INFLUENCE OF INITIAL DENSITY ON INVENTORY PARAMETERS OF UNTHINNED NORWAY SPRUCE STANDS

Abstract

Initial density to large extent determined the stand development thus is crucial to ensure efficient transfer of genetic gain in forestry. Lower density may reduce the stand establishment costs, but also impact the stem quality and standing volume. Very limited information exists about older sparse plantations, therefore aim of the study was to characterize the forest inventory parameters of low-density Norway spruce (Pice abies (L.) Karst.) stands. Data were collected in two planted, un-thinned, 47 year old, pure stands in central part of Latvia (56⁰N, 25⁰E) with initial density 600 and 1600 trees ha^-1, growing on fertile mineral soil. Even the sparsest stand (600 trees ha^-1) had standing volume that was not significantly different from the average in Norway spruce forests in similar conditions at the age of 80 years (294±28.8 and 318±18.7m³ha^-1, respectively), based on National Forest Inventory data. Mean height (21-22 m) and length of branch-free part (<1 m) as well as diameter of the thickest branch in bottom 2m of the stem (<2 cm) and proportion of trees with stem cracks (4%) was not affected by initial stand density. Mean breast height diameter decreased and lengths of dry-branch section increased with increasing initial stand density. The proportion of browsed trees was smaller in sparser stand (23% vs. 31%). Notably lower initial density of planted stands than currently required (2000 trees ha^-1) can be used while avoiding negative impact on forest inventory parameters.