Spherical Crown Densiometer, Concave

Total light incident on the stream and the resulting heat load are important factors regulating biological activity in the stream.

The water column is the medium of support and movement for fish and other aquatic organisms and is strongly controlled by its bordering riparian vegetation. The amount of sunlight, which is the energy base for photosynthesis and stream temperature, is also controlled by the surrounding vegetation.

The concave Spherical Densiometer, Model B can be used on permanent points or transects to estimate relative vegetative canopy closure or canopy density caused by vegetation. Vegetative canopy closure is the area of the sky over the selected site (stream channel) bracketed by vegetation.

The concave mirror surface of the Densiometer has 37 grid intersections forming 24 squares. At a probability level of 95 percent, tests show that average measurements of the same overstory area can be expected to be within ±2.4 percent of the mean.

To take readings, hold the instrument level, 12" to 18" in front of body and at elbow height. Assume four equi-spaced dots to each square of the grid and systematically count the dots equivalent to quarter-square openings. Multiply the total count by 1.04 to obtain percent of overhead area not occupied by canopy. The difference between this and 100 is an estimation of overstory density in percent. Units are housed in a 3" x 3" x 1" thick walnut case with operating instructions permanently affixed to the lid. A leveling bubble is also included for accurate positioning during estimations.

Two models are available: Convex and Concave. The readings from the Convex Densiometer are representing a larger sample size area than those of the concave unit.

607-090 Concave Densiometer 1 lb.