%0 Journal Article
%T Efficiency of Inventory in Uneven-Aged Forests on Sample Plots with Different Radii
%A Anamarija Jazbec
%A Mislav Vedri£¿
%A Mario Bo£¿i£¿
%A Ernest Gor£¿i£¿
%J Croatian Journal of Forest Engineering
%D 2011
%I University of Zagreb
%X For the purpose of forest management planning in Croatia, forest inventory is performed on sample plots of permanent sizes, generally from 500 to 1,000 m2. Such plots have been accepted in practice on the basis of experience. Thus, the plot size has only partially been adjusted to different forest types. Although methods of sample selection are regulated by Forest Management Regulations and are limited to plots of permanent sizes, the Regulations still allow plot sizes to be adjusted to specific stand conditions. This article compares the results of forest measurement on differently sized plots in order to estimate their efficiency in selection fir and beech stands. Research was carried out in Gorski Kotar, where the stand structure was recorded using a sample of experimental plots. Systematic sampling with a random start was used to establish 103 sample plots in the management units of  Delnice  and  RavnaGora . Breast height diameters over 10 cm and tree heightsweremeasured on circular plots of 20mradius, set up across a 100 x 100 m square grid, and their positions in the space (azimuth and distance from the centre) were recorded. The values of structural elements (number of trees, basal area and volume) were calculated from the obtained data bymeans of a specially constructed computer programme CirCon for the plots and stands. The precision of estimates was expressed as a relative sample error with 95% confidence. Thanks to spatial data for all the trees, a calculation was made of the structure for sample plots in the radius range from 4 to 20 m. The precision of structural elements estimate (sample error) was calculated for each plot size. The average values in differently sized plots were compared with repeated measurement analysis of variance (RM ANOVA) with significance level of 0.05. The results of different plot sizes were subsequently tested by means of the Fisher¡¯s LSD 'post hoc' test. On a sub-sample of 24 standpoints, the time needed for field measurements on differently sized plots was later measured in order to estimate the efficiency of differently sized plots. From these data measurement time (t) for all plot sizes was assessed in dependence on plot area (P) using the equation t=a*P b. Walking time and distance between the plots were measured, from which the travel speed in the field was calculated. The efficiency of plots of a particular size was evaluated by the precision of estimate and the time needed for measurements. The achieved efficiency index was evaluated as the product of squared sample error and total time expressed in relat
%K Forest inventory
%K sample plots
%K stand structure
%K precision
%K measurement time
%K efficiency
%K fir-beech stands
%U http://hrcak.srce.hr/file/101820