Assessment of Pinus sylvestris L. tree health in urban forests at highway sides in Lithuania

Abstract

Trees are often grown alongside roads in urban areas for their aesthetic and ecological values but are exposed to an array of natural and man-made stresses that impact on their overall health. The aim of this study was to determine the health of Scots pine (Pinus sylvestris L.) trees growing in urban forests alongside the Vilnius–Kaunas–Klaipėda highway in Lithuania. Long-term monitoring was conducted between 1998 and 2014, when health indicators were evaluated in 714 trees at different distances from the highway. The decrease of crown defoliation, amount of dead branches and foliage discolouration at all distances from the roadbed was detected. The results showed that trees furthest (450–500 m) from the roadbed were in better health than those growing close to the highway, exhibiting lowest crown defoliation (25.8 ± 1.6% in 1998, 12.3 ± 1.6% in 2014) compared with trees growing close to highway (47.2 ± 1.6% in 1998; 25.1 ± 1.7% in 2014), lowest foliage discolouration (14.8 ± 1.2% in 1998, 9.8 ± 0.8% in 2014), a lower amount of dead branches (14.8% ± 1.2% in 1998, 9.8% ± 0.8% in 2014) and a longer needle retention (3.2 ± 0.03 years in 2014 comparing with to 1.9 ± 0.02 close to the highway). The condition of the tree tops was good throughout the study period, with 77% of assessed trees being healthy. Statistically significant improvement in tree health was observed between 1998 and 2014, indicating an improvement in the overall health of the environment.