Regeneration of Scots pine Pinus sylvestris L. in the Carpathians depends on site fertility

The aim of this work was to determine the biometric features of Scots pine Pinus sylvestris L. regeneration in terms of their susceptibility to weather-inflicted damage. We compared the damage between three sites located in the Polish part of the Carpathians: Scots pine planted in (I) fertile sites of mountain broadleaved and mixed broadleaved forest, (II) poor sites of mountain coniferous forest and (III) sites of Scots pine natural refuges during the post-glacial period. In each of the three sites of pine regeneration, 11 research plots were established with 50 pine trees on each plot. For each tree, the following biometric measurements were taken: diameter at breast height, height, 3-year height increment, crown length and crown width measured along the contour line. The Scots pine regeneration was found to vary in terms of their biometric features depending on the site fertility. In fertile sites, the biometric parameters of the trees increased at a faster rate compared to low-fertility sites causing an increase in their susceptibility to damage by adverse weather conditions such as snow and rime. Therefore, the silvicultural risk in fertile sites is high and thus the introduction of pine for regeneration should be avoided in fertile broadleaved and mixed broadleaved forests even if pine provenances from a mountain origin are to be planted. Furthermore, tending cuts in regeneration should be made frequently, but with moderate intensity so as to avoid excessive reductions in tree density. Intensive cuts, especially in fertile sites, promote the expansion of pine crowns, which further increases the risk of damage.

Waldrandaufwertungen: Einfluss von Exposition und Wüchsigkeit des Standorts

Upgrading of forest edges: impacts of orientation and site fertility Wide, species-rich forest edges are rare in Switzerland. For some years now, the ecological improvement of forest edges has therefore been encouraged by the federal government. In order to make optimal use of the limited resources, we need a good knowledge of the site factors that influence the success of upgrading treatments. We studied 48 improved forest edges in Canton Aargau to understand the impacts of orientation and site fertility on the success of the improvement measures. The results showed that both orientation and site fertility had a significant impact on the quality of the enhanced forest edges. On south-facing and nutrient-poor sites, the ecological quality of the improved forest edges was significantly better than on nutrient-rich sites oriented towads other directions. On sites which were not south-facing fertility had no significant effect on the ecological quality of the improved forest edges. On nutrient-poor sites, the risk that problematic or invasive plant species become dominant after upgrading treatments was much smaller than on nutrient- rich sites. The orientation of the forest edge, on the other hand, had no significant effect on that risk. In the future, therefore, forest edge enhancement projects should preferably be carried out on south-facing and nutrient-poor sites. On sites with other expositions or with high fertility, successful upgradings are less likely but not impossible.

Variation in understory and canopy reflectance during stand development in Finnish coniferous forests

Inherent variability in the spectral properties of boreal forests complicates the retrieval of canopy properties such as canopy leaf area index from satellite images. Understanding the drivers of this variability could help provide better estimates of desired canopy cover properties. Field plot data from the Finnish National Forest Inventory and Landsat thematic mapper (TM) images were used to investigate the variation in canopy and understory reflectance during stand development in coniferous boreal forests. Spectral data for each plot were obtained from the Landsat pixel within which the plot center coordinates fell. Nonlinear unmixing was used to estimate the bidirectional reflectance factors (BRFs) of the “sunlit understory” and “canopy and shaded ground” components by site fertility and stand development classes. A forest albedo model was used to estimate the contribution of diffuse radiation reflected downwards from the canopy to the sunlit understory component. The sunlit understory BRF in the near-infrared spectral band decreased as the site fertility decreased and the forest matured, whereas the sunlit understory BRFs in the red and shortwave-infrared spectral bands concurrently increased. The BRFs of the canopy and shaded ground component decreased slightly during stand development, mostly in the near-infrared spectral band. Adding the diffuse contribution to the sunlit understory component changed the estimated component BRFs only a little (0.1%–1.7%) compared with those obtained using a linear mixing assumption. This effect was largest in the near-infrared spectral band and smallest in the red spectral band. For Norway spruce plots, the measured and estimated forest variables were well correlated with the BRFs in all of the studied spectral bands, but for the Scots pine plots, the correlations were notably weaker. Results show a greater importance of the fraction of visible sunlit understory on forest reflectance in Scots pine than in Norway spruce forests.