Structural and demographic analysis of a multilayered forest in southern Sweden

Detta är en Master-uppsats från SLU/Southern Swedish Forest Research Centre

Sammanfattning: A structural and demographical analysis of a multilayered heterogeneously structured stand in southern Sweden has been conducted. The stand is characterized by an old pine oversto-rey where spruce and oak grow beneath out of natural regeneration. The purpose of the structural analysis was to identify differences regarding basal area, volume, tree species composition and diameter/height-distributions within two treatments, control and target diam-eter harvesting, which have been placed throughout the whole stand in three different blocks. In addition a development comparison between the last data collection in spring 2006 and spring 2014 was made. A later on derived future stand development was simulated to get a prediction on the future growing levels and stand composition after 50-years. Based on the present structural analysis the diameter and height distributions inside the dif-ferent treatments do not differ very much from each other. Spruce and pine clearly form the most dominant tree species in the stand, where the diameter is nearly consistent throughout all plots. Broadleaved tree species, especially oak, show higher diameters and highest in-crement in the target diameter harvesting treatment where the light conditions due to prior harvest interventions and wind throw seem to have the biggest influence on growth. In addi-tion block 2 showed the largest increment for all tree species. Oak however can be found suppressed in the control, where spruce has a share of the tree species composition of 71%, and in block 3, due to high stand density. The height distribution shows a clear pattern where the pine forms the upper canopy, followed by spruce in the middle layer, followed by oak sharing the middle canopy with spruce in the target diameter harvesting plots, but forms the low canopy inside the control treatment. The derived development comparison between spring 2006 and beginning of 2014 showed an underestimation of the volume increment by 33% for the target diameter harvesting and 46% for the control treatment. The future devel-opment of the stand with Heureka showed a trend to a more even diameter distribution, which is less diverse in tree species and less structured. The original form of an uneven-aged and multilayered stand, the reversed J-shape, will almost get lost in both of the ob-served treatments. An alternative that could be done to prevent this structural development is to perform a target diameter harvesting combined with a removal of some of the trees in the medium-range di-ameter sizes. This would grant a more diverse and multilayered structure, where also broad-leaved tree species could profit, in order to enhance nature values and form a more stable stand for the future.

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