Windbreak thinning at Carrington REC.

A windbreak 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. 

The windbreak 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. 

This 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 Dakotans. 

JDZ

13.May.2004

Windbreak thinning at Carrington REC.

Update - 21.July.04 (JDZ)

The windbreak 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. 

Another of 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.