CONIFEROUS TREE ADMIXTURE AFFECTING SUMMER STORM DAMAGE IN BIRCH STAND: CASE STUDY IN LATVIA.

Frequency of storms and wind speeds in gusts had been increasing in Northern Europe in last decades, causing more damages to forest stands. Establishment of mixed stands had been suggested as one of the methods to reduce wind damages in future, however, empirical information on actual efficiency of this approach is still limited, especially in relation to summer storms. Therefore aim of our study was to assess summer storm damages in mixed birch spruce stands. Area influenced by the storm of June 2021 in Northern part of Latvia, where silver birch (Betula pendula Roth.) growth with admixture of conifers – Scots pine (Pinus sylvestris L.) and Norway spruce (Pice abies (L.) H. Karst.) had been selected and sample plots (500 m2 ) systematically placed. Tree heights, height of the green crown base and diameter at breast height (DBH) were measured for wind-affected and unaffected trees. For broken trees the damage height was measured, for tilted (bent or leaning) the angle from vertical position. Tree parameters influencing their wind resistance were assessed: higher proportion of birch were damaged than that of spruce and the most significant damages (snapping and uprooting) were characteristic to larger trees on average. Significant influence of summer storm on the birch spruce mixed stand was demonstrated. [ABSTRACT FROM AUTHOR]