Spatial variability of close-to-primeval Fagus–Abies–Picea forests in the Western Carpathians (Central Europe): a step towards a generalised pattern

Abstract

The research objective was to provide a generalised model of spatial variation in the basal area of live and dead trees in primeval beech–fir–spruce forests in the Western Carpathians region. The study was carried out in three primeval stands located in the Polish part of the massif. In each research area, small sample plots (0.015 ha) were localised in a regular 20 × 20 m grid covering approximately 10 ha. In each sample plot, the diameters at breast height (d 1.3) and species of all live and dead trees were recorded. The spatial pattern was tested statistically using a variance-to-mean ratio on a single sample plot scale (0.015 ha) and a paired-plot approach for the distance range between 20 and 200 m. Simulation techniques were then used to model variation in the basal area of live and dead trees dependent on spatial scale. The spatial patterns of live and dead canopy trees (d 1.3 > 50 cm) were regular when analysed on a single sample plot scale (0.015 ha) but most often random at distance lags ≥20 m. The spatial variability in the basal area of live and dead trees also tended to be random. These results suggest that the patch-mosaic assumption is inapplicable to the primeval beech–fir–spruce stands in the Western Carpathians. In all three stands studied, the basal area recorded on the plots 0.015 ha in area had a very similar pattern of variation, which could be generalised as either a truncated normal distribution (live trees) or a negative exponential distribution (dead trees). The bell-shaped frequency distribution of the basal area of live trees suggests a dynamics model in which extreme values of biomass accumulation are rare and disturbances frequent but quickly balanced by stand increment.