Data och metodik för utbytesberäkning - en studie på Medelpads Skogsförvaltning
To manage the industry?s need of wood assortments in a optimal and cost effective way the forest companies need to have knowledge of the actual standing volume and the yield of the planned clear cuts. The mean volume of the trunk is also important since it is important for the contractors prices. Today the total volume are estimated either with Näslund (1940) or Brandels (1990) functions of volumes, and the yield is estimated with Rune Ollas (1980) function for trunks and stands. The purpose of this study has been to answer the following questions: How good is the yield forecast with data collected with currently used methods? How well can the yield forecasts became with data collected according to the instructions? How well can the yield forecast be with data collected according to the instruction and calculated with the program Aptan for theoretical bucking? The study has been initiated and financed by SCA Skog AB.The material consisted of a number of randomly selected objects ready for clear cut. Diameter at breast height and height were measured in field. Other mandatory information has been taken from the company register. Yield forecasts were done with existing functions. The simulation program Aptan requires loss frequency as input, which was collected from pri-files of the harvesters. From these the frequency has been compiled. Also price lists are important inputs that been used. Yield has then been simulated.The study indicates that the existing procedure that is currently used at SCA Skogs own forest holding gives more accurate results than the routine that is more frequently used when calculating yield at forest belonging to private forest owners. The trials with the existing data show both under- and overestimates of the yield for both own forest and private forest. This is also also true of the trial with the new data. This makes the functions difficult to calibrate. The use of the Aptan program results in an overestimation of yield per assortment, though with an evenness, especially for private forest. The evenness makes the results more easy to calibrate and in that way makes the function more specific for the company.