Abstract
Tree regeneration is essential for res-establishing and extending our valuable early and existing woodland in the forest. Tree regeneration increases biodiversity, provide habitat, shelter and conserve genetic stock. Therefore, it has been considered as one of important biological process takes place in the forest. Tree regeneration can be affected by many factors including physical and biological impacts. The objectives were to quantify the regeneration pattern of Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) in three inventory cycles of National Forest inventory data (NFI) in Norway. Norway spruce is the main dominant specie in Norway. The study aimed at site class impact on tree regeneration regimes of these species. Statistical analyses were performed in R studio software and some calculations were made by using equations. Regeneration rate was quantified relative to the dendrometric variables DBH, basal area, volume with bark and site index. The data also provided the chance to estimate the regeneration rate of these two species in all five regions across Norway. Eastern region of Norway favors the condition for regeneration compared to the rest of regions in Norway. Meanwhile, pine had lowest regeneration rate in Northern region of Norway. The Regeneration rate of spruce specie was significantly increased over the years with the mean value of 106.76 trees per hectare while found to be slightly different pattern in pine specie. Stand Basal area of pine was observed increased over the measurement periods with mean value of 3.29m2 per hectare while spruce had 1.93m2 per hectare. Pine specie showed more extent of regeneration rate 86.65 trees per hectare in medium site class. This way of analyzing may serve an example for quantifying regeneration and it requires furthered statistical analysis to check core factors responsible for success of regeneration.