Root reinforcement dynamics in subalpine spruce forests following timber harvest: a case study in Canton Schwyz, Switzerland

Abstract

Root reinforcement is a key factor when dealing with slope stability problems and is an important quantitative criterion for the evaluation of the protective function of forests against shallow landslides, as well as for the adoption of appropriate practices in protection forest management.Although many models have been developed to estimate root reinforcement, a reliable quantification that considers both its spatial and temporal variability still remains a challenge. This work aims to extend the understanding of the long term spatial and temporal dynamics of root reinforcement after forest harvest in subalpine spruce forests by supplying new experimental data and applying a state-of-the-art model.We estimated root reinforcement decay 5, 10 and 15 years after timber had been harvested in spruce stands in a small catchment in the Swiss Alps. We collected root distribution data at different distances from the trees and calibrated and validated a root distribution model (RootDis). To

Tree-root control of shallow landslides

“…In the long term, root strength can vary by orders of magnitude (Vergani et al, 2016), and estimation of slope stability and landslide initiation is necessary for an integrated management of mountain catchments for risk reduction and control of sediment balance. In the short term, estimations of safety factors for rooted slopes provide important data for risk assessment in forested mountain catchments.…”

“…In the long term, the presence of vegetation (i) increases soil production rates through mechanical and chemical processes (Wilkinson et al, 2005;Phillips et al, 2008) (100-1000 years); (ii) increases soil residence time on hillslopes due to root reinforcement and protects against runoff erosion (Istanbulluoglu and Bras, 2005) (10-100 years; note that in the case of natural or human driven disturbances, the response time of the system (i.e., root decay) is of the order of a few years (Vergani et al, 2016)); and (iii) enhances soil diffusion rates on hillslopes due to tree wind throw (Pawlik, 2013;Roering et al, 2010), root mounds (Hoffman and Anderson, 2014), and biological activity (Gabet and Mudd, 2010) (100-1000 years).…”

“…The spatial and temporal heterogeneity of root reinforcement is related to several factors such as topography, soil water content, soil disturbances, resistance and resilience of forest cover to disturbances, and animal browsing (Schwarz et al, 2012a;Vergani et al, 2016).…”

Large roots dominate the contribution of trees to slope stability

“…; Sidle and Bogaard, ; Vergani et al. ; Sidle and Ziegler, ; Cohen and Schwarz, ; Giadrossich et al. ).…”

“…Wu et al, 1979;Gray and Leiser, 1982;Stokes et al, 2009Stokes et al, , 2014. In addition to hydrological effects (e.g., rainfall interception, pore water pressure reduction) the main effect of vegetation on slope stability is the mechanical reinforcement of soils by roots (Sidle and Ochiai, 2006;Stokes et al, 2014;Sidle and Bogaard, 2016;Vergani et al, 2016;Sidle and Ziegler, 2017;Cohen and Schwarz, 2017;Giadrossich et al, 2017).…”