Wednesday, January 9, 2013

Beaver Timber Stand Improvement

Our recent Battle with Beavers left me with a question.  Why do beavers cut down trees far bigger than they can use?  They had girdled over 15 trees in the 8-14 inch range on a small patch of creek side bank between Bull Creek and an adjacent oxbow pond.  Animals adapt to their territory and rarely spend energy on activities that aren't necessary for survival such as eating, procreating and escaping danger.  This was far more that they could ever eat and yet they used a lot of energy in the effort.

Willow cuttings
Beavers eat mostly soft herbaceous plants in the summer and woody species in the winter.  In general, they prefer eating the soft xylem wood under the bark of young trees and limbs, especially willow.  Unfortunately in the area where we had to trap beaver recently there are nice high banks for dens but few young tender trees.  They therefore have been girdling and felling mature ash trees of 6 to 14 inch diameters.  I couldn't understand why they would invest that much time an effort on big mature trees until I read about coppicing, the practice of cutting a tree to produce basilar shoots.
Greeneway Tree Care

In the middle ages, coppicing was a common method of managing a forest.  It was a lot of work to cut a large tree with the crude axes of the timeSince the King and his nobility owned the forests and controlled wood harvesting, the peasants weren't allowed to cut any trees.  They were allowed to harvest any dead sticks for firewood, including dead branches they could break off a standing tree.  They used a hooked tool for this, felt to be the origin of the saying "by hook or by crook."

The king and nobles owning the forest could control the frequency of cutting trees and the number of mature trees left for future construction of buildings. By cutting a tree and using the lumber for construction, they would also produce a future dozen smaller shoots around the base of the stump to harvest in a few years.  This could be more easily cut for fire wood.  
"The shoots (or suckers) may be used either in their young state for interweaving in wattle fencing (as is the practice with coppiced willows and hazel) or the new shoots may be allowed to grow into large poles, as was often the custom with trees such as oaks or ashes. This creates long, straight poles which do not have the bends and forks of naturally grown trees.  Coppiced hardwoods were used extensively in carriage and shipbuilding, and they are still sometimes grown for making wooden buildings and furniture."  Wikipedia
Beaver Coppice- Click to enlarge
When a tree is girdled by a beaver, the stump usually will produce a dozen or so shoots around the base.  Left alone, these will grow into nice bite size small trunks, just perfect for beaver food.  They get some of the branches from the felled tree and produce a food factory for coming years, their own quick shop.  How they discovered this old forestry technique is unknown, but I suspect that they learned it before we did.

 Unfortunately they tend to girdle more trees than they fell, not necessarily saving some for the future.  Our beavers did something even more puzzling.  They chewed one large trunk into a "string of pearls" configuration.  The area they had settled in has only mature trees instead of their preferred willow.  I have to think that they weren't finding enough young branches and were eating into the more dense heart wood.  Or maybe they just wanted more fiber in their diet to improve their colon function.
Little innocent beaver with beaver log

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