Long-term edge effect of strip roads in pine stands (Pinus sylvestris L.)

Crowns of trees neighboring a strip road are exposed to greater amounts of sunlight, which may result in the so-called edge effect, leading to enhanced tree growth. The aim of this study was to assess the edge effect after twenty years since the clearing of strip roads in terms of diameter at breast height (DBH), tree height, crown base height, and crown length. Based on the results of earlier measurements, temporal changes in tree diameters at strip roads were also evaluated. The analyses were conducted in a pine stand, where strip roads 3.5 m or 2.5 m wide had been cleared at a stand age of 31 years, and after eight years the width of the narrow strip roads had been increased to 3.5 m. Measurements were taken on trees growing immediately adjacent to strip roads (edge trees) and those approximately 4.5 m from the road axis, as well as those in the middle of the distance between neighboring strip roads (as a reference). Trees growing at the edge of strip roads had statistically significantly larger diameters at breast height than trees growing farther from strip roads. The differences in tree height were slight and statistically non-significant, whereas the crowns of trees growing at the edges of strip roads had lower bases and were longer than the crowns of other trees. Analysis of DBH data recorded from measurements over 20 years showed a gradual reduction in the effect of strip roads on the diameters of trees growing at their edges.