Height growth of pedunculate oak Quercus robur L. in hemiboreal stands in Latvia

In Northern and Eastern Europe, improvements in the growth and yield of pedunculate oak (Quercus robur L.) are anticipated due to the extension of the vegetation period. To quantify such changes, height growth has been shown as the proxy of yield, competitiveness, and sustainability of trees. In this regard, accurate and locally adapted height growth models are essential for the assessment and projection of responses of forest ecosystems. Based on repeated measurements of 253 National Forest Inventory plots in Latvia, yielding data on 449 individual canopy trees, height growth was modelled using a generalised algebraic difference approach; 12 derivatives of non-linear growth models commonly used within the region were tested. The Strand model provided the best compromise between fit statistics and biological realism, predicting rapid early growth with a gradual cessation at the mature age, yet with higher asymptotes compared to Northern and Central Europe. Based on the estimated height growth curves, pedunculate oak in Latvia, however, has a longer establishment period and later growth culmination, suggesting a longer rotation cycle, which favours biodiversity. Still, for the higher site indices, early growth was rapid, suggesting commercial feasibility.