Effects of stand features on aboveground biomass and biomass conversion and expansion factors based on a Pinus sylvestris L. chronosequence in Western Poland

Although Scots pine (Pinus sylvestris L.) is one of the most economically important European timber trees, there is still insufficient data about biomass variability and its relationships with stand features. Therefore, we aimed: (1) to develop biomass models for different aboveground biomass components at tree and stand levels, as well as biomass conversion and expansion factors (BCEFs), (2) to assess the relationships between stand parameters and aboveground biomass and BCEFs and (3) to compare stand biomass obtained using BCEFs with models developed based on stand parameters (age, basal area, stand volume and mean height). Using a chronosequence (3–117 years old) of 120 plots within even-aged pure Scots pine stands and 791 sample trees, we prepared tree- and stand-level allometric equations and BCEFs for aboveground biomass determination. Using stand age, density, stand volume and mean height, we prepared a set of models for biomass and BCEFs. Our study indicated that stand biomass increased with increasing height, volume and age and with decreasing stand density during stand development. Stand-level models provided better accuracy than BCEF-based models. The best predictors of biomass were stand volume and mean height. We also confirmed highly dynamic increases in stand biomass and decreases in BCEFs in the youngest phase of stand growth and relative stabilization in later stages of Scots pine stand development. The models obtained may be used in large-scale forest biomass inventories and increase our knowledge of carbon sequestration in forest biomass.