Erosion Rates of Wood During Natural Weathering. Part II. Earlywood and Latewood Erosion Rates

This is the second in a series of reports on the erosion rates of wood exposed outdoors near Madison, Wisconsin. In the work reported here, the erosion rates of earlywood and latewood were determined for smooth-planed vertical-grained lumber for an exposure period of 14 years. The specimens were oriented vertically, facing south; erosion was measured annually for the first 6 years and biannually the remainder of the exposure. Wood species were ponderosa pine, lodgepole pine, Engelmann spruce, western hemlock, and red alder. Large differences were observed between earlywood and latewood erosion rates during weathering. Erosion rates varied from 33 μm/year for lodgepole pine latewood to 58 μm/year for western hemlock and red alder earlywood. In general, no practical differences in erosion were observed for different orientations of the specimens on the test fence (vertical or horizontal longitudinal axis). Some specimens showed considerable decay after 10 years of exposure