Silviculture Highlight: Crop Tree Release with Canopy Gap Formation

Fall is a great time to be out in the forest. The vibrant colors of summer songbirds, all but gone now to spend the winter in the tropics, replaced by fall foliage. Along with cooler temperatures, autumn is ideal for planning forest stewardship activities. One of these activities that can help enhance bird habitat and improve the overall health and resilience of the forest is the application of a silvicultural method called Crop Tree Release with Canopy Gap Formation.

Silviculture is the art and science of tending forest trees. Effectively applied, silviculture plays a role in directing forest establishment, its composition of species, and its growth to help create and maintain a forest that meet stewardship objectives; whether that be wildlife habitat, forest products, recreation, etc.

Crop tree release focuses on retaining and continuing to grow the best formed, healthiest, and otherwise most desirable trees in the forest by harvesting surrounding trees that are competing for resources. Once the crop trees are selected, some of the trees competing with the crop tree for light and space are removed. In addition to releasing crop trees, the creation of small openings in the forest canopy, referred to as gaps, can help improve forest structure by promoting the growth of young trees and shrubs.

When and where is it used?
  • In forest areas where desirable trees may benefit from reduced competition; generally most beneficial in areas with immature trees, between 6”-10” in diameter
How is it done?
  • When a crop tree is selected as a preferred tree to grow, trees with crowns touching the crop tree may be selected for removal
Why does it work?
  • By removing trees competing for the same light and space as the crop trees, this treatment can be effective at promoting the growth of the most desirable trees, while retaining trees that are not limiting a crop tree’s growth
Bird habitat tips
  • Consider among your crop trees those with particular value for forest birds such as yellow birch, red oak, black cherry, and softwoods in hardwood forests
  • Expand the crop tree management goals to include promoting forest structure (young trees and shrubs in the forest understory) by creating “canopy gaps” ranging from 30-75 ft in diameter by removing all trees >1 in in diameter
Birds that may benefit
  • Blackburnian Warbler
  • Black-throated Blue Warbler
  • Eastern Wood-Pewee
  • Scarlet Tanager
  • Wood Thrush

Our partners at the VT Department of Forests, Parks, and Recreation have put together an excellent video showing the principles of crop tree release in action. Check it out here.
Audubon VT’s “Silviculture with Birds in Mind” provides additional information on the crop tree method and other treatments for integrating timber and songbird habitat management.

Crop tree release diagram shown from above.
Crop tree release diagram shown from above. The green circle is the crop tree. Photo: USDA

Please Note: As with any forest management, we highly recommended that you consult professional foresters when planning for and implementing practices. Ensure training in the proper felling of trees and equipment use prior to taking on any work in the woods yourself.

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