A common paradigm holds that, to satisfy mineral nutrient demand, plants and associated soil microbiota accelerate rock weathering which in turn aids to regulate the silicate weathering – CO₂ cycle. However, from investigating the dependence of ecosystem nutrition on 1) erosion rate; 2) biomass growth a more complex picture emerges. To derive this picture, novel metrics for budgeting element fluxes were employed in a global gradient of field sites (refs 1,2,3) that differ in erosion rate and precipitation (and thus plant growth). The metrics are based on weathering zone geochemical composition, soil production rates from cosmogenic nuclides, biomass growth, and plant stochiometry.

1) Dependence on erosion rate: From sites that differ in erosion rate it is found that in slowly eroding mountain landscapes mineral grains that contain nutrients in the regolith are depleted. As a consequence, plants are nourished by recycling, and losses are replaced by atmospheric inputs. In fast-eroding regimes, permanent natural erosion rejuvenates the weathering zone. Erosion exerts the principle control over weathering.

2) Dependence on biomass growth: Because these sites also differ in climate and biomass growth neither the degree of weathering nor the weathering rates increase systematically with precipitation or biomass growth along the gradient. A nutrient recycling factor can be quantified that increases inversely with erosion rate and shows that the increase in nutrient demand with increasing biomass growth is accommodated by faster nutrient recycling between plants and soil.

If weathering does not impact biomass growth and biomass growth does not impact weathering, what then is the influence of biota on element Critical Zone budgets? I hypothesize that plant growth might in fact dampen weathering rates. Deepening the rooting depth, modifying subsurface water flux, or reduction of porosity by precipitation of secondary minerals after enhanced mineral dissolution may induce such a negative feedback.

1. von Blanckenburg, F., Schuessler, J.A., Bouchez, J., Frings, P.J., Uhlig, D., Oelze, M., Frick, D.A., Hewawasam, T., Dixon, J., Norton, K., 2021. Rock weathering and nutrient cycling along an erodosequence. American Journal of Science 321, 1111-1163.

2. Oeser, R.A., von Blanckenburg, F., 2020. Do degree and rate of silicate weathering depend on plant productivity? Biogeosciences 17, 4883-4917.

3. Uhlig, D., von Blanckenburg, F., 2019. How Slow Rock Weathering Balances Nutrient Loss During Fast Forest Floor Turnover in Montane, Temperate Forest Ecosystems. Frontiers in Earth Science 7.

How to cite: von Blanckenburg, F.: Does Plant Growth accelerate Rock Weathering?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1441, https://doi.org/10.5194/egusphere-egu22-1441, 2022.

Many of Earth's steepest, wettest, and rapidly denuding landscapes are covered by dense temperate rainforests. Chilean Patagonia hosts some of Earth's largest swaths of temperate rainforests where landslides frequently strip hillslopes of soils, rock, and biomass.

The susceptibility to shallow landslides can increase following deforestation because of limited root reinforcement, altered soil infiltration, and permeability rates. The wind is a common driver of forest disturbance. While anchoring soils, trees also transfer dynamic-wind force as a turning moment (torque) to the soil mantle via the tree bole, causing tree throw or even shallow slope failure. Despite the above, inquiries into the role of wind in landslide initiation have been anecdotal and unclear about cause and effect.

Assuming that wind loads on trees cause slope instability, we explore the role of forest cover and wind disturbances in promoting such landslides using a hierarchical Bayesian logistic regression model that predicts from crown openness and wind speed the probability of detecting landslides terrain. To control for effects of local terrain steepness, our multi-level model admits different landform types such as channels, ridges, or valley floors.

We find that higher crown openness and wind speeds credibly predict higher probabilities of detecting landslides regardless of topographic location, though much better in low-order channels and on midslope locations than on open slopes. Wind speed has less predictive power in areas that were impacted by tephra fall from recent volcanic eruptions, while the influence of forest cover in terms of crown openness remains.

Distinguishing between landforms in a hierarchical model context improves an otherwise moderate average performance of the classification, but highlights topographic locations for which the prediction needs to be refined.

Our study is the first of its kind in one of the windiest spots on Earth and encourages further inquiry into the rarely investigated role of wind speed in promoting slope instability in southern Chile and densely forested mountain regions elsewhere, especially with weather and wind extremes being on a projected rise in a warming world.

How to cite: Parra Hormazábal, E., Mohr, C., and Korup, O.: Predicting Patagonian Landslides: Roles of Forest Cover and Wind Speed, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9548, https://doi.org/10.5194/egusphere-egu22-9548, 2022.

The interaction between abiotic and biotic development in glacier forelands depends on species traits and the frequency and magnitude of geomorphic events as shown on plot-scale studies. However, upscaling of biogeomorphic interactions is still scarce and it remains unclear how these interactions form and shape dynamic patches.

In this study, we combined traditional field based methods of geomorphology and ecology with remote sensing and soil erosion modelling. Geomorphic mapping allows the delineation of process domains for further methods specification. Field based plot sampling along a chronosequences provides insight into distribution of species composition. Catchment wide patterns of functional groups of vegetation (graminoids, forbs, woody) were analyzed with a random forest algorithm using UAV-based multispectral imagery recorded. Small scale geomorphic events are described through simulated annual sediment transport rates derived from the revised universal soil loss equation model (RUSLE).

The dataset will show temporal and spatial distribution of the stabilizing effect of plant functional types. Analyses of potential erosion rates will show the relationship of small scale sediment transport with species distribution. Results of this study will contribute to our understanding of processes that form biogeomorphic landscape patterns in glacier forelands at different scales.

How to cite: Haselberger, S., Scheper, S., Zangerl, U., Ohler, L.-M., Otto, J.-C., Junker, R. R., and Kraushaar, S.: Catchment-scale patterns of biogeomorphic interaction in an alpine glacier foreland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7777, https://doi.org/10.5194/egusphere-egu22-7777, 2022.

Historic maritime structures, including harbours and breakwaters that are valued as heritage assets, are common along the coastlines of Europe. As with other hard substrates in coastal environments, these structures often support the growth of marine wildlife. As well as contributing to the geomorphic evolution of rocky coasts, sessile organisms including those that form dense biological covers (e.g., seaweed, barnacles, mussels etc.) alter engineering materials by both enhancing and retarding weathering and erosion. Due to their age and traditional construction, historic maritime structures may support unique abiotic-biotic interactions. However, compared to natural rock and modern infrastructure constructed of concrete, there is limited understanding of how biogeomorphological processes operate on built heritage assets. This includes on materials such as natural cement that is commonly used as a hydraulic binder in the construction and restoration of maritime built heritage across Europe. An improved understanding of these interactions should allow practitioners responsible for the conservation of marine biodiversity and the historic built environment to make more informed decisions about their long-term sustainable management.

As part of a larger project exploring the two-way interactions between marine wildlife and historic maritime structures, this study assesses the influence of seaweed canopies (Fucus vesiculosus and F. serratus) on the deterioration of natural cement. After six months exposure to intertidal conditions at Portland Port (Dorset), UK, sample blocks of natural cement attached to substrates with 95–100% seaweed cover were compared to those attached to bare surfaces. Preliminary analysis suggests that surface hardness, surface roughness, and material loss vary between seaweed-covered blocks and those left uncovered, indicating they may have experienced different levels of breakdown during exposure to intertidal weathering and erosion. Monitoring of near-surface microclimates showed that temperature extremes and fluctuations were significantly dampened under seaweed canopies compared to adjacent areas of uncolonised rock. As mechanical rock weathering processes are influenced by surface temperature regimes, we infer that these stabilising effects may translate to a reduction in the efficacy of particular rock breakdown processes over a relatively short period of time.

Overall, this study presents the first empirical evidence of the bioprotective potential of seaweed on materials commonly used to construct and repair historic maritime structures. This implies that opportunities exist for the application of nature-based solutions for the management and protection of historic structures in marine environments alongside habitat provision and biodiversity conservation. Future work is now needed to examine the geomorphic roles of seaweed and other marine organisms on different types of materials used in built heritage conservation, and the extent to which the impacts of these organisms vary in time and space in relation to other biological, chemical, and physical agents of change.

How to cite: Baxter, T., Coombes, M., and Viles, H.: Bioprotection and Maritime Built Heritage: A Preliminary Investigation of the Protective Role of Seaweed on Natural Cement , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8577, https://doi.org/10.5194/egusphere-egu22-8577, 2022.

Natural rocky shore landforms show high habitat heterogeneity, as they have pools, crevices, groves and holes, which accommodate large variety of intertidal species. Urban coasts are often armed with smooth hard flood defences that lack the geomorphological features of natural rocky shores where biodiversity thrives. Hard coastal infrastructure can be ‘greened’ by improving habitats using ecotiles inspired by the natural coastal biogeomorphology to mimic geodiversity of rocky shores and support key species. The tiles for ecological enhancement were designed based on scientific evidence (ecology and biogeomorphology science) to support species richness, abundance and diversity. The highly and less textured tiles were deployed on City of Edinburgh’s coastal protection assets, rock armour and seawalls, in 3 sites in 2020, enabling comparision between two tile types in two locations, as well as comparison to the rock armour and walls. Tiles on rock armour showed higher settlement than tiles on seawalls, which were positioned high in the intertidal zone but are expected to colonise with time, and will be especially important to prevent coastal squeeze with sea level rise. Our data suggest that there was no difference in settlement patterns based on time of deployment (March vs May) suggesting that timing in the settlement season has little ecological impact. The results show that highly textured tiles enhanced habitat on rock armour for seaweed species, notably fucoids, which showed limited presence on rock armour prior to installation. The finer grooves and crevices and biomimicry features on the textured ecotile provided sites for sessile and mobile species, such as barnacles and littorinids, showing statistical differences between the two tile types tested. The less textured tiles on rock armour had colonised by seaweed species contrary to the hypothesis. This finding suggests that the selection of biogeomorphologically informed engineering materials is important for biodiversity enhancement. Active grazing of limpets was observed, which shows that the ecotiles provide foraging habitat for intertidal species that serve as food source for seabirds. The ecotile project represents a pioneer example of greening the grey to support biodiversity on urban coasts in Scotland; and one of the first known to be funded by nature conservation initiatives. This project shows that our understanding of the abiotic-biotic interactions can benefit in designing nature-based solutions to increase resilience and adapt to climate change-related coastal impacts.

How to cite: Naylor, L. A., Kosova, E., Vovides, A., and James, K.: Ecotiles designed to mimic natural rocky shore biogeomorphic interactions: evidence of colonisation patterns after 12 and 18 months , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10602, https://doi.org/10.5194/egusphere-egu22-10602, 2022.

How do plant roots protect streambanks from fluvial erosion? Multiple root mechanisms are considered important in reducing fluvial erosion rates, including increasing soil resistance to erosion or roots extending out of the streambank face and altering the applied hydrodynamic force. Limited work has been done to determine the relative importance of these mechanisms; thus, the purpose of this research was to quantify the physical and biological effects of roots on streambank fluvial erosion.

This research addressed the following hypotheses: 1) The fiber matrix created by densely packed synthetic (inert) roots will reduce fluvial erosion rates due to their impact on the boundary layer; 2) Soil amended with organic matter will enhance soil resistance to fluvial erosion through higher aggregate stability and the production of extracellular polymeric substances (EPS); and 3) The fiber matrix of live roots will provide the most reduction in erosion rates due to their impact on both soil resistance and stream hydrodynamics. Ultimately, this research seeks to identify whether the physical presence of fibers or the biological root-microbe interactions play a dominate role in reducing fluvial erosion rates.

Laboratory-scale testing was conducted using a recirculating flume. A randomized complete block design was used for the experimental setup with six replicates of eight soil treatments: 1) no roots (NR, control); 2) no roots, amended soil (NR-A); 3) flexible synthetic roots (FSR); 4) flexible synthetic roots, amended soil (FSR-A); 5) rigid synthetic roots (RSR); 6) flexible rigid synthetic roots, amended soil (RSR-A); 7) live roots (LR; switchgrass [Panicum virgatum]); and 8) live roots, amended soil (LR-A). Amended soil treatments were included to enhance microbial activity by adding 1 g dried and pulverized grass clippings per 100 g soil. SR treatments were “planted” at root length densities (RLD) between 0.67 to 2.8 cm/cm³. All treatments were established in 10.2-cm diameter and 24.8-cm long PVC pipes in a greenhouse prior to flume erosion testing.

Regression analysis of unamended and rooted soil treatments (FSR, RSR, and LR) revealed a significant and negative trend between RLD and erosion rate. However, the erosion rates of FSR and RSR treatments were statistically equivalent to the NR control treatment. While the RLD of synthetic roots does appear to decrease erosion rates, the results were not statistically different from the control. On the other hand, amended (NR-A, FSR-A, RSR-A, and LR-A) and LR soil treatments significantly reduced erosion rates compared to the control. These results highlight the dominant role that soil microorganisms, and their interaction with living roots, play in protecting soil from fluvial erosion, particularly for streambanks with low root length density (< 1.0 cm/cm³). From a riparian vegetation management standpoint, the results of this study underscore the importance of focusing on soil-root biological mechanisms when undertaking stream restoration projects with the goal of reducing bank erosion.

How to cite: Smith, D. and Wynn-Thompson, T.: Interactions Between Roots and Soil Microorganisms in Promoting Streambank Fluvial Erosion Resistance, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-233, https://doi.org/10.5194/egusphere-egu22-233, 2022.

Seasonal variations in biogeochemical processes are characteristic in temperate environments and are known to modulate the dynamics of intertidal channels. These changes are primarily caused by the seasonality of solar forcing that drives changes in temperature and light which alters primary production. The biostabilization in temperate tide-dominated channels induced by the presence of surface biofilm follows this seasonality, with lower surface biofilm growth in winter and higher values in summer. These patterns have also been associated with spring and early summer microphytobenthos blooms. Additionally, the seasonal patterns in wind and wave forcing, with higher frequency and magnitude storms in winter than summer, will contribute to the seasonality of bed stability. In fact, when strong hydrodynamic forces are acting on the bed, the surface biofilm can be completely removed, exposing the less well-consolidated sediment underneath, which is not influenced by the effect of biological cohesion. Furthermore, sediment particles often combine into larger aggregates, called flocs, that affects sediment transport processes. Flocculation efficacy depends on the cohesive forces of clay minerals and the influence of microbial products consisting of extracellular polymeric substances. The amount of biological material, regulated by seasonality, in turn affects floc size distributions, floc strength and density.

Herein we report on development of a physics-based model which includes these ecologically-driven processes in simulating sediment morphodynamics, allowing us to simulate the time evolution of these environments. Using hydro-sediment dynamic records from a field prototype, the primary objective of this study is to validate this bio-morphodynamic model which is coded to incorporate the effect of biostabilization due to the presence of microphytobenthos, and the effect of bio-flocculation on sediment transport. Field data from the Eden estuary (UK) provided the links between morphodynamics, hydrodynamic forcing and biological processes across the four seasons, and thus enable us to investigate the effect of seasonality on these processes. Samples from a sandy, mixed and muddy sites across the estuary will be used to improve our understanding of the interactions between flow, sediment transport and substratum properties. Furthermore, the model deals with the stratigraphy of the deposits over time, allowing us to compare predicted stratigraphy created from the model runs. This technique helps explore how a range of abiotic-biotic interrelationships in these tidal channels are recorded within the geological rock record.

How to cite: Bastianon, E., Hope, J. A., Paterson, D. M., and Parsons, D. R.: Validation of a biomorphodynamic model for biofilm biostabilization; the effects of varying substrata and seasons at the field scale, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12102, https://doi.org/10.5194/egusphere-egu22-12102, 2022.

The structure and development of river corridors are controlled by an interplay of hydrological, geomorphological and ecological processes over a range of spatial and temporal scales. This is why rivers have been termed biogeomorphological systems by some scholars. Despite the acknowledgement of the relevance of multiple scales, the majority of existing studies on fluvial biogeomorphology focus either on conceptual development or on investigations on the scales of single geomorphic units or study reaches. With this study, we extend the view on biogeomorphology beyond the reach scale using time series of multispectral satellite imagery. We take the Naryn River in Kyrgyzstan as an example for demonstrating our satellite time series approach to biogeomorphological analysis of river corridors. The Naryn is still in a natural state on an entire flow length of more than 600 km with full longitudinal and lateral connectivity. In the central part of the catchment, the Naryn is a highly dynamic braided river system shaped by the annual summer floods of a glacial discharge regime. This makes this river ideal to study large scale biogeomorphological dynamics. In our study, we follow the well-established concept of biogeomorphological succession proposed by Dov Corenblit and his colleagues. We mapped the different succession phases in the field and used the results to derive spectral-temporal indices characterizing the different biogeomorphological succession phases. The normalized difference vegetation index (NDVI) and modified normalized difference water index (MNDWI) have been found to be well suited in the fluvial environment. Monthly time series of these indices derived from the Landsat archive as well as from the more recent Sentinel-2 imagery have now been used to compute statistical trends and changepoints by means of a Bayesian time series decomposition algorithm. The results are then evaluated regarding biogeomorphological succession and disturbance events. The results show that such dense time series of optical satellite imagery are well suited to derive indicators of biogeomorphological interactions on large spatial scale. The temporally continuous nature of this kind of observations allows an observation of processes and an interpretation for instance against the background of the theory of adaptive cycles and panarchy. In conclusion, such satellite time series approach has the potential to give new insights in the structure and functioning of biogeomorphological dynamics of entire river corridors or networks. In particular the recently available Sentinel imagery will allow to observe biogeomorphological processes in a spatially and temporally continuous way at a reasonable spatial resolution. 

How to cite: Betz, F., Lauermann, M., Egger, G., and Cyffka, B.: Biogeomorphology from space: Using optical satellite imagery time series for spatially and temporally continuous observation of the interaction of vegetation and hydromorphology along the Naryn River, Kyrgyzstan, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9824, https://doi.org/10.5194/egusphere-egu22-9824, 2022.

Riparian vegetation and river hydro-morphodynamic processes are strongly interconnected by feedback mechanisms that act at various spatial and temporal scales. Such feedbacks affect water and sediment fluxes along river channels and across floodplains, in turn shaping the river planform style and vegetation structure. In the face of profound changes in climate and increasing anthropogenic pressure, the quantification of these processes is paramount to understand future river dynamics and better design restoration projects and management solutions.

Despite recent advances in river eco-morphodynamic modelling, numerical models including feedbacks between plants, flow, and sediment transport in rivers are still limited. Here we introduce BASEveg, a modelling framework that allows combining the freeware tool BASEMENT, simulating river hydro-morphodynamic processes, and an open-source python module for vegetation growth simulations. The model structure and implementation follow the basic assumption that morphodynamic processes and vegetation growth occur at very different timescales. We consider that over long periods of time the riverbed is essentially stable because of the low flow discharges and modifies only when discharges peak, generating erosion and deposition processes. When the discharge is low enough to expose bare surfaces, vegetation can grow undisturbed until the next high discharge peak. During this time, plants can be uprooted by the flow or buried under sediments.

Here we present a model test case based on the Alpine Rhine river, Switzerland, to illustrate the main functionalities and potentials of BASEveg. The vegetation growth module simulates the plant growth rate depending on the water table level fluctuations during low flow, vegetative periods. This results in a vegetation distribution that well compares with observations and previous modelling results. We show also how the vegetation pattern and riverbed topography co-evolve depending on species-specific traits, which can be simulated within the model. Although the model includes experimental features that still require proper data for calibration and validation, it represents an important step towards the integration of river hydro-morphodynamic processes and vegetation dynamics in common 2D numerical models. The model can be used to understand long-term river morphological trajectories depending on the hydrological regime and climate forcing, helping the design of river restoration projects and management practices. 

How to cite: Caponi, F., Vetsch, D. F., Siviglia, A., and Vanzo, D.: BASEveg: A modelling framework integrating vegetation dynamics and river hydro-morphodynamic processes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8683, https://doi.org/10.5194/egusphere-egu22-8683, 2022.

In river ecosystems riparian vegetation, flow field and sediment transport are interconnected by non-linear complex feedback.

Riparian vegetation grows and encroaches river ecosystems developing a capacity of recovery against the morphodynamic disturbance. In literature there are evidence that the ratio between vegetation recovery and morphodynamic disturbance can play a key-role in the equilibrium of river ecosystems. The “intermediate disturbance hypothesis” postulates that an intermediate ratio between vegetation recovery and disturbance can amplify vegetation dynamics response. Instead, high or low ratio create stability and a low vegetation dynamics response.

Not many models are designed to address such complex relationships in a coupled and quantitative way. Therefore, in this study we aim at quantifying numerically the response of vegetation dynamics to the morphodynamic disturbance in a simplified case study. The case study is a homogeneous straight channel with a vegetated patch perturbed periodically by a succession of sinusoidal floods of constant amplitude.  The frequency of floods is changed during the analysis with the purpose of modifying the ratio between recovery and disturbance, analysing different vegetation responses.

We performed numerical simulations through the new version of the 2D shallow water model BASEMENT coupled with a vegetation growth component (BASEveg). BASEveg is able to simulate the main feedback between river morphodynamic processes and vegetation dynamics (growth and uprooting). In the case study, the intensity of the morphodynamic disturbance itself is strictly dependent on the vegetated patch, infact vegetation modifies the flow field and sediment transport, causing erosion and uprooting.  Vegetation grows during low flow periods and it may be uprooted during flood events, determining biomass oscillations in time.

Model results highlight that for low frequency of disturbance, vegetation dynamics is low, in fact the recovery mechanism (growth) prevails over the collapse mechanism (uprooting) and vegetation settles in a stable configuration, reaching the carrying capacity after every low flow period. For high frequency of disturbance, vegetation dynamics is still low but in this case the uprooting mechanism prevails over the recovery mechanism and vegetation tends to settle in a bare soil configuration. For intermediate frequency the behaviour of the system is more complicated, vegetation dynamics shows larger fluctuations not reaching a stable configuration and resembling a chaotic behaviour. 

Our results paves the way to better understand the relation between recovery and disturbance providing insights into how to avoid irreversible anthropogenic modifications, and implement efficient restoration projects and possibly mitigating the effects of climate change.

How to cite: Cunico, I., Siviglia, A., Bertoldi, W., and Caponi, F.: Intermediate hydro-morphodynamic disturbances amplify riparian vegetation dynamics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8495, https://doi.org/10.5194/egusphere-egu22-8495, 2022.

The majority of river networks globally are expected to go dry for at least part of the year, and the number and frequency of ephemeral and intermittent rivers are projected to increase with a changing climate. Understanding drivers of morphology and diversity in temporary rivers is therefore crucial to managing current and future watersheds. Large wood (LW) and coarse particulate organic matter (CPOM) were historically more abundant in dryland river corridors, but reduction in forested riparian and upland areas as well as targeted removal of wood have decreased wood loads, potentially leading to unintended geomorphic, hydrologic, and ecologic consequences. However, studies of LW and CPOM in ephemeral and intermittent rivers are lacking compared to perennial counterparts, which limits the ability to understand the importance of woody material in dryland watersheds. Questions remain such as: how do woody abundance and volumes vary spatially across and within watersheds, and do LW abundance and distribution in ephemeral streams correlate to increased geomorphic heterogeneity, as they do in perennial rivers? Wood loads were quantified in 37 total reaches (including the channel and floodplain) across six dryland ephemeral watersheds in the southwestern United States using field surveys and aerial imagery. The location and size of LW and CPOM accumulations (termed jams) were noted, and in places where field mapping was conducted, individual logs were measured and included in wood load totals. Jam spatial densities were compared to metrics of heterogeneity, such as sinuosity and braiding index, as well as vegetation density within each surveyed reach. Jam spatial densities ranged from less than 5 jams per kilometer of stream channel to approximately 150 jams per kilometer of stream channel, exceeding previous reported jam densities on temporary rivers. Jam spatial density positively correlates with sinuosity and vegetation cover, highlighting potential positive feedbacks between jam occurrence and increased complexity, which in turn creates additional trapping mechanisms for future wood. Results indicate that wood and organic material are a natural part of ephemeral river systems, and that natural and engineered jams could be used to restore geomorphic processes and heterogeneity in temporary rivers globally.

How to cite: Scamardo, J. and Wohl, E.: The abundance and importance of wood in dryland ephemeral streams across the southwestern United States, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-390, https://doi.org/10.5194/egusphere-egu22-390, 2022.

To date, hillslope-wide effects of burrowing animals on soil erosion, infiltration, surface runoff, water storage and field capacity are hardly understood. Consequently, the effects of burrowing animals are not yet included in erosion models. A suitable approach considering their impacts in erosion models is lacking but needed in order to fully understand the feedbacks between biosphere and sediment fluxes.

For this presentation, we combined in-situ measurements, high resolution remote sensing data and machine-learning methods with a Daily based Morgan-Morgan-Finney soil erosion model for hillslopes along a climate gradient from arid to humid Chile. To parameterize the erosion model, we trained random forest models to upscale in-situ measured soil properties and the presence of animal burrows to each catchment using high-resolution WorldView-2 data. We conducted a land cover classification to provide the vegetation cover. ith this data, we parametrised one model per climate zone. The model was validated using in-situ installed sediment traps. Model experiments in- and excluding animal burrows were conducted to determine the daily and yearly impacts of burrowing animals on soil erosion, infiltration, surface runoff, subsurface runoff, water storage and field capacity on the burrow and hillslope scale at 0.5 m grid resolution.

The presence of burrows increased sediment erosion, infiltration and water storage and decreased surface runoff and field capacity. The effects were most pronounced on the daily and burrow scale in the semi-arid and mediterranean climate zone. In the semi-arid climate zone, the burrows heavily increased surface infiltration and subsurface runoff. In the mediterranean climate zone, the distribution of burrows had an impact on the surface runoff and increased the erosion rate in the adjusting areas without burrows. In the arid zone, the impact of burrowing animals was solely detectable during sporadically occurring heavy rains.

Our study presents, to our knowledge, for the first time a soil erosion model which includes burrowing animal activity. The results clearly underpin the general importance to consider burrowing animals in erosion modelling.

How to cite: Grigusova, P., Larsen, A., Brandl, R., Chifflard, P., Farwig, N., Kraus, D., Übernickel, K., and Bendix, J.: Effects of burrowing animals on soil erosion for Chile derived with a fully parameterized erosion model based on in-situ measurements, remote sensing and machine learning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4603, https://doi.org/10.5194/egusphere-egu22-4603, 2022.

The weathering front, the boundary beneath Earth’s surface where unweathered bedrock is converted into weathered rock, is the base of the critical zone. Typically, this front is located no more than 20 m deep in granitoid rock in humid climate zones and its depth is commonly linked to oxygen transport and fluid flow. To disclose the depth of the weathering front in dry climate, we conducted a drilling campaign in the semi-arid climate zone of the Chilean Coastal Cordillera to investigate a complete weathering profile by mineralogical and geochemical methods as well as geophysical borehole measurements.

We found multiple weathering fronts of which the deepest is located at 76 m beneath the surface. Dioritic rock is weathered to varying degrees, contains core stones, and strongly altered zones featuring intensive iron (Fe) oxidation and high porosity. We found more intense weathering where fracturing is extensive, and in these zones porosity is higher than in bedrock. Only the uppermost 10 m feature a continuous weathering gradient towards the surface. Porosity was preserved throughout the weathering process, as secondary aluminium-silicon minerals were barely formed due to the low fluid flow.

We suggest that tectonic fractures act as major pathways for oxygen to greater depth, generating porosity by oxidation of Fe-bearing minerals. The depletion of soluble elements is also concomitant with high fracture density and highest elemental loss is detected in the proximity of planar fractures or fractures zones. The orientation and dip angle of the fractures are consistent with the arrangement of tectonic faults in the area and the general strike and kinematics of the Atacama fault system. We interpret that most of these fractures have formed during the Late Mesozoic activity of the fault system. Further fractures in the study area may be related to the cooling of the diorite or may be modern and have formed either by stress relief during denudation or through Fe oxidation. We hypothesise that advection of fluids and gases through tectonic fractures sets deep weathering at multiple weathering fronts, since we found elevated degrees of chemical depletion close to larger fractures and no continuous weathering gradient exists. Although the fluid flow is minor, the slow turnover of the weathering zone provides sufficient time to form and preserve these deep weathering features. For the drill sites’ denudation rate of 29.6 t km^-2 year^-1 from cosmogenic nuclides, corresponding to about 11 m Myr^-1, the entire weathering may get turned over about every 7 Myr, if steady state denudation is assumed.

This study is prerequisite to detailed investigation of the microbial processes involved at weathering at great depth.

Krone, L.V., Hampl, F.J., Schwerdhelm, C. et al. Deep weathering in the semi-arid Coastal Cordillera, Chile. Sci Rep 11, 13057 (2021). https://doi.org/10.1038/s41598-021-90267-7.

How to cite: Krone, L., Hampl, F. J., Schwerdhelm, C., Bryce, C., Ganzert, L., Kitte, A., Übernickel, K., Dielforder, A., Aldaz, S., Oses-Pedraza, R., Perez, J. P. H., Sanchez-Alfaro, P., Wagner, D., Weckmann, U., and von Blanckenburg, F.: Deep weathering in the semi-arid Coastal Cordillera, Chile, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8025, https://doi.org/10.5194/egusphere-egu22-8025, 2022.

Soil formation under hyperaridity is governed by the limited availability of water, biotic activity, and unfavourable soil properties, which results in a group of taxa subsumed under Aridisols according to the USDA soil taxonomy. In the Atacama Desert, previous investigations have focussed on the hyperarid core of the desert, describing and identifying soils with salic, gypsic, or nitric characteristics. Contrarily, and although also classified as hyperarid, the coastal sector of the Atacama Desert receives much larger amounts of moisture, mainly due to the orographic blocking of advective fog by the Coastal Cordillera between ~500 and ~1,200 m above sea level. Adapted to this conditions by being able to comb out precipitation equivalents of several hundreds of mm/a, Loma vegetation populates the western Coastal Cordillera and coastal plain. Despite the large climatic contrast to the core of the desert, neither the soil properties, the pedogenic processes nor the timescales on which the coastal soils evolved have as yet been studied. We therefore assessed the physical and chemical parameters of a soil catena at an alluvial fan system at Paposo, composed of four morphostratigraphic units over minimal spatial and thus climatic variation. From each alluvial fan surface generation, we sampled four upper soil profiles. On the one hand, examining the soil physicochemical parameters across the chronosequence allows to deduce the pedogenic processes that are active under coastal hyperaridity. On the other hand, we established an absolute morphochronology based on exposure dating of the depositional surfaces using in situ cosmogenic ¹⁰Be, which enables us to indirectly assess rates of soil formation.

The results show mostly monotonic relationships of physicochemical soil properties with increasing time since abandonment of the first fan surface in the Mid-Pleistocene. Contrary to the expectation, a trend towards desalinization seems to prevail. Moreover, complete decalcification of the oldest soils is closely related to a drop of pH values from slightly alkaline to neutral and slightly acid conditions. Spectrophotometric analysis of the soil colour as well as the geochemistry of pedogenic iron oxides indicates that rubification is a major pedogenic process active under coastal hyperaridity. The combined effects of soil-forming and weathering processes on the soil texture are reflected by a continuous fining towards older soils. Strong indication for in situ formation of clay-sized particles and colloids is provided by the difference of the grain size distributions calculated between two optical laser diffraction models. However, different proxies derived from bulk geochemistry do not support a relevant role of hydrolytic feldspar weathering. In contrast, a significant cumulative effect of biotic activity becomes apparent in the organic carbon content as well as the concentrations of colloidal plant nutrients, both featuring a high temporal and spatial variability.

How to cite: Walk, J., Tittmann, C., Schulte, P., Mörchen, R., Sun, X., Bartz, M., Binnie, S., Stauch, G., Bol, R., Brückner, H., and Lehmkuhl, F.: Assessing soil formation under coastal hyperaridity since the Mid-Pleistocene using a chronosequence dated by in situ cosmogenic 10Be at Paposo, Atacama Desert (N Chile) , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7889, https://doi.org/10.5194/egusphere-egu22-7889, 2022.

Subsurface imaging of the critical zone, where are regolith is produced from bedrock, plays a significant role in understanding the geological and biological interaction at depths. The depth where we can find the intact bedrock is also often referred to as the weathering front. In the scheme of the EarthShape project, we assess one of the hypotheses which link the advance of weathering front to different climate conditions. We present the seismic investigation result from Santa Gracia National Reserve, Chile, one of the main EarthShape sites, which is in a transitional area between the arid to the semi-arid climatic zone. We investigate the weathering profile of this area by acquiring a 500 m long near-surface seismic profile using weight drop sources and 3-component geophones. With the acquired data, we perform two different seismic imaging methods: 1) Body wave tomography, and 2) Multichannel Analysis of Surface Wave (MASW) with Bayesian inversion. Both methods allow us to image the P- and S-wave velocity of the subsurface down to 80 and 60 meters depth, respectively. In addition to the absolute velocity models, we also produce the vertical velocity gradient model, which also provides us with extra tools in interpreting the weathering structure. The resulting models were then validated by existing borehole data located in the middle of the profile. Using the 87 meters deep borehole information, we identified three major layers in the weathering profiles: saprolite, weathered bedrock, and bedrock. The layers were identified by the different seismic velocities, which represent different stages of weathering in the subsurface. Across the profile, the identified weathering front can be traced down to 30 meters depth and is relatively parallel to the surface topography. The interpreted weathering layers also correlate with existing geochemical analysis of the borehole coring and even another perspective in the multi-disciplinary interpretation of the weathering zone. Accordingly, seismic imaging of the critical zone using different methods allows us to improve the critical zone interpretation, either as a combined or independent approach in regions without borehole data available.

How to cite: Trichandi, R., Bauer, K., Ryberg, T., Bataille, K., and Krawczyk, C. M.: Integrated seismic and borehole investigation of the deep weathering structure – case study of Santa Gracia Reserve, Chile, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2580, https://doi.org/10.5194/egusphere-egu22-2580, 2022.

The Earth’s surface is shaped by a complex interplay between tectonics, lithology, climate and biota. Previous work has shown that vegetation cover effects on erosion rates are non-linear and depend on the ecosystem investigated. Vegetation cover is not only influenced by climate (via changes in precipitation, temperature and solar radiation) but also by changes in the atmospheric CO₂ concentration through a fertilization effect and increased water use efficiency. However, disentangling the influence of variable climate or atmospheric CO₂ concentrations on vegetation cover, and hence erosion rates, is difficult. Here we present results from a series of coupled model runs aimed at quantifying the non-linear interactions between these different processes.

We apply a landscape evolution model (Landlab) that is coupled to a dynamic vegetation model (LPJ-GUESS) driven by general circulation model predictions of climate change over the last 21 kyr. Three different scenarios are simulated from the Last Glacial Maximum to present-day: 1) Changing climate and changing atmospheric CO₂ concentration; 2) Changing climate but constant atmospheric CO₂ concentration; and 3) Constant climate but changing atmospheric CO₂ concentration. The simulations are adapted to represent four study areas along the extreme climate and ecological gradient of the Chilean Coastal Cordillera (26 º to 38º S). Results indicate that transients in climate and CO₂ from glacial to interglacial conditions induce a ~10-25% temporal change in catchment erosion, and should be detectable with different measurement techniques. In more detail, we find that precipitation changes exert a stronger influence on erosion rates than changing atmospheric CO₂ concentrations. However, the relative roles of precipitation vs. plant-physiological CO₂ effects on catchment erosion varies with the climate and ecological zone investigated such that the effects of CO₂ fertilization on erosion are larger in temperate than arid settings.

How to cite: Schaller, M., Ehlers, T., Hirsch, P., Hickler, T., Fuentes-Espoz, J.-P., Maldonado, A., and Paulino, L.: Influence of climate change and CO2 fertilization on vegetation and catchment erosion: A coupled modelling approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-885, https://doi.org/10.5194/egusphere-egu22-885, 2022.

Precipitation in wet seasons is the main driver of fluvial erosion and accounts for a significant contribution to annual erosion rates. However, wet seasons also encounter an increase in vegetation cover, which helps to resist erosion. This study quantifies the implications of present-day seasonal variations in rainfall and spatially variable vegetation cover on erosion rates over distinct climate-vegetation settings. We do this using the Landlab-SPACE landscape evolution model modified to account for weathering, rainfall-infiltration-runoff, and the effects of vegetation cover on hillslope and fluvial processes. The input parameters also include present-day SRTM DEM (90m) for the initial condition, MODIS NDVI, and weather station observations of precipitation (between 2000 – 2019). The soil properties (input parameters) and dynamically evolving soil depths were considered to estimate soil-water infiltration using the Green-Ampt method. Simulations were tuned to four selected catchments in the Chilean Coastal Cordillera (~26 °S – ~38 °S) which contains a steep climate (from arid to temperate humid) and ecological gradient with similar granodiorite lithology and tectonic forcings. The size (and mean slopes) of the catchments range from 64 (8°) – 142.5 km² (23°). These catchments are not in steady-state with a background uplift rate of 0.05 mm yr^-1. We designed multiple sets of simulations to explore the sensitivity of catchment scale erosion rates to seasonal variations in precipitation and/or vegetation cover. The simulations were conducted for 1,000 years (20 years of vegetation and precipitation observations repeated 50 times) with a time-step of 1 season (3 months). After detrending the results for long-term transient changes, the last 20 years were analyzed. Results indicate that when vegetation cover is varied but precipitation is held constant then the amplitude of change in erosion rates is very low (e.g. 17% in the humid setting). Whereas, in simulations with variable precipitation change and constant vegetation cover, and coupled variations in both precipitation and vegetation cover, the amplitude of change in erosion rates is higher and in a similar range (e.g., 95% in the humid setting). The results during wet seasons also indicate that erosion in the semi-arid region is ~2 times and ~4 times more sensitive than mediterranean and humid regions respectively. However, minimal erosion is observed in the arid setting, due to low precipitation subjected to soil infiltration which leads to lower runoff than the erosion threshold. Overall, we found that at a seasonal scale, erosion rates are significantly influenced by precipitation variations and base vegetation cover (moderately by seasonal variations). Secondly, the vulnerability of erosion rates to weather seasonality increases from humid to semi-arid regions.

How to cite: Sharma, H., Ehlers, T. A., and Glotzbach, C.: Effects of seasonal variations in vegetation cover and precipitation rates on catchment-scale erosion rates, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-891, https://doi.org/10.5194/egusphere-egu22-891, 2022.

Lycopsids are one of the earliest occurring groups of vascular plants, encompassing a long evolutionary history from its early bushy herbaceous structures during the late Silurian into forests of tree-like structures in the Middle Devonian. These early plants may have contributed to substantial changes in the composition of Earth’s atmosphere, partly related to the biotic enhancement of weathering. To achieve a more quantitative assessment of the biogeochemical impacts of these organisms, it is necessary to quantify their physiological characteristics, spatial distribution, carbon balance, and their hydrological impacts during their span of evolution starting from the Silurian. Here, we present a process-based Lycopsid
Model (LYCOm), developed for the estimation of the influence of the Lycopsids on biogeochemical cycles, which has been applied at the global scale.
The model provides reasonable coverage of the lycopsids for today besides the estimation of weathering rates. The current model features ranges of
key physiological traits of lycopsids to predict the emerging characteristics of the Lycopsida community under any given climate by implicitly simulating the process of natural selection. In this way, extinct plant communities can also be represented. In addition to physiological properties, the model also simulates weathering rates using a simple limit-based approach and estimates the biotic enhancement of weathering by these plants. The model has been locally validated using net primary productivity from on-site observations. The model includes key features such as the distribution of biomass above and below ground, along with a plausible root distribution in the soil affecting water uptake by plants. LYCOm can simulate realistic properties of today’s lycopsid communities with Net Primary Production (NPP) ranging from 100 g carbon m⁻² year⁻¹ to 245 g carbon m⁻² year⁻¹. Our limit-based weathering model predicts a mean chemical weathering rate ranging up to 45.1 cm ka⁻¹ rock, thereby highlighting the potential importance of such vegetation for the enhancement of chemical weathering. This step brings us closer to predicting the abundance and weathering impacts of the lycophytes in the geological past when they were prevalent. Although our method is fraught with some constraints and uncertainties, it represents a novel, complementary approach towards estimating the impacts of lycopsids on biogeochemistry and climate.

How to cite: Halder, S., Dahl, T. W., Benca, J., and Porada, P.: Realizing the impacts of early vegetation on global biogeochemical cycles through a process-based model (LYCOm), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8750, https://doi.org/10.5194/egusphere-egu22-8750, 2022.

Soil moisture is one of the most important parameters of the terrestrial environments in Antarctica. The seasonal amount and availability of liquid water have an essential impact on the abundance and health of the vegetation. Simultaneously, soil water can significantly affect the periglacial environments as its variability can moderate the heat conditions and transport in the active layer and permafrost. It can significantly influence many geomorphological or soil-forming processes. Our contribution evaluates the interactions between surficial soil water content, active layer thickness, and vegetation abundance in the study site on James Ross Island, northern Antarctic Peninsula.

The study area called Berry Hill slope is located in the northern part of James Ross Island. The area is a part of the Circumpolar Active Layer Monitoring – South (CALM-S) network. The study site is about 1 km far from the coastline, about 50 to 60 m a.s.l. In the area, the probing measurements of active layer thickness and surficial volumetric soil moisture in the layer of 0-12 cm were done in February 2018 and 2020. Further, the topography and vegetation extension mapping was carried out using UAV.

The active layer thickness in the CALM-S ranged between 75 and 100 cm. Notably, the lowest values of ALT were detected in the wettest area with an abundance of vegetation. We expect this fact to be caused by both thermal insulations of vegetation carpets and very high soil moisture. The high moisture and almost fully saturated soils prevent active layer thawing propagation due to high latent heat consumption. We found a clear pattern between the abundance of vegetation connected to soil moisture. We observed that the soil moisture threshold allowing vegetation abundance is around 40 %. In contrast, the vegetation misses the rest of the study site, which also has relatively high soil moisture (ca 25-35 % VWC). Considering the warming and drying climate scenario for the region of north-eastern AP, we assume that the active layer will be getting warmer and thicker due to the ongoing climate warming. Active layer deepening might lead to the redistribution of the soil water and the drying of the surficial layers of soil. Consequently, a lack of available soil moisture in the surficial parts can significantly threaten the area's vegetation communities.

How to cite: Hrbáček, F., Kňažková, M., and Smolíková, J.: The linkage between active layer thickness, soil moisture and vegetation on James Ross Island, Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-972, https://doi.org/10.5194/egusphere-egu22-972, 2022.

The Ganga River ecosystem in the Indo-gangetic plains is under severe anthropogenic stress. Flow regulation and habitat fragmentation caused due to structural barriers are responsible for the degradation of biodiversity in a river system. Determining the suitability of river habitats under contemporary modification is detrimental for river health management. Habitat suitability of several reaches of the Ganga River is impacted by the barriers through hydrological alteration leading to poor hydraulic condition and loss of lateral connectivity.

We study the hydrological, hydraulic, and geomorphic suitability of the Ganga River between Bijnor and Narora barrage for the Ganga river dolphin (Platanista gangetica), an indicator species of the Ganga, Brahmaputra- Meghna River system. The discharge data measured downstream of the Bijnor barrage shows that the minimum flow required for the biodiversity and the fluvial process is available only during the Indian summer monsoon period (June- September). While the river reaches upstream of the Narora barrage has maintained the required flow for biodiversity throughout the year. The channel hydraulics influences the habitat selectivity in a river system. The minimum preferred depth for navigation and foraging activity of the Ganga river dolphin is 1-2 m. We calculate the reach averaged hydraulic parameters of the Ganga River at the upstream of Narora barrage using the Geomorphic instream flow tool (GIFT) and altimeter derived water level for different flow conditions. The minimum required depth is available only when the water level is >178.95 m. This only suggests the reach averaged condition and does not reflect the cross-section level depth. The channel geometry analysis of several cross-sections shows that the mean depth of the reach upstream of Narora barrage is 2 m (range 1-2.8 m, SD= 0.8 m) in the low flow season (March)  and the maximum depth ranged from 2.4 to 12 m (SD= 2.8 m). During the high flow season (September), the mean depth is 2.8 m (range 2.2-4 m, SD= 0.53) and the maximum depth ranges from 4.4 to 14.4 m (SD= 2.8 m). This suggests that the reach upstream of the Narora barrage has adequate depth during the low and high flow seasons.  

How to cite: Sonkar, G. K. and Gaurav, Dr. K.: Assessing the habitat suitability of the Ganga River under anthropogenic influence, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-256, https://doi.org/10.5194/egusphere-egu22-256, 2022.

The abandonment of traditional agricultural land is a challenge of increasing importance in recent years. In Spain, the annual abandonment rate of agricultural lands has been growing leading to several social and economic impacts. The environmental consequences of abandonment of cultivation can directly impact the benefits that human beings obtain from them. Furthermore, land abandonment affects ecosystem services, defined as the benefits that humans obtain directly or indirectly from ecosystems (Constanza et al., 1997).  Besides product provision, ecosystem services help to regulate, mediate and provide a better environment, supporting human life as well as climate change adaptation or biodiversity. This research aims to evaluating the effect of the abandonment of agricultural lands on three relevant regulation ecosystem services such as global climate regulation, soil stabilization, and protection and pollination.

The study was conducted for the Comunitat Valenciana (East of Spain), where agricultural land change and abandonment are especially remarkable because of the importance of traditional orchards around cities and villages and their slow fading out in the last three decades.

Agricultural abandoned areas, during the 2012-2019 period, have been delineated using the Temperature - Vegetation Dryness Index (TVDI). The TDVI is a water stress index based on the relationship between land surface temperature and the normalized difference vegetation index (NDVI) from remote sensing data (i.e., MODIS). The selected area corresponds to a zone that was cultivated in 2012 but with persistent water stress (i.e., TVDI > 0.8) for the rest of the period.

The estimation of gains and losses of ecosystem services in the selected abandoned areas was computed using a set of remote sensing methodology-based indicators. More specifically, carbon sequestration computed from Gross Primary Production (GPP) and Net Primary Production (NPP) was used to evaluate the potential to mitigate climate change. Soil stabilization was evaluated by using the Universal Soil Loss Equation (USLE). Finally, pollination was evaluated by computing nesting and floral resources.  

The assessment of the ecosystem services throughout the 2012-2019 period indicates that there is a loss of ecosystem services in the study area. Furthermore, the results show a balance of gains and losses of each service all along the study period. The outcomes could be implemented in a decision-making process to improve land management.

How to cite: Rivero, C., Pérez-Hoyos, A., Albero, E., Gilabert, M. A., and López-Baeza, E.: Agricultural land abandonment and regulation ecosystem services balance in the Mediterranean area of Spain, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12400, https://doi.org/10.5194/egusphere-egu22-12400, 2022.

The evolution of the Amazonian landscape is directly related to the development of the Andean Cordillera and its interaction with climate and other geodynamic processes. The Andean orogeny shaped the climate in South America and changed the precipitation rates across the continent. The continuous increase in erosion rates mainly along the eastern flank of the cordillera amplified the influx of sediments in Amazonia, culminating in the formation of the transcontinental Amazon Drainage Basin nearly 10 million years ago (Ma), connecting the Andean Cordillera and the Equatorial Atlantic Margin. Concomitantly, flexure of the lithosphere due to the load of the Andes and dynamic topography induced by the subduction of the Nazca plate under the western margin of South America modified the landscape in Amazonia.

Due to the complexity of the different processes associated with the geodynamic evolution of northern South America during the last 40 Ma, a natural approach to this study is the use of numerical models that take the interaction of the different geodynamic processes into account. Based on numerical models that combine orogeny, surface processes, flexure of the lithosphere, mantle dynamics, and paleoclimate scenarios, we show how the different habitats in Amazonia probably evolved during the formation of the Andean Cordillera. We observed that the continuous uplift of the Andes created an asymmetric influx of sediments and nutrients in Western Amazonia, inducing the eastward expansion of várzea and terra firme forests during the Miocene. Consequently, the igapó forests retracted and were preserved mainly adjacent to the Guiana and Brazilian shields. Additionally, before the formation of the transcontinental river, large aquatic environments were formed in Western and Central Amazonia, with spatial and temporal extent modulated by climate, sea-level fluctuations, and amplitude of dynamic topography, controlling the transition from the intermittent marine environment to lacustrine conditions, similar to the long-lived lakes of the Pebas System during the Late Miocene. We propose that these landscape evolution scenarios are compatible with the flourishing and extinction of endemic species during the Late Miocene and can explain part of the present pattern of biodiversity observed in the largest rainforest on Earth.

How to cite: Sacek, V., Mutz, S., Ehlers, T., Bicudo, T., and Almeida, R.: Andean geodynamics and the evolution of the Amazonian ecosystem, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1783, https://doi.org/10.5194/egusphere-egu22-1783, 2022.

Understanding origins of biodiversity likely requires explanation of how species richness and environment co-vary across the scales of interest, here 10-10,000 km (e.g. river reaches to latitudinal diversity gradients). We focus on quantifying scale and location dependent coherence between terrestrial vertebrate species (carnivorans, bats, songbirds, hummingbirds, amphibians) and topography, mean annual temperature, temperature range, and precipitation. We test the following three hypotheses by developing and applying wavelet spectral techniques. First, as in most geophysical systems, processes operating at long length scales generate most of the topographic and biotic signals observed. Second, scaling regimes can be identified from topographic and biological spatial series, e.g. transects through topographic or species richness, and they indicate that distinct physical regimes govern biodiversity at different scales. Finally, similarities and dissimilarities exist between topographic or biotic spatial series and environmental variables at a range of locations and scales. We examined latitudinal transects through the Americas, Africa, Australia, Asia and global averages. Species richness is shown to be highly coherent and anti-phase with elevation and temperature range, and in-phase with mean annual precipitation and temperature, at scales >1000 km. Coherence between carnivorans and temperature range is low across all scales, which suggest that their richness is insensitive to daily or seasonal changes in temperature. Amphibians, meanwhile, are highly correlated with temperature range at large scales. At scales <1000 km, all species examined, bar carnivorans, show highest richness in the tropics. Terrestrial plateaux are foci of high coherence between carnivorans and elevation at scales centred on 1000 km, which is consistent with the idea that tectonic processes can contribute to biodiversity. The results obtained by spectral analyses of terrestrial species richness and environmental variables highlight the scale-dependent sensitivities of mammals, birds and amphibians to global and local environmental changes.

How to cite: Roberts, G. G. and O'Malley, C.: Scale-dependent coherence of terrestrial species richness, topography, temperature and precipitation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4106, https://doi.org/10.5194/egusphere-egu22-4106, 2022.

In the geomorphological literature biota are indicated as major drivers of landscape development, where vegetation and soil fauna can act as ecosystem engineers, changing the environment. However, soil landscape evolution models (SLEMs) have until now mostly neglected these biotic processes, such as bioturbation.

We also know that vegetation with different litter qualities can trigger different degrees of animal bioturbation, which can lead to a heterogeneous soil and landscape development both in space and over time. Soil-landscape evolution models have succeeded in incorporating soil development with landscape evolution. However, in these models the roles of biota, biotic interactions and their  connections with soil and landscape evolution processes are still underrepresented.

We identified current SLEMs by a scoping review, and then outlined the role of biota in SLEMs and compared the coverage of processes of SLEMs. From this analysis we selected one of the high-coverage models to testify the hypothesis that landscape patterns can emerge from long-term interactions between biotic processes and soil-landscape processes. In this case we used trees with different litter qualities as biotic factor, and how this can explain the emergence of landscape patterns. We used a test area where topographic differences among species-specific patches are clearly present, taking a well-documented seminatural forest on marls in Central Luxembourg as an example. This system is characterized by a spatially heterogeneous forest pattern dominated by patches of European hornbeam (Carpinus betulus L.) and patches of European beech (Fagus sylvatica L.) showing also a clear differentiation in hydro-geomorphological process domains. Our hypothesis is that these patterns and process domains emerge over time as a result of these biotic-abiotic interactions. We tested our current landscape process understanding and hypothesis using the SLEMs Lorica with incorporation of these biotic components. The first results shows that after calibration with field data and the inclusion of the litter cycle, the adjusted Lorica model succeeded in simulating the geomorphic processes as affected by different litter qualities in the study area, and that the results are promising in explaining the observed spatial patterns.

Keywords: Soil-landscape evolution model; Biota; Litter quality

How to cite: Meng, X., Temme, A., van der Meij, M., Kooijman, A., and Cammeraat, E.: Can litter quality explain landscape evolution: testing a soil-landscape evolution model. , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12237, https://doi.org/10.5194/egusphere-egu22-12237, 2022.

South America is home to the highest freshwater fish biodiversity on Earth. The hotspot of species richness is located in the western Amazon Basin, and richness decreases downstream along the Amazon River towards the mouth at the Atlantic coast. This pattern contradicts the commonly observed positive relationship between stream size and biodiversity in river systems across the world. We investigate the role of river capture events caused by Andean mountain building and repeated episodes of flooding in western Amazonia in shaping the modern-day richness pattern of freshwater fishes in South America. To this end, we combine a reconstruction of river networks since 80 million years ago with a model simulating dispersal, allopatric speciation and extinction over the dynamic landscape of rivers and lakes. We show that Andean mountain building and consequent numerous small river capture events in western Amazonia caused freshwater habitats to be highly dynamic, leading to high diversification rates and exceptional richness. The history of marine incursions and lakes, including the Miocene Pebas megawetland system in western Amazonia, played a secondary role. This study is a major step towards the understanding of the processes involved in the interactions between the solid Earth, landscapes, and life of extraordinary biodiverse South America.

How to cite: Boschman, L., Carraro, L., Cassemiro, F., de Vries, J., Altermatt, F., Hagen, O., Hoorn, C., and Pellissier, L.: South American freshwater fish diversity shaped by Andean uplift since the Late Cretaceous , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10548, https://doi.org/10.5194/egusphere-egu22-10548, 2022.

In the Miocene, a large wetland extended from the Andean foothills into western Amazonia. This system plays an important part in current biogeographic models and is thought to have acted as an evolutionary ‘cradle’ for aquatic species and an ‘inhibitor’ for terrestrial taxa. The generating mechanisms of this system are not fully understood, but dynamic topography, Andean uplift and eustasy are all thought to have controlled deposition. Orbital forcing is likely an additional driver that could explain the succession of shallowing upwards cycles that characterize the sedimentary record. In this study we investigated the presumed cyclicity at the Los Chorros (Colombia), a site that constitutes a representative example for the sedimentary record in the Miocene wetland system. We integrated lithological, palynological and malacological data from a sequence biostratigraphic perspective. In this approach, the Los Chorros succession is visualised to be composed of a series of flood-fill packages, with a rapid initial flood, with marine-influenced conditions at the time of maximum flood, and followed by a longer regressive infill phase. Based on the palynology we could differentiate local vegetation, such as swamps, from sources of regional origin such as terra firme vegetation (non-flooded Amazonian Forest) and montane forest (Andean), while also separating local and regional sediment sources.  Marine influences are intermittently evident in this section, based on the occurrence of short-lived maxima of mangrove pollen, foraminiferal test linings, dinoflagellate cysts, some mollusc species, and an episodic decline in terrestrial biomarkers. At the times of flooding, the lacustrine conditions in the wetland system were characterized by the presence of algae, floating ferns, and mollusc assemblages that indicate alternating oligotrophic and eutrophic conditions, while intervening subaquatic debris points to proximal submerged lowlands. The palynology also shows that the shallow lakes were fringed by a succession of Mauritiinae palm swamps, ferns, and grasses, with a diverse rainforest in the wider periphery. The sequence biostratigraphic evaluation suggests that the deposition of this sediment sequence took place prior to the 13.8 Ma global sea level fall, and most likely the period just after 14.5 Ma, towards the end of the Middle Miocene Climatic Optimum. We propose that the studied succession comprises eight 41 ka obliquity-driven depositional cycles, with rapid phases of transgression, and that mangrove elements would have colonised within the timeframe of each sea level rise.

How to cite: Hoorn, C., Tyler, K., Bogota-Angel, G., Catalina, G. A., Wesselingh, F., Val, P., Vonhof, H., and Morley, R.: Cyclic sediment deposition in the Miocene wetland of Western Amazonia is controlled by orbital forcing, uplift of the Andes and sea level change, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12770, https://doi.org/10.5194/egusphere-egu22-12770, 2022.

Terrestrial biodiversity is higher in topographically complex regions than in low relief ones, and this diversity evolved over millions of years along elevation gradients with disequilibrium of climatic conditions and biological interactions. Also, the mountainous complex is heterogeneous, consisting of orogenic and volcanic mountains with different geological and climatic features. However, there has not been an investigation in regard how a volcanic environment may have influenced ecosystem changes or faunal evolution to. Rodents are an excellent model to explore these questions because they are the most speciose clade of mammals and many species live in montane regions. Hypotheses of the ecological evolution in different volcanic provinces in America were discussed during the Workshop on Volcanism and Rodent Evolution organized by the Research Group “Mammal diversification about dynamic landscapes of the North American Rodents Landscapes, Evolution & Ecology”. Workshop consisted of two modules: 1) origin and development of volcanic provinces in North America during the late Cenozoic with an emphasis on the geological process crucial to the ecosystem; 2) some examples of ecosystems in volcanic regions and evolutive patterns related to sky-island process. In both modules, we discuss the evolution of different lineages of rodents, fossil and extant species, and how we can distinguish the volcanic influence on their biodiversity. The topics were: speciation, endemism, genetic drift, geographic-range shifts, environmental sorting, and sky-island processes.

How to cite: Pacheco Castro, A., Arroyo Cabrales, J., Fox, D., Hopkins, S., and Badgley, C.: Volcanism and Rodent Evolution: ecological interactions in different geological provinces in America discussion from a workshop , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13018, https://doi.org/10.5194/egusphere-egu22-13018, 2022.

Reconstructions of topography and surface uplift histories of mountain ranges over geological time help constrain the geodynamic evolution of collisional domains and improve our understanding of the interactions between climate, tectonics, and surface processes. Stable isotope palaeoaltimetry is a powerful tool to estimate past surface elevations. However, recent studies suggest that knowledge of climate conditions is needed to accurately interpret the isotopic composition of water recorded in geologic archives. Furthermore, the geodynamic history of the European Alps is hypothesized to have resulted from the eastward propagation of surface uplift that could be reflected in palaeoaltimetry data. In this study we apply high-resolution isotope-tracking ECHAM5-wiso General Circulation Model (GCM) to forward-model the climate and water isotopes in meteoric water for different surface uplift histories of the Alps. Our emphasis is on understanding the climate and topographic signals preserved in the isotopic composition of precipitation (δ¹⁸O_p) which is eventually recorded in paleosol carbonates. More specifically, we test the hypothesis that different topographic configurations for Eastern and Western Alps result in significantly different regional climates and spatial distributions of δ¹⁸O_p. We present sensitivity experiments with two free parameters: the height of the Western/Central Alps and the height of the Eastern Alps. Results indicate a different response of δ¹⁸O_p, precipitation, surface temperature, low level wind patterns and isotopic lapse rate for the different topographic scenarios. In addition, we find δ¹⁸O_p locally increases up to 2‰ when the Eastern Alps are reduced to 0% of their current height, and decreases up to -8% when uplifted to 200%. The precipitation amount increases by ~60 mm/month in response to surface uplift due to orographic effects. The surface temperature locally decreases by -4°C in response Eastern Alps uplift due to both adiabatic and non-adiabatic cooling and increases by -8°C for reduced elevation scenario. The results of our study suggest that the hypothesized west-to-east surface uplift should be reflected in the isotopic composition of meteoric water. Furthermore, our simulated isotopic response to different uplift scenarios provides a basis for the interpretation of isotopic composition derived from geological archives in a stable isotope palaeoaltimetry approach.

How to cite: Boateng, D., G. Mutz, S., and A. Ehlers, T.: How would the eastward propagation of surface uplift in the Alps affect regional climate and isotopic composition of precipitation?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-843, https://doi.org/10.5194/egusphere-egu22-843, 2022.

Quantifying surface elevation over geological time is essential for reconstructing coupled climatic and mountain building processes. Surface uplift of an orogen, such as the European Alps, results from the interplay between subsurface geodynamic processes and climate-induced denudation. Although being one of the most studied mountain ranges worldwide, knowledge about the elevation history of the European Alps is still scarce. Stable isotope paleoaltimetry is a robust tool to reconstruct paleoelevations of orogens. The method is based on the systematic inverse relationship of isotope ratios of oxygen (δ¹⁸O) and hydrogen (δD) in precipitation with elevation. Recent stable isotope paleoaltimetry studies that focused on the Central Alps indicate elevations locally exceeding 4 km during the Mid-Miocene. Here, we reconstruct past Alpine surface elevations by applying stable isotope paleoaltimetry coupled with clumped isotope, T(Δ₄₇), temperature reconstructions in Miocene paleosols of the Alpine foreland basins. Knowledge of low-elevation (near sea level) temperature conditions allows to refine low-elevation, near sea level estimates for δ¹⁸O in precipitation. Contrasting these low-elevation isotope in precipitation values with age equivalent records from high elevation counterparts hence permits calculation of surface elevation differences between the foreland basin and the orogen interior. With a spatio-temporally enhanced coverage of the European Alps, we present a long-term terrestrial climate record covering the time interval between ca. 23 and 14 Ma including sites in the Western and Central Alps. Pedogenic carbonate nodules from paleosols of the Digne-Valensole basin (Western Alps, France) indicate relatively warm and stable temperatures (ca. 26°C) for the early Miocene (23-20 Ma) followed by enhanced temperature variability with maximum values of 34°C at ca. 16.5 Ma. By contrasting temperature-corrected foreland basin pedogenic carbonate δ¹⁸O values from the Digne-Valensole Basin with δD values of dated, clay-bearing fault gouge from the Periadriatic Fault in Val Morobbia (Switzerland), we conclude that the stable isotope paleoaltimetry data permit peak elevations of 4-5 km in the Central Alps during the earliest Miocene (ca. 23 Ma).

References

Krsnik et al., 2021: SED, doi: 10.5194/se-2021-59

Zwingmann & Mancktelow, 2004: EPSL, doi: 10.1016/j.epsl.2004.04.041

How to cite: Ballian, A., Meijers, M. J. M., Cojan, I., Huyghe, D., Fiebig, J., and Mulch, A.: Early-Miocene stable isotope paleoaltimetry estimates for the Central Alps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2346, https://doi.org/10.5194/egusphere-egu22-2346, 2022.

Spatial compilations of stable isotopes may be used to disentangle the competing effects of mountain uplift and paleoclimate change. Because both changes in paleoelevation and changes in paleoclimate result in fluctuations in the δ¹⁸O recorded in authigenic materials, large-scale spatial compilations of oxygen isotope data are required to discern the main driver of isotopic change in the past. Spatially limited studies may lack sufficient geographic range to robustly attribute isotopic shifts to either climate or tectonics. To elucidate potential hydroclimate changes or orographic changes across Eurasia in the Cenozoic, we compile previously published analyses of oxygen isotopes, recorded in authigenic materials such as paleosol, lacustrine, and speleothem carbonates, and mammal tooth enamel, to generate a dataset of over 14,500 δ¹⁸O datapoints spanning Cenozoic Eurasia. Compiled Quaternary δ¹⁸O data across Europe indicate that different proxy materials reliably record the same or similar local meteoric water signatures, signifying the validity of a multi-proxy approach. Across the continent, these Quaternary data capture the decrease in δ¹⁸O with increasing longitude that is observed in modern waters, indicating that the same proxies can be applied to reconstruct meteoric δ¹⁸O during the Cenozoic. Preliminary results from pre-Quaternary Cenozoic proxy data show that the longitudinal δ¹⁸O gradient is not markedly reduced or steepened relative to the modern, even during globally warmer periods such as the Miocene. This result suggests that westerly moisture transport across Eurasia during the Cenozoic resembled modern-day moisture transport processes, despite large changes in atmospheric CO₂ and paleogeography. Although this first-order isotopic trend appears throughout the Cenozoic record, many sites—particularly those nearer to the Paratethys—have elevated estimated paleo-precipitation δ¹⁸O relative to modern. Disparities between the Cenozoic record and modern data may reflect elevation changes due to multiple small orogens that developed during the Cenozoic along the Tethyan margin, changes in moisture sources as the Paratethys shrank, differences in the seasonality of authigenic mineral formation, and changes in atmospheric CO₂ that affect moisture transport. Nevertheless, given the constancy of the overall decrease in δ¹⁸O with increasing longitude, we find that tectonics and paleogeographic changes appear to be a secondary control on continental-scale moisture transport, as there are large changes in paleogeography and orography in the Cenozoic that are not substantially reflected in large-scale spatial patterns of δ¹⁸O. These paleogeographic changes appear to have local impacts, but do not drive continental-scale changes in δ¹⁸O. Consequently, we attribute first-order changes in δ¹⁸O gradients to climatic effects rather than changes in paleogeography or topography.

How to cite: Driscoll, E. and Rugenstein, J.: Oxygen Isotopes as Indicators of Climate Change or Tectonics in Eurasia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1937, https://doi.org/10.5194/egusphere-egu22-1937, 2022.

We present results of apatite fission-track (AFT) and other geochronological data (apatite U-Pb (LA-MC-ICPMS) and Rb-Sr dating) from several intrusions located within the Siberian Traps Large Igneous Province: (1) alkaline-ultramafic ring plutons of Odikhincha, Yessey and Magan, (2) intrusions of Norilsk-1 and Kontay, (3) Padunsky sill and (4) Kotuy dike. The studied intrusions were emplaced close to the age of the voluminous phase of the Siberian Traps LIP based on the new apatite U-Pb and Rb-Sr ages, as well as other results obtained earlier by other researchers. The obtained AFT ages are distributed between ca. 207 and ca. 173 Ma, and are much younger than the available latest Permian to earliest Triassic U-Pb and Ar/Ar data on the Siberian Traps. We interpret the AFT ages as a consequence of sedimentary burial of the studied magmatic complexes to below the closure temperature of the AFT system, which took place after the formation of intrusions ca. 252-250 Ma. Later cooling as a result of exhumation of the studied rocks to near surface temperatures and decreasing of thermal flow then took place in the Late Triassic-Early Jurassic.

How to cite: Bagdasaryan, T., Latyshev, A., Thomson, S., and Veselovskiy, R.: New insights from low-temperature thermochronology into the tectonic-thermal evolution of the Siberian Traps Large Igneous Province, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10416, https://doi.org/10.5194/egusphere-egu22-10416, 2022.

The Late Cenozoic growth of the Himalaya is mainly thought to be a result of basal accretion due to duplexing at the subsurface. However, over geological time, the complex nature of the response of Himalayan topography and erosion rates to the basal accretion along the Main Himalayan Thrust (MHT) fault remains ambiguous. Mandal et al. 2021 hypothesized that the punctuated basal accretion along the MHT brings the landscape out of equilibrium and results in periodic temporal variations in erosion rates. We seek to build on this idea by exploring the growth of the topography and resulting erosion rates due to long-term basal accretion processes along the MHT.  To simulate the changes in topography and consequent variation in precipitation pattern, we are linking an orographic precipitation model (Hergarten & Robl, 2021) to the landscape evolution model used in Mandal et al. 2021. We introduce a migrating zone of high uplift (HUZ) in the model landscape, where the uplift rates are ~5 times greater than the background uplift rate. The orographic precipitation model works by controlling the influx of water in the cells of the model space and subsequently distributing the water volume based on the changes in topography due to overall surface uplift patterns. We calculate the spatially-averaged erosion rates, integrated over the time step length, by considering the uplift rate and the elevation difference between the previous time step and the current, updated elevation grid. In Mandal et al. 2021, feedbacks among the basal accretion-driven rock uplift, river steepening, and erosion rate were observed with the upstream migration of knickpoints and the migration of the ramp over time. With the introduction of the orographic precipitation model, we aim to understand the coupling between duplex-induced growth of the topography and rainfall variation and consequent temporal variability in erosion rates. 

How to cite: Das, S., Scherler, D., and Mandal, S. K.: Quantifying the basal accretion-induced erosion rate variability – A numerical landscape evolution modeling approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12135, https://doi.org/10.5194/egusphere-egu22-12135, 2022.