Biogeomorphic feedbacks and their role for sediment erosion and connectivity along a climatic gradient in Chile

 

Investigator Names and Contact Info:

• Thomas Hoffmann (Geomorphology). Bundesanstalt für Gewässerkunde, Koblenz, Germany
• Lothar Schrott (Geomorphology). University Bonn, Germany
• Jana Eichel (Biogeomorphology). Physical Geography, Utrecht University, Netherlands
• Sebastian Schmidtlein (Vegetation Dynamics). Karlsruher Institut für Technologie (KIT), Germany

 

Chilean Collaborators Involved:

• Luca Mao (Geomorphology). Pontificia Universidad Catolica de Chile & University of Lincoln, UK
• Felipe Aburto (Pedology, Biogeochemistry). Universidad de Concepción, Chile
• Javier Lopatin (LIDAR remote sensing). University of Chile, now at KIT, Germany

 

PhD:

Sediment transport and connectivity under changing biogeomorphic feedbacks.

• Malte Kügler. Federal Institute of Hydrology Koblenz, Germany

66% Co-Supervisor: PD Dr. Thomas Hoffmann, 33% Co-supervisor: Prof. Lothar Schrott

 

BSc:

Sediment transport and connectivity under changing biogeomorphic feedbacks.

• Jonas Alsleben. University of Bonn, Germany

Supervisor: Prof. Lothar Schrott, Co-supervisor: PD Dr. Thomas Hoffmann

 

Fieldwork Assistant:

• Philipp Gewalt. University of Tübingen, Germany

Supervisor: Dr. Jana Eichel

 

 

 

 

 

Project summary:

This proposal is a continuation of our work conducted in EarthShape phase 1. In phase 1, we quantified how climate and vegetation affected the long-term geomorphic conditions of the four EarthShape study areas. Therefore we focused on source to sink sediment connectivity along the flow path of water and sediment in river catchments. We state that biotic effects on sediment routing are scale dependent: on short (biotic) time scales, vegetation disconnects flow path, while on long (geologic) time scales vegetation increases connectivity through biotic weathering.

Table 1: Vegetation-modulated transport conditions on hillslopes and channels in arid and humid catchments.

 

Climate	Vegetation   cover / biotic weathering	Dominant grain size	Transport conditions		Sediment residence time
			Hillslope	Channel	Hillslope	Channel
Arid	low	coarse	Weathering limited	Transport limited	short	long
humid	high	fine	Transport   limited	Supply      limited	long	short

  

In phase 1, we focused the analysis on the long time scales and achieved detailed geomorphic maps of the study sites, used geophysical soundings to estimate the thickness of sediment deposits and investigated the grain size distributions of the soils and sediment along the flow path from eroding hillslopes to the channel outlet. We found significant differences of the spatial configuration of geomorphic process domains and the related transport conditions in the four study sites that can be linked to specific grain size distributions that are modulated by the climatic and biotic conditions within the study areas (compare table 1). These results motivated us to gain a more detailed process understanding on the biogeomorphic feedbacks in the study sites. We do this by:

1.     Improving the representation of vegetation in sediment transport modelling through vegetation surveys, mapping and assessment of the 3D vegetation structure.

2.     Quantifying contemporary sediment dynamics (erosion and deposition) at selected sites in the EarthShape catchments, using repeated drone surveys and structure from motion photogrammetry

3.     Modelling contemporary and catchment-integrated sediment budgets of the four ES-sites and quantify biotic influences on hillslope erosion and sediment deposition using the model Erosion3D at the catchment.

4.     Finalizing work from the first phase and derive long-term sediment budgets

5.     Identifying and comparing biogeomorphic feedbacks along a climatic gradient at short and long timescales and integrating results using hierarchical biogeomorphic concepts