Material & Methods

The occurerence and population dynamics were analysed using two different sets of data, one being the Swedish National Forest Inventory (NFI), and the other being open geodata. The NFI is a large scale inventory carried out all over Sweden, with both random and permanent (revisited) plots being surveyed.

Foto: SLU, fotograf: Hilda Mikaelsson

Occurrence, extinction and colonisation probability were modelled against a variation of habitat factors, such as basal area, the age of the forest, the hight of the trees, and more. The statistical tests were performed in R by applying a fitted generalized linear mixed effect models. The habitat variables having a significant effect on the occurence probability were then used to predict the occurrence probability of G. repens for all of Östergötland county. This prediction was validated using observational data of the orchid from Artportalen.