GM1.2

EDI
Biogeomorphology/Ecogeomorphology: process understanding and application

Biogeomorphology addresses the two-way interaction between biotic and abiotic elements that shape landscapes at various spatio-temporal scales. Yet, developing theory, methods and quantifying processes at the abiotic/biotic interface remains challenging due to the interdisciplinarity of biogeomorphology, integrating concepts from ecology, evolutionary biology, engineering, geomorphology, geology and Quaternary science. On the other side, there is an urgent need to understand the interactions among abiotic and biotic processes in natural and managed systems to adapt to for instance climate change.
Consequently, a wide range of interdisciplinary projects in fields related to biogeomorphology have emerged. Such projects have included field, computational, and laboratory studies across a wide range of scales to understand the effects of underlying physical and ecological processes on biogeomorphic interactions.
This session focuses on the lessons learned from such approaches: advantages, limitations, best practices, and the future of the discipline of biogeomorphology. Research topics include, but are not limited to: 1) Biogeomorphic processes, rates and feedbacks, 2) Organism-Habitat interaction, 3) Biota as ecosystem engineers, 4) Effects of biogeomorphic interactions on nutrient and pollutant transport, 5) Biogeomorphology for the development of nature-based-solutions.

Public information:
Biogeomorphology addresses the two-way interaction between biotic and abiotic elements that shape landscapes at various spatio-temporal scales. Yet, developing theory, methods and quantifying processes at the abiotic/biotic interface remains challenging due to the interdisciplinarity of biogeomorphology, integrating concepts from ecology, evolutionary biology, engineering, geomorphology, geology and Quaternary science. On the other side, there is an urgent need to understand the interactions among abiotic and biotic processes in natural and managed systems to adapt to for instance climate change.
Consequently, a wide range of interdisciplinary projects in fields related to biogeomorphology have emerged. Such projects have included field, computational, and laboratory studies across a wide range of scales to understand the effects of underlying physical and ecological processes on biogeomorphic interactions.
This session focuses on the lessons learned from such approaches: advantages, limitations, best practices, and the future of the discipline of biogeomorphology. Research topics include, but are not limited to: 1) Biogeomorphic processes, rates and feedbacks, 2) Organism-Habitat interaction, 3) Biota as ecosystem engineers, 4) Effects of biogeomorphic interactions on nutrient and pollutant transport, 5) Biogeomorphology for the development of nature-based-solutions.
Co-organized by BG3/NH8
Convener: Nico BätzECSECS | Co-conveners: Jana Eichel, Annegret LarsenECSECS, William Nardin, Wietse van de Lageweg
vPICO presentations
| Tue, 27 Apr, 15:30–17:00 (CEST)
Public information:
Biogeomorphology addresses the two-way interaction between biotic and abiotic elements that shape landscapes at various spatio-temporal scales. Yet, developing theory, methods and quantifying processes at the abiotic/biotic interface remains challenging due to the interdisciplinarity of biogeomorphology, integrating concepts from ecology, evolutionary biology, engineering, geomorphology, geology and Quaternary science. On the other side, there is an urgent need to understand the interactions among abiotic and biotic processes in natural and managed systems to adapt to for instance climate change.
Consequently, a wide range of interdisciplinary projects in fields related to biogeomorphology have emerged. Such projects have included field, computational, and laboratory studies across a wide range of scales to understand the effects of underlying physical and ecological processes on biogeomorphic interactions.
This session focuses on the lessons learned from such approaches: advantages, limitations, best practices, and the future of the discipline of biogeomorphology. Research topics include, but are not limited to: 1) Biogeomorphic processes, rates and feedbacks, 2) Organism-Habitat interaction, 3) Biota as ecosystem engineers, 4) Effects of biogeomorphic interactions on nutrient and pollutant transport, 5) Biogeomorphology for the development of nature-based-solutions.

vPICO presentations: Tue, 27 Apr

Chairpersons: Annegret Larsen, Wietse van de Lageweg, Francesco Caponi
15:30–15:35
Coastal biogeomorphology
15:35–15:45
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EGU21-9406
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ECS
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solicited
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Highlight
Valérie Reijers

Biogeomorphic landscapes emerge through feedback interactions between geophysical processes and biota. Plants can stabilize the soil with their extensive root systems or modulate flows of wind and water with their aboveground canopy, promoting local sediment deposition. Different plant species have evolved different suites of traits that affect their landscape-modifying ability. Here, I will present our recent work on the interactions between individual-scale organization patterns and sediment capture for dune building grasses. Using a combination of field surveys, experiments, and simple numerical models, we demonstrate that different species exhibit different clonal expansion strategies, which determine their sediment capture efficiency. Additionally, even within the same species individuals can express different organizational patterns depending on sediment dynamics. Understanding how individual plants engineer their environment depending on prevailing geophysical conditions, and how these individual-scale interactions affect both plant and landscape dynamics, is crucial for unravelling the dynamics of complex biogeomorphic landscapes.

How to cite: Reijers, V.: Embracing the “I” in biogeomorphology - on the role of individuals in self-organised coastal landscapes    , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9406, https://doi.org/10.5194/egusphere-egu21-9406, 2021.

15:45–15:47
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EGU21-3048
Gerben Ruessink, Niels van Kuik, Job de Vries, and Christian Schwarz

Foredune trough blowouts are wind-eroded trough-shaped hollows in the most seaward coastal dune with their adjoining depositional lobes. They evolve on time scales ranging from strong wind events, seasons to multiple decades due to biogeomorphic interactions. Trough blowouts play an essential role in the sand budget of many coastal dune systems by connecting the beach with the backdune. There, the deposited sand can lead to vegetation rejuvenation and an overall larger floral diversity. In Northwestern Europe, nature and coastal managers have started to experiment with constructing trough blowouts in the hope that a positive sand budget beyond the foredune in concert with enlarged biodiversity improves coastal resilience in times of climate change. The spatio-temporal evolution of trough blowouts and the factors driving this evolution are not well understood, despite their common natural occurrence and construction for nature-based management.

The aim of this contribution is to quantify the spatio-temporal development of selected trough-blowout systems around the globe utilizing cloud-free medium-resolution Landsat and Sentinel-2 spectral imagery available in the Google Earth Engine platform. Linear spectral unmixing was applied on a single image basis to extract blowout surface area over time at one man-made blowout system (Zuid-Kennemerland, Netherlands) and two natural systems (Haurvig, Denmark; Padre Island, Texas, USA), assigning pixels with a fractional vegetation cover less than 50% to the blowout. At Zuid-Kennemerland and Haurvig, the blowout surface area fluctuated predominantly on seasonal time scales, with the smallest and largest values in late summer/early autumn and late winter/early spring, respectively. This seasonal variability reflects plant phenology in combination with increased sand accumulation in winter because of the more energetic wind conditions. In summer, vegetation regrew mainly at the edges of the depositional lobes and on the foredune between individual blowouts. The blowout surface area at the subtropical Padre Island varied predominantly on a multi-annual time scale. Most notably, multi-annual area decay was observed when a blowout progressed inland and lost its open connection to the beach, likely resulting in less physical disturbance and hence a dominance of ecological processes. In future work, we will combine our results with auxiliary information (e.g., multitemporal digital elevation models, time series of external forcing conditions, plant species and traits) to develop and test an eco-geomorphological model for blowout evolution. Such a model is adamant to understand what factors contribute to the success or failure of dune restoration projects involving blowouts as nature-based solutions to increase coastal resilience.

How to cite: Ruessink, G., van Kuik, N., de Vries, J., and Schwarz, C.: Biogeomorphic development of foredune trough blowouts quantified from medium-resolution satellite imagery, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3048, https://doi.org/10.5194/egusphere-egu21-3048, 2021.

15:47–15:49
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EGU21-5669
Cindy Palinkas and Lorie Staver

Living shorelines, defined in this study as narrow marsh fringes with adjacent sills, have been gaining traction as the preferred management strategy to mitigate shoreline erosion. These nature-based features provide the same ecosystem services as natural marshes while protecting coastlines. However, they also are threatened by the same environmental changes (sea-level rise, changing sediment supply) as natural marshes and may change characteristics of adjacent subtidal sediments. This study evaluates the role of plants in both the created marshes of living shorelines and, where present, beds of submersed aquatic vegetation (SAV) in the adjacent subtidal in the effectiveness, impacts, and resiliency of living shorelines over ~10 years in mesohaline Chesapeake Bay. At study sites, there is a net seaward movement of shorelines with living shoreline installation due to construction technique. This movement replaces shallow-water habitat immediately adjacent to the pre-existing shoreline; farther offshore, sedimentological changes vary among sites but do not appear to drive changes in the presence/absence of subtidal SAV. While current accretion rates in the created marshes are greater than local relative sea-level rise, there is evidence that accretion rates increase with marsh age, suggesting that living shorelines are most vulnerable in the first few years after installation. Because nutrient burial is maximized when SAV occur next to living shorelines, a management strategy that considers the subtidal and intertidal as integrated components of the coastal system is needed to optimize co-benefits of coastal protection.

How to cite: Palinkas, C. and Staver, L.: Integrating biogeomorphic feedbacks in the coastal zone to bolster coastal resiliency, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5669, https://doi.org/10.5194/egusphere-egu21-5669, 2021.

15:49–15:51
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EGU21-11017
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ECS
Giannis Saitis, ‪Konstantinos Tsanakas, Anna Karkani, Satoru Kawasaki, and Niki Evelpidou

Many studies have been published concerning the occurrence and formation mechanism of beachrocks around the world. However, there are only few quantified data on the precipitation mechanism and the parameters affecting it. The formation mechanism of beachrocks is directly related to their palaeoenvironmental significance, as it provides insights into sea level evolution and palaeogeographic evolution. In this study we corelate analytical data of natural and artificial beachrocks, which were created by the microbially induced carbonate precipitation (MICP) technique using sediments and ureolytic bacteria from the coastal zone of Diolkos, Corinth, Greece.

A multiproxy analysis was accomplished which included the mineralogical and geochemical analysis of both natural and artificial beachrocks, and the sedimentological and mechanical properties analysis of the artificial ones. This study focuses on four parameters that concern the cementation processes of artificial beachrocks: (a) sediment granulometry, (b) CaCO3 content, (c) bacteria type and (d) cement type. Diolkos, due to its location and history, presents great palaeo-geographic and geoarchaeological interest; for this reason, luminescence dating was accomplished on selected beachrock samples, in order to elucidate the relative sea level changes (RSL) and palaeogeographic evolution of the site.

For the artificial beachrocks formation, we conducted solidification test using ureolytic bacteria Micrococcus yunnanensis sp. and Virgibacillus sp. isolated from local sand samples. In order to determine the solidification of the beach sediments we estimated the unconfined compressive strength (UCS) by using needle penetration test on the surface of each sample. Furthermore, the precipitated CaCO3 cement of the artificial beachrock samples, was calculated using HCl rinsing method. The artificial beachrocks were examined under SEM-EDS, XRD and XRF for their mineralogical and chemical composition accordingly.

Microscopy studies (optical and SEM-EDS) revealed that the cement of the artificial beachrock consists of calcite, in form of acicular sediment coating forming fans and multilayer concentrations. The cement in many cases was amorphous calcite crystals or microcrystalline, with thickness varying between 5 μm and 40 μm. The analysis from the artificial beachrock was correlated with the natural beachrock of Diolkos area. Our results revealed that the artificial beachrocks had different type of cement with microstratigraphy of an early digenesis. Moreover, amongst the artificial beachrocks, the sample with very well sorting (in terms of granulometry) has shown high values of CaCO3 content, which corresponds to cement, a mean value of UCS 11 MPa and the best cement precipitation.

How to cite: Saitis, G., Tsanakas, ‪., Karkani, A., Kawasaki, S., and Evelpidou, N.: Insights in beachrock formation mechanism using multiproxy experimental data: Case study of Diolkos, Corinth, Greece, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11017, https://doi.org/10.5194/egusphere-egu21-11017, 2021.

15:51–15:53
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EGU21-1133
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ECS
Dongxue Li

Coastal wetlands play an important role for both human society and coastal ecosystems. The intradelta lobe avulsion, which causes channel shift inside the delta lobe, can create new coastal wetlands and benefit wetland restoration. Previous studies suggest that intradelta lobe avulsion is controlled by the river mouth bar stagnation that results in back filling of the river channel, which further increases the overbank flow at the natural levees and eventually leads to the avulsion. However, the natural levees are commonly colonized by vegetation, and its relevant effects on the avulsion at the levees are still elusive. In this study, we aim to quantify the effects of vegetation on the occurrence of intradelta lobe avulsion at the natural levees through numerical experiments using Delft3D. Numerical simulations of vegetated and non-vegetated scenarios were conducted with different combination of vegetation height and density, river discharge, suspended-sediment concentration and Chezy coefficient. The model results show that the existence of vegetation results in shorter levee length and river mouth bar distance relative to those of non-vegetated scenarios. The levee length and the river mouth bar distance are primarily dictated by the Chezy coefficient and the representative Chezy coefficient for non-vegetated and vegetated scenarios, respectively. In addition, the time scales of river mouth bar stagnation and the intradelta lobe avulsion tend to be shorter for vegetated scenarios, which is presumably due to the shorter river mouth bar distance that leads to a smaller accommodation space for back filling of the river channel. Our findings have important implications for predicting the future avulsion of intradelta lobe and improving the management of deltas and estuaries.

How to cite: Li, D.: Numerical Study on the Effects of Vegetation on the Intradelta Lobe Avulsion, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1133, https://doi.org/10.5194/egusphere-egu21-1133, 2021.

15:53–15:55
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EGU21-200
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ECS
Muriel Brückner, Christian Schwarz, Giovanni Coco, Anne Baar, Márcio Boechat Albernaz, and Maarten Kleinhans

Benthic species that live within estuarine sediments stabilize or destabilize local mud deposits through their eco-engineering activities, affecting the erosion of intertidal sediments. Possibly, the altered magnitudes in eroded sediment affect the large-scale redistribution of fines and hence morphological change. To quantify this biological control on the morphological development of estuaries, we numerically model i) biofilms, ii) two contrasting bioturbating species present in NW-Europe, and iii) their combinations by means of our novel eco-morphodynamic model. The model predicts local mud erodibility based on species pattern, which dynamically evolves from the hydrodynamics, soil mud content, competition and grazing, and is fed back into the hydromorphodynamic computations.

We find that biofilms reduce mud erosion on intertidal floodplains and stabilize estuarine morphology, whereas the two bioturbators significantly enhance inter- and supratidal mud erosion and bed elevation change, leading to a large-scale reduction in deposited mud and a widening of the estuary. In turn, the species-dependent changes in mud content redefines their habitat and leads to a redistribution of species abundances. Here, the eco-engineering affects habitat conditions and species abundance while species interactions determine species dominance. Our results show that species-specific biostabilization and bioturbation determine large-scale morphological change through mud redistribution, and at the same time affect species distribution. This suggests that benthic species have subtly changed estuarine morphology through space and time and that aggravating habitat degradation might lead to large effects on the morphology of future estuaries.

How to cite: Brückner, M., Schwarz, C., Coco, G., Baar, A., Boechat Albernaz, M., and Kleinhans, M.: Benthic species as mud patrol - modelled effects of bioturbators and biofilms on large-scale estuarine mud and morphology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-200, https://doi.org/10.5194/egusphere-egu21-200, 2021.

Fluvial biogeomorphology
15:55–16:00
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EGU21-1588
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solicited
Walter Bertoldi and Angela M. Gurnell

We present recent results of field observations on an island braided reach of the middle Tagliamento River, Italy, where riparian vegetation survival and establishment depends on an unstable balance between vegetation growth and flood disturbance. We combined field observations and information extracted from aerial images, airborne lidar data, and river flow time series for the period 1986-2017 to investigate the changing spatial distribution of woody vegetation and the associated changes in river topography. We also explored the role of Alnus incana (a member of the Betulaceae family), in an environment dominated by the Salicaceae family (e.g. Populus nigra).

We observed that gaps between established islands and/or floodplain offer shelter to vegetation, supporting higher colonisation success and different vegetation-landform evolution pathways.

In particular, A. incana predominantly grows in lines along channel, island and floodplain edges, bordering wooded areas dominated by P. nigra. Given their association with floodplain and island edges and the relationship of taller (older) trees with more elevated surfaces, A. incana in the study reach appears to complement the physical engineering of the dominant species, P. nigra. This suggests that P. nigra may facilitate colonisation by alder but then both species trap sediments to aggrade channel edges and bar surfaces and build island and floodplain landforms.

Time sequences of aerial images in combination with the flood disturbance time series allowed us to interpret vegetation dynamics and to identify the fate of sexual and asexual reproduction strategies by observing vegetation expansion from lines of young plants and shrubs and from uprooted deposited trees and pioneer islands, respectively. Field observations are then generalized to extend a conceptual model of island development.

Growing conditions, disturbance energy, and time (window of opportunity) between major floods are the main controls on vegetation colonization. These vary among rivers, among reaches along the same river and locally, as in the investigated gaps, allowing different tree species with different life history traits (e.g. Populus nigra, Alnus incana) to engineer local river landforms in different and complementary ways.

Although the conceptual model is inspired by observations on the Tagliamento River, consideration of species life history traits and the joint influences of growing conditions, disturbance energy and windows of opportunity provide a framework that may be applied to other temperate rivers where trees drive landform development.

How to cite: Bertoldi, W. and Gurnell, A. M.: Mind the gap: extending the conceptual model of river island development to different environmental conditions and tree species, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1588, https://doi.org/10.5194/egusphere-egu21-1588, 2021.

16:00–16:02
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EGU21-6450
Sabine Fink, Erik van Rooijen, Davide Vanzo, David F. Vetsch, Annunziato Siviglia, and Christoph Scheidegger

The distribution of sessile riparian plant species and their habitats along riverways are highly dependent on river dynamics and connectivity. River restoration and conservation of riparian plant species rely on expert knowledge and more recently also on modelling approaches to predict species’ occurrence. Ecological modelling on habitat suitability for terrestrial species is usually based on climatic and topographic features, whilst river hydrodynamics is rarely considered.

Our study aims at predicting suitable habitat for a characteristic pioneer species for dynamic riverine habitats, the German Tamarisk (Myricaria germanica). Habitat predictions are tested in a case study on a floodplain along Moesa river in canton Grisons in South-East Switzerland. We link two modeling approaches having two different spatial scales using a hierarchical process. First, we define a large-scale habitat suitability matrix based on climatic, geological and topographic predictors. Using a two-dimensional hydrodynamic model, inundation frequency maps and flood level maps for several significant months for German Tamarisk establishment are constructed, to further refine the niche for the riparian plant.

The predicted habitat suitability is evaluated with species presence data for both adult and offspring plants. Our results allow gaining insights into the importance of linking ecological and hydraulic models having different spatial and temporal scales, for more refined predictions of riparian species distribution.

How to cite: Fink, S., van Rooijen, E., Vanzo, D., Vetsch, D. F., Siviglia, A., and Scheidegger, C.: A hierarchical approach linking hydraulic and ecological modeling for habitat predictions for riverine pioneer vegetation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6450, https://doi.org/10.5194/egusphere-egu21-6450, 2021.

16:02–16:04
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EGU21-10083
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ECS
Ilaria Cunico, Damiano Fantin, Annunziato Siviglia, Walter Bertoldi, Nico Bätz, and Francesco Caponi

The morphological trajectory of gravel bed rivers is often dictated by the interaction between riparian vegetation, flow and sediment transport. Vegetation encroachment on riverbed can significantly reduce channel mobility, preventing bank erosion and ultimately confining the river to a single-thread planform. The rate at which plants can encroach the riverbed has been mainly associated to the frequency and magnitude of flooding removing vegetation. However, recent observations indicate that the groundwater dynamics can drive distinct morphological patterns, because of its effect on the spatial distribution of vegetation and growth. However, the quantification of the processes that links groundwater to river morphological changes through vegetation remains unclear.

Here we aim at investigating the ecomorphodynamics of a gravel bed river induced by spatial variations in vegetation density by means of numerical simulations. Our case study is a 3 km long reach of the Allondon river, Switzerland, characterized by a wandering river morphology and that underwent spatially contrasting river planform changes in the last decades. Field observations suggest that deep groundwater in the upper part of the reach limited vegetation growth over years, with the main channel keeping a larger active width and dynamic behavior. On the other hand, a shallower groundwater in the downstream part provided accessible water resources for plants, which encroached the riverbed and confined the channel into a single-thread type of morphology. We performed numerical simulations with the 2D shallow water model BASEMENT, considering a mobile bed composed by uniform sediment and including the main feedbacks between vegetation growth and erosion, the flow field, and the sediment transport processes. We set up the model parameters to reproduce different vegetation spatial distributions, associated with different groundwater depths, and investigated the effect of a 10-years return period flood on the river planform change.

Model results highlight that a low vegetation biomass density, particularly at lower riverbed elevations, caused no significant effect on scour and deposition processes, favoring channel mobility and plant removal by uprooting. This behavior is in line with the observations in the groundwater-deep part of the reach. In contrast, the occurrence of high biomass density at low elevations reduced significantly the channel mobility and the river active width. In this case, vegetation was able to trigger sedimentation on bars and reduce scouring in the main channel, which are key processes for the formation of vegetated, stable riverbeds.

This study represents a step forward to the understanding of the role of the complex link between vegetation dynamics and gravel bed rivers morphodynamics and shows the potential of ecomorphodynamic modeling to interpret river morphological trajectories.

 

 

How to cite: Cunico, I., Fantin, D., Siviglia, A., Bertoldi, W., Bätz, N., and Caponi, F.: Modeling groundwater-driven morphodynamic evolution of a gravel bed river in presence of riparian vegetation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10083, https://doi.org/10.5194/egusphere-egu21-10083, 2021.

16:04–16:06
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EGU21-12515
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ECS
Miles Clark, Georgie Bennett, Aldina Franco, Sandra Ryan-Burkett, and David Sear

Bedload transport is a fundamental process by which coarse sediment is transferred through landscapes by river networks and is characterized by cyclic sequences of particle motion and rest. Bedload transport has many complex physical controls but may be well described stochastically by distributions of grain step length and rest time obtained through tracer studies. To date, none of these published tracer studies have specifically investigated the influence of large wood on distributions of step length or rest time, limiting the applicability of stochastic sediment transport models in these settings. Large wood is a major component of many forested rivers and is increasing because of disturbances such as wildfire and insect infestations as well as its use in rivers as part of ‘Natural Food Management’ (NFM) practice. This study aims to investigate and model the influence of large wood on grain-scale bedload transport. 

St Louis Creek, an alpine stream in the Fraser Experimental Forest, Colorado, is experiencing increased wood loading resulting from the infestation of the mountain pine beetle in the past decades. We inserted 957 Passive Integrative Transponders (PIT) tagged cobbles in 2016 upstream of a wood loaded reach and measured and tagged > 20 pieces of large wood in the channel. We resurveyed the cobbles and wood on an annual basis after snowmelt, building distributions of rock-step lengths as well as observing any changes and transport of large wood. Additionally, a novel modelling approach based on linear mixed modelling (LMM) statistical approaches is implemented to establish the significance of wood and other factors on probability of particle entrainment, deposition and step length.

Tracer sediments accumulated both up and downstream of large wood pieces, with LMM analysis confirming a reduction in the probability of entrainment of tracers closer to wood. In addition, when tracers were remobilised, their subsequent step lengths were shorter the closer they were deposited to large wood. In 2019, large wood significantly reduced the step lengths of tracer particles, forcing premature deposition of tracers. This study demonstrates the role of large wood in influencing bedload transport in alpine stream environments, with implications for both natural and anthropogenic addition of wood debris in fluvial environments.

How to cite: Clark, M., Bennett, G., Franco, A., Ryan-Burkett, S., and Sear, D.: Rock and Roll: RFID Tracking of Fluvial Bedload Transport and Interaction with Large Wood , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12515, https://doi.org/10.5194/egusphere-egu21-12515, 2021.

16:06–16:08
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EGU21-10684
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ECS
Sophia Dosch, Hovius Niels, Repasch Marisa, Scheingross Joel, Turowski Jens, and Sachse Dirk

Rivers are natural conveyor belts distributing the products of erosion across Earth’s surface. If river biospheric organic matter survives long-distance transport and fluvial reworking, it can be deposited and buried in marine depozones, acting to remove carbon from the short-term carbon cycle and draw down CO2 from the atmosphere to a carbon sink over geological time scales.      

It is estimated that globally, river suspended sediment fluxes deliver up to 230 MtC yr-1 biospheric particulate organic carbon (POC) to the ocean. In addition to this commonly measured POC, coarse particulate organic matter (CPOM, > 1mm) has been observed to travel with bedload in modern rivers. Several studies describe terrestrial coarse litter and woody debris buried in sandy turbidite layers and capped by muddy sediment, suggesting effective transport and burial of coarse, relatively fresh organic material to marine depozones.

However, it is unknown whether this CPOM derives from distal sources and survives long-distance fluvial transit, or if distal material is degraded during transit and replaced by CPOM from sources proximal to the coasts. Furthermore, fluxes of CPOM travelling at the river bed are largely unknown, making it an important, yet largely unconstrained term of the carbon budget. Here we investigate the fate of bedload CPOM transported over long distances to determine whether it is preserved, deposited, or degraded and replaced during fluvial transit.

We sampled river bed material from several locations along the Río Bermejo, an intracontinental lowland river in northeast Argentina. At each sampling location, we found substantial amounts of organic matter, together with clastic sediment, from the river bed. To trace the source of the CPOM, we extracted leaf wax n-alkanes and measured their stable hydrogen isotope ratios (d2Hwax). We compared d2Hwax of bed CPOM to d2Hwax of river suspended sediment, soil and litter samples from the river catchment in order to determine its provenance and transport pathway.

Changes in biomarker distribution suggest that the organic matter is recruited from local sources along the river, either as plant debris or as partly degraded litter. In addition, CPOM becomes more degraded, while the n-alkane concentration increases with increasing downstream transport. Our initial data suggests that CPOM is derived partly from distal sources and preserved during fluvial transit. While some part of the CPOM is likely to be oxidized to CO2, fresh input is added along the way, potentially overprinting the upstream signal.

With additional measurements of stable carbon isotope ratios, we expect to verify the source and the fate of the bed CPOM. While it is difficult to quantify the flux of bedload CPOM, we plan to present a first-order approximation by combining river bed flow velocities measured via acoustic doppler current profiler (ADCP) and measurements of CPOM mass collected over our sampling times.

How to cite: Dosch, S., Niels, H., Marisa, R., Joel, S., Jens, T., and Dirk, S.: Terrestrial biospheric carbon export from rivers by bedload transport, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10684, https://doi.org/10.5194/egusphere-egu21-10684, 2021.

Hillslope biogeomorphology
16:08–16:13
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EGU21-16278
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ECS
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solicited
Stefan Haselberger, Lisa-Maria Ohler, Jan-Christoph Otto, Robert R. Junker, Thomas Glade, and Sabine Kraushaar

Proglacial slopes provide suitable conditions to observe the co-development of abiotic and biotic systems. The frequency and magnitude of geomorphic processes and composition of plants govern this interplay, which is described in the biogeormorphic feedback window for glacier forelands. The study sets out to quantify small-scale sediment transport via mechanical erosion plots along a plant cover gradient and to investigate the multidirectional interactions between abiotic and biotic processes. We aim to generate quantitative data to test the biogeomorphic feedback window.

Small-scale biogeomorphic interactions were investigated on 30 test plots of 2 x 3 m size on proglacial slopes of the Gepatschferner (Kaunertal) in the Austrian Alps during snow-free summer months over three consecutive years. The experimental plots were established on slopes along a plant cover gradient. A detailed vegetation survey was carried out to capture biotic conditions and specific sediment yield was measured at each plot. Species abundance and composition at each site, as well as plant functional types reflected successional stages.

We observed a strong decline in geomorphic activity on plots with above 30% plant cover. Mean monthly rates of specific sediment yield decreased from 111 g m-2 to 37 g m-2. Non-metric multidimensional scaling showed distinct vegetation composition for the three stages of biogeomorphic succession. Quantified process rates and observed vegetation composition support the concept of biogeomorphic feedback windows. The findings help to narrow down a stage during succession where the importance of biotic processes start to dominate.

How to cite: Haselberger, S., Ohler, L.-M., Otto, J.-C., Junker, R. R., Glade, T., and Kraushaar, S.: Quantification of biogeomorphic interactions between small-scale sediment transport and primary vegetation succession on proglacial slopes of the Gepatschferner, Austria, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16278, https://doi.org/10.5194/egusphere-egu21-16278, 2021.

16:13–16:15
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EGU21-4179
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ECS
Matteo Roncoroni, Davide Mancini, Tyler Joe Kohler, Floreana Marie Miesen, Mattia Gianini, Tom Ian Battin, and Stuart Nicholas Lane

Biofilms have received great attention in the last few decades including their potential contribution to carbon fluxes and ecosystem engineering in aquatic ecosystems. Quantifying the spatial distribution of biofilms and their dynamics through time is a critical challenge. Satellite imagery is one solution, and can provide multi- and hyper-spectral data but not necessarily the spatial resolution that such studies need. Multi- and hyper-spectral data sets may be of particular value for not simply detecting the presense/absence of biofilms but also indicators of primary productivity such as chlorophyll-a concentrations. Spatial resolution is sensor quality dependent, but also controlled by sensor elevation above the ground. Hence, higher resolutions can be achieved either by using a very expensive sensor or by decreasing the distance between the target area and the sensor itself. To date, sensor technology has advanced to a point where multi- or even hyper-spectral cameras can be easily transported by UAVs, potentially yielding wide-range spectral information at unprecedented spatial resolutions. That said, such set ups have often exorbitant costs (several 1000s of US$) that few research institutions can afford or, due to the high probability of sensor lost, are risky to use. This is particularly true for glacier forefields where low air temperatures, dust and sudden wind gusts can easily damage both UAV and sensor components.

In this paper we test the performance of visible band ratios for mapping both biofilms and chlorophyll-a concentrations in an alpine glacier forefield characterized by a well-developed and heterogeneous (kryal, krenal and rhithral) stream system. The paper shows that low-cost and consumer grade UAVs can be easily deployed in such extreme environments, delivering high temporal resolution datasets and with sufficient quality RGB images for photogrammetric (SfM-MVS) processing and post-processing image analysis (i.e., band ratios). This paper shows also that visible band ratios correlates with chlorophyll-a concentrations yielding reliable chlorophyll-a information of the forefield and at the centimetric scale. This in turn allows for precise identification of the environmental conditions that lead to both biofilm development and removal through perturbation.

How to cite: Roncoroni, M., Mancini, D., Kohler, T. J., Miesen, F. M., Gianini, M., Battin, T. I., and Lane, S. N.: UAV-based cm-scale mapping of biofilms and Chl-a patterns in glacial forefields using visible band ratios, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4179, https://doi.org/10.5194/egusphere-egu21-4179, 2021.

16:15–16:17
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EGU21-4239
María Rosario Vidal-Abarca Gutiérrez, Alberto Martínez-Salvador, Carmelo Conesa-García, María Luisa Suárez-Alonso, Francisco Alonso-Sarria, Pedro Pérez-Cutillas, and Francisco J. Gomáriz-Castillo

Semiarid basins contribute significantly to sediment loads, as they are often characterized by torrential flows, source areas with high sediment-producing rates, great availability of erodible material subjected to intense weathering processes, and poor vegetation cover. Vegetation, despite its scarce presence, is a dynamic component of this environment, which provides a range of important ecosystem services such as biodiversity, flood retention, nutrient sink, erosion control and groundwater recharge. This study examines the vegetation responses to the magnitude of peak flows and its contribution to the changes in runoff and sediment yield during the period 1997-2020 in a catchment Mediterranean semiarid basin: The Rambla de la Azohía (southeastern Spain).Vegetation type, density, preferred location and degree of permanence in each sub-basin were analyzed in order to determine their degree of influence on surface runoff and erosion control. Changes in riparian vegetation cover was quantified at large scale for the analysis period (1997-2020), using remotely sensed spatial information, such as satellite images and aerial photographs separated by two years on average (at scales from 1:15000 to 1:30000, and resolution between 0.22 and 0.50 m/pixel). A geo-spatial erosion prediction model was applied to estimate the runoff and sediment load generated at the event scale, taking into account the variability of the vegetation cover in each sub-basin. The simulated outputs of this model were previously calibrated with water levels measured by pressure sensors and suspended sediment records.The results showed both a poor response of vegetation (low incidence in the runoff coefficient) in steep metamorphic watersheds, capable of supplying large sediment loads, and functioned as an efficient ecosystem service (stabilization of slopes and decrease in peak flow) in less steep sub-basins with slopes in the shadow, composed of limestone formations and alluvial fans. This suggests important spatial differences in the vegetation impact, according to other environmental conditions intrinsic to each sub-basin, but also a low overall influence on the temporal variability of sediment fluxes at the event scale. This research was funded by FEDER/Spanish Ministry of Science, Innovation and Universities—State Research Agency (AEI)/Projects CGL2017-84625-C2-1-R and CGL2017-84625-C2-2-R; State Program for Research, Development and Innovation Focused on the Challenges of Society.

How to cite: Vidal-Abarca Gutiérrez, M. R., Martínez-Salvador, A., Conesa-García, C., Suárez-Alonso, M. L., Alonso-Sarria, F., Pérez-Cutillas, P., and Gomáriz-Castillo, F. J.: Effects of vegetation as an ecosystem service on the changes in runoff and sediment yield in a Mediterranean semi-arid basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4239, https://doi.org/10.5194/egusphere-egu21-4239, 2021.

16:17–16:19
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EGU21-7882
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ECS
Malte Kuegler, Thomas Hoffmann, Jana Eichel, Lothar Schrott, and Juergen Schmidt

There are a multitude of factors that affect soil erosion and the process of sediment movement. One particular factor known to have a considerable impact is vegetation coverage within catchment areas.  Previous studies have examined the impact of vegetation cover on erosion. However, there is a lack of research on how the spatial distribution of vegetation influences erosion rates.

A greater understanding of hillslope erosion is fundamental in modelling previous and future topographic changes under various climate conditions. Here, the physical based erosion model EROSION 3D © is used to evaluate the impact of a variety of vegetation patterns and degrees of vegetation cover on sediment erosion and transport. The model was applied on a natural catchment in La Campana (Central Chile). For this purpose, three different vegetation patterns were created: (i) random distribution, (ii) water-dependent distribution (TWIR) and (iii) banded vegetation pattern distribution. Additional to this, the areas covered by vegetation generated in the first step were expanded by steps of 10% [0...100%]. The Erosion3D © model then was applied on all vegetation patterns and degrees of cover.

Our results show an initial increase of soil erosion with increasing plant coverage within the catchment up to a certain cover threshold ranging between 10 and 40%. At larger vegetation cover soil erosion rates decline. The strength of increase and decline, as well as the cover-threshold is strongly conditioned by the spatial vegetation pattern. In the light of this, future research should pay particular attention to the properties of the plants and their distribution, not solely on the amount of biomass within catchment areas.

How to cite: Kuegler, M., Hoffmann, T., Eichel, J., Schrott, L., and Schmidt, J.: How spatial vegetation distribution affects soil erosion and sediment transport, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7882, https://doi.org/10.5194/egusphere-egu21-7882, 2021.

Going global
16:19–16:21
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EGU21-10183
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Highlight
Heather Viles, Andrew Goudie, and Alice Goudie

Ants are active, numerous and widespread across most landscapes on Earth. They are known to be geomorphologically important, through a range of activities (such as production of galleries and mounds) by which they move and store sediment both above and below ground. They also co-exist and interact with a wide range of other geomorphologically-active organisms, sometimes resulting in complex influences on the landscape (as ant mounds can influence soils and plant biodiversity, for example). Human impacts in the Anthropocene are having direct and indirect impacts on the geomorphological importance of ants – through species invasions, climate change etc. A geolocated database of over 100 studies, covering more than 60 ant species, carried out in Europe, Africa, South America, southern Africa, USA and Australia, is used to produce some estimates of the global impacts of ants within the Anthropocene, including a first order estimate of 7.5 – 10 Gt sediment moved per year by ants across the land surface.

How to cite: Viles, H., Goudie, A., and Goudie, A.: Estimating the global geomorphological importance of ants in the Anthropocene, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10183, https://doi.org/10.5194/egusphere-egu21-10183, 2021.

16:21–16:23
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EGU21-2715
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ECS
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Highlight
Helen Beeson, Sean Willett, and Loïc Pellissier

Landscapes and their associated ecosystems coevolve over geologic time. Correlative approaches have elucidated the importance of topographic diversity and tectonic history but have not identified specific causal links between tectono-geomorphic processes and biodiversity metrics. To address this issue, we coupled the numerical landscape evolution model DAC (Divide and Capture) with a mechanistic model for biodiversity that simulates dispersal, allopatric speciation, and extinction to develop hypothetical biological signatures of different functional groups to a variety of landscape histories. In our coupled model, DAC-BIO, suitable habitat for terrestrial species is defined using a combination of elevation, slope, and aspect, which are measured at sub-grid scale from the simulated landscape and meant to represent more complex physical parameters such as temperature, precipitation, soil properties, and hydrologic environment. In addition to habitability requirements, species are assigned dispersal characteristics (rate and ability to cross uninhabitable terrain) and speciation rate (isolation time needed to form new species). We test whether distinct trends in the size and number of contiguous habitat patches emerge in response to various tectono-geomorphic processes, including a step change in uplift rate, a shift from uniform uplift to an uplift gradient, steady shortening (horizontal advection), and escarpment retreat. We find that these tectono-geomorphic processes do yield distinct trends in the size and number of habitat patches and that the resulting changes in habitat connectivity across the landscape leaves distinct biological signatures in diversification rates, species richness, and endemic richness.

How to cite: Beeson, H., Willett, S., and Pellissier, L.: Identifying causal links between tectono-geomorphic processes and biodiversity with a coupled landscape-biodiversity evolution model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2715, https://doi.org/10.5194/egusphere-egu21-2715, 2021.

General Q&A session: ~15 minutes
Break-out: Coastal
Break-out Fluvial
Break-out Hillslope
Break-out Going global & methodologies
16:23–17:00