Abstract
Climate change makes it necessary to re-evaluate the erosion potential of forest infrastructure. We used the Forest Service WEPP interfaces (FS WEPP) to compare soil erosion potentials of two competing logging practices in steep terrain in the Northern Black Forest, Germany: (1) Felling with harvesters and logging with forwarders in slope line with optional traction supporting winches. (2) Felling by chainsaw, logging with a cable winch, and further transport of logs via forest dirt roads. After forest harvest we measured erosion, runoff, and DOC concentration in runoff from 50 m sections of two machine tracks, two cable tracks, and a dirt road for 2 years. The erosion measurements were used to validate FS WEPP management options and a regionally adjusted CLIGEN input file. With these parameterizations we compared the erosion potential of the two practices on subcatchment scale by modeling return periods and total sediment export with FS WEPP. Model results show that logging operations with heavy machinery in slope line are less prone to soil erosion than logging operations including winch logging and additional dirt roads. The former produces less sediment in its worst-case configuration than the latter in its most moderate configuration by a factor of two. Model results also show that erosion prevention benefits from long periods of 10 years between two harvests.
Highlights
In European Forestry it is a common view that stable forest ecosystems are not prone to soil erosion (Borrelli et al 2016)
Given satisfactory model performance on this scale the two harvesting practices are evaluated against each other on the scale of the entire subcatchment, addressing the question: 3. Is logging infrastructure used in fully mechanized logging operations less prone to soil erosion than logging infrastructure used in cable winch logging operations?
To represent that revegetation we modeled the topography of the dirt road D7 in Disturbed WEPP with the Forest Service WEPP interfaces (FS WEPP) management option for tall grass, here RTALL
Summary
In European Forestry it is a common view that stable forest ecosystems are not prone to soil erosion (Borrelli et al 2016). Studies from North America have shown that up to 90% of sediment delivered from forested watersheds derive from logging infrastructure (Grace 2003; Basher et al 2011) such as machine tracks and skid-trails (Safari et al 2016) or unpaved roads (Ramos-Scharron and MacDonald 2005). In the context of climate change mitigation an intensification of use of wood as energy source and construction material is suggested (Abbas and Handler 2018). This causes a higher pressure to expand wood harvest into less used sites in steep terrain. Together with an expected rise in erosive precipitation events, as observed, e.g., in Southern Germany (KLIWA 2016), those sites have a higher potential of erosion
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