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One of the unfortunate aspects of the
road construction process is the creation of sites through the exposure of
mineral soil adjacent to the road bed which is conducive to the establishment of
alders and birches. While this assists in the rehabilitation of the exposed
areas, alders can quickly become both a nuisance and more importantly a safety
issue as lines of sight and road widths are reduced. It is estimated that alders
can become a problem within five to ten years of road construction given the
proper conditions (soil moisture, seed source); even sooner for some
areas.
This past fall the Resource Roads
Section initiated a comparative trial focusing on two possible solutions; the
age old method of manual cutting versus mechanical mulching (mechanical mulching
head attached to the boom of an excavator). The trial took place in Management
District 5 on the Drover’s Ridge Access Road. Here alders had
grown in to such a point that driving was seriously impaired.
Manual Removal
This portion of the trial involved the manual felling of
brush by eight experienced workers (plus one foreman) equipped with thinning
saws. Where thicker and larger brush was encountered, power saws were utilized.
100 m strips were marked off with the fellers instructed to cut all brush as low
as possible (15 - 25 cm average) within a 4 m corridor (wider on turns).
Following felling it was evident that a fair number of small alders
survived. This plus suckering will most likely result in the quick regrowth of
the vegetation. Cost of the project was approximately $850/km (both sides
treated).
Mulching
For the mechanical mulching of the trial a 690 John Deere excavator equipped with a
mulching head (as opposed to a cutting head) was contracted through GPA. As with
the manual system, operators were instructed to fell a 4 - 5 m swath, wider on
turns. Following mulching very little alders were evident in the strip and it is
hoped that shattering the root system of the alders will prevent suckering.
Costs were in the order of $2000/km.
Herbicide & Seeding
Whether manually felled or mechanically
mulched, alders have a way of rebounding quickly and as such, herbicides most
likely will have to be utilized to extend the length of time between treatments.
A number of products are available and all require application approval from the
Department of Environment as well as a valid herbicide application license.
Consideration is being given to treating the trial areas next spring
following green up. The ultimate solution is to correct the problem
before it arises and this most likely will be the future course of action
for the roads section. While it is normal procedure to seed around larger culverts
and embankments, consideration will be given to (grass) seeding all exposed areas
along the road right of way which should serve to reduce the establishment of
hardwoods. Those seeking more information on this trial are directed to a FEIS
Information report to be published early in 2001.
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