3. Friends of LHLFriends of Log House Landing
Presentation to city council 9-3-14
NATURAL RESOURCE INVENTORY
As you have heard tonight, the current city plan is to remove 21 trees that are 6"
in diameter or more. However, one needs to consider more than just the trees
being removed. There is good information that trees in close proximity to the
construction are likely to be negatively impacted by root disturbance and/or soil
compaction. Such damage can result in susceptibility to disease and death,
which occur over several years after the impact.
On 8/28/14, Joe Walton, an ecologist and forester, joined me in a site visit to
conduct a brief evaluation of the trees along the project area. Since the exact
project alignment is not visible on the ground, the evaluation consisted of
recording details of a few of the most notable trees, and counting all trees within
10 feet of the existing roadbed that were larger than 8 inches diameter.
Scandia's set -back rules to protect trees are to measure a tree's diameter in
inches and consider that distance in feet for set -back. So for example, a tree
with a 15" diameter needs to be 15' away from construction to avoid impact.
A total of 56 trees were recorded, ranging from about 8 to 45 inches diameter at
chest height that would likely be impacted by the proposed construction. The
larger the tree, the more harmful root disturbance is, as larger trees cannot
recover as well.
Five of the most notable trees recorded were as follows:
One 25" diameter white pine, slated for removal. About 90 ft tall. Roughly 80 (plus)
years old. Healthy.
One 45" diameter white pine, on the edge of proposed road. About 130 ft tall. Old
growth tree. Mostly healthy with some dead branches dead.
Three other trees were a 24 -inch diameter white pine, a 24 -inch sugar maple and a
14 -inch paper birch. All were near the construction edge, and all were healthy.
NATIVE ECOLOGY OF LOG HOUSE LANDING
The vegetation at Log House Landing is mostly native cover, reflective of the
white pine forests that historically covered the area. While most of the area was
logged, the regrowth is now at least 80 years old, and includes some relict "old-
growth" trees. This vegetation and the character of the road provide a sense of
place that ties in with the cultural history of the landing. The trees are a vital part
of the river ecology, serving to hold soil and prevent erosion, provide cooling
shade to the creek and the river, and of course habitat for birds and other wildlife.
If Scandia decides to pursue this current proposed plan, a more comprehensive
assessment is needed of exactly how many trees, what size, and what species
are in the construction limits, as well as any nearby trees that will also be
affected. The project boundaries need to be clearly visible on the ground so
everyone can have the same understanding. This is the most basic level
information, and is essential for making any meaningful assessment of the
project impacts.
However, as an ecologist and resident of Scandia, it is my personal hope that the
City Council will reconsider the scale of the current proposed plan and adopt a
much more sensitive solution, one provides maximum protection to the river, but
also has the least possible impact on the native ecology and character of the
area.
W=4 Protecting trees from construction - a homeowners guide: Yard and Garden: Garden: Uriversttycf Minnesota EAerW cn
The root of the matter...
Trees can be damaged or killed by a wide variety of construction activities. Some practices lead to obvious injuries
such as broken branches or tom bark. Open wounds of this type deplete a plant's energy resources and provide
entry points for insects, or for diseases such as oak wilt.
The worst damage, however, often remains hidden underground. Roots are one of the most vital parts of a tree.
They are responsible for nutrient and water uptake, store energy, and anchor the plant. Because they are so
important, it is critical that you protect roots that lie in the path of construction.
Trees are never the same shape below ground as they are above, so it is difficult to
predict the length or location of their roots. Typically, however, approximately 90-95 ;.
percent of a tree's root system is in the top three feet of soil, and more than half is in theAI
top one foot. The part of this root system in which construction damage should be avoided
is called the Protected Root Zone (PRZ). r
One common method used to identify the PRZ is to define it as the "dripline'—the area--------
directly
-.____adirectly below the branches of the tree (Fig. 1). However, many roots wdend beyond the
longest branches a distance equal to two or more times the height of the tree. For this Figure 1. A tree's protected
root zone (PRZ) is often
reason you should protect as much of the area beyond the dripline as possible. considered to be the part
, on most sites space is limited and this ruffle must be bent. Just how Gose an °f the rods that be directly
Unfortunately, P below its branches within
activity can come without seriously threatening the survival of a tree depends on the an area known as the
species, the extent of damage, and the plant's health. dripline.
Some healthy trees can survive after losing 50 percent of their roots. However, other
species are extremely sensitive to root cutting, even outside the dripline.
Table 1 shows the relative sensitivity of various tree species to root disturbance. If
d' percent of the roots within the dripline for tree,
possible, disturb no more than 25 p' rry
rotect intermediates ecies to the dripline, and allow extra space be and the dripkne for
P P Y
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sensitive species. For all trees, avoid needless or excessive damage. A qualified tree-care19
1
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specialist can help you determine how much root interference a particular tree can
tolerate.
Figure 2. Appro)dmate a
When dealing with trees that have been growing in the forest or that naturally have a
tree's PRZ by calculating
narrow growth habit, an approach caked the "critical root radius" is more accurate than the
the critical root radius
(CRR). First, measure the
dripline method for determining the PRZ. This is particularly true for columnar trees and for
tree diameter in inches at
those where competition has reduced the canopy spread.
breast height (DBH). Then
multiply that number by 1.5
To calculate critical root radius, begin by measuring the diameter at breast height (DBH).
or I.D. Egress the result in
This is done by measuring the tree's trunk diameter (thickness) at a point 4.5 feet above
feet.
the ground. The measurement should be done in inches. For each inch of DBH, allow for
1.5 feet of critical root radius for sensitive, older, or unhealthy trees, or 1.0 feet for tolerant,
younger, healthy trees.
For example, if an older tree's DBH is 10 inches, then its critical root radius is 15 feet (10 x 1.5 = 15). The PRZ is
then the area around the tree with a diameter of 30 feet (2x critical root radius), and is the area
in which a critical
amount of the tree's roots may be found. Whenever possible, isolate this area from construction disturbance (Fig. 2).
Table 1. Tree characteristics
Species Root Soil Soil pH Mature Mature Hazard
Damage- Landscape
Sevarancats Compaction Preferences Tree Crown Tree
Causing Value**t
& Floodings Height Spread Rating**
Roots
005 (ft.)e
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