Stem form and branchiness of Norway spruce as a sawn timber—Predicted by a process based model

Abstract

A process-based growth model, PipeQual was adapted to Norway spruce ( Picea abies [L.] Karst.) for describing stand development and timber properties (stem taper, heartwood formation and branchiness). PipeQual predictions on timber properties were tested against (1) the data set used for estimating the structural and metabolic parameters of the growth model, and (2) an independent data set. Both data sets consist of two stands located in southern and central Finland. Parameter values of the PipeQual model related to tree structure were estimated on the basis of measurements of tree characteristics. The metabolic parameters of the model were calibrated on the basis of stand-level predictions of basal area, dominant height, and stem volume. In addition, statistical models for branch characteristics were incorporated in the model. The predictions of stem taper, heartwood content and branchiness were consistent with measurements. However, the model slightly overestimated stem taper curve in the upper half of the stem in thinned stands. In addition, branch diameters were underestimated in the upper half of the stem in thinned and untreated stands, while branch diameters in the lower stem were somewhat overestimated. Overall, the results suggest that the PipeQual model has potential for simulating growth and properties of a Norway spruce stand.