Browsing by Subject "compartmentwise planning"

This study investigates the effect of the data input on the forest management plan. The objective was to determine the differences between a forest plan where simulation units were either traditional stand compartments, or alternatively subcompartments delineated around measured sample plots. The simulations were compared with respect to the growth of the compartments as well as timing, income and yield from the first harvet operation suggested. The data was collected from a forest area of 72 hectares in Juuka, Eastern Finland. It consisted of 682 sample plots placed in a 30 m x 30 m grid. Independently of the sample plots, the area was divided into compartments as in normal compartmentwise planning, with the exception that no stand data was collected. Instead, the compartmentwise data was calculated from the systematic sample plot inventory. Three simulations were carried out with a planning package SIMO for a period of ten years and using one-year time step. Sim(I) presented the traditional compartmentwise planning, where the variables on compartment level were aggregated from sample plot data in the beginning of the simulation, and then used as simulation units. The other two simulations used a mosaic of sample-plot-based subcompartments as the simulation unit, and aggregate compartmentwise values were only used to determine the harvest decisions and for the comparison of the simulations. Of these mosaic setups, sim(II) was used to evaluate differences in growth rate and harvest yield to sim(I). In this simulation, the operations were adopted from sim(I) and applied simultaneously for each subcompartment of the respective compartment. The third simulation, mosaic setup sim(III) used the same simulation data as sim(II), but harvested the compartments according to the subcompartmentwise values, although using the compartments as harvest units to enable direct comparison in operation timing. Only compartments where harvests were expected during the simulation period were studied further, resulting in 14 compartments in the study. The simulations resulted in a greater growth rate estimate for sim(I). The difference between sim(I) and sim(II) varied among the compartments from 0.1 m3ha-1a-1 up to 2.0 m3ha-1a-1. The timing differences of harvest operations were 0-3 years. Income estimates were 5-10 % greater in the mosaic simulations, as well as especially the yield estimate of logwood. The differences in pulpwood estimations were more moderate, except on final cuts where mosaic simulations expected a better yield in minor species pulpwood than sim(I) which neglected these almost totally. The most effective single factor behind the differences in the simulations seemed to be the variation of site class within the compartment. The amount of compartments in the study was, however, too small and the variation between the compartment results too large to allow the application of the results elsewhere. Based on this study, the choice of data unit has an effect on the forest plan. Especially the effects of variation in site class are likely to be taken better into account if the spatial information of stand characteristics is maintained in the planning calculations. Still, small units are not necessarily better in describing the forest development, as they may result in biased estimations in the growth models.