Global climate warming is widely recognised as one of the major challenges facing the modern world. To halt, or at least slow, this process, multiple lines of action have been proposed, including the concept of proforestation, which relies on the natural capacity of forests to absorb CO2, one of the principal greenhouse gases. Proforestation involves withdrawing comparatively young forests from management in order to maximise carbon storage in forest ecosystems. Against this background, the aim of this study was to examine how the withdrawal from silvicultural treatments of a young, even−aged Scots pine Pinus sylvestris stand established by artificial regeneration affected its stand volume, productivity, structural heterogeneity, the occurrence of deadwood, and the main growth parameters and allometric traits of Scots pine trees. The study was carried out in the Kampinoski National Park (KNP), in two ca. 60−year−old stands: one withdrawn from management ca. 40 years ago, and one subjected during the same period to standard tending operations (thinnings). In each stand, four square sample plots (25 m × 25 m) were established. All living and dead trees (standing and downed) were measured. Measurements involved all trees with diameter at breast height (DBH) 7 cm and included tree species identification, total height, height to the dead and live crown base, and the vertical extent of major stem morphological zones resulting from natural branch shedding. Field data were processed by BWINPro program, which was used to calculate key stand parameters (such as density, basal area, volume) and several structural diversity indices. Differences in morphological and allometric traits of Scots pine trees between experimental variants were tested using linear mixed−effects models. The results showed that after several decades of spontaneous development, the unmanaged stand exceeded the managed stand in total tree density, the volume of living and dead trees (and thus in the amount of carbon stored), and showed slightly higher structural heterogeneity. In contrast, the tended stand exhibited more favourable parameters of the dominant species (Scots pine), including a lower slenderness ratio (h/d) and longer crowns – traits that are critical for stand stability and resistance to detrimental biotic and abiotic factors. The managed stand clearly outperformed the unmanaged stand also in respect of the amount of wood harvested during silvicultural treatments. This amount was twice as high as the current difference in the total volume between the two studied stands.
Brzeziecki et al. (Thu,) studied this question.