Baders, E., Senhofa, S., Purina, L. and Jansons, A. 2017. Natural Succession of Norway Spruce Stands in Hemiboreal Forests: Case Study in Slitere National Park, Latvia. Baltic Forestry 23(2): 522-528.

   The dynamics of un-managed forest ecosystems is led by the natural disturbances, among which storms are one of the most important, especially due to occurring and predicted increase in their frequency. Mimicking of the natural disturbances is considered a part of the forest management strategy in the particular areas. However, the diversity of the possible initial stand and landscape composition leads to the various corresponding pathways of recovery after the disturbance. So far, a limited number of short term (up to 25 years after the windthrow) empirical studies have assessed them in the hemiboreal forests. In this study, the stand development 45–46 years after the stand replacing windthrow was assessed in the north-western part of Latvia, Slitere National Park. In the areas formerly dominated by Norway spruce, the post-storm tree species composition was significantly altered by the site type. Birch dominated in the overstorey; however, the dominance of spruce was found in 12 and 33 % of the areas in the mesic and wet sites, respectively; the understorey and the advanced regeneration were mostly (61 and 46 %, respectively) formed by spruce. In most cases, the diameter at breast height (DBH) of the overstorey spruce was similar or larger than for pioneer species (except aspen), regardless of the proportion of spruce in the stand composition. The dimensions of spruce were significantly larger in mesic than in wet sites: DBH and height was 23.8 ± 1.0 vs. 19.4 ± 1.5 cm and 22.5 ± 0.5 vs. 17.7 ± 1.0 m, respectively. Regardless of the distance from the undamaged stand, the number of the overstorey spruce was similar, indicating the sufficient seed dispersal from the windthrown trees. However, on the wet sites, the proportion of spruce from the total number of trees was significantly higher in the areas up to 50 m from spruce stand that remained after the storm. Also the abundance of the understorey spruce had significant positive relation to the distance to the undamaged stand. The results suggest that 45 years after the stand-replacing windthrow spruce is abundant within all stand layers and might dominate the overstorey besides the pioneer species.

Keywords: semi-natural dynamics, windthrow, stand replacing disturbance, post-storm regeneration.