CRITICAL ROOT ZONE
Laytonsville, MD
Central Maryland is in a drought and as of 10/5/07 BWI Airport states that
we are -9.21 inches below the normal precipitation amounts for
this
growing season. I was going to a job site today and noticed a hedge
row of sawtooth oak in a lawn area that distinctively showed
drought
stress and subsequent root zone. In order for the trees to respire
(evapotranspiration) they require the uptake of water from
the soil. As the turf competes within the trees root zone, it does not
fare as well as the adjacent turf beyond the tree's root zone.
The
color change in the turf was quite obvious.
In the first photo, I've highlighted in yellow, the extent of fibrous
tree roots that are more or less
consistent with the canopy drip line of
the tree, and which is competing with the turf.
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Each tree in the hedgerow had a ring more or less the same size as the trees
drip line. |
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Most all arboricultural books say that if you want to protect a tree during
construction (excavation,
fill and/or compaction) you need to protect the critical root zone. The
critical root zone is defined as being: tree diameter x 1.5 = critical root
zone. An example would be a 10-inch diameter tree (at chest height)
would have a critical root zone radius of 15-feet from the tree trunk out.
If you protect this area from all impact, then the tree should not ail or fail
from nearby impacts, in that it's shallow, fibrous, uptake roots would not be
compromised. |
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This set of photos is interesting because you rarely see visual evidence of the
root zone. |
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I thought you would enjoy this basic lesson in silvics. |
Submitted by Mark Burchick
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