Exploring the Potential of Portable Spectroscopic Techniques for the Biochemical Characterization of Roots in Shallow Landslides

Abstract

In the present work, Raman, Fourier Transform Infrared (FTIR) and elemental Laser-Induced Breakdown Spectroscopy (LIBS) spectroscopic techniques were used for the assessment of the influence of plant root composition towards shallow landslide occurrence. For this purpose, analyses were directly carried out on root samples collected from chestnut forests of the Garfagnana basin (northern Apennines, Italy) in different areas devoid and affected by shallow landslides due to frequent heavy rain events. Results have highlighted a correlation between the biochemical constituents of wooden roots and the sampling areas. In particular, different content of lignin/cellulose, as well as minerals nutrients, have been detected in roots collected where shallow landslides occurred, with respect to more stable areas. The results achieved are in line with the scientific literature which has demonstrated the link between the chemical composition of roots with their mechanical properties and, in particular, tensile strength and cohesion. Finally, portable spectroscopic instrumentations were employed without the need for either any sample preparation for Raman and LIBS spectroscopy or minimal preparation for FTIR spectroscopy. This novel and fast approach has allowed achieving information on the content of the major constituents of the root cell, such as cellulose and lignin, as well as their mineral nutrients. This approach could be reasonably included among the vegetation protection actions towards instability, as well as for the evaluation of shallow landslide susceptibility, combining geological, vegetational and biochemical parameters with sustainability.

Influence of Root Reinforcement on Shallow Landslide Distribution: A Case Study in Garfagnana (Northern Tuscany, Italy)

“…These results agree, in turn, with the work of Dietrich et al [88], which states that landslides most commonly occur in flow accumulation zones. Moreover, our results agree with the findings of Marzini et al [6], in which differences in terms of lignin and cellulose proportions (structural chemical components that provide root mechanical properties) were found moving from landslides (i.e., IN sites) to stable locations (decrease in the lignin/cellulose ratio moving from landslides to stable areas).…”

“…Karst.) [6]. The geological, tectonic and geomorphological evolution has made this area particularly interesting for research activities aimed at studying shallow landslide phenomena (Figure 3).…”

“…In order to assess the role of vegetation in shallow landslide occurrence, field measurements of root data (root area ratio-RAR) were carried out inside (IN), in the neighbor of (NEAR, within 10 m) and far from (FAR, < ca. 1 km) shallow landslide locations following the strategy adopted by Marzini et al [6] (Figure 4). Root features were assessed within soil by digging vertical trenches [55].…”

“…Rainfall-induced shallow landslides represent the most common gravitational mass movements on slopes [1]. These slope failures act as landscape processes of sediment transfer and erosion, and they represent one of the most hazardous categories of mass movements occurring in the world [2][3][4], even though they are characterized by both a ruptured surface that rarely extends beyond two meters depth and a small scar area [5,6]. According to the last Intergovernmental Panel on Climate Change (IPCC) report [7], climate modeling suggests increases in the frequency and magnitude of extreme precipitation events that may trigger increases in the frequency and possibly magnitude of instability phenomena [8], including shallow landslides.…”

“…Moreover, the negative effect of the vegetation load depends on the slope steepness [28]. Most studies focusing on the relationships between vegetation and slope stability have considered one of the aspects previously mentioned: the beneficial effect provided by the presence of root systems in the soil in terms of root density, root strength, root cohesion and root contents [6,12,18,40,41]; the adverse effect due to the vegetation load [15,16,39]; or the influences of canopy properties, forest litter and water preferential paths developed by continuous root channels [42][43][44].…”