Growing at the edge: Modelling sapling colonization, performance, and effective range of mountain birch (Betula pubescens ssp. tortuosa)
Description
We collected data on birch colonization and individual sapling performance from ten different field sites across Iceland. Four transects from each field sites were put out perpendicular to the woodland edge, and all birch plants were counted and measured for minimum 100 meters from the woodland edge. We measured both the length and total height of each birch sapling >20 cm, and calculated a morphology index characterizing individual sapling performance as the ratio between these numbers. We related this measurement to different environmental parameters, and tested for regional differences. Densities of birch seedlings and saplings were modelled using regional hyperbolic colonization kernels. We furthermore calculated the effective spatial range of birch colonization.