Crown Closure Measurement
When you're in the woods, how often do you look up to the canopy? Foresters do it all the time- but not only to admire the canopy, we also do it to measure crown closure!
Crown closure is one of the many important measurements used by forest professionals to determine the density of tree canopies, and how much light can reach the forest floor. Crown closure is expressed as a percent, and is determined by looking up at the canopy and estimating how much the tree crowns are taking up the view. The higher the percentage, the denser the canopy, and the less light can reach the forest floor. Although this is usually estimated, tools such as densiometers can be used to get a more accurate percentage.
Crown closure is one of the many important forest measurements used to help inform management decisions and assign an appropriate prescription that regenerates desired species and maintains stand structure. Reducing the the crown closure through thinning or creating small gaps brings more light to the forest floor and can create conditions favorable for new trees to grow. If your aim is to regenerate longer-lived, shade tolerant species you don't want to reduce the crown closure too much. Providing too much light to the forest floor with a heavier thinning or large gaps in the canopy may create light conditions suitable for regenerating fast growing, shade intolerant species which can inhibit the growth of shade-tolerant trees.
Next time you're in the woods, be sure to look up and see if you can estimate the crown closure!
This photo shows a canopy with about 90% closure, in this stand, there was very little light reaching the forest floor, and virtually no regeneration was found.
This photo shows approximately 75-80% crown closure, which meant that some light was reaching the forest floor, allowing for some shade tolerant regeneration to grow.
This third photo shows approximately 60% crown closure. In this stand, there were both shade tolerant and mid tolerant species growing in the understory.