a cycle known as forest succession.  On Vashon, logging in the middle of the last century was the disturbance setting the scene for a lot of the forests we have today.  If your woods are typical of those on many parts of the Island, your trees are likely what grew up after that logging, which was likely a clearcut.

To generalize and simplify (even more!), we can further say that your trees are the result either of someone replanting the logged area, in which case you have a strong cohort of Douglas-fir, or of the trees establishing themselves on their own, in which case you have a mixed cohort of Doug-fir and Western red alder or just red alder.  Your particular woods likely feature other tree species too, sporting shade-tolerant Western red cedar or Western hemlock, maybe some remnant of grand fir, or groups of bigleaf maple and Pacific madrone, to name a few common species whose presence improves forest diversity.

But there’s good reason to concentrate for a moment on those two Island-dominating cohort species—Doug-fir and alder—because both are at something of a turning point right now.

For our purpose, let’s limit talk of Doug-fir to those stands of it that seem to have been intended for future harvest.  Such stands were planted densely, with later thinning in mind, using tree seedlings of near-identical age.  The result now, some fifty to a hundred years later, is a forest of crowded stems, with roughly the same crown height (top of the tree) and crown depth (distance between the top and bottom of the branching part of the tree).  The tree canopy in these stands closed some time ago, creating a plant desert underneath by blocking light.

There’s something beautiful about these stands, with their uniform, straight boles (branchless trunks) plumed with lush, dense greenery above.  The Island would be a much poorer place without the pleasures their sounds and fragrances contribute to forest walks.  And let’s not forget the ecological services they provide, however inefficiently compared to those provided by healthy, “natural” stands.

But these forests, as much abandoned plantations as wild spaces, are potentially vulnerable to unnatural rates of disease and blowdown, threatening the stand’s dynamics.  In time, they may enter the typical cycle of forest succession mentioned above.  But your intervening now by thinning your stand thoughtfully (as described in an earlier post) and under-planting with shade-tolerant trees and forest-floor shrubs, could help your Doug-fir woods survive and start on its way to becoming a mature forest.

The other dominant Island tree species, Western red alder, will be addressed in the next post.