Influence of overstory on snow depth and density in hemlock-spruce stands: implications for management of deer habitat in Southeastern Alaska.

Abstract

Snow depth and density were measured in 33 stands of western hemlock-Sitka spruce (Tsuga heterophylla [Rat] Sarg.-Picea sitchensis [Bong.] Carr.) over a 3-year period. The stands, near Juneau, Alaska, provided broad ranges of species composition, age, over-story canopy coverage, tree density, and wood volume. Stepwise multiple regression analyses indicated that both overstory canopy coverage and gross wood volume were negatively related to snow depth in the forest, which was expressed as a proportion of the depth in a nearby open area. Multiple regression equations accounted for 53-79 percent of the variance in snow depth, but relationships were not consistent from one sampling period to another. Density of snow under the forest canopy, expressed as a proportion of the density of snow in the open, was less influenced by forest overstory than was snow depth. Regression equations accounted for 18-70 percent of the variance in snow density but, as with snow depth, were inconsistent from one sampling period to another. The following criteria are suggested in selecting stands for winter range for deer where snow accumulation is a problem: (1) topographic setting; (2) overstory canopy coverage at least 95 percent, as measured with a spherical densiometer (3) timber volume class at least 20,000 board feet per acre, net volume; and (4) an understory of relatively abundant, high-quality forage.

Citation

Hanley, Thomas A.; Rose, Cathy L. 1987. Influence of overstory on snow depth and density in hemlock-spruce stands: implications for management of deer habitat in Southeastern Alaska. Res. Note PNW-RN-459. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 12 p