EFFECTS OF ROADSIDE DISTURBANCE ON SUBSTRATE AND VEGETATION PROPERTIES IN ARCTIC TUNDRA

Tundra adjacent to the gravel Dalton Highway in northern Alaska was ex amined for effects of 15 yr of chronic road and road dust disturbance. Road effects at a nonacidic site (soil pH greater than or equal to 5. 0) and an acidic site (soil pH < 5.0) were compared to examine differe ntial susceptibility. Overall, effects on vegetation were more pronoun ced in acidic tundra. Initial substrate pH appears to control the degr ee of response to disturbance by road and calcareous road dust. Soil a t the acidic site is normally pH 4.0, whereas in the disturbed area ne xt to the road soil pH was as high as 7.3 +/- 0.07 (at 2 m from the ro ad edge). Soils next to the road had lower nutrient levels, altered or ganic horizon depth, higher bulk density, and lower moisture. Effects on snowpack include both increased drifting in the lee of the road and earlier meltout near the road due to dust-induced change in albedo. P ermafrost thaw was deeper next to the road at both sites, and potentia lly could affect road structure detrimentally. Vegetation biomass of m ost taxa was reduced near the road at both sites. Total aboveground bi omass of nonacidic tundra ranged from 330.0 +/- 34.72 g/m(2) (mean +/- 1 SE) at 2 m from the road to 690.7 +/- 94.52 g/m(2) at 100 m away fr om the road. Total biomass of acidic tundra ranged from 150.5 +/- 16.6 0 g/m(2) at 5 m from the road to 743.1 +/- 168.98 g/m(2) at 100 m from the road. Species richness in acidic tundra next to the road was less than half of that at 100 m away from the road. Community composition was altered most noticeably in acidic tundra. The moss Tomentypnum nit ens, dominant in nonacidic arctic tussock tundra, was nearly equally a bundant at all distances from the road at the nonacidic tundra site, w hereas Sphagnum mosses, dominant in acidic low arctic tussock tundra, were virtually eliminated near the road at the acidic tundra site. Sal ix lanata was more abundant next to the road at the nonacidic site. Or dinations indicate that variation in vegetation cover is explained by distance from the road. Knowledge of differential effects of road cons truction and use, including the long-term effects of hydrological alte rations and dust mobilization on focal corridors, is key information f or planning development in areas of arctic tundra. Planned placement o f roads in the future should consider the impact of such changes to se nsitive (acidic) tundra areas in the Arctic.