Coastal wetlands are susceptible to loss in both health and extent via stressors associated with global climate change and anthropogenic disturbance. Peat collapse may represent an additional ...phenomenon contributing to coastal wetland loss in organic-rich soils through rapid vertical elevation decline. However, the term “peat collapse” has been inconsistently used in the literature, leading to ambiguities regarding the mechanisms, timing, and spatial extent of its contribution to coastal wetland loss. For example, it is unclear whether peat collapse is distinct from general subsidence, or what biogeochemical changes or sequence of events may constitute peat collapse. A critical analysis of peer-reviewed literature related to peat collapse was supplemented with fundamental principles of soil physics and biogeochemistry to develop a conceptual framework for coastal wetland peat collapse. We propose that coastal wetland peat collapse is a specific type of shallow subsidence unique to highly organic soils in which a loss of soil strength and structural integrity contributes to a decline in elevation, over the course of a few months to a few years, below the lower limit for emergent plant growth and natural recovery. We further posit that coastal wetland peat collapse is driven by severe stress or death of the vegetation, which compromises the supportive structure roots provide to low-density organic soils and shifts the carbon balance of the ecosystem toward a net source, as mineralization is no longer offset by sequestration. Under these conditions, four mechanisms may contribute to peat collapse: (1) compression of gas-filled pore spaces within the soil during dry-down conditions; (2) deconsolidation of excessively waterlogged peat, followed by transport; (3) compaction of aerenchyma tissue in wetland plant roots, and possibly collapse of root channels; and (4) acceleration of soil mineralization due to the addition of labile carbon (dying roots), oxygen (decreased flooding), nutrients (eutrophication), or sulfate (saltwater intrusion). Scientists and land managers should focus efforts on monitoring vegetation health across the coastal landscape as an indicator for peat collapse vulnerability and move toward codifying the term “peat collapse” in the scientific literature. Once clarified, the contribution of peat collapse to coastal wetland loss can be evaluated.
Bacterial cell-to-cell interactions are in the core of evolutionary and ecological processes in soil and other environments. Under most conditions, natural soils are unsaturated where the fragmented ...aqueous habitats and thin liquid films confine bacterial cells within small volumes and close proximity for prolonged periods. We report effects of a range of hydration conditions on bacterial cell-level interactions that are marked by plasmid transfer between donor and recipient cells within populations of the soil bacterium Pseudomonas putida. Using hydration-controlled sand microcosms, we demonstrate that the frequency of cell-to-cell contacts under prescribed hydration increases with lowering water potential values (i.e., under drier conditions where the aqueous phase shrinks and fragments). These observations were supported using a mechanistic individual-based model for linking macroscopic soil water potential to microscopic distribution of liquid phase and explicit bacterial cell interactions in a simplified porous medium. Model results are in good agreement with observations and inspire confidence in the underlying mechanisms. The study highlights important physical factors that control short-range bacterial cell interactions in soil and on surfaces, specifically, the central role of the aqueous phase in mediating bacterial interactions and conditions that promote genetic information transfer in support of soil microbial diversity.
The system of industrial agriculture (IA), often implemented on a large scale and with high dependence on the supplies use, is reducing the soil organic matter (SOM) and increasing the glyphosate ...presence in the environment. An alternative approach to IA is agroecologywhich takes greater advantage of natural processes and beneficial on-farm interactions in order to reduce off-farm input use and to improve the efficiency of farming systems. In this study, a transition agroecological system (AT) is the alternative of the IA. Our objectives were: (i) to compare the agronomic productivity between AT and IA systems, (ii) to determine the effect of management practices on soil quality indicators such as soil organic matter content (SOM), soil bulk density, change in the weighted mean diameter (CMWD) and glyphosate and aminomethyl phosphonic acid (AMPA) concentration and (iii) to compare the economic results through a multi-temporal economic analysis between AT and IA systems. The soil sampling was carried out per soil-specific zones, delimited from apparent soil electrical conductivity (ECa) and elevation. Samples were taken at 0 to 2, 2 to 5, 5 to 10, 10 to 20, 20 to 30 and 30 to 40 cm of depth to determine the SOM content, the glyphosate concentration and main glyphosate metabolite, AMPA. Besides, the bulk density (δa) and CWMD were determined. The δa was lower in AT with respect to IA, both under no tillage (NT). No significant differences were found for CWMD between AT and IA systems, although a tendency to a lower value in AT system was observed. If we consider the percentage of organic matter as carbon matter per hectare, this means that in 6.5 years increase 540 kg ha−1 at 0 to 40 cm depth. The SOM content increased from 4,9 to 5,6% in AT with respect to IA. The content of glyphosate + AMPA at the first 40 cm was 0.06 kg ha−1 in the AT and 0.84 kg ha−1 in the IA system. In the AT system, the gross margin accumulated during 6.5 years, increased 244% with respect to IA. These results suggest that the AT system proposed could be applicable in extensive productions with temperate climates without interfering with the livelihood of the agricultural producers and it allows an improvement in soil conditions. It is important to carry out further studies in order to confirm the benefits of the AT system in other edaphic-climatic conditions, integrating productive, economic and environmental aspects.
•The gross margin accumulated, increased 244% in the Agroecological Transition system.•Organic matter increase in the surface soil in the Agroecological Transition system.•Glyphosate + AMPA were lower in the Agroecological Transition system soil.
Evaluating conflicting theories about the influence of mountains on carbon dioxide cycling and climate requires understanding weathering fluxes from tectonically uplifting landscapes. The lack of ...soil production and weathering rate measurements in Earth's most rapidly uplifting mountains has made it difficult to determine whether weathering rates increase or decline in response to rapid erosion. Beryllium-10 concentrations in soils from the western Southern Alps, New Zealand, demonstrate that soil is produced from bedrock more rapidly than previously recognized, at rates up to 2.5 millimeters per year. Weathering intensity data further indicate that soil chemical denudation rates increase proportionally with erosion rates. These high weathering rates support the view that mountains play a key role in global-scale chemical weathering and thus have potentially important implications for the global carbon cycle.
Core Ideas
Stock unearthing method assumes that soil surface is planar between vines.Improved stock unearthing method enhances the survey due to extra measurements.Indispensable to consider the ...timing of the measures in relation to tillage events.Stock unearthing method underestimates soil erosion rates by –14.2% in 1‐d plowed vineyards.Stock unearthing method underestimates erosion rates by –37.8% in 86‐d plowed vineyards.
Vineyards have proven to be one of the most degraded agricultural ecosystems due to very high erosion rates, which are typically measured at fine temporal and spatial scales. Long‐term soil erosion measures are rare, but this information may be indispensable for a proper understanding of the vineyard soil system, landscape evolution, and crop production. The stock unearthing method (SUM) is a common topographical measurement technique developed to assess long‐term erosion rates. The reliance of the SUM has been questioned and should be replaced by an improved measurement technique. In this paper, we demonstrate the added value (improved accurate, low cost, and faster than photogrammetrically methods) of the improved stock unearthing method (ISUM). It was shown that large errors may have been made in previous assessments of soil erosion on vineyards, as the old method did not make measurements in the inter‐row area or consider the timing of the erosion assessment in relation to tillage events. We found that this caused the SUM to severely underestimate soil erosion rates by –14.2 and –37.8% in 1‐ and 86‐d tillage vineyards in one location, respectively. Furthermore, the increased measurement resolution attained from the ISUM allowed for the detailed assessment of micro‐topographical change. Soil loss maps were able to detect the locational changes in soil depletion and accumulation, as well as continuous soil movement features in the inter‐row areas. Ultimately, this leads to a more accurate estimate of the actual soil erosion rates in vineyards.
Despite the increasing impact of heavy metal pollution in southern Mexico due to urban growth and agricultural and petroleum activities, few studies have focused on the behavior and relationships of ...these pollutants in the biotic and abiotic components of aquatic environments. Here, we studied the bioaccumulation of heavy metals (Cd, Cr, Ni, Pb, V, Zn) in suspended load, sediment, primary producers, mollusks, crustaceans, and fish, in a deltaic lagoon habitat in the Tabasco coast, with the aim to assess the potential ecological risk in that important wetland. Zn showed the highest concentrations, e.g., in suspended load (mean of 159.58 mg kg−1) and aquatic consumers (15.43–171.71 mg kg−1), particularly Brachyura larvae and ichthyoplankton (112.22–171.71 mg kg−1), followed by omnivore Callinectes sp. crabs (113.81–128.07 mg kg−1). The highest bioconcentration factors (BCF) of Zn were observed for planktivore and omnivore crustaceans (3.06–3.08). Zn showed a pattern of distribution in the food web through two pathways: the pelagic (where the higher concentrations were found), and the benthic (marsh plants, sediment, mollusk, fish). The other heavy metals had lower occurrences in the food web. Nevertheless, high concentrations of Ni and Cr were found in phytoplankton and sediment (37.62–119.97 mg kg−1), and V in epiphytes (68.64 mg kg−1). Ni, Cr, and Cd concentrations in sediments surpassed international and national threshold values, and Cd entailed a “considerable” potential risk. These heavy metals are most likely transferred into the food web up to fishes through the benthic pathway. Most of the collected fishes are residents in this type of habitat and have commercial importance. Our results show that the total potential ecological risk in the area can be considered as “moderate”. Nevertheless, heavy metal values were similar or surpassed the values from other highly industrialized tropical coastal regions.
•Coastal environment of southern Mexico had high levels of heavy metal.•Zn was the most frequent and abundant heavy metal in the environment and biota.•Cr, Pb and Cd concentrations in commercial species exceeded threshold values.•The sedimentary trophic web was the principal via to heavy metal distribution.•The potential ecological risk in San Pedrito Lagoon was classified as moderate.
We studied the behavior of heavy metal pollution (Cd, Cr, Ni, Pb, V, Zn) in a tropical aquatic biotic and abiotic components; our results indicate that main pollutant via is the sedimentary trophic web; ecological risk for Cd was “considerable”, whereas for others 5 metals was classified as “low”.
Although only representing 0.05% of global freshwater, or 0.001% of all global water, soil water supports all terrestrial biological life. Soil moisture behaviour in most models is constrained by ...hydraulic parameters that do not change. Here we argue that biological feedbacks from plants, macro‐fauna and the microbiome influence soil structure, and thus the soil hydraulic parameters and the soil water content signals we observe. Incorporating biological feedbacks into soil hydrological models is therefore important for understanding environmental change and its impacts on ecosystems. We anticipate that environmental change will accelerate and modify soil hydraulic function. Increasingly, we understand the vital role that soil moisture exerts on the carbon cycle and other environmental threats such as heatwaves, droughts and floods, wildfires, regional precipitation patterns, disease regulation and infrastructure stability, in addition to agricultural production. Biological feedbacks may result in changes to soil hydraulic function that could be irreversible, resulting in alternative stable states (ASS) of soil moisture. To explore this, we need models that consider all the major feedbacks between soil properties and soil‐plant‐faunal‐microbial‐atmospheric processes, which is something we currently do not have. Therefore, a new direction is required to incorporate a dynamic description of soil structure and hydraulic property evolution into soil‐plant‐atmosphere, or land surface, models that consider feedbacks from land use and climate drivers of change, so as to better model ecosystem dynamics.
Global environmental changes impact soil hydraulic functions through biophysical feedbacks. Here, we argue that biological feedbacks from plants, macrofauna and the microbiome influence soil structure, and thus the soil hydraulic parameters and the soil water content signals we observe. Incorporating biological feedbacks into soil hydrological models is therefore important for understanding environmental change and its impacts on ecosystems.
Human-induced landscape change is difficult to predict due to the complexity inherent in both geomorphic and social systems as well as due to the coupling relationships between them. To better ...understand system complexity and system response to changing inputs, “connectivity thinking” has become an important recent paradigm within various disciplines including ecology, hydrology and geomorphology. With the presented conceptual connectivity framework on geomorphic change in human-impacted fluvial systems a cautionary note is flagged regarding the need (i) to include and to systematically conceptualise the role of different types of human agency in altering connectivity relationships in geomorphic systems and (ii) to integrate notions of human-environment interactions to connectivity concepts in geomorphology to better explain causes and trajectories of landscape change. Geomorphic response of fluvial systems to human disturbance is shown to be determined by system-specific boundary conditions (incl. system history, related legacy effects and lag times), vegetation dynamics and human-induced functional relationships (i.e. feedback mechanisms) between the different spatial dimensions of connectivity. It is further demonstrated how changes in social systems can trigger a process-response feedback loop between social and geomorphic systems that further governs the trajectory of landscape change in coupled human-geomorphic systems.
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