Clay minerals play an important role in soil organic matter (SOM) accumulation. This study used a series of pot experiments to observe carbon (C) storage in rhizosphere of two plant species Festuca rubra and Lotus corniculatus growing in three soil forming substrates dominated by various clay minerals (kaolinite, illite, and montmorillonite). Plants were either grown in separate pots filled with different substrates or plants were grown in larger pots filled with sand where clay substrates were buried in mesh bags. We tested the hypothesis that mineral associated organic matter (MAOM) storage will increase with increasing surface area of clay minerals (kaolinite < illite < montmorillonite), while the volume of larger pores (Illite > kaolinite and montmorillonite) will promote the storage of particulate organic matter (POM). Overall, the largest C storage was in montmorillonite dominated substrates followed by illite and kaolinite. These trends were the same across both types of clay exposure and for both plant species used. Accumulation of MAOM followed a similar pattern. On the contrary, accumulation of free POM was not affected by clay mineral identity and accumulation of occluded POM was significantly higher in illite compared to the other two minerals. Our results suggest that total surface area of clay minerals is crucial for accumulation of MAOM while occluded POM is more affected by the availability of larger pores.
The temperature sensitivity of soil carbon (C) and nitrogen (N) mineralization commonly expressed as the Q10 coefficient, plays a pivotal role in regulating soil–atmosphere greenhouse gas exchanges in temperate ecosystems. This review synthesizes findings from 181 peer-reviewed studies (1960–2025) to evaluate how soil properties, substrate quality, microbial traits, and land-use history interact to shape Q10 dynamics under climatic warming. Using a structured, thematically coded literature review, we identify mechanistic pathways that govern mineralization responses across major temperate soil orders. Clay-rich soils with high short-range ordered (SRO) minerals consistently exhibit low Q10 values (1.3–2.0) due to mineral protection of soil organic matter (SOM). In contrast, coarse-textured and disturbed soils exhibit elevated thermal sensitivity (> 3.0). Microbial C use efficiency (CUE), enzyme activity, and functional group composition further modulate mineralization responses, especially under seasonal freeze–thaw or rewetting events. Land-use transitions, including tillage, afforestation, and organic amendments, significantly alter Q10 by altering aggregation, SOM accessibility, and microbial community structure. Despite advances, Earth system models often overlook the spatiotemporal heterogeneity of Q10, limiting prediction accuracy. We highlight the need for integrating depth-resolved mineralogical traits, microbial acclimation, and management history into climate–soil feedback frameworks. This synthesis advances a mechanistic foundation for improving biogeochemical models and informing soil-based climate mitigation strategies.
Freshwater ecosystems are major natural sources of methane (CH4) and carbon dioxide (CO2), with large amounts of these gases being produced in sediments. Bioturbators such as Tubifex spp. have been proposed to alter the dynamics of both gases as they inhabit the sediment–water interface, influencing biogeochemical processes. Although eutrophication generally leads to strong shifts in the benthic community, Tubifex spp. tolerate eutrophication. However, their role in modulating greenhouse gas (GHG) emissions requires further elucidation. We used 24 microcosm to assess the presence of Tubifex spp. on diffusive and ebullitive CH4 and CO2 emissions across three eutrophic sediments: one with clay (C) and two with peat, containing low and high organic matter content (P-lom and P-hom, respectively). The effects of Tubifex on carbon emissions varied across emission pathways and were modulated by sediment types. Tubifex presence tended to alter diffusive CH4 and CO2 fluxes, leading to higher mean CO2 and total mean CH4 emissions in P-lom sediments, whereas weak effects of bioturbation were observed in P-hom and C sediments. The variation in effects was likely associated with sediment-dependent differences in Tubifex bioturbation intensity, as well as Tubificid-mediated shifts in interactions among organic carbon dynamics, CH4-cycling microbial abundances, nutrient availability and gaseous carbon fluxes. We did not find evidence that Tubifex affected ebullitive CH4 emissions, sediment oxygenation or the abundance of methanogens and methanotrophs in the sediment. We conclude that to incorporate their effects in GHG emission estimates, more context-dependent insights are needed.
In highly productive shelf-seas, permeable sediments cover the majority of the benthic environment. However, most research has focussed on shallow environments where currents, tidal flows, terrestrial inputs and benthic productivity have a greater influence than in sediments in deeper shelf areas. Given the extent of permeable sediments across shelf-seas globally, it is imperative to ascertain their biogeochemical function. Here, we present for the first time a seasonal study of biogeochemical processes in deep temperate shelf-sea permeable sediments. Celtic Sea (North-Eastern European shelf) sediments were incubated to establish rates of consumption or production of oxygen (O2), nutrients and iron. Incubations remained oxic throughout, with a significant difference in O2 consumption across seasons, with rates post-bloom (-15.65 ± 0.99 μmol O2 L−1 h−1) two-fold higher than pre-bloom (-9.60 ± 1.68 μmol O2 L−1 h−1) and late-summer (-9.05 ± 0.68 μmol O2 L−1 h−1). There was a consistent release of phosphate and silicate across seasons and drawdown of nitrate post-bloom. A significant production of iron(II) was observed post-bloom. We find that the seasonal differences observed are driven by changes in the delivery of organic carbon from the pelagic environment and the advective flow through the sediment. Areal estimations of O2 fluxes across permeable sediments of the Celtic Shelf Sea reveal 3 × 104 mol O2 d−1 are consumed equating to 10 kmol C yr−1 being remineralised. Our findings provide direct evidence that advective flow in deep permeable sediments plays a key role in the biogeochemical cycling of nutrients and carbon in shelf seas globally.
Arctic permafrost regions contain the largest terrestrial carbon stocks on the globe. Thermokarst wetlands are increasingly forming in these Arctic systems due to ground subsidence caused by permafrost thaw, necessitating understanding of how these changing landscapes function and their feedback with global change and carbon cycling. We evaluated how the above- and belowground plant traits of dominant Arctic tundra sedge Eriophorum vaginatum impacted soil chemistry and trace gas fluxes in a greenhouse rhizobox experiment, using planted and unplanted treatments. Plants and soils used in this experiment were collected from a thermokarst wetland in the Arctic. We simultaneously quantified in situ soil chemistry and root growth dynamics, linking these belowground dynamics to aboveground fluxes of trace plant-soil gas fluxes of carbon dioxide (CO2) and methane (CH4) to improve our understanding of how shifting landscape and aboveground plant community will alter belowground biogeochemistry. Our results indicate how a single species of Arctic sedge shifts bulk soil chemistry over a single growing season. For example, spectroscopic techniques showed that porewater amino acid-like compounds were correlated with root production over time, indicating increased rhizodeposition with belowground growth over a simulated growing season. These exudates are partially responsible for increased CO2 flux in plant treatments. These findings indicate that rhizodeposition is a significant pathway in which an Arctic graminoid shapes the biogeochemical conditions within thermokarst-affected soils. These findings underscore how rapid environmental and landform change may alter elemental cycles in the Arctic.
Relationships between long-term data from the Fernow Experimental Forest (FEF) and historical records of precipitation, NOx (nitric oxide + nitrogen dioxide) emissions, and δ 15N tree-ring data were used to reconstruct a 123-year history of atmospheric nitrogen (N) inputs and stream water N outputs for a small watershed in West Virginia. This long-term perspective revealed that baseline rates (1900–1910) of atmospheric N deposition and N losses in stream water were 5 kg N/ha/yr and 1.5 kg N/ha/yr, respectively. Anthropogenic NOx emissions and atmospheric N deposition exhibited a temporal pattern of increasing N deposition from 1900 until ca. 1974, followed by a nearly complete return to baseline levels beginning ca. 1997 and after amendments to the Clean Air Act in the United States. In contrast, there was no temporal synchrony between atmospheric N inputs and the flux of N into stream water. The discharge of N in stream water remained low from 1900 until 1974 when it increased by 233
The U.S. Midwest exemplifies anthropogenically driven losses of soil organic carbon (SOC) following conversion of the North American prairie to agricultural over the past two centuries. The current near-equilibrium SOC of the agriculturally dominated Midwest is a new phase for this landscape—and stands to inform future trajectories of SOC. Understanding historical SOC change in the U.S. Midwest is particularly important because it is a global hotspot of both crop production and SOC deficits, and thus where unrealized SOC increase potential affords co-benefits to future agroecosystem productivity. Here we overview shifts in SOC equilibrium at the landscape level in the U.S. Midwest in three major phases: (1) post-glacial SOC accumulation, (2) rapid SOC loss to a lower equilibrium following agricultural land use, and (3) future potential trajectories assuming continued agricultural land use. For each phase, we evaluate changes in SOC as a dynamic equilibrium resulting from a balance of inputs and outputs, and synthesize climatic, ecological, and agricultural drivers of changes in carbon input and output to illustrate the magnitude and timescales of SOC change from past to present. Agricultural practices that may partially restore SOC to varying extents are discussed. While few are likely to fully recoup SOC stocks to the level of prairies, socioeconomics will likely pose greater challenges to rebuilding SOC—and to what extent is ideal is itself subjective. We conclude by proposing four major areas for future research relevant to SOC and carbon cycling in the U.S. Midwest: the amount and fate of relic prairie-derived SOC, the role of subsurface SOC, potentially large but irreversible loss of SIC, and water management impacts on SOC.
Cryptic (non-symbiotic) forms of nitrogen (N) fixation are increasingly recognized as a major source of N to natural and agroecosystems, yet the mechanistic controls on cryptic N fixation remain unresolved. A recent synthesis posited that both biophysical (temperature and moisture) and biogeochemical (nutrients) factors regulate N fixation rates, but that biophysical factors exert primary control. Given this conceptual framework, we tested the hypothesis that both biophysical and biogeochemical factors regulate N fixation rates in foliose cyanolichen and decaying wood, but that biogeochemical controls would be stronger when biophysical conditions were more favorable for fixation. We conducted two experiments to explore controls on rates of nitrogenase activity among cyanolichen and decaying wood samples from a temperate lodgepole pine (Pinus contorta var. latifolia) forest. We measured the effects of moisture, temperature, N and phosphorus (P) availability on acetylene reduction rates on samples in both field and growth chamber settings. Moisture and temperature exerted predominant control, but lichen nitrogenase activity responded more to moisture while wood nitrogenase activity responded more to temperature. We found little evidence of nutrient (N and P) controls on nitrogenase activity even when biophysical conditions were favorable for N fixation. Our study suggests that the nature and strength of biophysical and/or biogeochemical controls on cryptic N fixation vary in response to a range of environmental conditions, and that controls on cryptic N fixation may not be consistent across the broad array of cryptic N-fixing niches.
Urban greenspaces are increasingly recognized for their pivotal ecosystem services. Soil nutrients, such as nitrogen (N) and phosphorus (P), are essential to support plant growth, whereas the characteristics of soil N and P concentrations remain unexplored in global urban greenspaces. We compiled global databases of topsoil N and P concentrations, and N to P ratios (N:P, 0–20 cm depth) in (i) urban greenspaces across 175 cities and (ii) natural ecosystems at 277 sites, respectively. Compared with their natural counterparts, urban greenspaces have lower topsoil total N concentrations (1.69 ± 0.06 vs 2.28 ± 0.10 g·kg−1), comparable topsoil total P concentrations (0.70 ± 0.04 vs 0.61 ± 0.03 g·kg−1), and lower N:P (3.10 ± 0.28 vs 4.71 ± 0.30). Based on additional analyses of observed data on paired urban greenspaces and natural ecosystems, as well as model-predicted N and P concentrations in natural soils at the same sites as the urban greenspaces, we further confirmed the abovementioned differences between urban and natural soils. Topsoil total N and P concentrations both increase significantly toward higher latitudes in urban greenspaces and natural ecosystems, while no significant latitudinal trends are found for topsoil N:P. The global pattern of topsoil total N concentrations in urban greenspaces is significantly associated with climatic, anthropogenic, and vegetational drivers, whereas the topsoil P concentration is strongly correlated with climatic drivers. Unlike natural ecosystems, topsoil total N and P concentrations in urban greenspaces are not correlated significantly. Our findings highlight an unexpected topsoil N depletion and N-P decoupling in global urban greenspaces.
The transition to renewable energy sources is expected to reduce anthropogenic greenhouse gas emissions and the associated impacts on global climate but it entails an increased human pressure on land and water resources. Here we evaluate the associated shift in environmental costs from climate warming to increased human use of land and water. We evaluate the tradeoffs inherent to the different carbon, land, and water footprints of fossil vs renewable energy sources at local and global scales. While with the industrial revolution human reliance on fossil fuels has coupled economic growth to global CO2 emissions, it has greatly decoupled the energy system from land and water use. Conversely, the transition to renewable (or “green”) energy is now recoupling energy production to local land (and water) use.
Peatland drainage for agricultural purposes has transformed wetlands into major nutrient sources, but rewetting offers potential for nutrient retention and climate mitigation. We quantified hydrological and nutrient fluxes in a 14.5 ha former pump-drained fen (Strande Enge, Denmark) across 1 year before and 2 years after rewetting. Restoration involved removing pumping infrastructure and reconnecting upstream catchments with the aim to restore natural flow paths. Prior to rewetting, the site exhibited high hydraulic loading (5904 mm yr−1) dominated by groundwater inputs and acted as a strong nutrient source, with net losses of total nitrogen (TN: 123 kg ha−1 yr−1), total phosphorus (TP: 23 kg ha−1 yr−1), and total organic carbon (TOC: 1336 kg ha−1 yr−1). Following rewetting, hydraulic loading increased more than fourfold (24,258–27,160 mm yr−1), and the system shifted to a flow-through wetland dominated by surface water inputs. Despite substantially higher nutrient loads after rewetting, the fen became a large sink for TN (209–242 kg ha−1 yr−1; 21
Changes in soil nutrient cycling with warming are dependent on differing thermal responses and adaptation strategies of soil microbial communities and the interactions between substrate acquisition through extracellular enzyme activity and utilisation via respiration, metabolism and biomass accumulation. Understanding these processes is complicated by the complexity and variability of soil systems, along with differences in methodologies quantifying adaptation of soil microbial processes. Here we aimed to investigate thermal adaptation for extracellular enzyme activity of three enzyme classes (β-glucosidases, β-N-acetylglucosaminidases and phosphatases) using soils from a field setting with different mean annual temperatures across a long term (> 20 year) geothermal gradient in New Zealand. Extracellular enzyme thermal responses showed increasing rates up to the highest characterised temperature (60 °C) regardless of mean annual soil temperature and minimal adaptation across the gradient for parameters such as activation energy, curvature, and the optimum and minimum temperature of activity. These results are in direct contrast to the previously measured thermal response of respiration and growth rates measured at this site which have an optimum temperature of activity around 30–45 °C and show measurable rates of adaptation across the thermal gradient. This divergence in the thermal response of soil substrate depolymerisation via extracellular enzyme activity compared to respiration and growth rates raises questions around future nutrient bioavailability and utilisation if these two process are decoupled at elevated temperatures under future soil warming.
For watershed management, it is important to monitor the impact of mitigation practices on water quality. Effective monitoring can foster further adoption of conservation actions by demonstrating success. However, the spatial resolution of most agricultural watershed monitoring is low, and linking field-scale management or the influence of individual watershed features to a single downstream monitoring station is difficult. We investigated how surface flow path sampling can be used in low-order agricultural streams to gain a better understanding of processes controlling nitrate-nitrogen (NO3−-N) export. We characterize spatial patterns in stream NO3−-N concentrations and the temporal stability of these patterns in two contrasting agricultural stream reaches. In a watershed region with homogenous land use, NO3−-N concentrations are stable through time and spatial dependence persists across large distances. In a heterogeneous region of the watershed which includes wetlands, spatial patterns are variable through time and spatial dependence persists across variable distances during contrasting stream conditions. Our results indicate that surface flow path sampling is most valuable in landscapes with multiple, changing influences on analytes. In these landscapes, surface flow-path sampling can identify control points and capture how the influence of these control points change through time. In homogenous landscapes, surface flow-path sampling can be most valuable for establishing the location of control points to inform where fixed-site monitoring should occur. By coupling surface flow-path sampling with traditional fixed-site monitoring, researchers and watershed managers can develop a deeper understanding of watershed processes which can help plan for more effective management.
Dust has played a critical role throughout Earth’s origin and evolution and continues to do so in the present. The expanding scale and increasing pace of anthropogenic activities over the last few centuries have resulted in a dustier 21st-century world that influences all aspects of planetary life, from personal health to global biogeochemical cycling of elements and climate. In recent years, measurements and models have advanced our understanding of global dust flux. However, uncertainties remain over the quantification and role of low-level emissions and depositions, episodic and extreme dust events, high-latitude dust, bioaerosols, and anthropogenic dust. Furthermore, the ecological consequences of dust loss to source regions, its reactivity in the atmosphere, and dust gain in depositional ecosystems remain underappreciated. Even as dust influences climate and the changing climate impacts dust in a feedback loop, several aspects of the dust life cycle, such as the role of dust in the global carbon cycle and the contribution of anthropogenic dust to Earth’s radiation budget, remain poorly constrained. In a world wherein the continents are measurably losing freshwater and soil moisture (undergoing aridification), and wildland and urban fires are increasing in frequency and intensity, dust is emerging as a major player at local, regional, and global scales. Nevertheless, dust remains an underappreciated and understudied component of global biogeochemical cycles (especially its role in biospheric productivity) and climate models (especially its role in climate feedback). This commentary aims to inform, intrigue, and challenge Earth scientists to pursue research on the fast-evolving modern dust cycle—its sources, sinks, fluxes, size distribution, composition, abundance, reactivity, consequences, and fate in the Earth system.
Stream corridors play a critical role in reducing contaminant export, yet limited understanding of controls on riparian biogeochemical processes hinders effective water quality management. To infer outcomes from riparian biogeochemical processes, we analyzed nitrate and sulfate abundance and isotopic composition in water samples from upland groundwater, riparian groundwater, and stream water across three ca. 0.7-km reaches draining an extensively cultivated terrace landform. Nitrate showed net loss from upland groundwaters to stream water, with stream samples having nitrate-δ15N and δ18O values up to ca. + 12‰ and + 2‰, respectively, and lower nitrate concentrations (ca. 3 mg L−1) than terrace groundwater inflows (ca. 20 mg N L−1). Riparian groundwater samples had nitrate-δ15N and δ18O values up to + 40‰ and + 15‰, respectively, with low concentrations near 1 mg N L−1, indicating loss along riparian flow paths. Sulfate showed net gains in concentration, with stream water having low sulfate-δ34S values (ca. - 18‰) compared with terrace groundwater (ca. - 10‰), and high sulfate-δ18O values (up to + 6‰) compared to ambient riparian groundwater (water-δ18O: - 20 to - 14‰). These results suggest that sulfide oxidation during marine shale weathering is cycled through redox transformations under fluctuating saturation conditions in riparian systems. We use relationships in abundance and isotopic composition from uplands to streams to constrain the potential magnitude of gross gains and losses influencing observed net sulfate gains and nitrate losses. Our findings highlight how losses, gains, and mixing processes influence water quality through solute loss to gaseous phases, solute production in the riparian system, and redox cycling in stream corridors.
Iron (Fe) plays a key role in lake ecosystems by regulating the availability of phosphorus (P) as a limiting factor for primary production. This study investigates how microbial sulphate reduction in Lake Stechlin, a dimictic and initially oligotrophic lake in northeast Germany (zₘₐₓ = 69.5 m), has altered the mobility of Fe and P over several decades. Using long-term monitoring data combined with sedimentological investigations, the study examines long-term geochemical focusing, defined as the net accumulation of redox-mobilised Fe in the deepest basin driven by reductive dissolution, lateral transport, and re-precipitation. Under oligotrophic conditions prior to the 1960s, focusing of Fe toward the deepest site likely involved: (1) reductive dissolution of sedimentary Fe oxides in shallow areas, (2) diffusion of dissolved Fe into overlying water, (3) re-oxidation/complexation and stepwise lateral transport within the water column, and (4) final deposition and burial at the deepest zone. Chemical and mineralogical evidence indicates that Fe burial was facilitated by authigenic formation of stable Fe(II) minerals, most likely ankerite (CaFe[CO3]2) and vivianite (Fe3[PO4]2·8H2O). Fe enrichment at the deepest site has strongly weakened, coinciding with intensified pyrite (FeS2) formation in anoxic littoral and profundal sediments. This shift was likely driven by sufficient supply of organic matter and elevated sulphate inputs, which stimulated microbial sulphate reduction. Elevated S/Fe ratios indicate that sulphide efficiently competed with P for binding to Fe, potentially increasing susceptibility to external and internal P loading.
Agricultural drainage ditches have been recently identified as hotspots of methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) emissions. Ditches often experience inputs of fertilizers from adjacent agricultural fields, which increases the availability of organic carbon and nutrients in ditch sediments, thereby fueling greenhouse gas (GHG) production. Here, we quantify the effects of two types of fertilizers (manure and artificial fertilizer) on GHG dynamics from agricultural drainage ditch sediments subjected to oxic and anoxic conditions. We first measured rates of potential sediment N2O production, CH4 production, and aerobic CH4 oxidation under different fertilizer doses. We observed that manure additions (expressed here as ammonium (NH4+) dose, referring to the resulting NH4+ concentration in a given bottle after addition) strongly stimulated CH4 and N2O production. Methane production rates increased approximately threefold as a result of manure additions, ranging from 18.4 to 61.7 µmol CH4 gDW−1 d−1, whereas N2O production rates increased approximately 16-fold, and varied from 0.1 to 1.6 µmol N2O gDW−1 d−1 across manure doses. Aerobic CH4 oxidation was also stimulated by manure addition, while at resulting NH4+ concentrations above 2 mmol L−1, oxidation rates declined. In contrast, artificial fertilizer caused immediate inhibition of CH4 and N2O production and aerobic CH4 oxidation, even at the lowest NH4+ concentration tested (0.05 mmol L−1). Focusing on the effects of manure on GHG emissions, we observed that under anoxic conditions, sediment cores receiving high manure inputs emitted approximately 3.5 times more GHGs (in CO2-equivalents) than anoxic controls (no manure) and about 5.5 times more than oxic controls. Methane was the dominant driver of increased emissions at higher manure doses. As fertilizer use continues to rise globally, these results highlight the importance of implementing climate-smart water and nutrient management strategies in ditches and adjacent grasslands to mitigate climate trade-offs.
Phytoplankton in temperate regions typically exhibit spring and fall bloom patterns driven by interactions between physical and biogeochemical factors. In contrast, Gwangyang Bay, located along the southern coast of Korea, is a prominent bay exhibiting estuarine phenology, characterized by distinct peaks in winter and summer. To investigate the mechanisms underlying these uncommon bloom peaks, we employed a coupled physical–biogeochemical model that integrates the Regional Ocean Modeling System (ROMS) with a low-trophic ecosystem module, incorporating size-structured phytoplankton and zooplankton dynamics. The model simulated the temporal and spatial evolution of phytoplankton biomass and nutrient distributions under forcing averaged over the 2007–2015 period, and a suite of sensitivity experiments was performed to isolate the roles of temperature, light attenuation, shortwave radiation, wind, and riverine nutrient inputs. The model successfully reproduced observed seasonal patterns in temperature, nutrients, dissolved oxygen, and chlorophyll a concentrations. Summer blooms were driven by elevated dissolved inorganic nitrogen (DIN) loading from river discharge and high water temperatures, which collectively stimulated the growth of small-sized phytoplankton. Winter blooms, in contrast, were driven by large-sized phytoplankton growth under moderate nutrient conditions and low grazing of zooplankton due to low temperature. The vertical and horizontal structure of phytoplankton distributions was influenced by stratification patterns, with residence time and light availability playing secondary roles. Sensitivity experiments demonstrated that seasonality of water temperature and riverine DIN supply are critical for reproducing the observed seasonal bloom pattern. The results underscore the importance of size-specific traits and temperature-nutrient interactions in shaping seasonal phytoplankton dynamics in complex estuarine-bay environments.
Inland waters receive large quantities of carbon from the surrounding landscape and are active sites of carbon transport, transformation, and emission. Global carbon emission estimates are limited by sparse and unevenly distributed carbon flux observations, particularly in the tropics. We evaluated hydrological and metabolic controls on carbon export variability from a large peatland in a tropical ecosystem typical of the Northern Andes mountains. We recorded dissolved CO2 (pCO2), dissolved oxygen (DO), and discharge at 15-min intervals 5 m downstream of a peatland outlet (Station 1) and at 3 additional locations downstream (Stations 2, 3 and 4) from July 2019 until Jan 2020 and from June 2021 until March 2023. Continuous measurements of DO and discharge were also measured 2 km away in a stream draining an adjoining catchment (Station 5). Discrete measurements of dissolved organic carbon (DOC) and dissolved methane (pCH4) were collected in June-July of 2021 and 2022. Stream discharge was a primary control on pCO2 and DOC in the stream network at both seasonal and event scales. DOC concentration increased with discharge and while pCO2 decreased during higher flows, CO2 loading increased. Pronounced seasonal changes were observed with lowest pCO2 recorded at the peatland outlet in wet months (June–August: 5845 ± 2325 ppm, mean ± standard deviation), and the highest in dry months (Nov-Feb, 16,677 ± 3685 ppm). Anoxic or hypoxic conditions persisted for over half of our study and measurements of pCH4 at the peatland outlet were very high (982 ± 797 ppm), underscoring the importance of anaerobic activity in this system. Aerobic processes also influenced pCO2 dynamics. Aquatic metabolism at Station 5 (29 July–19 Oct 2021) was net heterotrophic, with ER exceeding GPP and net pCO2 production (mean ER: − 6.5 g O2 m−2 d−1, GPP: 0.44 g O m−2 d−1). Our study highlights the role of hydrologic connectivity and diverse biogeochemical processes in shaping carbon export and cycling in páramo streams, which results in pCO2 and pCH4 levels among the highest reported in streams and rivers worldwide.
A substantial part of terrestrial nitrous oxide (N2O) emissions originates from denitrification in wetlands, and this contribution is expected to rise with ongoing land-use changes, such as wetland drainage, agricultural conversion, and peatland degradation, as well as under global warming. Capturing the spatial and temporal dynamics of N2O emissions through measurements and numerical modelling remains challenging, as extreme N2O peaks occur during short-lived transient events (hot moments). In this study, we combined three experimental approaches (in situ field monitoring, mesocosm experiments, and slurry soil incubations in the laboratory) to characterise N2O hot moments of denitrification across 21 diverse European wetlands. Each approach captured different aspects of N2O emission dynamics, and their combination revealed additional features, including the timing and magnitude of N2O fluxes, denitrification efficiency (ratio of N2O to N2O + N2 emitted), and an estimate of the proportion of soil actively undergoing denitrification. We encourage the use of these key determinants to improve and parametrise future denitrification models that aim to quantify transient N2O hot moments.
