Windbreak thinning at Carrington REC.
thinning project was recently completed at the Carrington Research and
Extension Center. The single-row field windbreak is about 150 yards
long and was planted in the 1960s with golden willow. The trees are
approximately 50 feet tall and were
overhanging into the nearby fields, disrupting planting, tillage and
harvesting operations. There was a thick understory consisting of
chokecherry, boxelder, green ash, red-osier dogwood and honeysuckle. Many
dead and broken trees were cluttering up the stand. Therefore, the NDSU
Extension Forester began an effort to clean up the windbreak, allowing
easier access to the adjacent fields and beginning the process of
regenerating the willow trees.
The work was
completed in late April and early May 2004, just as the trees were showing
leaves and flowers. The majority of understory trees and shrubs and most of
the standing dead trees were cut. After these were taken out, any stems or
large branches that were leaning far out into the fields were cut. This
reduced the windbreak density substantially.
Because of the clumped growth habit of willow, some of the remaining trees
had as many as five individual stems remaining. In those spots, I harvested
one or two of the live trees, with the goal of encouraging sprouting from
the stumps and roots. Felling and pruning the trees took approximately 17
hours of labor (and 2 gallons of 2-cycle chainsaw gas). The bulk of the
slash (cut tops and stems) was chipped right back into the windbreak. These
chips will act as a mulch, increasing available soil moisture for the
remaining trees and keeping out weeds. As the chips decay, they will add
organic matter back into the soil, allowing further moisture retention and
encouraging nutrient cycling.
will be monitored for the next few years for regrowth. Ideally, the cut
trees will begin to sprout from the stumps or roots. As these new trees
become established, the overstory trees will be thinned again, encouraging
more sprouting and further creation of the next stand of trees. Once
regeneration is firmly established, then the final overstory trees will be
removed. This process will take as many as 5-10 years for completion.
However, following these methods, we hope to regenerate a new stand of trees
while still keeping protection for the adjacent fields and roads.
collaborative project presents a variety of benefits. Because neither
thinning nor establishing natural regeneration are common practices in North
Dakota windbreaks, this venture offers a great opportunity to demonstrate
two powerful renovation techniques. For the Carrington REC, it allows much
easier access to their fields and a healthier windbreak. The cooperation
established in this project will only lead to further benefits for all North
Windbreak thinning at Carrington REC.
Update - 21.July.04 (JDZ)
thinning project begun in May of this year is progressing nicely. The
project cleaned out the stems that were leaning into the field, opening up
this area for field work. Windbreak density
was reduced by thinning, but mainly at the bottom; density at the top has
increased since May because the trees are now in full
leaf. Although most of the stems that were cut were dead or nearly
so, some dead trees were left standing in certain areas to provide some
density where a large gap might otherwise exist.
The plan called for
chipping slash back into the windbreak.
That work has begun but has not yet been completed because there was a
large amount of slash created.
the original goals was to begin to regenerate the willow trees in this
windbreak; by cutting these trees, it was hoped that they would sprout from
the stumps. However,
sprouting from the willows
has been minimal. This is probably because (1) the bulk of the cutting
was in dead material, and (2) the trees that were cut were large-diameter
and older, large-diameter trees do not sprout as well as younger stems.
Interestingly, there were several logs (~6" diameter) that had been cut and
laid on the ground, and
these were sprouting.
Although the chance that these logs will take root is very slim, it does
point out a different direction to take in future regeneration attempts.
Willows, which often grow next to rivers, may regenerate by shedding
branches into the river, which carries them downstream where they take root
in a sandbar. Therefore, we may try simply placing some of cut
branches into the ground beneath the parent trees. Sprouting of the
understory species (chokecherry, green ash, rose)
was very good.