7/01/2012

Big Trees, Big Roots


Giant roots holding an old growth Douglas-fir as it slumps
 into the sea on Billings Spit, Sooke Harbour

The misty coastal forest is the place to see monumental trees. As awesome as these giants are, we are only seeing 3/4 of the total tree, and even less of the total forest life. There is a lot going on under our feet as our gaze is lifted skyward.


Roots can compose 25% or more of the total biomass of a tree. Scientists have found that up to 66% of a Douglas-fir forest's total biomass is out of sight underground.

Trees on Port Renfrew beach showing root remnants
A sapling can have several feet of roots, so it is not surprising that an ancient tree can have hundreds of kilometers of them. An old growth tree 150 meters (300 ft) tall and and 5 meters (15 ft) wide, needs an extensive root system to support the trunk and canopy.

Early settlers on Vancouver Island used bonfires and dynamite to extract the massive stumps and roots when clearing the big trees of the primal forest.
"Well into the 20th century 'stumping powder' (low-grade dynamite) was used to blow a stump apart, so that the fragments could be removed more easily. Someone wishing to remove a stump tunneled under it, inserted enough powder to break it apart (preferably without damaging the arable soil), lit a fuse and got out of the way. If the detonation didn't come, it was best to avoid the area for a day or so, as many a stump-wrangler lost life or limb to a belated blast."  - source

This Western red cedar's roots look a lot like octopus tentacles
Roots anchor the tree, provide uptake of nutrients and water for growth, store food reserves, and produce organic materials required for tree growth. Roots also interact with beneficial fungi, and with other trees.

Tree roots exposed by the flowing waters of Sooke River
Douglas-fir roots readily fuse together, blending the lines between individual trees (and species of trees) and the forest as one large organism. This crossover of roots can keep the stump of a cut Douglas-fir alive long enough to grow a layer of bark over the cut.

Roots are fragile structures that can't handle rough treatment. Soil compaction restricts water and oxygen uptake, and can be caused by heavy foot traffic over the tree's root zone. It is best to avoid, if possible, walking or driving over a tree's roots.

Small protective fence surrounding the Harris Creek Spruce, Port Renfrew
It is because of potential soil compaction and root damage that you will find fences and boardwalks around some of Vancouver Island's most visited big trees. The Harris Creek Spruce has a small protective fence around its ample base, but a raised boardwalk would be ideal.

Heaven Tree boardwalk, Carmanah/Walbran Park
Heaven Tree, in Carmanah/Walbran Park, has boardwalks built over the tree's roots and around the tree's circumference. Such measures prevent soil compaction over the root zone, and helps protect these trees from being loved to death.

Next time you are out in the forest, pause to consider all the activity that is occurring under your feet. Notice the places roots make their presence known, such as along hiking trails through the forest, and in areas that have been eroded, leaving roots exposed.

The 'feet' of the giants can be as fascinating as their more glamorous and obvious parts.

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