Occurrence and extent of facultative heartwood formation in beech located on limestone and claystone sites in southern Lower Saxony.

摘要

This paper presents a more comprehensive view of the different patterns of red heartwood formation in common beech (Fagus sylvatica) using a new approach. The dataset used includes 1252 buttlogs from 23 different assessments in limestone and claystone sites of the Bovenden State Forest in Lower Saxony, Germany. The age of the trees ranged from 113 to 141 years and diameter at breast height (dbh) from 32 to 93 cm. A two-stage modelling approach was performed because the lower part of the dependent variable, heartwood diameter, may (often) assume the value zero. The occurrence and extent was determined separately. The possible types of heartwood were grouped into 9 categories: no heartwood, red heartwood only at the butt end, red heartwood only at the top end, rot only at the butt end, rot only at the top end, red heartwood at butt and top end, rot at the butt and top end, red heartwood at the butt and rot at the top end and rot at butt and red heartwood at top end. The multinomial regression model developed in this study estimates the probability of occurrences of the different red heartwood and rot types in relation to dbh and considering the correlation between the butt and top end of logs. The high unexplained variation in heartwood diameter was estimated using univariate and bivariate distribution functions..