Modeller för brösthöjdsålder för tall och gran

Sammanfattning: The purpose of this study was to develop two types of prediction models for Scots Pine and Norway Spruce. The first type for calculation of the stump diameter under bark the year the tree reached breast height (Dstubh130). The second type for calculation of the annual difference, e.g. the number of growth years between stump height (0.2 m) and breast height (1.3 meters above ground level). The primary thought with these prediction models is to obtain the breast height age in the trees on basis of the number of annual rings at stump. If Dstubh130 is predicted when felling the trees, the breast height age calculates as the number of annual rings outside Dstubh130 at stump. The annual difference can be used to calculate the breast height age by subtract the annual difference from total age at stump. Breast height age can be used as an explanatory variable in prediction models for wood properties. To developing the models, data has been collected from 397 Scots Pines and 465 Norway Spruces. The data was collected from 43 stands with different site conditions and regeneration methods. The stands were selected from the 57th, 60th and 64th latitudes. The linear models were developed by using analyses of variance (ANOVA). There are three levels with increasing grade of explanation for both types of models. The levels are determined due to what kind of explanatory variables available to be used in the models. The grade of explanation measure how much of the variation in Dstubh130 and the annual difference that can be explained by the models. Level 1, with the explanatory variables site index, altitude and temperature sum were the grades of explanation for the Dstubh130-model for Scots Pine 1 % and for Norway Spruce 13 %. In level 2 when adding the variable regeneration method the grades of explanation increases for Scots Pine to 22 % and for Norway Spruce to 21 % or 27 % depended on how the variables were combined. In level 3 the variable annual ring width inside and outside Dstubh130 explains the variation in Dstubh130 for Scots Pine to 50 %. For Norway Spruce these variables don't increase the grade of explanation for Dstubh130. The variation in the annual difference was explained by the same variables as for Dstubh130. The grades of explanation for Scots Pine were 34, 66 and 77 % for each level respectively, for Norway Spruce 10, 53 and 78 % for each level respectively. When using the annual ring widths inside or outside Dstubh130 as variables, the limit for Dstubh130 need to be approximately known before calculation of the annual ring widths. This limit can be calculated by the Dstubh130-models in level 1 or 2, or be represented by each tree species mean value for Dstubh130. One thought with the Dstubh130-models was to simplify and rationalize the counting of the annual rings at stump by excluding the inner diameter e.g. Dstubh130. The annual difference models require total age at stump. What type of model used depends on if the objective is simplified annual ring counting or not. What you lose in simplification with the annual difference models, you win in grade of explanation in all levels with exception for the lowest grade Norway Spruce models. The models with low grade of explanation provides only small amounts of information, and can therefore be seen as unnecessary in practical application. In these cases each tree species mean value can be fair enough measurement for Dstubh130 (Scots Pine 24.84, Norway Spruce 22.52 mm) and annual difference (Scots Pine 5.7, Norway Spruce 8.5 years). The models with higher grade of explanation can however be useful in practical application.