Antal Kozak's research while affiliated with University of British Columbia - Vancouver and other places

Publications (5)

Article
The data used for the estimation of percent decay are bounded by zero and 100. Because a value of 100% indicates that the tree is completely decayed, this value is not observable in nature. However, a value of zero percent is often observed over a wide range of the independent variables. The distribution of percent decay is a combination of a trunc...
Article
Like several other taper equations, the predictive ability of Kozak's (1988. Can. J. For. Res. 18: 1363-1368) variable-exponent taper equations can also be improved by an additional upper stem outside bark diameter measurement. This study indicated that improvements were small and were mainly restricted to increasing the precision of the estimates....
Article
Results obtained by Kozak (A. Kozak. 1970. For. Chron. 46(5): 402–404.) concerning conditions for additivity of component biomass regression equations are formalized and extended. More specifically Kozak demonstrated, using multiple linear regression equations to model three biomass components (bole, bark, and crown) for individual trees, that corr...
Article
A detailed study using seven data sets, two standing tree volume estimating models, and a height–diameter model showed that fit statistics and lack of fit statistics calculated directly from a regression model can be well esti-mated using simulations of cross validation or double cross validation. These results suggest that cross validation by data...
Article
Full-text available
Crown class, site class, and breast-height age were incorporated into Kozak's variable-exponent taper equation (A. Kozak. 1988. Can. J. For. Res. 18: 1363–1368) for three species: Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), western red cedar (Thujaplicata Donn), and aspen (Populustremuloides Michx.). For lodgepole pine (Pinuscontorta Dougl.)...

Citations

... In contrast, the variable-exponent equations are based on the variable (from ground level to tree top) exponent of a simple power function (Lee et al., 2003) to successively describe the neiloid, parabolic and conic shapes of tree stems. Since the first introduction of the variable-exponent taper model in the late 1980 th by Newnham (1988) and Kozak (1988), a variety of forms of such equations were proposed in the literature (Bi, 2000;Kozak, 2004Kozak, , 1998Lee et al., 2003;Newnham, 1992). Different stem profile models for various tree species have been compared and widely discussed in regional studies (Fonweban et al., 2011;Li and Weiskittel, 2010;Özçelik and Brooks, 2012;Tian et al., 2022). ...
... Although no difference was found between CSS and POLY3 for fitting the DOB profile of SHU, for the DIB profile of SHU the FI of the CSS model was slightly lower than that of POLY3, while the RMSE of the CSS model was slightly higher than that of POLY3. As reported by Muhairwe et al. (1994), species could be an influencing factor for stem form variation. The MB model did not exhibit better performance than CSS. ...
... When modeling individual biomass components, it is worth considering the logical assumption that the sum of the component of the tree estimated using equations should be equal to the estimated biomass of the whole tree. This assumption can be met by seemingly unrelated regression application [32,33,48,49]. The assumption about the additivity of the biomass model system and the use of nonlinear models was the basis of elaboration of a consistent set of additive biomass functions for eight tree species and nine components in Germany [34]. ...
... The estimated parameters obtained by model fitting were used to predict the remaining one sample. The process of fitting and testing was repeated N times to complete the model validation (Kozak and Kozak, 2003). Afterward, mean absolute bias (MAB), mean percentage bias (MPB), and mean relative bias (MRB) were calculated to evaluate the performance of four additive model systems. ...