Browsing by Subject "tilavuuskäyrä"

Downy birch (Betula pubescens Ehrh.) is by far the most common tree species in Finland when considering stem count. The num-ber of the downy birches are almost double compared to pine (Pinus sylvestris). Downy birch is not very demanding of its sur-rounding and it grows in both dry and wet places in forests, marshes, shores and abandoned fields. Downy birch grows in all areas in Finland except the northernmost Lapland. Compared to Downy birch silver birch (Betula pendula) is smaller, short-lived and the appearance is more varied. Downy birch can grow up to 20 meters high and 70 to 90 years old. Downy birch has not been exceedingly popular tree in Finland, and it is mostly used as an energy wood. Downy birch and silver birch are not separated in commercial use. The aim for this study was to develop cumulative model for above ground volume and biomass for downy birch with 15 tree sample. Diameter, length and weight were manually measured from each section of the sample tree stems. Weight of branches were measured for every stems section. Volume and weight of each stem section and branches were measured by sinking them into water. Relative taper curves were calculated for each sample tree and with those the general taper curve was calculated. From stem and branch volumes separate volume curves were calculated. General volume curves for were calculated based on the separate curves. With those curves different cumulative whole tree volume curves were created. In addition to volumes, also densities for stem sections and branches were calculated. With those and volume curves biomass model can be calculated Calculated taper curves differed from Laasasenaho’s taper curves mostly on the base of the stem but above 10 % relative height the taper curves behaved similarly. Whole tree volumes were calculated with nine different methods and the results were com-pared to Hoppi’s and Repola’s equations and measured volumes. Equations where the tree height was the only explanatory factor gave much more varied results than those equations which also took the diameter in consideration. Smallest relative standard deviations were 4,1 %, 4,2 % and 4,6 %. Smallest standard deviations of the volume were 8,3 l, 7,4 l and 7,4 l. These equations used tree height and diameter. Hoppi’s and Repola’s equations gave relative standard deviations of 5,7 % and 12,7 % and stand-ard deviations of the volume were 10,7 l and 9,4 l, respectively. Similar comparisons were not done with biomass model because reliable results of the branch and stem densities were available only from three sample trees. The equations presented here are different than previous models because of the cumulative nature- Only other downy birch model was Hoppi’s model. Cumulative approach makes it possible to calculate volume (or biomass) from any relative height range and previous models do not offer that possibility. Other models give out the volume or the biomass of the whole tree (or stem). Comparison with the other models demonstrates that it is possible to create models that work well at the local level with very few sample trees. Comparisons with Repola’s model shows that result can be generalized well. Results verifies the assumption that the proportions of different size trees behave consistently.