Effects of forest roads on the growth of adjacent lodgepole pine trees

Abstract

The effects of roads on growth of adjacent lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) trees were studied in an area near Williams Lake, British Columbia. Plots were established in a range of stand ages, site qualities, stand densities (stems/ha), stand basal areas (m2/ha), edge aspects, and adjacent road widths. Plots were divided into five zones beginning at the road edge: 0–5 m (zone 1), 5–10 m, 10–20 m, 20–30 m, and 30–40 m (zone 5) from the edge. When the 5 years prior to road establishment were used to scale growth rates, relative tree basal growth rates for zone 1 differed significantly from those for the other zones, with zone 1 rates being 32.1% higher, on average, for 3 to 15 years after the road opening was established. Fewer dead standing trees were found nearest the road edge. Tree bole shapes at breast height were not significantly different among zones, and no significant increases in average basal area per tree or in average height were found. On average, zone 1 had a 31.3% greater stand basal area than zone 5. For a 23.4 m wide road, the increased stand basal area translates to 3.13 m (2 × 31.3% × 5 m for zone 1), or 13.4% recovery of timber losses, if both sides of the road were similarly impacted. This estimate can be improved by using stand basal area to reduce variability.