Effects of roadside conditions on plants and insects. I. Atmospheric conditions.
Effects of the roadside atmosphere were investigated by placing pots of Lolium perenne 0.5, 1.5, 3.5 or 9 m from the roadside. At each distance, pots were watered with a factorial combination of treatments: high or low N, with or without NaCl. Plants closest to the road attained highest DW and showed a trend towards higher total N content. These effects were most marked in plants given a low N treatment, similar to the nutrient status of roadside soils. Low N plants given a NaCl treatment (to simulate de-icing salt) showed a significant increase in DW and soluble N content close to the road. This suggests that salt in roadside soils may increase the availability of N from NOxto plants. The higher N content of plants close to the road correlates with more rapid increase of aphid numbers on these plants.