ZLV Online

Abstract

Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) is regarded as one of the most promising introduced tree species for Central European forestry due to its high productivity and adaptability. This study compares the diameter and height growth of Douglas-fir and Norway spruce (Picea abies (L.) Karst.) using data from the Czech National Forest Inventory (NFI). Fifty-seven inventory plots with co-occurring Douglas-fir and spruce of the same age (12–120 years) were selected, covering a range of ecological site types. The analysis was based on mean stem diameter (quadratic mean of DBH) and mean tree height, aggregated at the plot level. Results show that Douglas-fir exhibits significantly faster growth in both diameter and height across all ecological series. At 100 years of age, Douglas-fir achieved an average mean diameter of 50 cm and mean height of 31.5 m, compared to 35 cm and 28.2 m for spruce. The diameter ratio (qDg) between spruce and Douglas-fir decreased linearly with age, while the height ratio (qH) remained relatively stable. Generalized Additive Models (GAM) were used to analyze the dynamics of height-diameter ratio (HDR) and crown ratio (CR), revealing similar trends for both species, though Douglas-fir showed more favorable HDR values. The findings highlight Douglas-fir’s superior growth performance and support its potential for broader use in Central European forestry, especially on nutrient-rich and acidic sites.