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 diameters at breast height (DBH) and tree height, as well as crown base height and crown length. Based on the results of earlier measurements temporal changes in tree diameters at strip roads were also evaluated. Analyses were conducted in a pine stand, where strip roads of 3.5 m wide strip roads) and 2.5 m narrow strip roads) were cleared at the stand age of 31 years. After eight years the width of the narrow strip roads was increased to 3.5 m. Measurements were taken on trees growing directly at strip roads (edge trees) and those approx. 4.5 m from the road axis, as well as in middle of the distance between neighboring strip roads (as a reference). Trees growing at strip roads edge had statistically significantly larger diameters at breast height than trees growing farther from strip roads. These differences in tree height were slight and statistically non-significant, whereas crowns of trees growing at the strip road edges had lower bases and were longer compared to crowns of other trees. Analysis of DBH data recorded during 20-year measurements showed a gradual reduction in the effect of strip roads on diameters of trees growing at strip road edges.