Sapwood amount in Picea abies (L) Karst determined by tree age and radial growth rate

Relationships between tree age, radial growth rate and sapwood amount were studied in 125 Norway spruce [Picea abies (L.) Karst.] trees belonging to dominant and suppressed crown classes. The sapwood radial width and transverse area depend logistically on tree age, while the rate of sapwood increase and the asymptote value are determined by radial growth rate of the tree. The higher the growth rate, the larger the sapwood zone. The sapwood widening will be completed on an average by the age of 91, and the increase of the sapwood area, by the age of 114. The relative area of sapwood decreases with tree age, while the decline is faster in slow-growing trees. The tree age and growth rate combined describe 94, 93 and 70% of the total variation in sapwood width, transverse area and relative area, respectively.