Restorative Forestry I: conceptualizing growth

draft horse logging in the United States

(photo from Kissing Rock Camp)

This starts a week of forestry related posts covering everything from pollards and espaliers to coppice lots, hedgerows, restorative forestry, and draft animal logging.

Clear cutting is clearly problematic.  Is there another option?  Yes, Jason Rutledge, founder of a Virginia draft-horse logging school and the Healing Harvest Forest Foundation has figured out something very very cool.

Background Concepts for Restorative Forestry

How Forests Mature:  Very few of us have seen virgin forests, we’re much more familiar with the secondary and even tertiary regrowth after a site has been logged repeatedly.

Trees in a dense forest must "share the wealth" of growth each year.

Trees in a dense forest must "share the wealth" of growth each year.

Secondary growth starts off with the pioneer trees- those that are willing to grow in the bright sunlight and full force winds of an open area.  Pines, tulip poplars, and other softwoods get a forest started.  Over time, the pines die back and the hardwoods begin to gain in population percentages.  During these early successional stages, the forest is dense with slender trunks, and likely to be rife with understory shrubbery and vines, making passage difficult and the view less than “awe”-some.­

selective logging

A more open forest gains girth faster: the dense forest's purple growth ring plus the extra green ring, both in the same year.

How Forest Trees Grow: A forest gains biomass in the form of tree trunk girth at a predictable rate, regardless of forest density.  While both a dense forest and a more spacious forest will gain X amount of biomass per year, each tree will share in that percentage.  If it gains 8%, 100 trees will each get 1% of that, or 10 trees will get 10% of that.   (I’m making up numbers here.  Follow the concept, not the exact math.)

This difference is why the average tree in the forest gains ½” of circumference a year while a tree in an open field averages a full inch of girth.  (Yes, this works to give you a rough estimate of age: 60 inches around at “hug height” in a forest is about 120 years old and in a field is ballpark 60 years old.  It’ll vary by tree species and site history a bit, but the hug is a good starting point from which to guess up or down.)

How Ecological Timber Folks Tweak This: My diagrams above are clustered the way trees in forests tend to be clustered.  Unless you are on a monoculture tree plantation (a freaky sensation if there ever was one), you won’t find rhythmic spacing.  Foresters who are interested in increasing the speed at which individual trees gain girth will use spacing as one of selective logging criteria.

There are timber folks who take this to an extreme, cutting large clearings around valuable trees to maximize their gains, but that’s the difference between seeing the trees and seeing the forest.  Cut out a big clearing, let a tree gain girth for a number of years, take out that tree, and you have a clearing in the forest.

Canopies are not always centered over the base of the tree.

Given what we already know about deer and other forest-edge dwelling species proliferating at absurd rates in suburbia, creating more edges seems like something to avoid if possible.  Simply allowing trees to have enough spacing to keep their canopies basically centered over their roots ought to be plenty of room.  Remove a tree from the scenario, you still have a forest, just with one less tree.  The whole remains intact.

So spacing is a key criteria for which trees to selectively log, but what else?

Tomorrow:

The HUGE flaw in the diagrams on this page (can you spot it?), high-grading, and “Nature’s Tree Marking Paint

Related posts:

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>