Spatial pattern of relict beech (Fagus sylvatica L.) forests in the Sudetes of the Czech Republic and Poland

Horizontal structure of forest stands largely affects the competitive relationships between tree individuals and plays a significant role in the stand dynamics. The present study describes horizontal structure on nine permanent research plots (0.24-0.25 ha) in the regeneration and tree layer of autochthonous European beech (Fagus sylvatica Linnaeus) stands in the wide altitudinal gradient in protected areas in the Czech Republic and Poland. The spatial structure was classified in productive herb-rich beech sites, through acidophilic beech sites, exposed sites, to beech fragments near the timberline. The spatial pattern of tree layer was regular in the lowest parts of the altitudinal gradient of beech, random in the middle parts and aggregated in the beech forests under the hilltop phenomenon and extreme edaphic site. Nevertheless, trees in lower tree layers showed a tendency to the aggregated pattern, similarly like the strong aggregation of natural regeneration. In most cases, the parent stand had a significant negative effect on natural regeneration at a smaller distance (to 0.8-4.2 m). The spatial pattern of dead wood was mostly random. Because of the great plasticity of beech crowns, crown centroids were more regularly distributed than tree stems. The average displacement of crown centroids from the stem base was 1.5 m with the prevailing direction of 52.7% down the slope. Projected canopy cover was on average 10.7% higher compared to the canopy simulated by circular crowns.