Soil Properties Affected Vegetation Establishment and Persistence on Roadsides

Vegetation along roadsides reduces soil erosion, increases filtering of water runoff, and acts as a biodiversity corridor. The purpose of this study was to assess soil properties and evaluate their effect on vegetation establishment in roadsides. Furthermore, the effects of shoulder type (paved and unpaved) and time since seeding (0–1 year, 2–4 years, and ≥ 5 years) on soil properties were also evaluated. Roadside soil was sampled from 53 sites in three regions (Panhandle, Southcentral, and Southeastern) in Nebraska, USA. The soil was analyzed for pH, Na, Cl, electrical conductivity, exchangeable sodium percentage, and bulk density and heavy metals. At each site, vegetation was classified into one of four categories, (1) < 10% plant canopy cover; (2) 10 to 50% plant canopy cover; (3) > 50% plant canopy cover dominated by weedy annual grasses and forbs; and (4) > 50% plant canopy cover dominated by seeded perennial grasses. Sodium concentration exceeded the limits that can cause vegetation growth decline in all regions. Sodium and soil bulk density in all regions were clustered with the < 10% plant canopy cover category, meaning that these clustered soil properties have a significant influence on the amount of bare ground and establishment/persistence of vegetation. Heavy metal concentrations (lead, arsenic, zinc, cadmium, and nickel) were less than the thresholder in all regions. It was observed that 12–44% of roadside sites had less than 50% vegetation cover. Roadside soils of paved shoulders had lower Na and Cl concentrations than the roadside soils of unpaved shoulders. The 0–1 year since seeding had higher cadmium, arsenic, and nickel concentrations compared to ≥ 5 years since seeding. Soil degradation declined vegetation establishment along highways, and the degree of soil degradation of these roadsides varied depending on shoulder types and time since seeding.