Vegetation Shifts in Boreal Ombrotrophic Peatlands Following Road Construction

Abstract

Boreal ombrotrophic peatlands provide essential ecosystem services but are increasingly intersected by permanent roads. Roads can modify hydrology and water chemistry, but their impacts on plant communities remain poorly documented. The study compared plant communities near roads with those in undisturbed areas to estimate the extent of road impacts and identify the species, plant groups, and road‐altered environmental variables best explaining vegetation changes. Fourteen ombrotrophic peatlands, crossed by roads, perpendicular to groundwater flow, in Minganie and Lower North Shore regions, Quebec, Canada. Peatlands were surveyed along transects perpendicular to the road with vegetation plots (1 m 2 ) sampled at systematic distances up to 100 m on both sides of the road. Plant cover and environmental variables were measured. Redundancy analysis (RDA), indicator species analysis, and nonparametric tests were used to evaluate vegetation responses and identify disturbance‐associated species. Vegetation‐composition shifted within approximately 25 m of the road, and up to 75 m for certain species. Sphagnum mosses and lichens declined sharply near roads, whereas deciduous shrubs increased. Species richness decreased within 5–10 m of the road, mainly due to the loss of ombrotrophic species. Peat water pH and electrical conductivity (EC) were elevated near roads, especially downgradient. Mineral enrichment, likely from runoff and groundwater seepage of granular construction materials and road maintenance salts, appeared to be the main driver of vegetation change. Permanent roads transform ombrotrophic peatland ecology by altering nutrient and mineral availability, reducing specialized taxa, and promoting shrub‐dominated vegetation. These changes may weaken their long‐term carbon‐sequestration capacity. Mitigation should focus on reducing mineral inputs and stabilizing road embankments with native vegetation.