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Controlled drainage (CRD) is an agricultural water management practice designed to adjust the capacity of a drainage system under varying hydrological conditions. This simulation study aimed to quantify the potential of combining a controlled subsurface drainage (CS) with open ditch damming (CD) to manage the water table depth (WTD) and field water balance in Nordic conditions. Simulations with and without controlled drainage were run using a hydrological model that had been set up for a flat loamy field in Northern Ostrobothnia, Finland, for the period 2010-2021. All CRD scenarios reduced the probability of deep WTDs during growing seasons (May-Sep). The impact of CS on WTDs was greater and more uniform than CD. The CRD effects on water balance were seen in water outflow pathways, as CS reduced drain discharge while CD had the opposite effect. When both methods were applied simultaneously, annual evapotranspiration increased 5-12% compared with the free drainage scenario. The effects of CRD on evapotranspiration were greatest during the dry years indicating that CRD has potential to reduce drought in food production areas. None of the CRD scenarios could maintain optimal WTDs during the entire growing season, highlighting the complexity of optimizing field water management using CRD alone. [ABSTRACT FROM AUTHOR]

In Finland, the widespread drainage of boreal peatlands has led to increased forest productivity. The cost is a dramatic increase in soil greenhouse gas emissions. Empirical research of drained peatlands has found a correlation between greenhouse gas emissions and the ground water table. This suggests an opportunity to mitigate greenhouse gas emissions through forest management. We explore this opportunity at the landscape level through a simulation and optimization framework. We explore how forest management actions can impact the ground water table and the related greenhouse gas emissions. There are various economic and societal constraints for a set of forested peatland landscapes in Finland. First, we link forest simulations with hydrological and statistical models to predict CO2, CH4, and N2O emissions from the drained peatlands. We then present the range of landscape level solutions that prioritize between minimizing the net ecosystem greenhouse gas emissions, the economic timber value, and the even flow of timber income over time. Our results highlight the impact that integrating peatland soil greenhouse gas emissions will have on the planning process. This promotes the use of management options that benefit both biomass growth and reduced peatland soil greenhouse gas emissions. [ABSTRACT FROM AUTHOR]

Climate change‐driven vegetation changes can alter the ecosystem functions of northern peatlands. Several case studies have documented fen‐to‐bog transition (FBT) over recent decades, which can have major implications, as increased bog growth would likely cause cooling feedback. However, studies beyond individual cases are missing to infer if a common trajectory or many alternatives of FBT are in progress. We explored plant community and hydrology patterns during FBT of 23 boreal aapa mire complexes in Finland. We focused on mires where comparisons of historical (1940–1970) and new (2017–2019) aerial photographs indicated an expansion of Sphagnum‐dominated zones. Vegetation plot and water chemistry data were collected from string‐flark fens, transition zones with indications of Sphagnum increase, and bog zones; thus, in a chronosequence with a decadal time span. We ask, is there a common trajectory or many alternatives of FBT in progress, and what are the main characteristics (species and traits) of transitional plant communities? We found a pattern of fen‐bog transitions via an increase in Sphagnum sect. Cuspidata (mainly S. majus and S. balticum), indicating a consistently high water table. Indicators only of transitional communities were scarce (Sphagnum lindbergii), but FBT had apparently facilitated shallow‐rooted aerenchymatous vascular plants, especially Scheuchzeria palustris. Water pH consistently reflected the chronosequence with averages of 4.2, 3.9, and 3.8, from fen to transition and bog zones. Due to weak minerotrophy of string‐flark fens, species richness increased towards bogs, but succession led to reduced beta diversity and homogenization among bog sites. Decadal chronosequence suggested a future fen‐bog transition through a wet phase, instead of a drying trend. Transitional poor‐fen vegetation was characterized by the abundance of Sphagnum lindbergii, S. majus, and Scheuchzeria palustris. Sphagnum mosses likely benefit from longer growing seasons and consistently wet and acidic conditions of aapa mires. [ABSTRACT FROM AUTHOR]

Since the late 1800s, the source selection – surface water or groundwater – for urban water supply has faced several policy changes in Finland. First, groundwater was favored. In 1920, driven by cost and reliability issues, one major city turned to surface water which was a sourcing determination for the country. After WWII, groundwater gradually gained preference motivated by reliability, including managed aquifer recharge since 1970. Instead of identified policy decisions, this shift was based on accumulated strategy. Since the 1980s security issues have favored groundwater while environmental concerns manifest themselves controversially. As a sub-study, treated lake water and groundwater were tasted by 167 persons of whom 86% preferred the latter. An additional expert survey (n=14) showed several benefits for groundwater. Combining these findings, groundwater has several advantages over surface water for Finnish urban water. Yet, for the futures, we need to keep both water sources in as good condition as possible. [ABSTRACT FROM AUTHOR]

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Waterlogging causes hypoxic or anoxic conditions in soils, which lead to decreases in root and stomatal hydraulic conductance. Although these effects have been observed in a variety of plant species, they have not been quantified continuously over a range of water table depths (WTD) or soil water contents (SWC). To provide a quantitative theoretical framework for tackling this issue, we hypothesized similar mathematical descriptions of waterlogging and drought effects on whole-tree hydraulics and constructed a hierarchical model by connecting optimal stomata and soil-to-leaf hydraulic conductance models. In the model, the soil-to-root conductance is non-monotonic with WTD to reflect both the limitations by water under low SWC and by hypoxic effects associated with inhibited oxygen diffusion under high SWC. The model was parameterized using priors from literature and data collected over four growing seasons from Scots pine (Pinus sylvestris L.) trees grown in a drained peatland in Finland. Two reference models (RMs) were compared with the new model, RM1 with no belowground hydraulics and RM2 with no waterlogging effects. The new model was more accurate than the RMs in predicting transpiration rate (fitted slope of measured against modeled transpiration rate = 0.991 vs 0.979 (RM1) and 0.984 (RM2), R 2 = 0.801 vs 0.665 (RM1) and 0.776 (RM2)). Particularly, RM2's overestimation of transpiration rate under shallow water table conditions (fitted slope = 0.908, R 2 = 0.697) was considerably reduced by the new model (fitted slope = 0.956, R 2 = 0.711). The limits and potential improvements of the model are discussed. [ABSTRACT FROM AUTHOR]

Strip-cutting management has been proposed as an alternative to clear-cuts in drained boreal peatland pine (Pinus sylvestris L.) forests. We explored the hydrological feasibility of strip cutting, that is, under which conditions the post-harvest water table (WT) in peat remains sufficiently deep (here, a WT of −0.35 m during the late growing season) to enable undisturbed tree growth. We approached the question by (1) measuring the WTs in a harvested strip and an adjacent unharvested stand in peatland forests in southern Finland and (2) by simulating the WTs in different strip cut layouts, unharvested peatland, and clear-cut cases using a process-based hydrological model. The measured WTs were, on average, 0.06–0.12 m closer to the peat surface in the harvested strips than in the unharvested stands. The hydrological feasibility of strip cutting increased along with increasing site productivity and improving climate conditions. Strip cutting resulted in the rise in the WTs of adjacent unharvested stands, which can have undesired consequences. Depending on the stand density and strip cut layout, the share of the well-drained area in the harvested strips was slightly larger or even two times larger compared to a complete clear-cut of the forest. Narrow strips (here, 13 m in width) indicated better drainage in the harvested area than wider (20–30 m in width) strips. Even though strip cutting has limited capacity to maintain efficient drainage in the harvested strip on low hydraulic conductivity peat, the increase in the WT was smaller than after clear-cut. [ABSTRACT FROM AUTHOR]

This simulation study focused on the hydrological effects of climate change and controlled drainage operated with subsurface drains and an open collector ditch in an agricultural field. The objective was to understand the potential of controlled drainage and open ditch schemes for managing groundwater levels and field water balance in climate conditions projected to take place in Finland during the 21st century with representative concentration pathways 8.5 and 2.6. A methodological aim was to find ways to condense hourly hydrological results to understand future changes in field hydrology. During the historical reference interval (1970-2005), controlled drainage caused 17-36 cm higher mean groundwater levels and decreased the mean annual drain discharge by 11-23% compared to conventional subsurface drainage. Controlled drainage was projected to increase groundwater levels by additional 1-4 cm in the future compared to its effect on drainage during the reference interval. The effect on annual drain discharge did not change significantly. The open collector ditch lowered groundwater tables and diminished the effect of controlled drainage on groundwater levels in the vicinity of the ditch. Controlled drainage was shown to remain an effective method for countering early summer drought and reducing drain discharge. [ABSTRACT FROM AUTHOR]

Pristine boreal mires are known as substantial sinks of carbon dioxide (CO2) and net emitters of methane (CH4). Bogs constitute a major fraction of pristine boreal mires. However, the bog CO2 and CH4 balances are poorly known, having been largely estimated based on discrete and short-term measurements by manual chambers and seldom using the eddy-covariance (EC) technique. Eddy-covariance (EC) measurements of CO2 and CH4 exchange were conducted in the Siikaneva mire complex in southern Finland in 2011–2016. The site is a patterned bog having a moss–sedge–shrub vegetation typical of southern Eurasian taiga, with several ponds near the EC tower. The study presents a complete series of CO2 and CH4 EC flux (FCH4) measurements and identifies the environmental factors controlling the ecosystem–atmosphere CO2 and CH4 exchange. A 6-year average growing season (May–September) cumulative CO2 exchange of - 61 ± 24 gCm-2 was observed, which partitions into mean total respiration (Re) of 167 ± 33 (interannual range 146–197) gCm-2 and mean gross primary production (GPP) of 228 ± 46 (interannual range 193–257) gCm-2 , while the corresponding FCH4 amounts to 7.1 ± 0.7 (interannual range 6.4–8.4) gCm-2. The contribution of October–December CO2 and CH4 fluxes to the cumulative sums was not negligible based on the measurements during one winter. GPP, Re and FCH4 increased with temperature. GPP and FCH4 did not show any significant decline even after a substantial water table drawdown in 2011. Instead, GPP, Re and FCH4 were limited in the cool, cloudy and wet growing season of 2012. May–September cumulative net ecosystem exchange (NEE) of 2013–2016 averaged at about - 73 gCm-2 , in contrast with the hot and dry year 2011 and the wet and cool year 2012. Suboptimal weather likely reduced the net sink by about 25 gCm-2 in 2011 due to elevated Re, and by about 40 gCm-2 in 2012 due to limited GPP. The cumulative growing season sums of GPP and CH4 emission showed a strong positive relationship. The EC source area was found to be comprised of eight distinct surface types. However, footprint analyses revealed that contributions of different surface types varied only within 10 %–20 % with respect to wind direction and stability conditions. Consequently, no clear link between CO2 and CH4 fluxes and the EC footprint composition was found despite the apparent variation in fluxes with wind direction. [ABSTRACT FROM AUTHOR]

Remote sensing (RS) has been suggested as a tool to spatially monitor the status of peatland ecosystem functioning after restoration. However, there have been only a few studies in which post-restoration hydrological changes have been quantified with RS-based modelling. To address this gap, we developed an approach to assess post-restoration spatiotemporal changes in the peatland water table (WT) with optical (Sentinel-2 and Landsat 7–9) and radar (Sentinel-1) imagery. We tested the approach in eleven northern boreal peatlands (six restored, and five control sites) impacted by forestry drainage in northern Finland using Google Earth Engine cloud computing capabilities. We constructed a random forest regression model with spatiotemporal field-measured WT data as a dependent variable and satellite imagery features as independent variables. To assess the spatiotemporal changes, we constructed representative maps for situations before and after restoration, separately for early summer high-water and midsummer low-water conditions. To further quantify temporal changes during 2015–2023 and to test their statistical significance, we conducted a bootstrap hypothesis test for the areas near the restoration measures and similar areas in the control sites. The regression model had a relatively good fit and explanatory capacity (overall R2 = 0.71, RMSE = 6.01 cm), while there were notable site-specific variations. The WT maps showed that the post-restoration changes were not uniform and concentrated near the restoration measures. The bootstrap test showed that the WT increased more in the restored areas (4.7–8.8 cm) than in the control areas (0.1–5.2 cm). Our results indicate that restoration impact on surface hydrology can be quantified with multi-sensor satellite imagery and a machine learning approach in treeless peatlands. • We assess post-restoration changes in peatland water table with satellite imagery. • Random forest regression between field and satellite data functions well. • Optical imagery performs better than SAR imagery. • Restoration impacts are mostly local. • Developed approach can be used to assess restoration success in open peatlands. [ABSTRACT FROM AUTHOR]

The patterned microtopography of subarctic mires generates a variety of environmental conditions, and carbon dioxide (CO 2) and methane (CH 4) dynamics vary spatially among different plant community types (PCTs). We studied the CO 2 and CH 4 exchange between a subarctic fen and the atmosphere at Kaamanen in northern Finland based on flux chamber and eddy covariance measurements in 2017–2018. We observed strong spatial variation in carbon dynamics between the four main PCTs studied, which were largely controlled by water table level and differences in vegetation composition. The ecosystem respiration (ER) and gross primary productivity (GPP) increased gradually from the wettest PCT to the drier ones, and both ER and GPP were larger for all PCTs during the warmer and drier growing season 2018. We estimated that in 2017 the growing season CO 2 balances of the PCTs ranged from - 20 g C m -2 (Trichophorum tussock PCT) to 64 g C m -2 (string margin PCT), while in 2018 all PCTs were small CO 2 sources (10–22 g C m -2). We observed small growing season CH 4 emissions (< 1 g C m -2) from the driest PCT, while the other three PCTs had significantly larger emissions (mean 7.9, range 5.6–10.1 g C m -2) during the two growing seasons. Compared to the annual CO 2 balance (- 8.5 ± 4.0 g C m -2) of the fen in 2017, in 2018 the annual balance (- 5.6 ± 3.7 g C m -2) was affected by an earlier onset of photosynthesis in spring, which increased the CO 2 sink, and a drought event during summer, which decreased the sink. The CH 4 emissions were also affected by the drought. The annual CH 4 balance of the fen was 7.3 ± 0.2 g C m -2 in 2017 and 6.2 ± 0.1 g C m -2 in 2018. Thus, the carbon balance of the fen was close to zero in both years. The PCTs that were adapted to drier conditions provided ecosystem-level resilience to carbon loss due to water level drawdown. [ABSTRACT FROM AUTHOR]

Besides causing acidification, acid sulfate (AS) soils contain large nitrogen (N) stocks and are a potential source of N loading to waters and nitrous oxide (N2O) emissions. We quantified the stocks and flows of N, including crop yields, N leaching, and N2O emissions, in a cultivated AS soil in western Finland. We also investigated whether controlled drainage (CD) and sub-irrigation (CDI) to keep the sulfidic horizons inundated can alleviate N losses. Total N stock at 0–100 cm (19.5 Mg ha−1) was smaller than at 100–200 cm (26.6 Mg ha−1), and the mineral N stock was largest below 170 cm. Annual N leaching (31–91 kg N ha−1) plus N in harvested grain (74–122 kg N ha−1) was 148% (range 118–189%) of N applied in fertilizers (90–125 kg N ha−1) in 2011–2017, suggesting substantial N supply from soil reserves. Annual emissions of N2O measured during 2 years were 8–28 kg N ha−1. The most probable reasons for high N2O emission rates in AS soils are concomitant large mineral N pools with fluctuating redox conditions and low pH in the oxidized subsoil, all favoring formation of N2O in nitrification and denitrification. Although the groundwater level was higher in CD and CDI than in conventional drainage, N load and crop offtake did not differ between the drainage methods, but there were differences in emissions. Nitrogen flows to the atmosphere and drainage water were clearly larger than those in non-AS mineral soils indicating that AS soils are potential hotspots of environmental impacts. [ABSTRACT FROM AUTHOR]

In boreal peatlands felling and tree harvest are commonly carried out as part of peatland restoration. Stem‐only harvest is the principal harvest method and it leaves the live crown material (felling residue) containing most tree nutrients at the site. Whole‐tree harvest, where felling residue is removed, is not favored due to higher transport costs, although it might better promote the recovery of nutrient‐poor peatlands towards pristine conditions. We investigated whether initial differences in N mineralization and decomposition rates observed between tree harvest methods continued out to 6 years after restoration and whether the spatial variation in water table (WT) level and water nutrient concentrations parallels with the observed pattern in mineralization and decomposition rates. The study was done at 15 peatland sites in Natura 2000 protection areas in Finland during 2007–2013. Concentration of ammonium in soil water was higher in the stem‐only harvest treatment compared to that of the whole‐tree harvest treatment, whereas the previously observed differences in net N mineralization and decomposition rates had leveled out by the sixth year after restoration. The spatial variation created by the ditch network still affected the hydrology and peatland functions so that the nutrient concentrations were higher near ditches than in other locations, implying potential risk for nutrient leaching. Based on this study, there is no reason to prefer either harvest method over the other in nutrient‐poor drained peatlands with low tree volumes, which constitute the majority of available peatland restoration area in Finland. [ABSTRACT FROM AUTHOR]

The patterned microtopography of subarctic mires generates a variety of environmental conditions, and carbon dioxide (CO2) and methane (CH4) dynamics vary spatially among different plant community types. We studied the CO2 and CH4 exchange between a subarctic fen and the atmosphere at Kaamanen in northern Finland based on flux chamber and eddy covariance measurements in 2017-2018. We observed strong spatial variation in carbon dynamics between the four main plant community types (PCTs) studied, which were largely controlled by water table level and differences in vegetation composition. The ecosystem respiration (ER) and gross primary productivity (GPP) increased gradually from the wettest PCT to the drier ones, and both ER and GPP were larger for all PCTs during the warmer and drier growing season 2018. We estimated that in 2017 the growing season CO2 balances of the PCTs ranged from -20 g C m-2 (Trichophorum tussock PCT) to 64 g C m-2 (string margin PCT), while in 2018 all PCTs were small CO2 sources (10-22 g C m-2). We observed small growing season CH4 emission sums (< 1 g C m-2) from the driest PCT, while the other three PCTs had significantly larger emissions sums (mean 7.9, range 5.6-10.1 g C m-2) during the two growing seasons. Compared to the annual CO2 balance (-8.5 ± 4.0 g C m-2) of the fen in 2017, in 2018 the annual balance (-5.6 ± 3.7 g C m-2) was affected by an earlier onset of photosynthesis in spring, which increased the CO2 sink, and a drought event during summer, which decreased the sink. The CH4 emissions were also affected by the drought. The annual CH4 balance of the fen was 7.3 ± 0.2 g C m-2 in 2017 and 6.2 ± 0.1 g C m-2 in 2018. Thus, the carbon balance of the fen was close to zero in both years. The PCTs adapted to drier conditions provided resilience to carbon loss due to water level draw down. [ABSTRACT FROM AUTHOR]

Summary: Mining operations produce large quantities of wastewater. At a mine site in Northern Finland, two natural peatlands are used for the treatment of mining‐influenced waters with high concentrations of sulphate and potentially toxic arsenic (As). In the present study, As removal and the involved microbial processes in those treatment peatlands (TPs) were assessed. Arsenic‐metabolizing microorganisms were abundant in peat soil from both TPs (up to 108 cells gdw−1), with arsenate respirers being about 100 times more abundant than arsenite oxidizers. In uninhibited microcosm incubations, supplemented arsenite was oxidized under oxic conditions and supplemented arsenate was reduced under anoxic conditions, while little to no oxidation/reduction was observed in NaN3‐inhibited microcosms, indicating high As‐turnover potential of peat microbes. Formation of thioarsenates was observed in anoxic microcosms. Sequencing of the functional genemarkers aioA (arsenite oxidizers), arrA (arsenate respirers) and arsC (detoxifying arsenate reducers) demonstrated high diversity of the As‐metabolizing microbial community. The microbial community composition differed between the two TPs, which may have affected As removal efficiencies. In the present situation, arsenate reduction is likely the dominant net process and contributes substantially to As removal. Changes in TP usage (e.g. mine closure) with lowered water tables and heightened oxygen availability in peat might lead to re‐oxidation and re‐mobilization of bound arsenite. [ABSTRACT FROM AUTHOR]

There is growing concern that rapidly changing climate in high latitudes may generate significant geomorphological changes that could mobilise floodplain sediments and carbon; however detailed investigations into the bank erosion process regimes of high latitude rivers remain lacking. Here we employ a combination of thermal and RGB colour time‐lapse photos in concert with water level, flow characteristics, bank sediment moisture and temperature, and topographical data to analyse river bank dynamics during the open‐channel flow period (the period from the rise of the spring snowmelt flood until the autumn low flow period) for a subarctic river in northern Finland (Pulmanki River). We show how variations of bank sediment temperature and moisture affect bank erosion rates and locations, how bank collapses relate to fluvial processes, and elucidate the seasonal variations and interlinkages between the different driving processes. We find that areas with high levels of groundwater content and loose sand layers were the most prone areas for bank erosion. Groundwater seeping caused continuous erosion throughout the study period, whereas erosion by flowing river water occurred during the peak of snowmelt flood. However, erosion also occurred during the falling phase of the spring flood, mainly due to mass failures. The rising phase of the spring flood therefore did not affect the river bank as much as its peak or receding phases. This is explained because the bank is resistant to erosion due to the prevalence of still frozen and drier sediments at the beginning of the spring flood. Overall, most bank erosion and deposition occurrences were observed during the low flow period after the spring flood. This highlights that spring melt, while often delivering the highest discharges, may not be the main driver of bank erosion in sub‐arctic meandering rivers. © 2019 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

• Sprinkling infiltration is a form of artificial groundwater recharge. • Sprinkling infiltration results in the long-term neutralization of forest soil. • Added water affected tree growth and understory vegetation. • Soil recovery takes more than 15 years from the treatment. The artificial recharge of groundwater by infiltrating surface water through forest soil has been introduced as a groundwater producing practice in Finland. As a result, the forest soil, as well as the whole ecosystem, is subjected to extremely high inputs of carbon and nutrient rich lake water. The effects of sprinkling infiltration on forest soil, tree growth and understory vegetation and their respective recovery were studied on a forested esker in central Finland. The Scots pine-dominated experimental plots were sprinkled with lake water in 1998–2001 and sampled after a 12–15-year recovery period. Soil pH and base cation concentration, as well as the rate of net N mineralization were significantly higher at the plots that had been infiltrated. The concentrations of base cations calcium and magnesium were thousands of times higher in the infiltrated soil than in the untreated soil. In addition, sprinkling infiltration had favored early-successional herbs, grasses and forbs and negatively affected late successional, slow-growing mosses and lichens. Sprinkling infiltration had significantly increased tree radial growth. Sprinkling infiltration is an environment altering soil treatment method which, based on the findings of this study, can have long-term effects on tree growth, soil processes and understory vegetation. [ABSTRACT FROM AUTHOR]

We measured methane ebullition from a patterned boreal bog situated in the Siikaneva wetland complex in southern Finland. Measurements were conducted on water (W) and bare peat surfaces (BP) in three growing seasons (2014–2016) using floating gas traps. The volume of the trapped gas was measured weekly, and methane and carbon dioxide (CO2) concentrations of bubbles were analysed from fresh bubble samples that were collected separately. We applied a mixed-effect model to quantify the effect of the environmental controlling factors on the ebullition. Ebullition was higher from W than from BP, and more bubbles were released from open water (OW) than from the water's edge (EW). On average, ebullition rate was the highest in the wettest year (2016) and ranged between 0 and 253 mg m -2 d -1 with a median of 2 mg m -2 d -1 , 0 and 147 mg m -2 d -1 with a median of 3 mg m -2 d -1 , and 0 and 186 mg m -2 d -1 with a median of 28 mg m -2 d -1 in 2014, 2015, and 2016, respectively. Ebullition increased together with increasing peat temperature, weekly air temperature sum and atmospheric pressure, and decreasing water table (WT). Methane concentration in the bubbles released from W was 15–20 times higher than the CO2 concentration, and from BP it was 10 times higher. The proportion of ebullition fluxes upscaled to ecosystem level for the peak season was 2 %–8 % and 2 %–5 % of the total flux measured with eddy covariance technique and with chambers and gas traps, respectively. Thus, the contribution of methane ebullition from wet non-vegetated surfaces of the bog to the total ecosystem-scale methane emission appeared to be small. [ABSTRACT FROM AUTHOR]

Quantifying landscape-scale methane ( CH4) fluxes from boreal and arctic regions, and determining how they are controlled, is critical for predicting the magnitude of any CH4 emission feedback to climate change. Furthermore, there remains uncertainty regarding the relative importance of small areas of strong methanogenic activity, vs. larger areas with net CH4 uptake, in controlling landscape-level fluxes. We measured CH4 fluxes from multiple microtopographical subunits (sedge-dominated lawns, interhummocks and hummocks) within an aapa mire in subarctic Finland, as well as in drier ecosystems present in the wider landscape, lichen heath and mountain birch forest. An intercomparison was carried out between fluxes measured using static chambers, up-scaled using a high-resolution landcover map derived from aerial photography and eddy covariance. Strong agreement was observed between the two methodologies, with emission rates greatest in lawns. CH4 fluxes from lawns were strongly related to seasonal fluctuations in temperature, but their floating nature meant that water-table depth was not a key factor in controlling CH4 release. In contrast, chamber measurements identified net CH4 uptake in birch forest soils. An intercomparison between the aerial photography and satellite remote sensing demonstrated that quantifying the distribution of the key CH4 emitting and consuming plant communities was possible from satellite, allowing fluxes to be scaled up to a 100 km2 area. For the full growing season (May to October), ~ 1.1-1.4 g CH4 m−2 was released across the 100 km2 area. This was based on up-scaled lawn emissions of 1.2-1.5 g CH4 m−2, vs. an up-scaled uptake of 0.07-0.15 g CH4 m−2 by the wider landscape. Given the strong temperature sensitivity of the dominant lawn fluxes, and the fact that lawns are unlikely to dry out, climate warming may substantially increase CH4 emissions in northern Finland, and in aapa mire regions in general. [ABSTRACT FROM AUTHOR]

Introduction: The ~4 km-diameter, Mid-Miocene Steinheim Basin on the karstic Swabian Alb plateau of SW Germany is a well-preserved complex impact crater with a prominent central uplift. The impact crater, known for its shatter cones, is set in a sequence of Mesozoic sediments and lies some 40 km SW of the ~24 km-diameter Nördlinger Ries [1]. While geochronologic studies of impact melt samples from the Ries crater (tektites) yielded a high-precision Mid-Miocene (Langhian) Ar-Ar age of 14.81 Ma [2], several attempts to date the Steinheim impact using isotopic techniques failed to produce a meaningful geologic age. This is partly due to the fact that, in contrast to the Ries, impact melt lithologies at Steinheim are rather scarce and, if present, mainly of carbonatic composition [3] or intensely altered to sheet silicates [4]. An Ar-Ar study of a pebble of fluidal, partially melted sandstone found at the Steinheim central uplift [4] produced disturbed age spectra without any representative age signal. (U-Th/He) dating of zircon crystals from the central uplift yielded partially reset (Moldanubian?) ages between ~282 and 247 Ma [5]. The double impact theory: The general notion that the Ries and Steinheim craters must have been produced simultaneously by the impact of a binary asteroid [6,7] is, after all, mainly based on the assumption that two closely spaced asteroid impacts around the same time are (higly) unlikely to occur at random [8]. However, as shown for other suspected terrestrial impact crater pairs, such as the East and West Clearwater Lake impact structures in Canada [9] and the Suvasvesi North and South impact structures in Finland [10], 'false' impact crater doublets do exist on Earth. In such cases, misleading underlying theories can compromise an independent assessment of impact ages [11]. Biostratigraphic constraints: The most promising solution is offered by biostratigraphic constraints on the formation of the Ries and Steinheim impact structures and their respective crater lake deposits. One would assume both crater depressions filled up with freshwater soon after their formation, as expected in a deeply water-saturated, karstified paleolandscape with a high Mid-Miocene groundwater level [12]. Water saturation is, in fact, well demonstrated by aragonitic spring mound deposits (the 'Wäldlesfels') sitting on top of the Steinheim central uplift [1]. Likewise, the pervasive alteration of impact melt lithologies in the crater-filling impact breccia suggests the fresh Steinheim crater may have hosted a short-lived hydrothermal system [4]. For these reasons, we argue the basal crater lake sediments at Steinheim more or less accurately reflect the timing of the impact. While the Mid-Miocene paleofauna at the Ries crater lake has been assigned to the Mammal Neogene (MN) zone MN 6 (type locality: Sansan, France) [13], with a coarse-grained Ries ejecta horizon in the North Alpine Foreland Basin sitting at a stratigraphic level close to the MN 5/6 transition [14,15], Steinheim is known as a type locality for the somewhat younger MN 7 paleofauna [1,13,16]. The basal lake sediments at Steinheim (the so-called kleini, steinheimensis, and sulcatus beds, named after the gastropod Gyraulus) represent the upper MN 6 biozone (Langhian) and are overlain by younger lake sediments (the trochiformis, oxystoma, revertens, and supremus beds) that belong to MN 7 (Langhian and Serravallian) [15,17]. In other words, the oldest, basal crater lake sediments at the Nördlinger Ries and Steinheim are separated by approximately one entire mammal biozone. Discussion and conclusions: From a biostratigraphic point of view, the Steinheim impact appears to postdate the Ries event by several kyr (and potentially ~1 Myr) [1,13]. While the Ries impact has a precise mid-Langhian Ar-Ar age of ~14.81 Ma [2], the current best-estimate age for the Steinheim impact is derived entirely from biostratigraphic constraints. Taking into account stratigraphic correlation and recent geochronologic results for the Langhian/Serravallian boundary (~13.8 Ma [18]), a late Langhian Steinheim impact scenario between ~14.3 and 14.0 Ma appears most plausible. We, moreover, note the Ries and Steinheim impacts correlate well, biostratigraphically, with two spectacular continental seismite horizons in Molasse deposits of the North Alpine Foreland Basin [19]. It remains unclear at this point whether the two impacts are causally related to faunal turnover events in European land mammals at the MN 5/6 (within uncertainty Ries-age) and MN 6/7 (approximately Steinheim-age) transitions [20,21]. [ABSTRACT FROM AUTHOR]

Geochemical characteristics of precipitated fracture filling calcite and pyrite can provide much useful information about the deep bedrock environment at the time of their deposition. However, it has been difficult to identify fracture coatings precipitated from the present-day groundwater system. The aim of this study was to evaluate the relationship between the coexisting calcite and pyrite, and the groundwater present at the time of precipitation. Here we investigated fine-grained mineral precipitate deposited over a four-year period on the surface of groundwater monitoring equipment inserted into a drillhole at 530 m below sea level, at Olkiluoto, which is the planned site for a final repository of spent nuclear fuel. The experimental setting is also artificial in the sense that the drillholes have possibly affected groundwater circulation and a foreign object has been inserted into the drillhole. Combining the elemental and isotope geochemical composition of the precipitated calcite and pyrite with previously published compositional data on groundwater and evidence for microbial communities on this site, offered a possibility to get new insight of the precipitation and isotope fractionation processes taking place in deep crystalline bedrock. The concentration of the redox sensitive manganese in the precipitate gives supporting evidence for the influx of groundwater from overlying groundwater units. The δ13C (n = 13) and δ18O (n = 15) values of calcite vary from −13.2 to −9.7‰ and from −9.1 to −7.4‰, respectively. Comparison to the respective values in the local groundwater indicated that the precipitated calcite is in near isotopic equilibrium with its environment with respect to carbon and oxygen. The potential ultimate source of the carbon in the DIC and in the precipitate is likely in old fracture calcite coatings. The δ34S values of pyrite (n = 9) show relatively small variation from −5.7 to 8.3‰. This differs greatly from the huge span of δ34S values from −50 to 80‰ in fracture pyrites reported for the latest calcite fillings at Olkiluoto. The restricted range of δ34S values is interpreted to result from open system conditions during precipitation, with new dissolved sulfate entering from the large brackish SO 4 -type groundwater unit above. The isotopic fractionation of sulfur between dissolved sulfate and sulfide is estimated to be 25 ± 10‰, which is in agreement with the results reported in laboratory experiments for bacterial sulfate reduction. • Modern-day mineral-water pairs observed in deep crystalline bedrock. • Fractionation of sulfur between dissolved sulfate and pyrite related in BSR. • Calcite isotopes in near equilibrium with groundwater. [ABSTRACT FROM AUTHOR]

Highlights: [•] We studied P export after clear-felling from Scots pine dominated peatlands in Finland. [•] The water table level was the most significant factor contributing to the P export. [•] The harvest method was not significant in explaining harvest-induced P loads. [•] The peat P sorption characteristics were not significant in explaining the P loads. [Copyright &y& Elsevier]

In Finland, ditch network maintenance (DNM) is carried out annually on 60-70,000 ha of drained peatland to promote tree growth for forestry purposes. However, it is important to avoid ditching that contributes little to the stand growth and productivity, both to improve the economical profitability of forestry and to mitigate DNM-induced nutrient release to watercourses. We hypothesised that mature forest stands with substantial evapotranspiration potential do not necessarily need DNM, even if the ditch networks are in poor condition. We estimated evapotranspiration (EVT) of forest vegetation during the growing seasons (June- September) of 2007-2011 in four forested artificial peatland catchments dominated by Scots pine stands (Pinus sylvestris L.) (stand volume 93-151 m³ ha-1) located in southern, western, central and northern Finland. Precipitation (P), runoff (R) and water table level (WTL) were monitored continuously in the field. The water storage change (▵ S) was estimated on the basis of WTL measurements and peat pF curves determined from in situ peat samples. In addition, tree stand transpiration (T) was estimated in two of the catchments using the sap flow method. EVT was estimated as the residual term of the water balance equation. During the growing season, EVT (153-295 mm) was 49-161 % of the total accumulated P (155-368 mm), and decreased from south to north. Within each growing season, EVT was always largest in July or August. Tree transpiration was about 50 % of the total forest EVT in the two sites where it was measured directly. The mean WTL was at depth 36-63 cm during the growing seasons. Clear-cutting of a 100m³ ha-1 stand on one site resulted in an average rise of WTL by 18 cm. The results suggested that, in the southernmost site in particular, no drainage network management would be necessary to sustain satisfactory drainage conditions for tree growth because growing-season precipitation is transferred back to the atmosphere by forest EVT. In the northernmost site, ditch networks were considered important in controlling drainage conditions because of the low EVT potential of <100 m³ ha-1 tree stands. Further research is needed to fully understand the mechanisms behind forest EVT potential, as one site with high tree stand volume had surprisingly low EVT potential. [ABSTRACT FROM AUTHOR]

A process-based model was developed and validated to predict the regional dynamics of the water table (WT) in peatlands under climatic forcing. The model detailed the water-energy feedbacks in the common SVAT (soil–vegetation–atmosphere transportation) model and specified the differences in processes in pristine fens, pristine bogs and drained peatlands. The spatiotemporal changes in the WT of the peatlands throughout Finland were computed based on 10km×10km grids for the period 2000–2099. The calculations used country-scale data on vegetation, catchment topography and profiles of peat bulk density and water content in the three mire types. Furthermore, the ACCLIM climate scenarios representing the current climate and the changing climate were used to identify the climatic impacts on the WT throughout Finland. Sensitivity analysis showed that the WT drawdown in pristine fens was most sensitive to increases in temperature and/or decreases in precipitation, whereas the WT drawdown in drained peatlands was the most resistant to such changes. For all three mire types, a 10% increase in precipitation based on the current climate tended to offset the effect of a 2°C warming on WT drawdown and a 20% increase in precipitation tended to offset the WT drawdown caused by a 6°C warming. Based on the ACCLIM climate scenario, the model showed moderate changes in the annual values of the WT, which ranged from +0.2±1.5 to −4.3±0.93cm. The changes were most noticeable during the period 2060–2099. The WT drawdown was more pronounced in late spring than in summer and autumn. Additionally, the WT drawdown was most significant in the western parts of the northern aapa-mire region, where the peatlands were mostly pristine, and the increase of precipitation was more limited than in other parts of the country. These results show that the pronounced spatiality and temporality in the WT changes should be considered in studies addressing how climate change will affect mire ecosystems in terms of C balance and GHG emissions. [Copyright &y& Elsevier]

Ditch networks in drained peatland forests are maintained regularly to prevent water table rise and subsequent decrease in tree growth. The growing tree stand itself affects the level of water table through evapotranspiration, the magnitude of which is closely related to the living stand volume. In this study, regression analysis was applied to quantify the relationship between the late summer water table depth (DWT) and tree stand volume, mean monthly summertime precipitation (Ps), drainage network condition, and latitude. The analysis was based on several large data sets from southern to northern Finland, including concurrent measurements of stand volume and summer water table depth. The identified model demonstrated a nonlinear effect of stand volume on DWT, a linear effect of Ps on DWT, and an interactive effect of both stand volume and Ps. Latitude and ditch depth showed only marginal influence on DWT. A separate analysis indicated that an increase of 10 m3·ha–1 in stand volume corresponded with a drop of 1 cm in water table level during the growing season. In a subsample of the data, high bulk density peat showed deeper DWT than peat with low bulk density at the same stand volume. [ABSTRACT FROM AUTHOR]

We studied the effect of long-term water table drawdown on the vascular plant community in an ombrotrophic bog in central Finland by measuring aboveground biomass and belowground production (by in-growth cores) across plant functional groups including herbs, shrubs, and trees. We compared drained and undrained portions 45 years after the installation of a drainage ditch network, which has lowered water levels of 15–20 cm on average in the drained part of the site. Although shrub fine root production did not differ significantly between sites, water table drawdown increased belowground tree fine root production by 740% (3.8 ± 5.4 SD and 28.1 ± 24.1 g m−2 y−1 in undrained and drained sites, respectively) at the expense of herb root production, which declined 38% (27.62 ± 16.40 and 10.58 ± 15.7 g m−2 y−1 in undrained and drained sites, respectively) yielding no significant overall change in total fine root production. Drainage effects on aboveground biomass showed a similar pattern among plant types, as aboveground tree biomass increased dramatically with drainage (79 ± 135 and 2546 ± 1551 g m−2 in drained and undrained sites, respectively). Although total shrub biomass was not significantly different between sites, shrubs allocated more biomass to stems than leaves in the drained site. Drainage also caused a significant shift in shrub species composition. Although trees dominated the aboveground biomass following water table drawdown, understorey vegetation, mainly shrubs, continued to dominate belowground fine root production, comprising 64% of total root production at the drained site. Aboveground biomass proved to be a good predictor of belowground production, suggesting that allometric relationships can be developed to estimate belowground production in these systems. Increase in tree root production can counteract decrease in herb fine root production following water table drawdown, emphasizing the importance of plant functional type responses to water table drawdown. Whether these changes will offset ecosystem C loss via increased plant C storage or stimulate soil organic matter decomposition via increased above- and belowground litter inputs requires further study. [ABSTRACT FROM AUTHOR]

One fourth of the forests in Finland are growing on drained peatlands. Forestry operations such as ditch network maintenance increase the export of suspended solids and nutrients, and deteriorate water quality in lakes and rivers. Water protection presupposes an understanding of how forestry operations affect peatland hydrology. The objective was to study the hydrological impacts of ditch cleaning on the basis of water table level and runoff measurements from two pairs of artificially delineated catchments in drained peatland forests in Finland. Data from treated and control catchments indicated that ditch cleaning lowered the level of the water table in sites where a shallow peat layer was underlain by mineral soil. In sites with deep peat formation, the water table showed no detectable response to ditch cleaning. Runoff data suggested that annual runoff clearly increased after ditch cleaning, which was in conflict with the previously reported small impacts of ditch network maintenance. The hydrological model FEMMA was calibrated and applied to assess the conformity of the data and the experimental setup. In the model application, the catchments were assumed to behave as independent hydrological units. However, assessment of the model results and the measurements suggested that ditch cleaning had an impact on hydrological measurements in both treated and control catchments. It appeared that the independence assumption was violated and there was a hydrological connection between the artificial catchments and, therefore, the results of the data analysis were considered misleading. Finally, a numerical experiment based on the model simulations was conducted to explain how the assumed relationship between soil moisture and transpiration is reflected in the modelled runoff. Modelled runoff decreases and evaporation increases when ditches are cleaned in poorly drained sites, where the initial ditch depth is small and the depth of a highly conductive topsoil layer is low. The numerical experiment can be applied to assess when ditch cleaning does not improve evapotranspiration and is unnecessary. [ABSTRACT FROM AUTHOR]

The quantitative relationship between stand growth rate and water table level in peatland forest sites has not been fully ascertained in the literature. In this study, we investigated this relationship by means of a bivariate regression model. Tree and stand attributes, including volume and past 5-year volume growth as well as median water table depth (WTM) during the 1984 growing season, were observed in 69 Scots pine (Pinus sylvestris L.) sample stands with three subplots established in each stand. All stands were located in deep-peated, moderately rich to poor organic soil sites in Central Finland (61°45′–62°26′N, 22°40′–28°29′E) that had been ditched for forestry about 25 years earlier (1959–1961). Prediction models for the fixed mean functions for 5-year volume growth and WTM as well as estimates for variances and the correlation of random effects at plot and subplot levels were estimated simultaneously using bivariate regression methods. The correlation of model residuals at the plot level was highly significant. The model was applied to simulate stand volume development for a period of 20 years. Simulations illustrated the dynamic interaction of stand volume, volume growth, and soil water levels: deep initial WTM resulted in stand growth and volume-development increases and subsequently further deepened the WTM in the stand. The model can be applied to southern boreal drained Scots pine peatlands to estimate the WTM in different stand volume conditions and to assess the effect of stand management on WTM. La relation quantitative entre le taux de croissance d’un peuplement et le niveau de la nappe phréatique dans les tourbières boisées n’a pas été clairement établie dans la littérature. Dans cette étude, avons étudié cette relation à l’aide d’un modèle de régression bivariée. Les caractéristiques des arbres et du peuplement, incluant le volume, l’accroissement en volume des cinq dernières années et la profondeur médiane de la nappe phréatique (NPM) pendant la saison de croissance 1984, ont été observées dans 69 peuplements de pin sylvestre (Pinus sylvestris L.) à l’intérieur desquels trois sous-placettes ont été établies. Tous les peuplements étaient établis sur des sols organiques profonds, modérément riches à pauvres, situés au centre de la Finlande (61°45′–62°26′N, 22°40′–28°29′E) et qui avaient été drainés environ 25 ans plus tôt (1959–1961). Des modèles de prévision pour les fonctions fixes moyennes dans le cas de l’accroissement quinquennal en volume et de la NPM, de même que l’estimation de la variance et de la corrélation entre les effets aléatoires, aux échelles de la placette et de la sous-placette, ont été estimés simultanément à l’aide d’une méthode de régression bivariée. La corrélation des résidus du modèle à l’échelle de la placette était hautement significative. Le modèle a été utilisé pour simuler l’évolution du volume du peuplement pendant une période de 20 ans. Les simulations illustrent l’interaction dynamique entre le volume du peuplement, l’accroissement en volume et le niveau de la nappe phréatique. Ainsi, une NPM initialement basse a entraîné une augmentation de la croissance du peuplement et du volume, ce qui a par la suite abaissé davantage la NPM dans le peuplement. Le modèle peut être appliqué aux tourbières de pin sylvestre drainées situées au sud de la zone boréale pour estimer la profondeur de la NPM dans des peuplements supportant différents volumes et pour évaluer les effets de l’aménagement forestier sur la NPM. [ABSTRACT FROM AUTHOR]

Drainage of waterlogged sites has been part of the normal forestry practice in Fennoscandia, the Baltic countries, the British Isles and in some parts of Russia since the early 20th century, and currently, about 15 million hectares of peatlands and other wetlands have been drained for forestry purposes. The rate of forest clear-felling on drained peatlands will undergo a rapid increase in the near future, when a large number of these forests approach their regeneration age. A small-scale pilot survey was performed at two nutrient-rich and old peatland drainage areas in southern Finland to study if forest clear-felling has significant impacts on the exchange of nitrous oxide (N2O) and methane (CH4) between soil and atmosphere. The average N2O emissions from the two drainage areas during three growing seasons following clear-felling were 945 and 246 μg m-2 d-1. The corresponding CH4 fluxes were -0.07 and -0.52 mg m-2 d-1. Clear-felling had impacts on the environmental factors known to affect the N2O and CH4 fluxes of peatlands, i.e. clear-felling raised the water table level and increased the peat temperature. However, no substantial changes in the fluxes of CH4 following clear-felling were observed. The results concerning N2O indicated a potential for increased emissions following clear-felling of drained peatland forests, but further studies are needed for a critical evaluation of the impacts of clear-felling on the fluxes of CH4 and N2O. [ABSTRACT FROM AUTHOR]

• T and P are increasing consistently, particularly in the frost season. • Frost season trends in hydroclimate cannot explain groundwater level trends. • Frost-free season drying correlates with declining groundwater levels in S Finland. • Hydroclimate trends in SE Sweden cannot explain declining groundwater trends. In cold climate, the main annual recharge event is spring snowmelt. Projections of groundwater storage hence depend on winter hydroclimate. Winter recharge is a factor of rain, melt and ground frost. Increases in winter rain and melt have already been observed. However, due to complex processes involved in ground frost formation and its natural patchy coverage, the effect of ground frost on recharge is poorly understood. The objective of the study is to improve the understanding of the connection between groundwater storage and hydroclimate in Sweden and Finland, a region with temperate and cold climate, from a seasonal frost cover perspective. In the study, annual, frost-free season and frost season temperature and precipitation trends in the climate regions are compared between one global and two regional reanalysis datasets. Effective precipitation and wet day frequency trends between 1980 and 2010 are compared to groundwater level trends for the same period. Trends are calculated using the Mann-Kendall test and Sen's slope. The results show that the region is generally experiencing warming and increased precipitation. These trends are strongest in the frost season. Further, the global dataset systematically underestimates median temperatures and precipitation compared to the regional datasets. Effective precipitation trends are generally weak, and indicate wetting in the frost season and drying in the frost-free season. Wet day frequency trends are decreasing significantly on the regional scale in Finland, but with nearly no trends in Sweden. Groundwater levels in southern Finland and southeastern Sweden are declining significantly, while groundwater levels in southwestern Sweden are significantly rising. The results indicate that groundwater trends in southern Finland are linked to wet day frequency and effective precipitation trends in the frost-free season, and that trends in the frost season have no impact on annual groundwater level trends. In southern Sweden, groundwater level trends appear linked to annual and frost-free season trends in effective precipitation, though insignificantly. These trends may be explained by century-scale trends in precipitation drought indices identified by previous studies. [ABSTRACT FROM AUTHOR]

Drainage is an essential prerequisite in peatland forest management, which generally, but not always, increases stand growth. Growth response depends on weather conditions, stand and site characteristics, management and biogeochemical processes. We constructed a SUSI-simulator (SUoSImulaattori, in Finnish), which describes hydrology, stand growth and nutrient availability under different management, site types and weather conditions. In the model development and sensitivity analysis, we used water table ( W T ) and stand growth data from 11 Scots pine stands. The simulator was validated against a larger dataset collected from boreal drained peatlands in Finland. In validation, SUSI was shown to predict W T and stand growth well. Stand growth was mainly limited by inadequate potassium supply, and in Sphagnum peats by low oxygen availability. Model application was demonstrated for ditch network maintenance (DNM) by comparing stand growth with shallow (−0.3 m) and deep ditches (−0.9 m): The growth responses varied between 0.5 and 3.5 m3 ha−1 in five years, which is comparable to experimental results. SUSI can promote sustainable peatland management and help in avoiding unnecessary drainage operations and associated environmental effects, such as increased carbon emissions, peat subsidence, and nutrient leaching. The source code is publicly available, and the modular structure allows model extension to cost–benefit analyses and nutrient export to water courses. [ABSTRACT FROM AUTHOR]

• Water table level and energy fluxes monitored after clear-cut and partial harvest. • A multi-species soil-plant-atmosphere transfer model applied to explore changes. • Harvesting 70% of stand basal area had marginal effects. • Remaining stand's structure and species composition play key role. • Post-harvest vegetation recovery had high importance to energy balance. We quantified the response of peatland water table level (WTL) and energy fluxes to harvesting of a drained peatland forest. Two alternative harvests (clear-cut and partial harvest) were carried out in a mixed-species ditch-drained peatland forest in southern Finland, where water and energy balance components were monitored for six pre-treatment and three post-treatment growing seasons. To explore the responses caused by harvestings, we applied a mechanistic multi-layer soil-plant-atmosphere transfer model. At the clear-cut site, the mean growing season WTL rose by 0.18 ± 0.02 m (error estimate based on measurement uncertainty), while net radiation, and sensible and latent heat fluxes decreased after harvest. On the contrary, we observed only minor changes in energy fluxes and mean WTL (0.05 ± 0.03 m increase) at the partial harvest site, although as much as 70% of the stand basal area was removed and leaf-area index was reduced to half. The small changes were mainly explained by increased water use of spruce undergrowth and field layer vegetation, as well as increased forest floor evaporation. The rapid establishment of field layer vegetation had a significant role in energy balance recovery at the clear-cut site. At partial harvest, chlorophyll fluorescence measurements and model-data comparison suggested the shade-adapted spruce undergrowth was suffering from light stress during the first post-harvest growing season. We conclude that in addition to stand basal area, species composition and stand structure need to be considered when controlling WTL in peatland forests with partial harvesting. Our results have important implications on the operational use of continuous cover forestry on drained peatlands. A continuously maintained tree cover with significant evapotranspiration capacity could enable optimizing WTL from both tree growth and environmental perspectives. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The Virttaankangas interlobate esker with 100 m thick sediments has a complex depositional history. It is one of the largest groundwater reserves in Finland and hosts a managed artificial recharge plant providing potable water for the 300,000 inhabitants of the Turku region. We researched the characteristics of the esker aquifer both on a major fracture valley and on an esker ridge with a low groundwater table. This study presents the results of the first landstreamer-based high-resolution seismic reflection survey in Finland conducted in 2011. The esker core (main aquifer) position was delineated accurately throughout the entire area with continuous seismic data compared to a previous sedimentological model, gravimetric data and reference drillings. New features related to the widening of the coarse-grained unit of the esker core as well as a previously unknown daughter esker adjacent to the main esker core were revealed. These new findings are in agreement with the existing 3-D hydrogeological model. Our research provides valuable data on the high-resolution seismic reflection surveying of thick interlobate glaciofluvial deposits on two areas with differing bedrock topography on crystalline basement rocks. • Landstreamer-based, high-resolution seismic reflection data from SW Finland • Thick interlobate esker deposits with major groundwater reserves were researched. • Seismic profiling of over 50 m thick esker deposits down to the bedrock level • New unknown features related to the esker core were found. [ABSTRACT FROM AUTHOR]

Peatlands are actively drained and cultivated especially in Northern Hemisphere. In Finland peatlands comprise one third of the total land area while over half of these are drained. Cultivated peatlands are regionally important for food and grass production and for spreading cattle manure. Agriculture comprises one of the biggest sources of anthropogenic greenhouse gas (GHG) emissions and cultivated peatlands may have especially high emissions of carbon dioxide (CO2) and nitrous oxide (N2O). In addition to high GHG emissions, cultivated peatlands cause high nutrient and organic carbon loading to waterways.Water table level is known to be one the key factor affecting GHG emissions. Drainage increases the oxygen content of the peat and accelerates the peat decomposition as well as mineralization processes. Carbon is emitted as CO2, while CH4 emissions decrease significantly compared to pristine ones or peatland may turn into a CH4 sink. Nitrous oxide emissions can also increase substantially and drainage may cause high N2O emissions specifically in nutrient rich peatlands. Adjusting the water table level to certain depth is suggested to help to reduce GHG emissions. However, to control the water table level in peat soils is challenging with variable weather conditions. Also, too high water table disturb machinery operations in the fields. We study the effects of peatland cultivation on both GHG emissions and water run-off quality in Ruukki study site in Northern Finland. The site is operated by Finnish Natural Resources Institute (LUKE). The total area of the field is 19.5 ha and the peat depth varies between 30 and 70 cm. The field is divided to 6 different sections, where the water table, soil moisture, leaching of water and its quality can be monitored. We combine detailed hydrological analysis and modelling, soil analysis with high-resolution GHG measurements and utilize latest measurement technologies to study water table manipulation possibilities in cultivated peatlands.The aim of the project is to have integrated view of the effects of peatland cultivation on environment and climate by combining both hydrological and biogeochemical methods. The study is part of international PEATWISE-project (Wise use of drained peatlands in a bio-based economy: development of improved assessment practices and sustainable techniques for mitigation of greenhouse gases). [ABSTRACT FROM AUTHOR]

The largest areas of acid sulphate soils (AS) in Europe are located on the coasts of the Baltic Sea in Finland. Those soils are mostly ancient sediments that became exposed by the isostatic land uplift are still emerging from the Baltic Sea. In the 19th century the soils were reclaimed for cultivation without knowing their negative consequences to environment. Most AS fields were drained by subsurface pipes at the depth of 1.0 -1.2 meters before the 1990s. The fields are highly valued for their excellent crop yields but still cause chronic and acute environmental hazards for aquatic ecosystems. Therefore, environmental friendly cultivation and water management methods have been urgently sought. Studies in the 2000s showed that controlled drainage improved water quality where sulfidic materials occur below the drain depth. However, drop of groundwater level deep to sulphide bearing layers during winters and summers was found to be a problem. Sub-irrigation was introduced and implemented by farmers to improve yields and thus create a win-win situation for both the farmers and the environment. Seepage was identified as a common problem with sub-irrigation and a plastic sheet was installed to hinder seepage. Sub-irrigation and plastic sheet made it possible to maintain higher groundwater level at the Söderfjärden experimental field during summers, but groundwater level dropped deep occasionally during winters. The water quality improvements by sub-irrigation were only slight. In order to better understand the hydrology of AS soil fields and the effects of water management methods on water quality, a modelling study was initiated.In the modelling, the field data and simulation results from Söderfjärden experimental field were used for comparing the effect of conventional subsurface drainage (ND), controlled drainage (CD) and sub-irrigation (CDI) on groundwater level, water balance components and pH of drainage discharge. Two 1-D models were used: a Drainmod-based model and the ionic flow model HAPSU developed in Finland in the 1990s. The NSE-values for simulating groundwater level were good (0.62-0.68) for ND field but lower (0.38-0.47) for CD field. Based on the simulations the groundwater level was expected to be higher in CD and CDI fields and consequently improvement of the water quality should be stronger than was observed from the measurements. Modelling revealed that regardless of the plastic sheet water seeped into the main ditch, which explained the drop of groundwater level during winters. In addition, the simulations indicated that the topography of the field affected the efficiency of control structure to maintain groundwater level even though the slope of the field was only 0.14%. The results showed that the pumping of water to the lowest control well did not raise groundwater sufficiently to saturate sulphide bearing horizons at the upper end of the field. The modelling results suggested that the prevention of seepage could be improved by controlling the water level in the main ditch. In summer 2018, such a control dam was constructed in the main ditch and the preliminary observations suggested that groundwater level remained higher in the fields above the dam. [ABSTRACT FROM AUTHOR]

High water tables (WT) stabilise peatland carbon (C) through regulation of biogeochemical processes. The impact of peatland WT on ecosystem function, including C exchange, alters over time, and the factors that cause some peatlands to display resilience and others to undergo degradation are poorly understood. Here we use CO 2 flux measurements, measured by eddy covariance, to compare ecosystem function between two raised bogs; one drainage-affected, with a deep and fluctuating water table and the other near-natural, with a shallow and stable water table. The drainage-affected bog was found to be a moderate sink for CO 2 (69 g C m -2  yr -1 ), which was 134 g C m -2  yr -1 less than the near-natural bog (203 g C m -2  yr -1 ). Greater ecosystem productivity has allowed the drainage-impacted bog to act as a CO 2 sink despite higher ecosystem respiration; most likely due to an increase in photosynthetic capacity caused by expansion of ericaceous shrub cover. The tolerance of the vegetation community, particularly the main peat former Empodisma robustum (Restionaceae), to low and fluctuating WT appears to have been key in allowing the site to remain a sink. Despite the current resilience of the ecosystem CO 2 sink, we found gross primary production to be limited under both high and low water tables, even in a year with typical rainfall. This is best explained by the limited physiological ability of ericaceous shrubs to tolerate a fluctuating WT. As such we hypothesise that if the WT continues to drop and become even more unstable, then without further vegetation change, a reduction in gross primary production is likely which may in turn cause the site to become a source for CO 2 ., (Copyright © 2018 Elsevier B.V. All rights reserved.)