Condition dynamics of Scots pine (<i>Pinus sylvestris </i>L.) along suburban highways of Voronezh city in 1991-2007
The method of dendrochronological analysis studied the effect of vehicle emissions on the stands of Scots pine (Pinus Silvestrys L.). The objects are the even-aged pure culture in the most common conditions type for the Central forest-steppe (B2). M4 highway (Voronezh - Rostov part) is a major traffic artery of Voronezh region, so the bulk of research was conducted in the pine forests immediately adjacent to it. The study was conducted in three phases: in 1991, 1995 and 2007. The 2007 study also included pine forests along Voronezh - Repnoye road section with a low intensity of traffic. In 1991, the dendrochronological analysis showed that when approaching the highway the amplitude of growth fluctuations increases for the width of annual rings and the width of the recent timber. The average absolute increase in annual ring decreases when approaching the highway for 20 years (from 1972 to 1991). At the same time, in 1982-1991 it occurs with greater intensity. A statistically significant difference between the radial growth along the highway and the control (13 km from the road) is proved with 97% of probability value. The probability value of the differences between the radial growth of trees in 50 m from the highway and the control is 68%. The research of 1991 showed that the effect of air pollution on tree population is distributed locally, at a relatively small distance from the source (<100 m) and is differentiated by the distance from the road. In 1995 a second survey of the object was conducted by a modified method offered by I.Ya. Liepa, et al. (1983) to assess the impact of vehicles on the plantation for five linear areas laid out in narrow strips (5. 100 m) along the highway at various distances (0, 5, 10, 50, 100 m). Dendrochronological data analysis showed an increase in the amplitude of the radial growth when approaching the highway, deeper and more prolonged depressions of growth in the 5-meter strip along the highway and intensive decrease of growth in the last decade (1986-1995). The analysis of the radial growth of pine conducted in 2007 and its results are compared with the previous studies and show that stands located 100 meters away from the road with a heavy traffic flow (1300 vehicles per hour) are in the zone of influence of emissions. There is a greater area of negative impact. The comparison of the growth of the stands closest to the highway with the control shows its significant reduction with the probability of error-free forecasts > 0.999 (in 1991 - > 0.68), indicating a significant growth decrease by 2007. Year 2007 shows long-term (more than 30 years) depressed growth. It was concluded the effect of vehicles with relatively low traffic (180 vehicles per hour) also leads to long-term depression and significant decrease in the radial growth of pine.