Biogeosciences 

Due to a transitional zone between marine and terrestrial systems, coastal wetlands and seashores are dynamic and highly vulnerable ecosystems. The multi-scale and cross-scale spatio-temporal dynamicity of such systems in terms of various biophysical fluxes is currently poorly understood. A multi-sensor approach, including various active and passive remote-sensing and in situ sensor installations, can help in continuous monitoring and gaining a better understanding of these coastal ecosystems. A multi-sensor approach can account for long-term and cross-scale trends of the biophysical fluxes and their dynamics, providing a better understanding of how biotic and abiotic factors can influence such changes.

In this special issue, we encourage submissions that present innovative ways to implement multi-sensor approaches to monitor coastal wetlands and seashores, with particular interest in applications that integrate in situ with proximal and/or remote-sensing methods. Contributions including new modelling approaches for multi- and cross-scale data integration are also highly encouraged.

This special issue investigates the fascinating interactions between the geosphere and biosphere that are active near the Earth’s surface and within the critical zone. The special issue focuses on modelling and observational studies conducted along the extreme climate and ecological gradient of the Chilean Coastal Cordillera. We welcome submissions that address the physical or chemical processes whereby micro-organisms, animals, and plants influence the shape and development of the Earth’s surface over timescales ranging from the present day to the distant geologic past. As this topic is highly interdisciplinary in scope, we encourage submissions from diverse disciplines including geology, geography, geochemistry, surface geophysics, ecology, microbiology, soil sciences, hydrogeology, geomorphology, and climatology. Integrative studies that bridge between disciplines are particularly welcome. Two types of manuscript submissions are possible. These include either original and/or new scientific full-length research articles presenting new data and interpretations or review and synthesis papers that are invited by the editors and integrate data from different studies and disciplines to address state-of-the-science questions related to Earth surface shaping by biota.

Oxygen (O₂) is considered an effective indicator of ocean health and climate change. Its level, distribution and variability from sub-seasonal to multidecadal scales provide relevant information on the physical and biogeochemical functioning of the ocean and often act to constrain life in the ocean.

Current evidence indicates that the coastal (i.e., most directly influenced by land) and open-ocean areas have been losing O₂ since the middle of the last century, with consequences for living organisms and biogeochemical cycles that are not yet fully understood. In the open ocean the O₂ inventory has decreased by a few percent (i.e., 0.5–3%), and oxygen minimum zones (OMZs) are expanding, which is primarily attributed to global warming, although a quantitative understanding is still lacking. The number of hypoxic coastal sites has increased, predominantly in response to worldwide eutrophication, yet trends in deoxygenation in the global coastal zone remain ill-defined.

The development and extension of low-O₂ concentration areas degrade the living conditions and contract the metabolically viable habitat for a large number of pelagic, mesopelagic, and benthic organisms. The effects on individuals exposed to low O₂ can result in altered foodweb structures.

Deoxygenation affects many aspects of the ecosystem services provided by the ocean and coastal waters. For example, deoxygenation effects on fisheries include low oxygen affecting populations through reduced recruitment and population abundance and also through altered spatial distributions of the harvested species causing changes in fishing activity. This can lead to changes in the profitability of the fisheries and can affect the interpretation of the monitoring data, leading to misinformed management advice.

Model simulations for this century project a decrease in oxygen under both high- and low-CO₂ emission scenarios, while the projections of the coastal ocean at the land–ocean interface indicate that eutrophication will likely continue in many regions of the world. Warming is expected to further amplify deoxygenation in coastal areas influenced by eutrophication by strengthening and extending stratification.

This special issue will investigate new developments and insights related to low-oxygen environments and deoxygenation in open and coastal waters.

This special issue brings together a collection of articles on ecosystem manipulation experiments, which have the potential to inform mechanistic ecosystem models on the effects of global changes. Terrestrial ecosystem dynamics and the interplay of multiple biogeochemical cycles are responsible for unresolved uncertainties in Earth system change projections. The advancement of ecosystem experiments and mechanistic modelling has great potential for addressing this research challenge. However, finding answers requires diverse theoretical and empirical research to be integrated. Ecosystem manipulation experiments allow for empirical testing of theoretical hypotheses, model predictions, and their assumptions. However, results from manipulation experiments can only contribute to advance our ability to improve ecosystem–climate feedback if these are informed by and integrated into mechanistic models.

The scope of this special issue is centred around terrestrial ecosystem experiments. Papers contain an explicit theoretical component for evaluating results or generating hypotheses, address identified open challenges in modelling ecosystem responses to various experimental treatments, or are centred around a model–data synthesis, using results from ecosystem manipulation experiments. Manipulation experiments is to be understood in a broad sense, including (but not restricted to) nutrient, CO₂, and/or water manipulation; isotope labelling studies; and natural perturbations, ranging from ecosystem to planetary scale.

Climate change is exposing terrestrial ecosystems to warmer temperatures, increased CO₂ levels, and more frequent and intense drought and rainfall events. How different ecosystems respond to changing climatic conditions depends on a multitude of biological and geochemical processes which interact at different temporal and spatial scales.

On the one hand, plants assimilate carbon from the atmosphere and control carbon inputs into soil via plant detritus and rhizodeposition. On the other hand, soil fauna and microorganisms govern the decomposition of plant detritus and soil organic matter, which determines the cycling of carbon and of the nutrients necessary for plant growth. These interactions are further shaped by local environmental properties, such as vegetation type, relief, soil mineralogy, and physical structure, as well as the composition of plants and soil biota. Since soils represent the largest stock of organic carbon in terrestrial ecosystems and regulate carbon fluxes for about 10 times the current anthropogenic emissions, changes in the above-mentioned processes can have strong implications for global carbon cycling. Furthermore, the understanding of soil functioning is critical for improving predictions on the resistance and resilience of terrestrial ecosystems to climate change.

In this special issue, we seek to highlight research on biotic and abiotic interactions underlying terrestrial biogeochemical responses to climate, with a specific emphasis on elevated atmospheric CO₂, warming, drought, and drying–rewetting events. We invite contributions covering field and laboratory experiments, conceptual development, and modelling studies.