Schutzwaldmanagement in den Alpen – eine Übersicht | Management of protection forests in the Alps – an overview

Wehrli, André; Brang, Peter; Maier, Bernhard; Duc, Philippe; Binder, Franz; Lingua, Emanuele; Ziegner, Kurt; Kleemayr, Karl; Dorren, Luuk

doi:10.3188/szf.2007.0142

Cited by 23 publications

(9 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Forests in mountainous areas are vital in providing a variety of ecosystem services (Sonnier 1991;Hamilton 1992) such as protection of human infrastructure by aiding in the avoidance or reduction in natural hazards such as flooding, debris flows or landslides (Brang et al 2001;Berger and Rey 2004;Wehrli et al 2007). Depending on the local situation, the protection function, as specifically defined in the Austrian Forest Act 1975Act (amended 2002, is often more important than the production function since settlements and infrastructure must be protected to safeguard human life and livelihoods (Olschewski et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Forest–water dynamics within a mountainous catchment in Austria

Pötzelsberger

Hasenauer

2015

Nat Hazards

View full text Add to dashboard Cite

In this study, we assessed the role of forests in the local water budget within a 7.3 km 2 catchment that has measured river runoff and a long history of forest exploitation and disastrous flooding and debris flow events. Forests retain and absorb water from turning into runoff which is a possible trigger for catastrophic events. Forest water budgets (i.e. interception, transpiration, evaporation, sublimation, soil water storage and outflow) interact with ecosystem processes that are related to the carbon, nutrient and energy cycles and consequently affect forest growth rates. Therefore, we employed a biogeochemicalmechanistic ecosystem model, Biome-BGC, as a diagnostic tool to evaluate the dynamic relationships between key forest ecosystem characteristics and the water cycle. Our study was conducted in the Schmittental catchment with about 70 % forest coverage, situated in the Greywacke Zone of the Austrian Alps. Using stand and site information from 21 Norway spruce stands from the region and 29 years of total catchment runoff data for model validation, we demonstrated that the process-based ecosystem model mimics the interaction of forest growth and the water budget realistically. The weekly catchment runoff calculations based on Biome-BGC grid simulations compared well with observed runoff data. The analysis of the forest-water dynamics/relations showed that the water budget is affected by the size of the canopy and the physiological canopy behaviour in response to daily weather. The results suggested that for fully stocked stands and with a standing volume of [250 m 3 ha -1 , forest water outflow was minimised.

show abstract

Section: Introductionmentioning

confidence: 99%

Forest–water dynamics within a mountainous catchment in Austria

Pötzelsberger

Hasenauer

2015

Nat Hazards

View full text Add to dashboard Cite

show abstract

“…For instance, the global forest area managed for protection of soil and water is 25 % of all global forested areas (Miura et al, 2015). In Switzerland, protection forests occupy more than 50 % of all forested areas (Wehrli et al, 2007). Moreover, bio-engineering measures are often considered an important part of integrated risk management and disaster risk reduction strategies.…”

Section: Background and Motivationmentioning

confidence: 99%

“…In some regions, shallow landslides are the dominant regulating mechanisms by which soil is delivered from the hillslope to steep channels or fluvial systems (Jakob et al, 2005). The magnitude and intensity of these phenomena also has important societal impacts both in the long (landscape evolution and soil resource availability Istanbulluoglu and Bras, 2005;Montgomery, 2007) and short term (risks due to landslides, debris flows and sediment transport, water quality, soil productivity; Wehrli et al, 2007;Hamilton, 2008).…”

Section: Background and Motivationmentioning

confidence: 99%

Tree-root control of shallow landslides

Cohen

Schwarz

2017

Earth Surf. Dynam.

View full text Add to dashboard Cite

Abstract. Tree roots have long been recognized to increase slope stability by reinforcing the strength of soils. Slope stability models usually include the effects of roots by adding an apparent cohesion to the soil to simulate root strength. No model includes the combined effects of root distribution heterogeneity, stress-strain behavior of root reinforcement, or root strength in compression. Recent field observations, however, indicate that shallow landslide triggering mechanisms are characterized by differential deformation that indicates localized activation of zones in tension, compression, and shear in the soil. Here we describe a new model for slope stability that specifically considers these effects. The model is a strain-step discrete element model that reproduces the selforganized redistribution of forces on a slope during rainfall-triggered shallow landslides. We use a conceptual sigmoidal-shaped hillslope with a clearing in its center to explore the effects of tree size, spacing, weak zones, maximum root-size diameter, and different root strength configurations. Simulation results indicate that tree roots can stabilize slopes that would otherwise fail without them and, in general, higher root density with higher root reinforcement results in a more stable slope. The variation in root stiffness with diameter can, in some cases, invert this relationship. Root tension provides more resistance to failure than root compression but roots with both tension and compression offer the best resistance to failure. Lateral (slope-parallel) tension can be important in cases when the magnitude of this force is comparable to the slope-perpendicular tensile force. In this case, lateral forces can bring to failure tree-covered areas with high root reinforcement. Slope failure occurs when downslope soil compression reaches the soil maximum strength. When this occurs depends on the amount of root tension upslope in both the slope-perpendicular and slope-parallel directions. Roots in tension can prevent failure by reducing soil compressive forces downslope. When root reinforcement is limited, a crack parallel to the slope forms near the top of the hillslope. Simulations with roots that fail across this crack always resulted in a landslide. Slopes that did not form a crack could either fail or remain stable, depending on root reinforcement. Tree spacing is important for the location of weak zones but tree location on the slope (with respect to where a crack opens) is as important. Finally, for the specific cases tested here, intermediate-sized roots (5 to 20 mm in diameter) appear to contribute most to root reinforcement. Our results show more complex behaviors than can be obtained with the traditional slope-uniform, apparent-cohesion approach. A full understanding of the mechanisms of shallow landslide triggering requires a complete re-evaluation of this traditional approach that cannot predict where and how forces are mobilized and distributed in roots and soils, and how these control shallow landslides shape, size, loc...

show abstract

Section: Background and Motivationmentioning

confidence: 99%

Tree-roots control of shallow landslides

Cohen¹,

Schwarz²

2017

Preprint

View full text Add to dashboard Cite

Abstract. Tree roots have long been recognized to increase slope stability by reinforcing the strength of soils. Slope stability models include the effects of roots by adding an apparent cohesion to the soil to simulate root strength. No model includes the combined effects of root distribution heterogeneity, stress-strain behavior of root reinforcement, or root strength in compression. Recent field observations, however, indicate that shallow landslide triggering mechanisms are characterized by differential deformation that indicates localized activation of zones in tension, compression, and shear in the soil. These observations contradict the common assumptions used in present models. Here we describe a new model for slope stability that specifically considers these effects. The model is a strain-step discrete element model that reproduces the self-organized redistribution of forces on a slope during rainfall-triggered shallow landslides. We use a conceptual sigmoidal-shaped hillslope with a clearing in its center to explore the effects of tree size, spacing, weak zones, maximum root-size diameter, and different root strength configurations. The model is driven by root data of Norway spruce obtained from laboratory and field measurements. Simulation results indicate that tree roots can stabilize slopes that would otherwise fail without them and, in general, higher root density with higher root reinforcement results in a more stable slope. Root tension provides more resistance to failure than root compression but roots with both tension and compression offer the best resistance to failure. Lateral (slope-parallel) tension can be important in cases when the magnitude of these forces is comparable to the slope-perpendicular tensile forces. In these cases, lateral forces can bring to failure tree-covered areas with high root reinforcement. Slope failure occurs when downslope soil compression reaches the soil maximum strength. When this occurs depends on the amount of root tension upslope in both the slope-perpendicular and slope-parallel directions. Roots in tension can prevent failure by reducing soil compressive forces downslope. When root reinforcement is limited, hillslopes form a crack parallel to the slope near its top. Simulations with roots that fail across this crack always resulted in a landslide. Slopes that did not form a crack could either fail or remain stable, depending on root reinforcement. Tree spacing is important for the location of weak zones but tree location on the slope (with respect to where a crack opens) is as important. Finally, for the specific cases tested here, large roots, greater than 20 mm, are too few too contribute significantly to root reinforcement. Omitting roots larger than 8 mm predicted a landslide when none should have occurred. Intermediate roots (5 to 20 mm) appear to contribute most to root reinforcement and should be included in calculations. To fully understand the mechanisms of shallow landslide triggering requires a complete re-evaluation of the traditional apparent-cohesion approach that does not reproduce the incremental loading of roots in tension or in compression. Our model shows that it is important to consider the forces held by roots in a way that is entirely different than done thus far. Our work quantifies the contribution of roots in tension and compression which now finally permits to analyze more realistically the role of root reinforcement during the triggering of shallow landslides.

show abstract

Schutzwaldmanagement in den Alpen – eine Übersicht | Management of protection forests in the Alps – an overview

Cited by 23 publications

References 15 publications

Forest–water dynamics within a mountainous catchment in Austria

Forest–water dynamics within a mountainous catchment in Austria

Tree-root control of shallow landslides

Tree-roots control of shallow landslides

Contact Info

Product

Resources

About