GROWTH PATTERNS AND SPATIAL DISTRIBUTION OF COMMON ASH (FRAXINUS EXCELSIOR L.) IN LATVIA

In Latvia, common ash (Fraxinus excelsior L.) can form ecologically stable monoculture stands in localities with optimum growing conditions, but they are mainly found in mixed forests throughout the country on sites with fresh, fertile, sufficiently moist, yet well-drained soils. Over the last two decades, ash decline has become a serious problem for the whole of Europe; the causal agent for it is also present in Latvia. The aim of the given study was to investigate the growth patterns of ash in different populations at the age of maturity (over 80 years), tracing back their course of growth, and identify the spatial distribution of ash to identify localities with appreciable concentration of ash-dominated stands. The study revealed high variation in the juvenile growth of ash, and confirmed that the height and diameter growth for common ash peaks at an early age. Analysis of the spatial distribution of ash indicated considerable expansion of common ash over the country during the second half of the 20^th century, to some extent complementing natural overgrowing of abandoned lands by forest. Apart from the Zemgale Plain in the middle of Latvia, the highest concentration of ash stands is in upland areas with highly varying land relief conditions.