IAP-24-081

Long-term pastoral impact on mountain soils

​​Mountain landscapes are among the most vulnerable ecosystems in the world, threatened by accelerating climate and land-use change. The ruggedness of mountain terrain makes soil erosion a major issue in mountain regions [1], and recent research has shown that erosion is not only a modern problem in the mountains. The analysis of soil profiles and lakes sediments from European mountains indicates an increase in soil loss and accumulation since the 5th millennium BP, chronologically matching the intensification of pastoral practices in mountain environments [2]. Thousands of years of animal grazing seem to have triggered soil erosion processes whose consequences are still visible today. Nevertheless, the relationship between pre-modern pastoralism and mountain soil-erosion remains poorly understood. It is often difficult to disentangle human impact on soil from the long-term effects of climate change, and it is unclear whether alternative pastoral practices had different effects on mountain ecosystems. To solve this complex problem, a transdisciplinary approach is required.

​Different methodological approaches use soil to understand landscape dynamic under human pressure. Soil analysis and soil micromorphology are used in combination to infer surface processes and identify colluvial layers associated with human activities [3]. Luminescence field profiling and OSL dating help to investigate the chronology of soils and unravel the evolution of historic landscapes [4]. GIS-based erosion models simulate soil transport and deposition to explore the influence of different land-use strategies on slope processes [5]. All these methods work at different scales, from the micro- to the macro-, and build on different scientific traditions. Unfortunately, projects that integrate all these techniques into a transdisciplinary methodology are still very rare.

​This project will use a combination of geoarchaeology, geochronology and computer modelling to investigate the effect of pastoral activities on the mountain soils of the Alps. Extreme weather patterns and morphology make the Alps extremely vulnerable to soil erosion, and the historic importance of pastoralism in the region makes this research even more relevant. Within the Alps, the high-altitude area of Silvretta, in Engadin (Canton of Grisons, Switzerland) has been chosen as a case study. Archaeological and palaeoecological research have recently revealed that pastoral practices have shaped the landscapes of Silvretta since the Neolithic (6th millennium BP) [6].​

​​The main methods used in this research include GIS-based modelling of soil erosion, analysis of soil profiles, micromorphology and OSL profiling and dating.

​The model is implemented in GRASS GIS and combines agent-based and cellular automata methods to simulate the impact of alternative land-use strategies on land cover and soil erosion. The creation of the simulation scenarios requires a revision of the archaeological and palaeoecological information available for the case study.

​Fieldwork will be carried out in Silvretta, above 2000 m of elevation. Following an initial survey, to understand the main characteristics of the local landscape, a series of soil pits will be excavated. Soil profile will be described, and samples will be acquired for geopedological analysis (including XRF and phytoliths) and OSL profiling. Undisturbed samples will also be acquired for micromorphology and luminescence characterisation and dating.

​The information provided by the analysis of soil profiles will be used to calibrate and validate the results of computer simulation. The goal is to understand whether the pastoral strategies that can be inferred from the available archaeological data explain the variation in soil loss and accumulation in the Silvretta throughout the Holocene, or whether climate fluctuations were the main driving force of soil erosion.

Year 1

​​Literature review; acquisition of geological, ecological and climatic data for the erosion model; OSL training at CERSA (St Andrews); fieldwork 1: landscape and geoarchaeological survey, excavation of soil pits, description of soil profiles, soil sampling, micromorphological sampling and field-profiling luminescence (SUERC portable IRSL/OSL reader).​

Year 2

​​OSL data processing at CERSA (luminescence screening and characterisation, quantitative quartz OSL dating); thin sections sent to cutting lab; development and simulation of alternative scenarios in the GRASS GIS erosion model; fieldwork 2: survey, excavation of soil pits, description of soil profiles, sampling for soil analysis and luminescence.​

Year 3

​​fieldwork 2 data processing (soil analysis, OSL); analysis of thin sections at Wolfson Lab, Newcastle (Polarized Light Microscopy and, if needed, SEM); review of OSL results; validating and calibrating erosion model with fieldwork data; interpretation of the model outcomes; thesis drafting​

Year 3.5

combining the final results of the erosion model with the interpretation of soil descriptions, soil analysis, OSL, thin section; thesis drafting.

The student will be trained on the use of GRASS GIS and computer modelling by Dr Carrer and on OSL profiling and dating by Dr Kinnaird at the CERSA Lab. With the help of Prof Shillito and the staff of the Wolfson Lab in Newcastle, the student will acquire important skills in soil analysis and archaeological micromorphology. The student will be able to audit relevant UG/PG modules like “Environmental Archaeology” (led by Prof Shillito) and “Fundamentals of Digital Humanities” (led by Dr Carrer). With the help and the support of the three supervisors, the student will learn cutting-edge methods in archaeological and environmental research. The acquired skills will enable the student to develop a unique transdisciplinary expertise, at the intersection of archaeological, soil and geospatial sciences.