Cyclic and linear trajectories of ecosystem evolution on sand dunes in Siberian taiga: A comprehensive analysis.

Extensive unforested sandy areas on the margins of floodplains and riverbeds, formed by dunes, barchans, and accumulation berms, are a ubiquitous feature across northern Eurasia and Alaska. These dynamic landscapes, which bear witness to the complex Holocene and modern climatic fluctuations, provide a unique opportunity to study ecosystem evolution. Within this heterogeneous assemblage, active dunes, characterized by their very sparse plant communities, contrast sharply with the surrounding taiga (boreal) forests common for the stabilized dunes. This juxtaposition makes these regions to natural laboratories to study vegetation succession and soil development. Through a comprehensive analysis of climate, geomorphology, vegetation, soil properties, and microbiome composition, we elucidate the intricacies of cyclic and linear ecosystem evolution within a representative sandy area located along the lower Nadym River in Siberia, approximately 100 km south of the Arctic Circle. The shift in the Holocene wind regime and the slow development of vegetation under harsh climatic conditions promoted cyclical ecosystem dynamics that precluded the attainment of a steady state. This cyclical trajectory is exemplified by Arenosols, characterized by extremely sparse vegetation and undifferentiated horizons. Conversely, accelerated vegetation growth within wind-protected enclaves on marginally stabilized soils facilitated sand stabilization and subsequent pedogenesis towards Podzols. Based on soil acidification due to litter input (mainly needles, lichens, and mosses) and the succession of microbial communities, we investigated constraints on carbon and nutrient availability during the initial stages of pedogenesis. In summary, the comprehensive study of initial ecosystem development on sand dunes within taiga forests has facilitated the elucidation of both common phases and spatiotemporal dynamics of vegetation and soil succession. This analysis has further clarified the existence of both cyclic and linear trajectories within the successional processes of ecosystem evolution.

Division and retention of floating plastic at river bifurcations.

The transport of floating macroplastics (>2.5 cm) can be impacted by variations in hydrometeorological forcing. Several studies have demonstrated that river discharge, wind, and tides can either accelerate or impede the downstream travel path of plastic. However, there remains a substantial gap in our understanding of the impact of river geomorphological complexity on this process. In this context, the role that river bifurcations play in driving plastic dynamics under different hydrometeorological conditions is largely unexplored. Here, we show that specific plastic item categories react differently to the transport drivers, and bifurcation areas can function both as a retention and release site of plastic litter. We found that hard polyolefin appears to be the most responsive plastic to changes in flow discharge (ρ≈0.40, p≈0.01). Absolute wind velocity magnitude does not correlate to plastic transport. We explored correlations of the various plastic items types with wind vector components in all directions. Multilayer plastics correlated highest to the wind vector component that is most effective in driving plastics from an urban area to the river (ρ≈0.57, p≈0.0001). On a monthly scale, the bifurcation area retained up to 50% of the incoming upstream plastic flux. At other times, an additional 30% was released in the same area. Our results demonstrate how bifurcations distribute different plastic items types downstream under varied hydrometeorological conditions. These yields underscore the importance of assessing floating plastic transport in specific plastic item categories and taking river geomorphological complexity into account.

Permafrost extent sets drainage density in the Arctic.

Amplified warming of high latitudes and rapid thaw of frozen ground threaten permafrost carbon stocks. The presence of permafrost modulates water infiltration and flow, as well as sediment transport, on soil-mantled slopes, influencing the balance of advective fluvial processes to diffusive processes on hillslopes in ways that are different from temperate settings. These processes that shape permafrost landscapes also impact the carbon stored on soil-mantled hillslopes via temperature, saturation, and slope stability such that carbon stocks and landscape morphometry should be closely linked. We studied [Formula: see text]69,000 headwater basins between 25° and 90 °N to determine whether the thermal state of the soil sets the balance between hillslope (diffusive) and fluvial (advective) erosion processes, as evidenced by the density of the channel networks (i.e., drainage density) and the proportion of convex to concave topography (hillslopes and river valleys, respectively). Watersheds within permafrost regions have lower drainage densities than regions without permafrost, regardless of watershed glacial history, mean annual precipitation, and relief. We find evidence that advective fluvial processes are inhibited in permafrost landscapes compared to their temperate counterparts. Frozen soils likely inhibit channel development, and we predict that climate warming will lower incision thresholds to promote growth of the channel network in permafrost landscapes. By demonstrating how the balance of advective versus diffusive processes might shift with future warming, we gain insight into the mechanisms that shift these landscapes from sequestering to exporting carbon.

A submerged Stone Age hunting architecture from the Western Baltic Sea.

The Baltic Sea basins, some of which only submerged in the mid-Holocene, preserve Stone Age structures that did not survive on land. Yet, the discovery of these features is challenging and requires cross-disciplinary approaches between archeology and marine geosciences. Here, we combine shipborne and autonomousunderwater vehicle hydroacoustic data with up to a centimeter range resolution, sedimentological samples, and optical images to explore a Stone Age megastructure located in 21 m water depth in the Bay of Mecklenburg, Germany. The structure is made of 1,673 individual stones which are usually less than 1 m in height, placed side by side over a distance of 971 m in a way that argues against a natural origin by glacial transport or ice push ridges. Running adjacent to the sunken shoreline of a paleolake (or bog), whose youngest phase was dated to 9,143 ±36 ka B.P., the stonewall was likely used for hunting the Eurasian reindeer (Rangifer tarandus) during the Younger Dryas or early Pre-Boreal. It was built by hunter-gatherer groups that roamed the region after the retreat of the Weichselian Ice Sheet. Comparable Stone Age megastructures have become known worldwide in recent times but are almost unknown in Europe. The site represents one of the oldest documented man-made hunting structures on Earth, and ranges among the largest known Stone Age structure in Europe. It will become important for understanding subsistence strategies, mobility patterns, and inspire discussions concerning the territorial development in the Western Baltic Sea region.

Geodiversity in the Amazon drainage basin.

The Amazon is the largest drainage basin on Earth and contains a wide variety of abiotic landscape features. In spite of this, the geodiversity in this basin has not yet been objectively evaluated. We address this knowledge gap by combining a meta-analysis of an existing global geodiversity map and its components with a systematic literature review, to identify the key characteristics of geodiversity in the Amazon drainage basin (ADB). We also evaluate how these global geodiversity component maps, that are based on the geology, geomorphology, soils and hydrology, could be refined to better reflect geodiversity in the basin. Our review shows that geology-through lithological diversity and geological structures-and hydrology-through hydrological processes that influence geomorphology and soil diversity-are the main determinants of geodiversity. Based on these features, the ADB can be subdivided into three principal regions: (i) the Andean orogenic belt and western Amazon, (ii) the cratons and eastern Amazon, and (iii) the Solimões-Amazon river system. Additional methods to map geomorphological and hydrological diversity have been identified. Future research should focus on investigating the relationship between the geodiversity components and assess their relationship with biodiversity. Such knowledge can enhance conservation plans for the ADB. This article is part of the Theo Murphy meeting issue 'Geodiversity for science and society'.

Tidal channel meanders serve as stepping-stones to facilitate cordgrass landward spread by creating invasion windows.

Understanding the mechanisms by which the geomorphic structures affect habitat invasibility by mediating various abiotic and biotic factors is essential for predicting whether these geomorphic structures may provide spatial windows of opportunity to facilitate range-expansion of invasive species in salt marshes. Many studies have linked geomorphic landscape features such as tidal channels to invasion by exotic plants, but the role of tidal channel meanders (i.e., convex and concave sides) in regulating the Spartina alterniflora invasion remains unclear. Here, we examined the combined effects of tidal channel meander-mediated hydrodynamic variables, soil abiotic stresses, and propagule pressure on the colonization of Spartina in the Yellow River Delta, China, by conducting field observations and experiments. The results showed that lower hydrodynamic disturbance, bed shear stress, and higher propagule pressure triggered by eddies due to the convex structure of channel meanders facilitated Spartina seedling establishment and growth, whereas the concave side considerably inhibited the Spartina invasion. Lower soil abiotic stresses also significantly promoted the invasibility of the channel meanders by Spartina. Based on these findings, we propose a conceptual framework to illustrate the effects of the meandering geomorphology of tidal channels on the mechanisms that might allow the landward spread of Spartina and related processes. Our results demonstrate that the meandering geomorphic structures of tidal channels could act as stepping-stones to significantly facilitate the landward invasion of Spartina along tidal channels. This implies that geomorphic characteristics of tidal channels should be integrated into invasive species control and salt marsh management strategies.

A case for stronger integration of physical landscape processes in conservation science and practice.

I argue that the dynamic nature of contemporary, landscape-shaping (geomorphic) processes deserves more consideration in conservation science and practice. In an analysis of a sample of fundamental terms related to geomorphology and area-based conservation in the Web of Science, I found that the terms co-occurred in <2% of the analyzed entries (titles, abstracts, and keywords) from 2000 to 2020. This result is indicative of the rather peripheral attention that, more broadly, landscape-shaping processes seem to receive in the conservation literature. Among conservation scientists and practitioners, landforms that define the physical structure of habitat are often perceived as largely static, whereas the consideration of their dynamic adjustments to geomorphic processes is often limited to extreme events. I use examples derived from river-floodplain environments to illustrate strong, multifaceted, and reciprocal interactions between biota and various erosional and depositional processes. These ubiquitous interdependencies clearly demonstrate that geomorphic processes are an integral part of ecosystem dynamics at time scales relevant for conservation. Crucially, erosional and depositional processes modulate many environmental impacts of past and current anthropogenic activities. I conclude that the absence of a more explicit and widespread consideration of geomorphic processes in conservation science and practice is surprising and detrimental to their effectiveness. I call for bolstered efforts among the conservation and geoscience communities to better integrate landscape dynamics within the field of conservation. The rise of the ecosystem-based and social-ecological systems approaches to conservation and the growth of interdisciplinary geoscience branches (e.g., biogeomorphology, ecohydraulics, and geoconservation) will facilitate such an integration.

Un caso para una mayor integración de los procesos paisajísticos físicos en las ciencias y prácticas de la conservación Resumen En este artículo sostengo que la naturaleza dinámica de los procesos paisajísticos (geomórficos) contemporáneos merecen ser mejor considerados en las ciencias y práctica de la conservación. Con el análisis de una muestra de términos fundamentales de Web of Science relacionados con la geomorfología y la conservación basada en el área, encontré que los términos tuvieron una coocurrencia en <2% de las entradas analizadas (títulos, resúmenes y palabras clave) entre el 2000 y 2020. Este resultado indica que hay una atención relativamente periférica que, en términos más generales, parece que reciben los procesos paisajísticos dentro de la literatura de la conservación. Los científicos y practicantes de la conservación con frecuencia perciben el relieve que define la estructura física del hábitat como estático, mientras que la consideración de sus ajustes dinámicos a los procesos geomórficos está casi siempre limitado a eventos extremos. En las llanuras aluviales existen interacciones fuertes, multifacéticas y recíprocas entre la biota y varios procesos de erosión y deposición. Estas interdependencias predominantes demuestran con claridad que los procesos geomórficos son una parte integral de las dinámicas ambientales en escalas de tiempo relevantes para la conservación. Es destacable que los procesos de erosión y deposición modulan muchos impactos ambientales del pasado y actividades antropogénicas actuales. Concluyo que la ausencia de una consideración más explícita y extendida de los procesos geomórficos dentro de las ciencias y práctica de la conservación es sorprendente y nociva para su efectividad. Hago un llamado para fortalecer esfuerzos dentro de las comunidades de conservación y geociencias para integrar de mejor manera las dinámicas del paisaje dentro del campo de conservación. El incremento en las estrategias basadas en ecosistemas y sistemas socio­ecológicos en la conservación y el aumento de ramas interdisciplinarias de las geociencias (p. ej.: biogeomorfología, ecohidráulica y geoconservación) facilitarán dicha integración.

National assessment and variability of blue carbon in seagrass ecosystems in Thailand.

Seagrass ecosystems are important organic carbon (Corg) sinks with great potential to contribute to climate change mitigation strategies. However, the high spatial and temporal variability is a barrier to the accurate assessment of national Corg stocks. This study provides a national assessment of Corg within seagrass meadows, including spatial and temporal variations. The highest Corg stocks were within mangrove-associated (44.3 ± 8.27 Mg ha-1), while near-surface sediments were highest in reef-associated meadows (10.20 ± 3.69 Mg ha-1). Regionally, the highest stocks were in the Upper Andaman coast in monospecific meadows (51.7 ± 7.14 Mg ha-1). Corg stocks in near-surface sediments were significantly different across historical trends (p < 0.001), with the highest stocks in stable meadows (9.28 ± 3.39 Mg ha-1). The national Corg stock within seagrass meadows sediment was 40.45 ± 11.59 Mg C ha-1. The results of this study highlighted the complexity of blue carbon in seagrass meadows and the associated impacts on national Corg assessments, carbon accounting, and conservation strategies.

Emergence of tip singularities in dissolution patterns.

Chemical erosion, one of the two major erosion processes along with mechanical erosion, occurs when a soluble rock-like salt, gypsum, or limestone is dissolved in contact with a water flow. The coupling between the geometry of the rocks, the mass transfer, and the flow leads to the formation of remarkable patterns, like scallop patterns in caves. We emphasize the common presence of very sharp shapes and spikes, despite the diversity of hydrodynamic conditions and the nature of the soluble materials. We explain the generic emergence of such spikes in dissolution processes by a geometrical approach. Singularities at the interface emerge as a consequence of the erosion directed in the normal direction, when the surface displays curvature variations, like those associated with a dissolution pattern. First, we demonstrate the presence of singular structures in natural interfaces shaped by dissolution. Then, we propose simple surface evolution models of increasing complexity demonstrating the emergence of spikes and allowing us to explain at long term by coarsening the formation of cellular structures. Finally, we perform a dissolution pattern experiment driven by solutal convection, and we report the emergence of a cellular pattern following well the model predictions. Although the precise prediction of dissolution shapes necessitates performing a complete hydrodynamic study, we show that the characteristic spikes which are reported ultimately for dissolution shapes are explained generically by geometrical arguments due to the surface evolution. These findings can be applied to other ablation patterns, reported for example in melting ice.

Eco-evolution from deep time to contemporary dynamics: The role of timescales and rate modulators.

Eco-evolutionary dynamics, or eco-evolution for short, are often thought to involve rapid demography (ecology) and equally rapid heritable phenotypic changes (evolution) leading to novel, emergent system behaviours. We argue that this focus on contemporary dynamics is too narrow: Eco-evolution should be extended, first, beyond pure demography to include all environmental dimensions and, second, to include slow eco-evolution which unfolds over thousands or millions of years. This extension allows us to conceptualise biological systems as occupying a two-dimensional time space along axes that capture the speed of ecology and evolution. Using Hutchinson's analogy: Time is the 'theatre' in which ecology and evolution are two interacting 'players'. Eco-evolutionary systems are therefore dynamic: We identify modulators of ecological and evolutionary rates, like temperature or sensitivity to mutation, which can change the speed of ecology and evolution, and hence impact eco-evolution. Environmental change may synchronise the speed of ecology and evolution via these rate modulators, increasing the occurrence of eco-evolution and emergent system behaviours. This represents substantial challenges for prediction, especially in the context of global change. Our perspective attempts to integrate ecology and evolution across disciplines, from gene-regulatory networks to geomorphology and across timescales, from today to deep time.

A comprehensive review on spatial and temporal variation of arsenic contamination in Ghaghara basin and its relation to probable incremental life time cancer risk in the local population.

Spatial and temporal variations have been found in the levels of arsenic (As) throughout the groundwater of the Ghaghara basin. Fifteen out of twenty-five districts in this basin are reported to be affected by As, where the levels of As in groundwater and soil exceed the permissible limits set by the WHO (10 µgl-1) and FAO (20 mgkg-1) respectively. These districts include a total of four municipalities in Nepal and eighty-six blocks in India, all of which have varying degrees of As contamination. Approximately 17 million people are at risk of As poisoning, with more than two orders of magnitude higher potential lifetime incremental cancer risk, constituting over 153 thousand potential additional cases of cancer due to As-contaminated drinking water. Out of the 90 As-contaminated blocks in the Ghaghara basin, 4 blocks have about 7-fold higher potential risk of developing cancer, 49 blocks have 8-37-fold higher risk, and 37 blocks have up to 375-fold higher risk compared to the upper limit of the USEPA acceptable range, which is 1 × 10-6-1 × 10-4. High accumulation of As has been reported in the nails, hair, and urine of local inhabitants, with higher levels observed in females than males. The toxicity of As is manifested in terms of a higher occurrence of various diseases. Reproductive endpoints, such as increased incidences of preterm birth, spontaneous abortion, stillbirth, low-birth weight, and neonatal death, have also been reported in the basin. The level of As in tube wells has been found to be negatively correlated with the depth (r = -0.906), and tube wells with high levels of As (>150 µgl-1) are generally located within close proximity (<10 km) to abandoned or present meander channels in the floodplain areas of the Ghaghara river. In addition to As contamination, the water quality index (WQI) in the Ghaghara basin is poor according to the BIS standards for drinking water. Groundwater in six out of fifteen districts is unsuitable for drinking purposes, with a WQI exceeding 100. The levels of As in agricultural soil in many villages of Ballia, Bahraich, and Lakhimpur Kheri districts have exceeded the FAO limit. Water from deep tube wells has been found to be relatively safe in terms of As content, and thus can be recommended for drinking purposes. However, the use of surface water needs to be encouraged for irrigation purposes in order to preserve soil health and reduce As contamination in the food chain, thereby minimizing the risk of cancer.

Erosional exhumation of carbonate rock facilitates dispersal-mediated allopatric speciation in freshwater fishes.

A fundamental goal of evolutionary biology is to understand the mechanisms that generate and maintain biodiversity. Discovery and delimitation of species represent essential prerequisites for such investigations. We investigate a freshwater fish species complex comprising Etheostoma bellator and the endangered E. chermocki, which is endemic to the Black Warrior River system in Alabama, USA, a global hotspot of temperate freshwater biodiversity. Phylogenomic analyses delimit five geographically disjunct species masquerading as E. bellator. Three of these new species exhibit microendemic distributions comparable to that of E. chermocki raising the possibility that they also require protection. The species of the complex are found in streams flowing over carbonate rock and they are separated by waterways flowing over siliciclastic rock, a geographic pattern dictated by the underlying stratigraphy and structural geology. Over time, rivers have eroded downward through layers of siliciclastic rocks in the basin, gradually exposing underlying carbonate rock, the substrate of suitable habitat today. Our results suggest that episodic dispersal to patches of suitable habitat set the stage for allopatric speciation in the species complex. Our study suggests that the presence of heterogeneous rock can facilitate dispersal-mediated allopatric speciation in freshwater organisms in the absence of external tectonic or climatic perturbations.

Atolls of the world: A reappraisal from an optical remote sensing and global mapping perspective.

The Millennium Coral Reef Mapping Project (MCRMP) aimed to map coral reefs worldwide at geomorphological thematic scales using Landsat satellite images at 30 m spatial resolution. The 5-level hierarchical classification scheme implemented by MCRMP identified at Level 2 'Atolls' as one of the main types of coral reef complexes. In this review, the qualitative criteria used by MCRMP to identify atolls are presented. Then, we report on the global census of atolls, from which a consistent geomorphologic GIS database is provided. A total of 598 atolls are identified and mapped. The quantitative database provides surface areas for all geomorphologic units at Level 4 and 5 of the MCRMP classification scheme. It allows further work on atoll and coral reef classifications, regionally and globally, in order to identify geomorphic trends and outliers. It is also a convenient database to use in multivariate analyses with ancillary biodiversity, fishery, socio-economic or climate data.

Submarine groundwater discharge interacts with creek geomorphology to affect eastern oyster Crassostrea virginica growth rates in a coastal Georgia creek.

Eastern oysters, Crassostrea virginica, are commercially important coastal species that provide many ecosystem services for coastal communities. Unfortunately, 85% of oyster reefs have been lost globally, prompting investments in restoration efforts to rebuild populations. Managers often consider several well-studied environmental and water quality parameters when making restoration site decisions. However, recent research suggests that submarine groundwater discharge (SGD) may play a role in driving the distribution of oysters in some estuaries. Specifically, SGD may result in localized areas of low dissolved oxygen and low pH that could inhibit oyster recruitment and survival. However, SGD may interact with other potential oyster stressors, including creek geomorphology. On point bars, sediment accumulation could alter growth rates of oysters and physiology, and it is possible that the two factors, SGD and creek geomorphology, could interact to impact oyster growth. We conducted a field experiment to examine the effects of SGD and creek geomorphology on oyster growth rates in a marsh-lined tidal creek in Georgia, USA. High and low SGD sites were paired within point bars and cut banks. Oysters were deployed in cages for 72 days and growth rates were determined. We found a significant interaction between SGD and creek geomorphology on oyster growth rates. Oysters grew at significantly faster rates at locations on accretionary point bars regardless of SGD flux, whereas, on erosional cut banks, high SGD flux significantly reduced oyster growth rate relative to low SGD flux. It appears that SGD may negatively influence oyster growth at specific creek locations, likely due to the presence of other stressors. Therefore, it is important to consider potential interacting and confounding stressors when managing oyster populations. As SGD is still a relatively understudied potential stressor for oysters, it is critical to continue to examine how groundwater might influence oysters in other locations and in combination with other stressors. Regardless, this study provides further evidence that SGD should be considered in future management efforts.

Geoforensic search to crime scene: Remote sensing, geophysics, and dogs.

In the absence of surface indications of burial sites, law enforcement or humanitarian organizations are faced with the difficult task of focusing large-scale ground searches to a manageable excavation area. A geoforensic-based survey may exclude parts of the landscape for reasons such as diggability or viewshed analysis but leave areas still too large for invasive exploration. This work examines how drone-based remote sensing, geophysics, and search dogs may be combined to narrow such searches. Here, we ask the reader to consider two examples where forensic geomorphology and land use provided a range of possible burial locations. Following this is a multi-proxy approach to similar dilemma, with a search-to-scene case study using remote sensing (drone photography), geophysics, ground probes, and search dogs. This approach is not presented as a definitive guide, but serves as an example of the conjunctive use of well-studied methods to approach a common problem in geoforensics.

Archaeological sites in Grand Canyon National Park along the Colorado River are eroding owing to six decades of Glen Canyon Dam operations.

The archaeological record documenting human history in deserts is commonly concentrated along rivers in terraces or other landforms built by river sediment deposits. Today that record is at risk in many river valleys owing to human resource and infrastructure development activities, including the construction and operation of dams. We assessed the effects of the operations of Glen Canyon Dam - which, since its closure in 1963, has imposed drastic changes to flow, sediment supply and distribution, and riparian vegetation - on a population of 362 archaeological sites in the Colorado River corridor through Grand Canyon National Park, Arizona, USA. We leverage 50 years of evidence from aerial photographs and more than 30 years of field observations and measurements of archaeological-site topography and wind patterns to evaluate changes in the physical integrity of archaeological sites using two geomorphology-based site classification systems. We find that most archaeological sites are eroding; moreover, most are at increased risk of continuing to erode, due to six decades of operations of Glen Canyon Dam. Results show that the wind-driven (aeolian) supply of river-sourced sand, essential for covering archaeological sites and protecting them from erosion, has decreased for most sites since 1973 owing to effects of long-term dam operations on river sediment supply and riparian vegetation expansion on sandbars. Results show that the proportion of sites affected by erosion from gullies controlled by the local base-level of the Colorado River has increased since 2000. These changes to landscape processes affecting archaeological site integrity limit the ability of the National Park Service and Grand Canyon-affiliated Native American Tribes to achieve environmental management goals to maintain or improve site integrity in situ. We identify three environmental management opportunities that could be used to a greater extent to decrease the risk of erosion and increase the potential for in-situ preservation of archaeological sites. Environmental management opportunities are: 1) sediment-rich controlled river floods to increase the aeolian supply of river-sourced sand, 2) extended periods of low river flow to increase the aeolian supply of river-sourced sand, 3) the removal of riparian vegetation barriers to the aeolian transport of river-sourced sand.

Towards integrated modelling of Watershed-Coast System morphodynamics in a changing climate: A critical review and the path forward.

The term "Watershed-Coast System" refers to the entities consisting of watersheds and the areas adjacent to their outlets, where sediment delivery from rivers and natural streams plays a key role in the evolution of coastal morphology. Climate change implications in these complex systems are projected to extend from morphological to ecological and socio-economic ones, threatening ecosystems, cultural heritage, settlements, infrastructure and human life itself. Accordingly, the design of protection and adaptation measures that will enhance resilience against relevant hazards has emerged as an imperative need in both research and policy. Understanding how watershed and coastal processes are intertwined into a web of dependencies that shape morphology evolution, how climate change would affect watershed/coastal dynamics and how scientists can design effective protection/adaptation measures, can only be achieved on the basis of integrated modelling systems that simulate the morphodynamics of the watershed-coast continuum. Within this context, the present work provides a critical review of the theoretical background and state-of-the-art of research on the modelling of Watershed-Coast System morphodynamics, and through this: (a) presents a scheme for the integrated modelling of Watershed-Coast System morphodynamics in a changing climate and analyses its core aspects, (b) proposes a methodological framework for adapting integrated modelling approaches for management and engineering purposes, (c) identifies and evaluates the major scientific and modelling challenges ahead, and (d) systematises the path towards informed decision-making for building resilient Watershed-Coast Systems by bridging the gaps between science, society and governance. The overall approach is applied as proof-of-concept to a hypothetical case study of a Watershed-Coast System located in the Mediterranean.

Paleo-Geomorphology Determines Spatial Variability of Geogenic Ammonium Concentration in Quaternary Aquifers.

Naturally occurring (i.e., geogenic) ammonium in groundwater has been widely detected globally, but the major controls on its regional distribution have been poorly characterized. Here, we identified the dominant role of paleo-geomorphology driven by paleo-climate in controlling the spatial variability of geogenic ammonium in groundwater using random forest algorithm and revealed the underlying mechanisms based on borehole sediment analysis of data obtained from the Dongting Lake Plain of the central Yangtze River basins in China. In the paleo-channel (PC) area, the aquifer depth-matched sediments were deposited during the last deglaciation when warm climate resulted in rapid filling into incised valleys, and terrestrial organic matter (OM) mainly as lignin experienced less degradation prior to sedimentation and had lower humification, higher N abundance, and nominal oxidation state of carbon (NOSC). In the paleo-interfluve (PI) area, the depth-matched sediments were deposited during the last glaciation, followed by intensive erosion in the surface during the last glacial maximum, and terrestrial OM mainly as lignin had been partly degraded into aliphatics prior to sedimentation and had higher humification, lower N abundance, and NOSC. As a result, under the present anaerobic conditions, less-humic and N-rich OM with more oxidized C tends to be more intensively mineralized into ammonium in the PC area than those in the PI area. These findings highlight the importance of paleo-geomorphology with paleo-climate in controlling the enrichment of geogenic ammonium in groundwater, which has a universal significance for understanding the genesis and distribution of high N loads in the aquatic environment worldwide.

Source-sink dynamics within a complex life history.

Source-sink patch dynamics occur when movement from sources stabilizes sinks by compensating for low local vital rates. The mechanisms underlying source-sink dynamics may be complicated in species that undergo transitions between discrete life stages, particularly when stages have overlapping habitat requirements and similar movement abilities. In these species, for example, the demographic effects of movement by one stage may augment or offset the effects of movement by another stage. We used a stream salamander system to investigate patch dynamics within this form of complex life history. Specifically, we tested the hypothesis that the salamander Gyrinophilus porphyriticus experiences source-sink dynamics in riffles and pools, the dominant geomorphic patch types in headwater streams. We estimated stage-specific survival probabilities in riffles and pools and stage-specific movement probabilities between the two patch types using 8 years of capture-recapture data on 4491 individuals, including premetamorphic larvae and postmetamorphic adults. We then incorporated survival and movement probabilities into a stage-structured, two-patch model to determine the demographic interactions between riffles and pools. Monthly survival probabilities of both stages were higher in pools than in riffles. Larvae were more likely to move from riffles to pools, but adults were more likely to move from pools to riffles, despite experiencing much lower survival in riffles. In simulations, eliminating interpatch movements by both stages indicated that riffles are sinks that rely on immigration from pools for stability. Allowing only larvae to move stabilized both patch types, but allowing only adults to move destabilized pools due to the demographic cost of adult emigration. These results indicated that larval movement not only stabilizes riffles, but also offsets the destabilizing effects of maladaptive adult movement. Similar patch dynamics may emerge in any structured population in which movement and local vital rates differ by age, size, or stage. Addressing these forms of internal demographic structure in patch dynamics analyses will help to refine and advance general understanding of spatial ecology.

ArcGIS-based protocol to calculate the area fraction of landslide for multiple catchments.

The area fraction of specific kinds of information in a catchment provides parameters to be utilized in catchment-scale analyses. For example, the area fraction of soil movement caused by landslides is an indicator for the estimation of the magnitude of landslides. However, catchment-scale analyses often require applying the same processing to higher numbers of study catchments, making it a time-consuming process. Here an ArcGIS-based method has been presented to reduce cumbersome procedures for the calculation of the area fraction of several target surface data. The method applies automated and iterative processing to multiple catchments, whose location and scale are defined by users. This method may prove to be useful for calculating the area fraction of parameters other than landslide area (e.g., specific land use or lithology) within a framework of catchment-scale analysis.•An Arcgis-based method to calculate the area fraction of landslide area in catchments.•Manual work is reduced by automated and iterative processing based on ModelBuilder.•It can be used to get the area fraction of several surface information in catchments.