Abstracted/indexed

Water-soluble salt and nutrient concentrations of soils collected along the Shackleton Glacier, Antarctica show distinct geochemical gradients related to latitude, longitude, elevation, soil moisture, and distance from coast and glacier. Machine learning algorithms were used to estimate geochemical gradients for the region given the relationship with geography. Geography and surface exposure age drive salt and nutrient abundances, influencing invertebrate habitat suitability and biogeography.

Freshwater reservoirs emit greenhouse gases (CO₂ and CH₄) to the atmosphere, however, the sources underlying these emissions are numerous and their magnitude is not well known. This study quantifies surface CO₂ and CH₄ emissions and all their potential sources in a tropical reservoir. Findings show that emissions are mostly influenced by internal metabolic processes rather than external inputs. However, results highlight the challenges and uncertainties related to estimating internal metabolism.

We investigated the role that OM quality plays in the stability of the OM-Fe association in freshwater sediments. It was found that non-humic components enhance OM-Fe stability, while humic components enhance the reductive dissolution of OM-Fe. This information is useful for predicting the fate of OM-Fe in freshwater systems with discrete sources of OM. Stable OM-Fe complexes improve aqueous environments by reducing the release of greenhouse gases, heavy metals and excess nutrients, such as P.

This study documents and quantifies a significant recent oxygen decline in the upper layers of the Arabian Sea and explores its drivers. Using a modeling approach we show that the fast local warming of sea surface is the main factor causing this oxygen drop. Concomitant summer monsoon intensification contributes to this trend, although to a lesser extent. These changes exacerbate oxygen depletion in the subsurface, threatening marine habitats and altering the local biogeochemistry.

Bioavailable Fe is necessary component for phytoplankton to survive and will play a crucial role in reducing the carbon dioxide in the atmosphere. The Fe increase the primary productivity of ocean which is rare in the isolated region of the ocean. Here, the role of extraterrestrial dust become significant as smoke from the ablation and etching also contribute Fe to this organism which in turn reduces the adverse effect on the climate by acting as sink of carbon dioxide.

We studied forest floor methane exchange over an area of ten hectares in a boreal pine forest. The results demonstrate high spatial variability in soil moisture and consequently in the methane flux. We detected wet patches emitting high amounts of methane in the early summer, however, these patches turned to methane uptake in the autumn. We concluded that the small-scale spatial variability of the boreal forest methane flux highlights the importance of soil chamber placement in similar studies.

The Barents Sea is a rapidly changing, shallow sea within the Arctic. Here, we found that over the growing season, nitrate, an essential nutrient, is fully consumed and likely to be the main limiting nutrient to algae. We found no evidence for nitrogen loss in the Barents Sea sediments, which may be because this region is dominated by energetic ocean currents. We suggest that future nutrient availability in the Barents Sea will depend on the source waters supplied from the Atlantic.

Grasslands in North America provide multiple ecosystem services and drive production for the majority of grain, beef, and other staples. We evaluated a grassland productivity model using nearly 500 years of grassland camera data and found the areas where the model worked well, and locations where it did not. Long-term grassland forecasts for the suitable locations can be made immediately with the current model, while other areas, such as the Southwest, will need further model development.

Solar-induced chlorophyll fluorescence (SIF) has the potential to facilitate the monitoring of photosynthesis from space. This study presents a systematic analysis of the physical and physiological meaning of the relationship between fluorescence and photosynthesis at both leaf and canopy levels. We unravel the individual effects of incoming light, vegetation structure and leaf physiology and highlights their joint effects on the relationship between canopy fluorescence and photosynthesis.

Global climate models are the scientist's tools used in studying past, present, and future climate conditions. This work examines the ability of a group of our tools in reproducing and capturing the right timing and length of the season when plants show their green leaves. This season, indeed, is fundamental for CO₂ exchanges between land and atmosphere, and climate. This work shows that discrepancies compared to observations remain demanding further polishing of these tools.

Diatoms are crucial for Arctic coastal spring blooms and their growth iscontrolled by nutrients and light. At the end of the bloom inorganic nitrogen or silicon can limit be limiting, but nitrogen can be regenerated by bacteria, extending the growth phase. Modelling these multi-nutrient dynamics and the role of bacteria is challenging, yet crucial for accurate modelling. We recreated spring bloom dynamics in a cultivation experiment and developed a representative dynamic model.

In a multi-year field study alpine grassland growth increased with 1.3 °C warming. Even at the maximum warming of 2.4 °C the yield was larger than at the reference site. At the same time −1.7 °C cooling did not reduce growth. Thus, alpine grassland growth has likely not increased during the past century, but, despite growing soil moisture deficits, will do so with continued warming in the near future. Ecosystem services (eg. fodder production, erosion control) will benefit from moderate warming.

This paper addresses the phenology of the Deep Chlorophyll Maximum (DCM) in the Black Sea (BS). Our results show that the DCM is initiated in March at a density level corresponding to the depth of the maximum mixing of the water column in winter. It remains attached to this layer until the end of September before it starts to be eroded in October. The DCM seems to be a self-sustaining structure rather than being shaped by external factors and is important for further ecosystem studies in the BS.

The concentration of carbon dioxide (CO₂) in water samples is often measured using a gas chromatograph. Depending on the chemical composition of the water this method can produce wrong results. We quantified the possible error and how it depends on water composition and the analytical procedure. We propose a method to correct wrong results by additionally analysing alkalinity in the samples. We provide an easily usable computer code to perform the correction calculations.

This is the first experimental setup combining a complex set of methods (microbial inhibitors and isotopic approaches) to differentiate between N2O produced by fungi or bacteria during denitrification in three soils. Inhibitors confirmed the expected effect on N2O production only in one out of four experiments, but coincided with isotopic approaches in showing dominance of bacterial denitrification. We present a discussion on artefacts occurring with microbial inhibition to determine N2O fluxes.

The oceans sequester more than 1/4 of the anthropogenic CO₂, mainly through the sinking of organic particles (POM) to the seafloor. POM samples are collected on filter; the filtrate is expected to contain only dissolved organic material, but we found unexpectedly high POM when the filtrate was refiltered. We interpret this POM as gels that were formed in the filtrate by hydraulic stress during the filtration. In deep water samples the POM collected can be less than the POM in the filtrate.

The unique observations by a biogeochemical-Argo float in Northwest Pacific Ocean captured the impact of a super typhoon on upper ocean physical and biological processes. Our result reveals typhoon can increase the surface chlorophyll through strong vertical mixing without bringing nutrients upward from the depth. The vertical re-distribution of chlorophyll contributes little to enhance the primary production which is contradictory to many of former satellite-based studies related to this topic.

In Southeast Asia, oil palm plantations have largely replaced tropical forests. The impact of this shift in land-use on greenhouse gas fluxes and soil microbial communities remains uncertain. We have found emission rates of the potent greenhouse gas nitrous oxide on mineral soil to be higher from oil palm plantations than logged forest over a 2-year study and concluded that emissions have increased over the last 42 years in Sabah, with the proportion of emissions from plantations increasing.

The Atlantic north of 50° N is an intense ocean sink area for atmospheric CO₂. Observations in the vicinity of Iceland reveal a previously unrecognized Arctic contribution to the North Atlantic CO₂ sink. Sustained CO₂ influx to waters flowing from the Arctic Ocean is linked to their excess alkalinity derived from sources in the changing Arctic. The results relate to the question: Will the North Atlantic continue to absorb CO₂ in the future as it has in the past?

Forest fires have a significant impact on carbon dioxide emissions. The present study from pine forest in Portugal is one of the few where measurements of CO₂ fluxes were started immediately (one and a half months) after the forest fire. Carbon dioxide emissions were linked to soil humidiy. Therefore, they started after the beginning of the rainfall in autumn. Due to the beginning of vegetation, the site was already a carbon dioxide sink the following year.

Understanding controls on the persistence of organic matter in soils is essential to constrain its role in the carbon cycle. Emerging concepts suggest that the soil carbon pool is predominantly comprised of stabilized microbial residues. To test this hypothesis we isolated microbial membrane lipids from two Swiss soil profiles and measured their radiocarbon age. We find that the ages of these compounds are in the range of millenia and thus provide evidence for stabilized microbial mass in soils.

Mercury (Hg) uptake by trees from the air is an important mechanism for the distribution of Hg in the environment. However, on the scale of a whole forest the amount of net Hg uptake is rarely measured which motivated us to our study. We determined Hg uptake fluxes by leaves and needles at 10 European forests and found that these Hg uptake fluxes are indeed large relative to other fluxes. The amount of Hg uptake by leaves and needles depended on their age and growing height on the tree.

Few studies investigated interactions of ocean acidification and seasonal changes in temperature and daylength on marine diatoms. We cultured a marine diatom under two CO₂ levels and three combinations of temperature and daylength, simulating different seasons, to investigate combined effects of these factors. Results showed acidification had contrasting effects under different combinations, indicating that future ocean may show differential effects on diatoms in different cluster of factors.

Monitoring leaf phenology (i.e., seasonality) allows for tracking the progression of climate change and seasonal variations in a variety of organismal and ecosystem processes. Recent versions of the Geostationary Operational Environmental Satellites allow for the monitoring of a phenological-sensitive index at a high temporal frequency (5–10 minutes) throughout most of the western hemisphere. Here we show the high potential of this new data to measure the phenology of deciduous forests.

The El Niño‐Southern Oscillation (ENSO) describes changes in the sea surface temperature patterns of the Pacific Ocean. This influences the global weather, impacting vegetation on land. There are two types of El Niño: Central–Pacific (CP) and Eastern–Pacific (EP). In this study, we explored the long-term impacts on the carbon balance on land linked to the two El Niño types. Using a dynamic vegetation model, we simulated what would happen if only either CP or EP El Niño events had occurred.

Rivers are being polluted by human activities, especially in urban areas. We studied the greenhouse gas (GHG) emissions from an urban river system. The results showed a clear trend between water quality and GHG emissions in which the more polluted the sites were, the higher were their emissions. When river water quality worsened, its contribution to global warming can go up by 10 times. Urban rivers emitted 4-times more than of the amount of GHGs compared to rivers in natural sites.