Age-independent diameter increment models for mixed mountain forests

Abstract Mixed mountain forests with an uneven-aged structure are characterized by a high tree-growth variability making traditional age-dependent growth models inapplicable. Estimating site productivity is yet another impediment for modelling tree in such forests. Uneven-aged mixed-stand known their resilience, resistance and productivity, being promoted as suitable alternative to even-aged, pure plantations climate change adaptation mitigation. However, must be accurately measured predicted, but diameter at the breast height ( dbh ) increment specifically designed mixed still rare. Using permanent sampling network data 465 cores, we built two age-independent $${i}_{d}$$ i d main species of study area, namely Norway spruce Picea abies (L.) Karst.), silver fir Abies alba Mill.) European beech Fagus sylvatica L.). effects algebraic difference approach were employed develop based on empirical commonly used theoretical functions. A past index was further developed introduced model order explain variability. Several calibration strategies assessed obtain most accurate localized curve new plots. Tree size, competition biogeoclimatic variables found through function, while significantly improved function spruce. The optimization strategy framework enables implementation forest practice method estimating productivity. accuracy similar: root mean squared error varied between 0.940 1.042 cm spruce, fir, obtained only 1.105 cm. basal area prediction plot level reached 0.043 m 2 using 0.047 . underlines suitability predicting can easily integrated into estimates.