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Fig. 3 | Forest Ecosystems

Fig. 3

From: Analysing the effect of stand density and site conditions on structure and growth of oak species using Nelder trials along an environmental gradient: experimental design, evaluation methods, and results

Fig. 3

Schematic excerpt from a Nelder wheel demonstrating different methods of calculating the competitive status of plants. a) growing space (grey area) defined by location on a certain spoke and circle; b) distance-independent competition index: local stand density index (SDI l ); c) distance dependent competition index according to Hegyi (1974) and d) growing space calculated by Voronoi polygons (Turner 2014). Large numbers: tree number, small numbers: tree diameter (mm), black circle: search radius for competitors, empty symbols: previously dropped out trees, D ij : distance from centre tree to neighbouring tree

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