The effect of individual birch trees interplanted amongst spruce on radiation

In order to manage mixed stands in the long term, it is necessary to investigate the effects of the relevant tree species and their mixing ratios. The aim of this study is to investigate the influence of birch trees introduced individually into spruce pure stands on the radiation balance. Put simply, the aim is to measure how the solar radiation reaching the forest floor changes spatially around the birch trees. This is because radiation, as a site factor, has a wide-ranging impact on ground vegetation, regeneration, soil conditions and the water balance of the trees. The initial hypothesis was that introducing the light-demanding species birch would result in significantly more radiation reaching the ground of the pure spruce stand than would be the case without such introduction. However, this study was unable to confirm this hypothesis. It was not evident that the introduction of individual birch trees, a light-demanding species, resulted in significantly more radiation reaching the forest floor of the pure spruce stand than would be the case without such an introduction. The reasons for this are primarily to be found in the heterogeneous nature of the stands studied.