The nitrogen (N) cycle involves intricate interactions affected by the spatial and temporal variability. Hot moments, occurring short-lived across seasons, significantly contribute to temporal nitrous (N2O) emission fluctuations. Likewise, N2O emissions exhibit localized spatial variability as hot spots. Year long monthly based studies of soil N cycle microbiome dynamics in peatland forests are unknown. This study investigates the relationship between soil microbial communities and N2O gaseous fluxes within a drained peatland forest throughout a year. Key research questions are: how are the genes responsible for N cycling in the peatland spatially and temporally distributed?; what patterns are there between soil characteristics (e.g., soil water content, soil temperature and pH) and N cycling gene abundances? Soil samples from 12 sites within a drained peatland forest in south-eastern Estonia were collected over a year and analysed for their physical and chemical properties and the abundance of genes associated with N cycling. Quantitative polymerase chain reaction was used to evaluate the bacterial and archaeal community abundances by quantifying the abundances of specific 16S rRNA genes and to evaluating the abundances of 10 genes associated with N cycling: denitrification (nirS, nirK, nosZ clade I, nosZ clade II, and fungal nirK), nitrification (bacterial, archaeal, and comammox amoA), DNRA (nrfA), and N fixation (nifH). This data was paired with N2O flux data collected in automatic dynamic gas chambers throughout the study period. Spatial variations apparent in the soil's chemical and physical composition reveal distinct vegetation and microbial communities across the area. Archaeal 16S rRNA, along with genes associated with N cycling (fungal nirK, nosZI, bacterial and comammox amoA), exhibited correlations with N2O emissions. Archaeal 16S rRNA, bacterial amoA, fungal nirK, and nosZI were positively correlated with N2O emissions. Throughout the year, water table levels and volumetric water content significantly influenced both N2O emissions and the abundance of N cycling genes. The site encompasses specific areas with consistently higher N2O emissions (hot spots) and periodic peaks in emissions (hot moments) due to the combined interplay of physical, chemical, and genetic attributes within the peatland soil.

Earth’s climate is tightly connected to carbon and nitrogen exchange between the atmosphere and ecosystems. Wet peatland ecosystems take up carbon dioxide in plants and accumulate organic carbon in soil but release methane. Man-made drainage releases carbon dioxide and nitrous oxide from peat soils. Carbon and nitrous gas exchange and their relationships with environmental conditions are poorly understood. Here, we show that open peatlands in both their wet and dry extremes are greenhouse gas sinks while peat carbon/nitrogen ratios are high and prokaryotic (bacterial and archaeal) abundances are low. Conversely, peatlands with moderate soil moisture levels emit carbon dioxide and nitrous oxide, while prokaryotic abundances are high. The results challenge the current assumption of a uniform effect of drainage on greenhouse gas emissions and show that the peat microbiome of greenhouse-gas sources differs fundamentally from sinks.

Constructed wetlands (CW) treating runoff from agricultural catchments reduce the nutrient load of water, however, they can also be significant sources of greenhouse gases, especially methane (CH4). We simultaneously assessed CH4 emission potentials and phosphorus (P) removal efficiency in a 0.45 ha in-stream surface flow CW to determine the main drivers of CH4 emissions, and to analyze the temporal dynamics of CH4 emissions and P removal during an almost 4-year period. The TP (total phosphorus) removal efficiency had a clear seasonal dynamic, with the highest removal occurring during summer and early autumn (monthly average 60.5%), when the flow rate was lowest and water residence time longest. Due to increasing sedimentation and related anaerobic conditions, the mean hourly CH4 emissions for each year demonstrated an increasing trend over the years: from 88 mu g CH4-C m- 2 h-1 in 2018-2505 mu g CH4-C m- 2 h-1 in 2021. There was a clear seasonality in CH4 emissions: up to 90% of CH4 fluxes occurred during the warm period (from May to October). We assume that maintenance of treatment wetlands is essential and predominantly regular removal of aboveground vegetation at the second half of the growing season would decrease CH4 emissions. Nevertheless, due to the P saturation in sediments, regular sediment removal in the long term is also necessary.

Coastal ecosystems, facing threats from global change and human activities like excessive nutrients, undergo alterations impacting their function and appearance. This study explores the intertwined microbial cycles of carbon (C) and nitrogen (N), encompassing methane (CH4), nitrous oxide (N2O), and nitrogen gas (N2) fluxes, to determine nutrient transformation processes between the soil-plant-atmosphere continuum in the coastal ecosystems with brackish water. Water salinity negatively impacted denitrification, bacterial nitrification, N fixation, and n-DAMO processes, but did not significantly affect archaeal nitrification, COMAMMOX, DNRA, and ANAMMOX processes in the N cycle. Plant species age and biomass influenced CH4 and N2O emissions. The highest CH4 emissions were from old Spartina and mixed Spartina and Scirpus sites, while Phragmites sites emitted the most N2O. Nitrification and incomplete denitrification mainly governed N2O emissions depending on the environmental conditions and plants. The higher genetic potential of ANAMMOX reduced excessive N by converting it to N2 in the sites with higher average temperatures. The presence of plants led to a decrease in the N fixers' abundance. Plant biomass negatively affected methanogenetic mcrA genes. Microbes involved in n-DAMO processes helped mitigate CH4 emissions. Over 93 % of the total climate forcing came from CH4 emissions, except for the Chinese bare site where the climate forcing was negative, and for Phragmites sites, where almost 60 % of the climate forcing came from N2O emissions. Our findings indicate that nutrient cycles, CH4, and N2O fluxes in soils are context-dependent and influenced by environmental factors and vegetation. This underscores the need for empirical analysis of both C and N cycles at various levels (soil-plant-atmosphere) to understand how habitats or plants affect nutrient cycles and greenhouse gas emissions.

Amazonian swamp forests remove large amounts of carbon dioxide (CO 2 ) but produce methane (CH 4 ). Both are important greenhouse gases (GHG). Drought and cultivation cut the CH 4 emissions but may release CO 2 . Varying oxygen content in nitrogen-rich soil produces nitrous oxide (N 2 O), which is the third most important GHG. Despite the potentially tremendous changes, GHG emissions from wetland soils under different land uses and environmental conditions have rarely been compared in the Amazon. We measured environmental characteristics, and CO 2 , CH 4 and N 2 O emissions from the soil surface with manual opaque chambers in three sites near Iquitos, Peru from September 2019 to March 2020: a pristine peat swamp forest, a young forest and a slash-and-burn manioc field. The manioc field showed moderate soil respiration and N 2 O emission. The peat swamp forests under slight water table drawdown emitted large amounts of CO 2 and CH 4 . A heavy post-drought shower created a hot moment of N 2 O in the pristine swamp forest, likely produced by nitrifiers. All in all, even small changes in soil moisture can create hot moments of GHG emissions from Amazonian wetland soils, and should therefore be carefully monitored.

The carbon (C) budgets of riparian forests are sensitive to climatic variability. Therefore, riparian forests are hot spots of C cycling in landscapes. Only a limited number of studies on continuous measurements of methane (CH4) fluxes from riparian forests is available. Here, we report continuous high-frequency soil and ecosystem (eddy-covariance: EC) measurements of CH4 fluxes with a quantum cascade laser absorption spectrometer for a 2.5-year period and measurements of CH4 fluxes from tree stems using manual chambers for a 1.5 year period from a temperate riparian Altus incana forest. The results demonstrate that the riparian forest is a minor net annual sink of CH4 consuming 0.24 kg CH4-Cha(-1) y(-1) Soil water content is the most important determinant of soil, stem, and EC fluxes, followed by soil temperature. There were significant differences in CH4 fluxes between the wet and dry periods. During the wet period, 83% of CH4 was emitted from the tree stems while the ecosystem-level emission was equal to the sum of soil and stem emissions. During the dry period, CH4 was substantially consumed in the soil whereas stem emissions were very low. A significant difference between the EC fluxes and the sum of soil and stem fluxes during the city period is most likely caused by emission from the canopy whereas at the ecosystem level the forest was a clear CH4 sink. Our results together with past measurements of CH4 fluxes in other riparian forests suggest that temperate riparian forests can be long-term CH4 sinks. (C) 2021 Elsevier B.V. All rights reserved.

Climate change and the continuing increase in human population creates a growing need to tackle urban stormwater problems. One promising mitigation option is by using nature-based solutions (NBS) – especially sustainable urban stormwater management technologies that are key elements of NBS action. We used a synthesis approach to compile available information about urban stormwater retention capacity of the most common sustainable urban drainage systems (SUDS) in different climatic conditions. Those SUDS targeting stormwater management through water retention and removal solutions (mainly by infiltration, overland flow and evapotranspiration), were addressed in this study. Selected SUDS were green roofs, bioretention systems (i.e. rain gardens), buffer and filter strips, vegetated swales, constructed wetlands, and water-pervious pavements. We found that despite a vast amount of data available from real-life applications and research results, there is a lack of decisive information about stormwater retention and removal capacity of selected SUDS. The available data show large variability in performance across different climatic conditions. It is therefore a challenge to set conclusive widely applicable guidelines for SUDS implementation based on available water retention data. Adequate data were available only to evaluate the water retention capacity of green roofs (average 56±20%) and we provide a comprehensive review on this function. However, as with other SUDS, still the same problem of high variability in the performance (min 11% and max 99% of retention) remains. This limits our ability to determine the capacity of green roofs to support better planning and wider implementation across climate zones. The further development of SUDS to support urban stormwater retention should be informed by and developed concurrently with the adaptation strategies to cope with climate change, especially with increasing frequency of extreme precipitation events that lead to high volumes of stormwater runoff.

Constructed wetlands (CW) treating runoff from agricultural catchments can efficiently reduce nitrate contamination, however, most wetlands are inherently net sources of methane (CH4), which is of environmental concern due to its potent global warming capacity. For the mitigation of this negative aspect of CWs we need investigations on the CH4 emission dynamics and environmental conditions governing CH4 production and consumption in CWs. This study integrates results from 4-years (2014-2017) investigations in an off-stream CW in Rampillon, France (0.53 ha, depth 0.3-0.8 m, est. 2010) and from 4-years (2018-2021) studies in an in-stream CW in Vända, Estonia (0.45 ha, depth 0.1-0.6 m, est. 2015). In Rampillon, during four 2-weeks measurement campaigns throughout all seasons CH4 fluxes were measured using floating automated chambers connected to the QCLAS laser system. In addition, gas was sampled twice day from manual floating chambers for further analysis in lab. In Vända in-stream CW, CH4 fluxes were measured twice a month using manual chambers and gas-chromatographs. The average annual CH4 emission in Rampillon for 2014-2015 was 7.7 g CH4-C m-2 yr-1, showing highest values from deeper (0.5-1.0 m) parts in summer and autumn. The highest values reached up to 180 mg CH4-C m-2 h-1, mainly due to ebullition. The emissions in winter and spring were up to 10 times lower, however no negative values were observed. There was an increasing trend in CH4 fluxes: in 2017 the average emission reached to 12.0 g CH4-C m-2 y-1. Differences between the emission values gathered from authomated chambers were about 10% higher than those measured from manual chambers. In Vända in-stream CW, a clear increase in average annual emissions was found: from 0.4 in2018 to 10.5 g CH4-C m-2 yr-1 in 2021. It was correlated with increasing Typha latifolia-dominated vegetation cover. Emissions showed strong correlation with air and water temperature while no clear relationship was found with the depth of various parts. Large CH4 emission from CWs is a major concern and therefore a smart management is needed. Our previous studies in surface flow CWs treating nitrate-contaminated runoff demonstrate that above-ground biomass harvesting of plants can decrease the CH4. The end of growing season is likely the best time for biomass harvesting while avoiding the excessively high CH4 emissions that the summer harvest may produce.

Wetlands that are restored for carbon sequestration or created for water treatment are an important sources of greenhouse gases, especially methane. The emission of nitrous oxide (N2O) from these systems is often considered negligible due to the inundation and anerobic conditions that support complete denitrification. We used closed chamber method to analyze N2O fluxes over a long-term period across heterogeneous wetland ecosystem constructed for treating nitrate-rich agricultural runoff. Our results showed that the water depth and temperature were most important factors affecting high N2O emissions. The shallow areas where water depth was less than 9 cm created N2O hot spots that emitted 48.8% of the total wetlands annual emission while only covering 6% of the total area. The annual emission from shallow-water hot spots with dense helophytic vegetation was 4.85 +/- 0.5 g N2O-N m(-2) y(-1) while it was only 0.37 +/- 0.01 g N2O-N m(-2) y(-1) in deeper zones. While the water depth was the main factor for high N2O emissions, the temperatures increased the magnitude of the flux and therefore summer droughts and water drawdown created even larger hot spots. These results also suggest that IPCC benchmarks could underestimate N2O emission from shallow waterbodies. Thus, it is important that the shallow zones and water level drawdown in the created or restored wetlands is avoided to minimize the N2O flux.

Peatland drainage based on ditch systems is a widely used forestry management practice in the boreal and hemiboreal forests to improve tree growth. This study investigated the morphological variation in absorptive roots (first- and second-order roots) across the distance gradient from the ditch with four sampling plots (5, 15, 40, and 80 m) in six drained peatland forests dominated by Downy birch and Norway spruce. The dominating tree species had a significant effect on the variation in absorptive root morphological traits. The absorptive roots of birch were thinner with a higher specific root area and length (SRA and SRL), higher branching intensity (BI), and lower root tissue density (RTD) than spruce. The distance from the ditch affected the absorptive root morphological traits (especially SRA and RTD), but this effect was not dependent on tree species and was directionally consistent between birch and spruce. With increased distance from the ditch (from plot 5 to plot 80), the mean SRA increased by about 10% in birch and 5% in spruce; by contrast, the mean RTD decreased by about 10% in both tree species, indicating a potential shift in nutrient foraging. However, soil physical and chemical properties were not dependent on the distance from the ditch. We found a species-specific response in absorptive root morphological traits to soil properties such as peat depth, pH, and temperature. Our results should be considered when evaluating the importance of morphological changes in absorptive roots when trees acclimate to a changing climate.

Wetland soils are the greatest source of nitrous oxide (N 2 O), a critical greenhouse gas and ozone depleter released by microbes. Yet, microbial players and processes underlying the N 2 O emissions from wetland soils are poorly understood. Using in situ N 2 O measurements and by determining the structure and potential functional of microbial communities in 645 wetland soil samples globally, we examined the potential role of archaea, bacteria, and fungi in nitrogen (N) cycling and N 2 O emissions. We show that N 2 O emissions are higher in drained and warm wetland soils, and are correlated with functional diversity of microbes. We further provide evidence that despite their much lower abundance compared to bacteria, nitrifying archaeal abundance is a key factor explaining N 2 O emissions from wetland soils globally. Our data suggest that ongoing global warming and intensifying environmental change may boost archaeal nitrifiers, collectively transforming wetland soils to a greater source of N 2 O.

Northern peatlands are important terrestrial carbon (C) stores, but their ability to sequestrate C is at delicate balance affected by management and also by climate change. The climate change causes less snow pack and warmer winters with faster water table drop in spring and drier summers in most boreal areas. Due to those changes natural peatlands may become C source instead of sink.This study presents ecosystem respiration (ER) over five-year period and the annual estimates of net ecosystem exchange (NEE) of CO2 in Umbusi and Laukasoo in Estonia along disturbance gradient from drained to natural ombrotrophic bog. Both study sites locate next to the active cutaway peatlands. There were four CO2 flux measurements plots with three measurements points at different distance from the drainage ditch (10, 50, 100 and 200 m in Umbusi; 3, 40, 50, 125 m in Laukasoo) to form a water table depth and soil moisture gradient on both study sites. ER was measured using opaque static chamber throughout of the year in period 2012-2016. A vented and thermostated transparent plastic chamber with removable opaque cover was used for CO2 exchange measurements. NEE measurements occurred biweekly from April to December in 2015, totally were done 648 measurements. NEE was derived from modelling of ER and gross primary production with temperature, photosynthetically active radiation, water level and days of year (as phenological phase) as driving variables.Annual mean NEE at four different distance from the ditch toward undisturbed area in Umbusi and Laukasoo were 0.37, 0.28, 0.15, 0.08 and 0.44, 0.34, 0.04, 0.21 kg C m-2 y-1, respectively. Although mean NEE was positive for all plots on both sites, there were also negative annual NEE values in some points in undisturbed plots (100 and 200 m from the ditch in Umbusi and 50 and 125 m in Laukasoo).Average water level at four different distance from the ditch toward undisturbed area in Umbusi and Laukasoo during growing period (from the beginning of May to the end of October) in 2015 were -94, -45, -22, -22 and -124, -33, -21, -22 cm, respectively. Monthly mean air temperature and sum of precipitation were not different from the long-term measurements in studied growing period in 2015 while winter was significantly warmer.Modelled ER remained high for cold period because of higher air temperature in 2015. Due to higher respiration rate from non-frozen peat layer in cold season, more CO2 was released back to atmosphere and annually less C was accumulated. Monthly mean air temperature for cold period was 3.5 ºC warmer than the long-term average.

Earth and Space Science Open Archive This preprint has been submitted to and is under consideration at Journal of Geophysical Research - Biogeosciences. ESSOAr is a venue for early communication or feedback before peer review. Data may be preliminary.Learn more about preprints preprintOpen AccessYou are viewing the latest version by default [v1]Remotely sensed land surface temperature is a proxy of ecosystem respiration in intact and disturbed northern peatlandsAuthorsIuliiaBurduniDAinKulliDMartinMaddisonGertVeberOleksandrKarasoviDValentinaSagrisÜloManderiDSee all authors Iuliia BurduniDCorresponding Author• Submitting AuthorInstitute of Ecology & Earth Sciences, Department of Geography, University of TartuiDhttps://orcid.org/0000-0002-1436-2550view email addressThe email was not providedcopy email addressAin KulliDInstitute of Ecology & Earth Sciences, Department of Geography, University of TartuiDhttps://orcid.org/0000-0002-7534-3927view email addressThe email was not providedcopy email addressMartin MaddisonInstitute of Ecology & Earth SciencesDepartment of GeographyUniversity of Tartuview email addressThe email was not providedcopy email addressGert VeberInstitute of Ecology & Earth Sciences, Department of Geography, University of Tartuview email addressThe email was not providedcopy email addressOleksandr KarasoviDInstitute of Ecology & Earth SciencesDepartment of GeographyUniversity of TartuiDhttps://orcid.org/0000-0001-6121-4625view email addressThe email was not providedcopy email addressValentina SagrisInstitute of Ecology & Earth SciencesDepartment of GeographyUniversity of Tartuview email addressThe email was not providedcopy email addressÜlo ManderiDUniversity of TartuiDhttps://orcid.org/0000-0003-2340-6989view email addressThe email was not providedcopy email address

Abstract. Amazonian peat swamp forests remove large amounts of carbon dioxide (CO2) but anaerobic decomposition of the peat produces methane (CH4). Drought or cultivation cuts down on the CH4 production but may increase the CO2 emission. Varying oxygen content in nitrogen-rich peat produces nitrous oxide (N2O). Despite the potentially tremendous changes, greenhouse gas emissions from peatlands under various land uses and environmental conditions have rarely been compared in the Amazon. We measured CO2, CH4 and N2O emissions from the soil surface with manual opaque chambers, and environmental characteristics in three sites around Iquitos, Peru from September 2019 to March 2020: a pristine peat swamp forest, a young forest and a slash-and-burn manioc field. The manioc field showed moderate peat respiration and N2O emission. The swamp forests under slight water table drawdown emitted large amounts of CO2 and N2O while retaining their high CH4 emissions. Most noticeably, a heavy shower after the water-table drawdown in the pristine swamp forest created a hot moment of N2O. Nitrifier denitrification was the likely source mechanism, as we rule out nitrification and heterotrophic denitrification. We base the judgement on the lack of nitrate and oxygen, and the suppressed denitrification potential in the topsoil. Overall, our study shows that even moderate drying in Peruvian palm swamps may create a devastating feedback on climate change through CO2 and N2O emissions.

Constructed wetlands (CW) can efficiently remove nitrogen from polluted agricultural run-off, however, a potential caveat is nitrous oxide (N2O), a harmful greenhouse gas and stratospheric ozone depleter. During five sampling campaigns, we measured N2O fluxes froma 0.53 ha off-stream CW treating nitrate-richwater fromthe intensively fertilized watershed in Rampillon, France, using automated chambers with a quantum cascade laser system, and manual chambers. Sediment samples were analysed for potential N-2 flux using the He-O-2 incubation method. Both inlet nitrate (NO3-) concentrations and N2O emission varied significantly between the seasons. In the Autumn and Winter inlet concentrations were about 11 mg NO3--N L-1, and < 6.5 mg NO3--N L-1 in the Spring and Summer. N2O emission was highest in the Autumn (mean +/- standard error: 9.7 +/- 0.2 mu g N m(-2) h(-1)) and lowest in the Summer (wet period: 0.2 +/- 0.3 mu g N m(-2) h(-1)). The CW was a very weak source of N2O emitting 0.32 kg N2O-N ha(-1) yr(-1) and removing around 938 kg NO3--N ha(-1) yr(-1), the ratio of N2O-N emitted to NO3--N removed was 0.033%. The automated and manual chambers gave similar results. From the potential N2O formation in the sediment, only 9% was emitted to the atmosphere, the average N-2 N O-2 ratio was high: 89:1 for N-2-N-potential: N2O-N-potential and 1353:1 for N-2-N-potential: N2O-N-emitted. These results indicate complete denitrification. The focused principal component analysis showed strong positive correlation between the gaseous N2O fluxes and the following environmental factors: NO3--N concentrations in inlet water, streamflow, and nitrate reduction rate. Water temperature, TOC and DOC in thewater and hydraulic residence time showed negative correlations with N2O emissions. Shallow off-stream CWs such as Rampillon may have good nitrate removal capacity with low N2O emissions. (C) 2021 Elsevier B.V. All rights reserved.

Coastal ecosystems are suffering increasing degradation in many parts of the world and the ecological integrity and biodiversity of those ecosystems have been greatly threatened due to the high load of pollutants produced largely through anthropogenic processes. Agricultural, industrial and domestic applications pollution mainly affect coastal zones via riverine inputs from contaminated urban and rural areas near shore, atmospheric deposition and direct dumping. Beside the different other pollutants, excessive nutrients have become major concerns which can completely change the functioning and appearance of coastal ecosystems. A variety of plants complete the ecological system of coasts and coastal vegetation may even govern the microbial processes and greenhouse gas emissions. With the need to better protect and manage the coastal areas, it is important to understand the decisive microbial processes of nutrients cycling in coastal ecosystem, especially in the face of the changing climate. The aim of this study was to assess the abundances of soil bacteria and archaea and their potential to perform different carbon and nitrogen cycling processes in coastal zones and relate these nutrient transformation processes to greenhouse gas emissions. The study was carried out in Estonian and Chinese coasts which were affected by brackish water (mixed saline and fresh water) because of riverine inputs. Twice a month during the most intensive vegetation period, the gas samples (CO2, CH4, and N2O) were taken and different parameters of plant (Schoenoplectus tabernaemontanii and Phragmites australis in Estonia; Spartina alterniflora and Scirpus mariqueter in China) and water were measured in situ. Soil (from the 0–10 cm top layer) and plant samples were collected in the end of study. Besides different chemical parameters measured of soil samples, the archaeal and bacterial community abundance was evaluated by quantitative PCR. To characterise methane cycle, the abundances of methanogenic marker gene mcrA and methanotrophic marker gene pmoA were assessed. Genetic potential of nitrogen transformation processes was evaluated by targeting the following functional genes: bacterial, archaeal and COMAMMOX(complete oxidation of ammonium)-specific amoA (nitrification); nirS, nirK, nosZ clade I and nosZ clade II (denitrification); nifH (N2 fixation); nrfA (DNRA, dissimilatory nitrate reduction to ammonium); ANAMMOX- (anaerobic ammonium oxidation), and n-damo-specific 16S rRNA genes (nitrite dependent anaerobic methane oxidation). The results concluded that different plant species played a critical role in mediating gas emissions, where their age composition and biomass was important. Relevance of n-damo process and its high genetic potential for CH4 reduction was detected in coastal areas. Still, four times higher CH4 emissions were observed on the Chinese coast compared to Estonia. DNRA process showed the greatest genetic potential in the Chinese research area, but this process was less likely to occur in the soil of Estonian Phragmites australis. As a result of nitrification and denitrification, N2O was emitted from the coasts to the atmosphere.

Riparian forests are known as hot spots of nitrogen cycling in landscapes. Climate warming speeds up the cycle. Here we present results from a multi-annual high temporal-frequency study of soil, stem, and ecosystem (eddy covariance) fluxes of N2O from a typical riparian forest in Europe. Hot moments (extreme events of N2O emission) lasted a quarter of the study period but contributed more than half of soil fluxes. We demonstrate that high soil emissions of N2O do not escape the ecosystem but are processed in the canopy. Rapid water content change across intermediate soil moisture was a major determinant of elevated soil emissions in spring. The freeze-thaw period is another hot moment. However, according to the eddy covariance measurements, the riparian forest is a modest source of N2O. We propose photochemical reactions and dissolution in canopy-space water as reduction mechanisms.

Besides water table depth, soil temperature is one of the main drivers of greenhouse gas (GHG) emissions in intact and managed peatlands. In this work, we evaluate the performance of remotely sensed land surface temperature (LST) as a proxy of greenhouse gas emissions in intact, drained and extracted peatlands. For this, we used chamber-measured carbon dioxide (CO2) and methane (CH4) data from seven peatlands in Estonia collected during vegetation season in 2017–2020. Additionally, we used temperature and water table depth data measured in situ. We studied relationships between CO2, CH4, in-situ parameters and remotely sensed LST from Landsat 7 and 8, and MODIS Terra. Results of our study suggest that LST has stronger relationships with surface and soil temperature as well as with ecosystem respiration (Reco) over drained and extracted sites than over intact ones. Over the extracted cites the correlation between Reco CO2 and LST is 0.7, and over the drained sites correlation is 0.5. In natural sites, we revealed a moderate positive relationship between LST and CO2 emitted in hollows (correlation is 0.6) while it is weak in hummocks (correlation is 0.3). Our study contributes to the better understanding of relationships between greenhouse gas emissions and their remotely sensed proxies over peatlands with different management status and enables better spatial assessment of GHG emissions in drainage affected northern temperate peatlands.

Remotely sensed land surface temperature (LST) enables global modeling and monitoring of CO 2 fluxes from peatlands. We aimed to provide the first overview of the potential for using LST to monitor ecosystem respiration ( R eco ) in disturbed (drained and extracted) peatlands. We used chamber‐measured data (2017–2020) from five disturbed and two intact northern peatlands and LST data from Landsat 7, 8, and MODIS missions. First, we studied the strength of the relationships between fluxes and their in situ drivers (i.e., thermal and moisture conditions). Second, we examined the association between LST and in situ temperatures. Third, we compared chamber‐measured R eco with the modeled R eco driven by in situ measured water table depth and (a) in situ measured surface temperature and (b) remotely sensed MODIS LST data. In situ temperatures were a stronger driver of CO 2 fluxes in disturbed sites (repeated measures correlation rmR = 0.8–0.9) than in intact ones (rmR = 0.5–0.8). LST had a higher association with in situ measured temperatures in disturbed sites (mean rmR = 0.79 for MODIS) and weaker in the intact (hummocks and hollows) peatlands (mean rmR = 0.38 for Landsat and 0.48 for MODIS). R eco models driven by MODIS LST and in situ surface temperature yielded similar accuracy: R 2 was 0.27, 0.66, and 0.67 and 0.29, 0.70, and 0.66 for intact and for drained and extracted sites, respectively. Overall, these findings suggest the applicability of LST as a proxy of the thermal regime in R eco models, particularly for disturbed peatlands.

Constructed wetland-microbial electrochemical snorkel (CW-MES) systems, which are short-circuited microbial fuel cells (MFC), have emerged as a novel tool for wastewater management, although the system mechanisms are insufficiently studied in process-based or environmental contexts. Based on quantitative polymerase chain reaction assays, we assessed the prevalence of different nitrogen removal processes for treating nitrate-rich waters with varying cathode materials (stainless steel, graphite felt, and copper) and sizes in the CW-MES systems and correlated them to the changes of N2O emissions. The nitrate and nitrite removal efficiencies were in range of 40% to 75% and over 98%, respectively. In response to the electrochemical manipulation, the abundances of most of the nitrogen-transforming microbial groups decreased in general. Graphite felt cathodes supported nitrifiers, butnirK-type denitrifiers were inhibited. Anaerobic ammonium oxidation (ANAMMOX) bacteria were less abundant in the electrochemically manipulated treatments compared to the controls. ANAMMOX and denitrification are the main nitrogen reducers in CW-MES systems. The treatments with 1:1 graphite felt, copper, plastic, and stainless-steel cathodes showed higher N2O emissions.nirS- andnosZI-type denitrifiers are mainly responsible for producing and reducing N2O emissions, respectively. Hence, electrochemical manipulation supported dissimilatory nitrate reduction to ammonium (DNRA) microbes may play a crucial role in producing N2O in CW-MES systems.