Abstract
Aim of study: The present study evaluates a set of competition indices including spatially explicit indices combined with different competitor selection approaches and non-spatially explicit competition indices. The aim was to quantify and describe the neighbouring effects on the tree diameter growth of silver birch trees.Area of study: Region throughout Estonia. Material and methods: Data from the Estonian Network of Forest Research Plots was used. After quantifying the selected indices, the best non-spatial indices and spatial indices (combined with neighbour selection methods) were separately devised into a growth model as a predictor variable to assess the ability of the diameter growth model before and after adding competition measures. To test the species-specific effect on the competition level, the superior indices were recalculated using Ellenberg’s light indicators and incorporated into the diameter growth model. Main results: Statistical analyses showed that the diameter growth is a function of neighbourhood interactions and spatial indices were better growth predictors than non-spatial indices. In addition, the best selections of competitive neighbours were acquired based on the influence zone and the competition elimination angle concepts, and using Ellenberg’s light values had no significant improvement in quantifying the competition effects. Research highlights: Although the best ranking spatial competition measures were superior to the best non-spatial indices, the differences were negligible.Keywords: Competition indices; zone of influence; stem diameter increment; Betula pendula Roth.ERRATUM PDF
Highlights
Competition among individual trees is a fundamental ecological process that plays a major role in population dynamics, survival, growth and species replacement (Peet & Christensen, 1987)
To investigate the effect of competition on the diameter growth of trees, we focused our study on silver birch (Betula pendula Roth)
BAL and BALMOD as the best non-spatial competition indices (CIs) did not perform better than the superior spatial indices SdrAng and Heg
Summary
Competition among individual trees is a fundamental ecological process that plays a major role in population dynamics, survival, growth and species replacement (Peet & Christensen, 1987). Several case studies have been conducted in ecology and forestry to develop, improve or modify different competition indices (CIs). Such indices quantify the competition level for an individual tree and are classified into two major groups of non-spatially explicit indices Whenever spatial indices are used to measure the influence of local neighbours on a central tree (the subject tree), the dimensions and the relative location of neighbour trees are required for the computation (Tomé & Burkhart, 1989; Corral Rivas et al, 2005)
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