Epsilon Archive for Student Projects

Abstract

In recent years, there has been growing interest in Sweden in utilizing biomass from short-rotation forestry with fast-growing tree species, as well as increasing interest in storing more carbon in standing forests. This is part of Sweden’s aim of becoming a fossil-free country until 2045. In short-rotation forestry, poplars play an important role and are widely used due to their high productivity over short rotation periods. Considering the available agricultural land and the vulnerability of spruce plantations to bark beetles in southern Sweden, poplars could be considered a viable alternative.
Data for this study were collected in the winter of 2025 from 23 poplar stands across southern Sweden, in the Götaland region, and represent two types of land that were used differently in the past: forest arable land and arable land. All sites were planted using poplar clone OP42. The study covers sites in the counties of Skåne, Halland, Kalmar, Kronoberg, and Västra Götaland. The objectives of the study are to compare growth parameters between arable and forest arable land types, evaluate the potential of poplar as an alternative to spruce, analyze variations in site conditions and geographic locations, and examine the differences in productivity and diameter distribution among stands.
Poplar stands age distribution range is between 11 and 20 years on forest arable land and between 12 and 18 years on arable land. Stem densities range from 480 to 1.728 stems per hectare on forest arable land and from 752 to 2.224 stems per hectare on arable land.
The results show that in a comparison of growing parameters between arable and forest arable lands, the mean diameters of the stands don’t differ significantly between land types but the mean height tends to be higher for the stands on arable land. This suggests that stands on arable land tend to have a higher productivity, and this can be seen from the volume distribution on age, where stands on arable land have in most of the cases, a higher volume per hectare than in forest arable land case.
Despite the differences in age, density, and plots number, stands on arable land also showed a higher mean annual increment (21.3 m3/ha/year) compared to forest arable land (15.8 m3/ha/year), indicating approximately 35% greater increment yearly. Regional comparisons showed higher mean annual increment (MAI) on arable land in both Skåne and Västra Götaland regions, with differences of 2.5 and 9.3 m3/ha/year, respectively. The highest MAI was recorded in Kalmar on arable land (27 m3/ha/year). From a general observation, stands on forest arable land showed greater variation in tree diameter compared to arable land. Diameter class distribution was more regular across sites on arable land, indicating more uniform growth. These findings offer valuable insights for landowners, showing that although productivity can be lower on forest arable land compared to arable land, poplar still demonstrates relatively high growth and can be considered a viable alternative for spruce.