Shallow landslides as drivers for slope ecosystem evolution and biophysical diversity

Abstract

Shallow landslides may be seen as local disturbances that foster the evolution of slope landscapes as part of their selfregulating capacity. Gaining insight into how slope ecosystems function and evolve could make eco-engineering interventions on slopes more successful. The objective of the present study is to detect traits of shallow landslide-triggered ecosystem evolution, self-regulation and biophysical diversity in a small-scale landslide-prone slope in Northeast Scotland. A protocol was defined to explore the emergence of landslide-driven slope habitats. This protocol studied plant diversity, species richness and plant biomass differences and their interactions with certain soil and topographic attributes at three slope strata during two consecutive growing seasons following an assemblage of shallow landslide events. Plant species and soil properties with potential as indicators of the different landslide-driven slope habitats and landscape evolution were also considered. Shallow landslides contributed to biophysical diversity and created distinct slope habitats within the landscape. Habitat differences in terms of species richness and composition were a direct consequence of the slope self-regulation. Certain plant species were found to be valid indicators of landslide-driven biophysical diversity. Soil total nitrogen and resistance to penetration were related to slope habitat and landscape evolution. As expected, plant establishment relied upon light and nitrogen trade-offs, which in turn were influenced by landscape topography. The insights derived from this study will be useful in slope restoration, particularly in harmonising effective actions with the functioning of landslide-prone ecosystems. Further research directions to clarify the observed variability and interactions are highlighted.

The Effect of Willow (Salix sp.) on Soil Moisture and Matric Suction at a Slope Scale

“…The effect of willow on the studied soil-water variables was strongest at the toe zone as a result of a denser vegetation cover established on this zone than on the middle and crest zones ( Table 1). The denser vegetation established at the toe of the monitored hillslope may have been due to more optimal conditions for plant growth in terms of soil water and nutrients availability, which tend to accumulate naturally downslope (e.g., [34]). It is worth noting that willow-vegetated soil exhibited higher θ v levels than fallow soil during part of the monitoring period (Figures 2 and 3), suggesting that vegetated soil can have a higher water retention capacity than fallow soil (e.g., [21]).…”

“…The aboveground traits of the monitored willow individuals are shown in Table 1. The other transect (i.e., fallow transect) had a sparse vegetation cover mainly comprising pioneer grasses and herbs [34]. (a) Hillslope transects selected for study, in which monitoring of soil-water dynamics (i.e., volumetric soil moisture content and matric suction) was undertaken at the toe, middle, and crest zones in both willow-vegetated and fallow transects; (b) Illustration showing the experimental setup deployed onsite to study soil moisture and matric suction dynamics in the fallow and willow-vegetated hillslope transects at the toe, middle, and crest zones.…”

Soil and water bioengineering: Practice and research needs for reconciling natural hazard control and ecological restoration

“…Therefore, most engineers use readily available numerical geotechnical models that include the effects of vegetation. Different types of models have been implemented over the years to predict landslide risk (see Stokes et al, 2014;Gonzalez-Ollauri and Mickovski, 2017b), many of which calculate a global Factor of Safety (FoS) at the slope level, but are not suitable for calculating the efficacy of individual bioengineering structures. Several uncertainties exist in model parameters, which can be overcome by using a probabilistic approach to e.g.…”

A Simple GIS-Based Tool for the Detection of Landslide-Prone Zones on a Coastal Slope in Scotland

“…Connected to this is the build-up of positive pore water pressures in the soil due to precipitation and/or groundwater ponding, which cause saturation and reduction of the strength of the soil. Additionally, in these situations, the evapotranspiration potential of the vegetation present on the slope may not be enough to control the pore water pressure build up and the roots of vegetation will only contribute to the strength of the soil from a mechanical aspect [8,9]. Thus, landslide forecasting has traditionally been based on the establishment of rainfall triggering thresholds on steep areas [10].…”