Utvärdering av metod för att morfologiskt särskilja björkarterna Betula pendula och Betula pubescens

Abstract: Birch is the third most common tree species in Sweden and has previously been seen as a weed in the forests. In the last 20 years, birch has had a clearly increasing trend in Swedens growing timber stock, but there are still many knowledge gaps regarding management, regeneration, processing, and its impact on the environment. In the national forest assessment's inventories, the two birch species silver birch (Betula pendula) and downy birch (Betula pubescens) are not separated from each other, and are only registered as birch. The two birch species have some morphological differences that allow them to be separated from each other, but these differences are not always distinct, which creates uncertainty in species identification. The purpose of this work is to validate the morphological separation method for the two birch species by using a proven chemical method. This is to estimate the possible margin of error over how safe the morphological method is. Having a reliable species determination method is necessary as the birch species can be used for different end products and have different preferences regarding plant habitat. The data for the study were collected through a transect inventory at three different premises in northern Sweden. Bark samples were collected at each site from three fellings, all of which were felled in 2014, a total of 90 bark samples were collected from each birch species. The result from the chemical separation method was 100% consistent with the morphological one. This means that the morphological separation method seems to be highly reliable for younger birches. In addition, the benefits of a greater involvement of birch in terms of biodiversity and risk reduction are discussed, as well as why it is justified to distinguish the two birch species.