Foresters Now Monitoring Tree Populations from Space [Slide Show]
Scientists know surprisingly little about what is growing in our forests. New techniques for analyzing satellite data are about to change that
One traditional tool of a forester, an angle gauge, determines which trees must be measured in a sample of forest. Holding the gauge at arm’s length, a forester will spin 360 degrees in the middle of a sampling spot and examine each tree visible through the notched hole in the gauge. If a tree’s trunk completely fills the view hole, the tree is “in” the sample area and must be measured. (Trees too thin to fill the hole are either far away or too small to bother measuring). In densely stocked forests one sample spot could require dozens of individual tree measurements.
Credit: Shane Hetzler, Back Forty Forestry
Not surprisingly, a tree's size indicates how much wood it contains. Foresters have long used a Biltmore stick, invented before World War I at the Biltmore Estate in North Carolina, to quickly ascertain the diameter and hence circumference of any tree. Using one is simple: march to a trunk and hold it up, perpendicular to the ground.
Credit: Shane Hetlzer, Back Forty Forestry
Zack Parisa, co-founder of SilviaTerra, measures a tree by hand with a girthing tape, an alternative to the Biltmore stick. Satellite timber-assessment technology, employed by companies like SilviaTerra, can make assumptions about the variability of trees within a landscape to dramatically reduce the number of hand measurements like these that must be taken.
Parisa examines a tree with a laser hypsometer while leaning on a Biltmore stick. The former tells him the tree’s height, the latter its diameter.
Credit: SilviaTerra Advertisement
A satellite image of an industrial forest in Alabama (a) contributed to this tree “heat map” depicting the density of timber present (b), which is given by both the probable number of trees present and their sizes. Satellite data is making it easier to determine the sizes and species of trees that grow in America’s forests.
Credit: SilviaTerra Advertisement Expertise. Insights. Illumination.
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