Abstract
In southeast Europe, silvicultural measures for improving forest protective effects against rockfall are often based on unsystematic observation and experience. We compared formalised expert assessment of forest protective effects and silvicultural decision-making with an approach supported by modelling (Rockyfor3D, Rockfor.NET, shadow angle method). The case study was conducted in Fagus sylvatica dominated Alpine forests above the regional road leading to the Ljubelj pass, in Slovenia. We analysed rock sources, silent witnesses, forest structure and regeneration. Expert assessment indicated acceptable protection effects of the forest and their decline in the future. Modelling revealed several road sections endangered by rockfalls. It also indicated subtle differences between silvicultural alternatives: current forest, current forest with cable crane lines, selection forest and non-forested slope. This outcome may be due to short transition zones, small rock sizes, low rock source heights and low resolution of the digital elevation model. Modelling requires more initial input than formalised expert assessment but gives spatially explicit results that enable comparison of silvicultural alternatives, coordination of silviculture and forest operations, and delineation of protection forests. Modelling also supported prioritising of silvicultural measures, where the necessity of silvicultural measures increases with increasing rockfall susceptibility and decreasing long-term stability of stands.
Highlights
Mountain forests in Alpine countries provide protection from various natural hazards [1]
The purpose of this study is to assess existing and future forest protective effects against rockfall and to develop silvicultural measures based on formalised expert assessment and a susceptibility modelling approach
We analysed the sustainability of forest protective functions according to four criteria: stand history, stand structure, dominant trees and natural regeneration
Summary
Mountain forests in Alpine countries provide protection from various natural hazards [1]. The majority of Alpine forests were intensively managed [2] and this maintained or, in the case of overuse, decreased their protective effects. The prevailing even-aged stand structure is a result of past large-scale and clear-cut management [4]. These changes have increased the susceptibility of Alpine forests to natural disturbances and decreased their long-term protective effectiveness. Some countries have developed effective countermeasures, including special silvicultural guidelines, protocols for setting priorities, delineation of forests with direct protective functions, and provision of subsidies [5,6,7]
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