Spatially explicit basal area growth of Norway spruce

Presented Models describe the current growth rate. These models are good tools for growth prediction in the near future and will be compareable with further models; they will demonstrate the Norway spruce growth changes considering the climate change. Tree growth depends on genetic, climatic, microsite conditions and stand structure variations. A new evaluation method was carried out for studying mutual tree competition based on the social area of each trees. Nine Norway spruce (Picea abies (L.) Karst.) stands were investigated. The objectives of this study were to quantify each individual tree basal area increment during the years 2008-2012 with respect to the social area of the individual trees, competition indexes and the dendrometric characteristics of the trees. The social area of the trees in the investigated plots varied from 0.06 to 43.04 m(2) where correlation coefficient (R (2)) with each individual basal area increment was significantly high. Distance characteristics [e.g. minimum weighted distance (D (i min)) and maximum weighted distance (D (i max))] provided a correlation coefficient (with individual tree basal area increments) varying from 0.69 to 0.84. Values of the R (2) between individual basal area increments and nearest trees dependent (NTD6) competition indexes varied from 0.41 to 0.66, while for distance-dependent competition indexes it varied from 0.59 to 0.78. To facilitate 5-year individual basal area increment inventories (I (g5)), linear models were used to develop the new specific functions. Individual tree growth models based on the distance measurement components and their combinations resulted in very high estimation accuracy. Therefore, the best model to determining basal area increment is the proven linear model using a social tree area, stem diameter at the breast height and crown length as input variables.