Przegląd Geograficzny T. 91 z. 1 (2019)

W artykule dokonano przeglądu literatury zagranicznej i polskiej dotyczącej wpływu pozyskiwania drewna na wybrane procesy naturalne i elementy środowiska na terenach górskich. Skoncentrowano się przede wszystkim na oddziaływaniu gospodarki leśnej na strukturę gleby i tempo erozji oraz na reakcji hydrologicznej w skali stoku i zlewni, w tym na natężenie i częstotliwość przepływów szczytowych oraz transport fluwialny. Z przeglądu literatury wynika, że zrywka jest tym elementem procesu pozyskiwania drewna, który w największym stopniu oddziałuje na glebę i reakcję hydrologiczną zlewni górskich, a sieć dróg leśnych może przyczyniać się do zwiększenia nawet o kilkanaście procent natężenia przepływów maksymalnych i wynikających z nich powodzi błyskawicznych.

This work should acquaint Polish readers with the current state of knowledge on the impact of that the management of mountain forests exerts on soil and on the circulation of water and matter, including via such phenomena as erosion, sediment transport and flooding. It draws abundantly on foreign review papers on specific issues, at the same time augmenting the theses formulated with findings from most recent works and relating to Polish conditions. This literature review has provided a basis for it to be concluded that: 1) forest management, and above all the associated roads and skid trails, accelerate both water erosion and landslide processes in mountainous areas; 2) the movement of matter along forest roads (by both of the above mechanisms) is usually one to more than two orders of magnitude greater than that occurring on steep forested slopes; 3) unpaved forest roads, skid trails and wood-storage areas are the main sources of sediment in forest areas, while paved roads contribute to accelerated surface runoff; 4) the type and location of roads in mountain forest have a significant impact on the intensity of water erosion and landslides processes, as well as peak flows and resulting flood risk in lower locations; 5) roads and skid trails leading along the slope gradient and directly crossing roads and streams intensify further both erosion and the deposition of sediments into streams; 6) the network of forest roads may contribute by up to several percent to increases in peak flows, as well as the resulting flash floods; 7) in the years immediately following clear-cutting, a two- to four-fold increase in the frequency of large flooding events is to be anticipated; 8) annual streamflow usually increases significantly where at least 20% of the tree basal area in a forest is removed; 9) the return of the hydrological system to its pre-harvest state is extremely slow (lasting up to 80 years); 10) there has recently been no universal confirmation of previously demonstrated associations between streamflow increase in mountain catchments and reductions in plant cover.

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