Träd och buskar i kantzoner : en undersökning av kanteffekter i några av östersjöregionens skogar

Sammanfattning: Around the world, forests are generally being fragmented and as plant populations decline in both sizeand number of individuals, the genetic variation will also decrease whitch in the end leads to totalextinction of the plant. In this paper, I wanted to investigate what specific species of trees and shrubsyou usually find in the edge and core habitats in some of the forests in the Baltic Sea region. I alsowanted to identify the edge effects and their sources and finally compare the results between thedifferent regions.The data sources used are derived from the ongoining research project Landscape structures, patterns ofbiodiversity and conservation strategies in the Baltic Sea region by Kari Lehtilä, Patrik Dinnétz ochTiina Vinter who have made a record of all herbaceous plant species in four randomly chosen forestregions situated around the Baltic Sea: Estonia, Skåne, Södermanland and Germany. I made statisticalanalyses, using the computer program R, concerning the distribution of species in the edge habitats ofthe forests as well as in the core habitats. I performed generalized linear models and then variationanalyses with the factors light and biomass in order to investigate wether edge effects might appear dueto these factors. I also used the ecological characteristics – Ellenberg indicators – light, soil pH andnitrogen performing linear regression models. I then compared the results – within the regions but alsobetween them.As the results showed great variancy both within the regions and between them no general explanationto the edge effects could be affirmed. The Ellenberg analyses showed no difference between the species,i. e. the ecological characteristics could not explain why some species were associated to edge habitatsand some were not. All four regions had in common that the greatest biodiversity were to be found inthe edge habitats, which is characteristical for a habitat in an early successional state. Due to the thefeatures of the forests, the specific species that received the label ”edge species” or ”core species” werenot always mutual in all regions. For example Quercus robur turned out to be a typical forest species inGermany while in Estonia it was strongly associated to edge habitats and in this investigation one mightdiscuss later states of successions in Germany rather than stronger edge effects in Estonia.