Girdling Trees to Create Snags and Coarse Wood Debris and to Improve Wildlife Habitat
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Girdling Trees to Create Snags and Coarse Woody Debris and to Improve Wildlife Habitat By John Lampe Green Shoots, LLC January 28, 2014
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This presentation describes the benefits of thinning trees in a woodland by girdling trees to kill them and to create snags. Snags are dead standing trees. Research indicates snags and coarse woody debris - all forms of dead wood - are vital to wildlife. The presentation also describes how to girdle trees. The techniques for girdling trees include both mechanical girdles where the phloem layer is completely removed with a hatchet or other implement and chemical girdling where an herbicide is applied to the girdle. Some trees such as aspen can be girdled without using herbicides. Some trees are tougher to kill and require applying an herbicide into the cuts. Another way to create a snag is to cut off all the branches. This method won't work for most deciduous trees.
Transcript of Girdling Trees to Create Snags and Coarse Wood Debris and to Improve Wildlife Habitat
Girdling Trees to Create Snags and Coarse Woody Debris and to Improve Wildlife Habitat
By John Lampe Green Shoots, LLCJanuary 28, 2014
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Three Reasons to Create Snags
• Thin trees in dense woodlands• To open up areas for prairies and savannas• To create habitat for wildlife
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Woodlands Are Becoming Too Dense
• Big trees need space – With less natural fire, forests are becoming too
dense. See e.g., Knapp et al. 2013.• Prairies and savannas are becoming scarcer
partly because of woody encroachment
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North American Oak Savannas
• One of “most threatened plant communities in the world.”
• Only 30,000 acres today. SavannaOak.org.
• Less than 0.01% of original oak savannas remain. NRCS Missouri 2003.
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“Christmas tree plantation” 1964; planted in oak savanna habitat
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Same Location April, 2013
Dense woodland with small trees: poor wildlife habitat
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We have too many (small) trees
• Fire suppression• Thinning in conventional ways is very labor
intensive, especially for small landholder without sophisticated equipment
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• Pile of trees from 35 acres thinned to restore oak woodland• Whether burned or cut and hauled – lots of biomass !• With sawmills closing, low quality, tree biomass is less and
less valuable on the open market
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One small way to reduce excess biomass is to create snags and “Coarse Woody Debris”
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Coarse Woody Debris and Snags
• “More than a third of our wildlife species . . . are dependent on dead and dying wood for their survival and well-being.” Bottorff 2009.
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Too Little Coarse Woody Debris in Forests
National Park Service, Northeast Temperate Network, 2009: “good coarse woody debris abundance requires that CWD [coarse woody debris] volume be greater than 15% the volume of live tree volume.”
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Girdling and topping as way to:
• Thin woodlands• Open prairie areas• Increase dead wood
13Girdling and topping opens area for prairie
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Does girdling and “non-natural” tree mortality create good snags?
• Some research says “artificially created” snags are not as “biologically rich.” Shea et al. 2002.
• The following photos are of trees created either by topping or girdling; all trees indicate heavy foraging by woodpeckers
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Topped Scots pine
16Girdled Scots pine
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Girdled aspen
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Girdled aspen
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Scots pine; uncertain mortality; but very attractive!
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Aspen; uncertain mortality
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Artificially Created Snags
• Artificially created snags may not be optimal; not much data
• However, they do appear to add substantial benefit based simply on signs of heavy foraging
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Snag Creation
• Pines – one person can girdle about 20 to 50 trees (10 to 15 in dia.) in an afternoon
• With a snag you also don’t have to haul away the tree or burn debris
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Versus Cutting as Method of Thinning
• In contrast, cutting down even 5 trees in dense woodland might be tough in same time
• Cut trees are constantly caught in branches
• My belief: You can thin a forest much faster by girdling than you can by cutting a tree down
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Timing of Girdling
• Some sources may advocate girdling in spring or fall when bark is “slipping.”
• Outer bark may come off easier at these times• However, I have found that it may be harder
to fully remove phloem layer at these times; phloem becomes slippery
• (It’s also messier because of sap flow.)
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Timing of Girdling (con.)
• I like to girdle trees in late fall or winter• Sap is not flowing heavily• Phloem seems to be easier to remove• Easier to move through forest with less foliage• Work is physical and keeps you warm
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How to Create Snags
• I divide into two categories:– Easy to girdle trees (examples: Scots pine, aspen,
box elder)– Hard to girdle trees (example: red pine and, I
believe, most trees with fire resistance)
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Easy to Girdle Trees – Mechanical Method
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Steps to mechanical girdle (no herbicide):
• Strip bark around circumference of tree using a draw knife (Make sure it’s sharp!)
• Create band of stripped bark about foot high• Remove all the phloem (live, inner bark) or
tree will survive; even a small, connected strip may be enough to support tree.
• Wait – it may take up to 1.5 years to die
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Tough to Girdle Trees
Some trees are very tough to kill with a mechanical girdle; I believe these are probably trees that are also more fire resistant
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This red pine has
been girdled 3 times;
we’ll see if it finally dies.
1st girdle
2nd girdle
3rd girdle
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Steps to kill a hard-to-kill tree with herbicide
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First, cut frills with hatchet or similar tool near base of tree; be sure you penetrate into phloem,i.e., the live, inner bark. Don’t space cuts more than inch apart.
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Apply herbicide to frill cuts; this example shows foam herbicide with blue indicator dye.
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Note on Applying Herbicide
• I have used glyphosate at label rates for frill or cut stump (typically tank solution has 20% to 30% active ingredient)
• It will still take a year or so for pine tree to die even though herbicide is used. (not sure why.)
• As always, follow herbicide label.
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Other factors to consider: fire hazard
• Fire hazard – Stephens et al 2012 most to least dangerous fuel types in forest:– Surface fuels dead and down woody materials,
litter, grasses, herbaceous plant materials. shrubs– Ladder fuels – small trees and tall shrubs– crown fuels – overstory; small component (This is
presumably where snags fit in.)– Ground fuels – duff and material on soil surface
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Snags as fall hazard
• General advice: don’t create snags near trails, roads, or where people will be.
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In my experience: as tree rots it becomes very light; most snags that fall in a forest catch in the branches of other trees.
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Topping Trees
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Topping Trees
• Advantages:– Great way to rapidly open up an area; especially
helpful in prairie areas– Works best for small trees– Create really nice perches for birds
• Disadvantages:– More time consuming than girdling– Have to climb tree
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Conclusions (based on experience; not hard data):
First: Girdling and topping trees does create snags that are good food sources, i.e., “artificially created” snags provide benefits to wildlife.
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Conclusions
• Second: You can thin a woodland far faster by girdling than by cutting down trees (unless highly mechanized).
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Conclusions
Third: Girdle patches of multiple trees or trees near openings so they can be found by woodpeckers; trees in the middle of dense woods seem less attractive or may be tougher for woodpeckers to find.
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Conclusions
• Fourth: for trees that are not fire-resistant (e.g., aspen, Scots pine), girdling can be done without herbicide.
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Conclusions
• Fifth: for trees that are fire resistant (like red pine) or are tough to girdle (e.g., lots of knots or thick bark), girdling should include injections of herbicide into frills cut around the tree.
