Lowering Of Water Table Research Articles

Origin of the Coloured Karst Fills in the Neogene Extensional System of NE Iberia (Spain)

Karst fills from the onshore Penedès Basin and offshore València Trough display red, pink, orange and ochre colours. Their Mössbauer spectra indicate that Fe3+ contained in goethite is the dominant species in reddish-pink fills, whereas Fe2+ contained in dolomite and clays is more dominant in the orange and ochre ones. The lower δ13C values and higher 87Sr/86Sr ratios of the karst fills with respect to their host carbonates can reflect the input of soil-derived CO2 and an external radiogenic source into the karst system. This geochemical composition, together with the non-carbonate fraction of the fills, consists of authigenic and transported illite, illite-smectite interlayers, as well as kaolinite, chlorite, pyrite, quartz, ilmenite, magnetite, apatite and feldspar, account for a mixed residual-detrital origin of fills. This polygenic origin agrees with that of the terra rossa sediments described worldwide. The different colours of karst fills are attributed to fluctuations in the water table, which control the Eh/pH conditions in the karst system. Thus, reddish colours reflect low water table levels and oxidising episodes, and orange and ochre ones reflect high water table levels and more reducing episodes. The greenish colours of fills could be related to fluctuations in the Fe3+/Fe2+ ratio.

Variations in wetland hydrology drive rapid changes in the microbial community, carbon metabolic activity, and greenhouse gas fluxes

Wetlands play a crucial role in the carbon cycle as they are the largest natural source of methane, a potent greenhouse gas. Changes in wetland hydrology can alter the rate of greenhouse gas release from wetlands and have the potential to alter Earth’s carbon budget. However, the microbial dynamics underpinning these observations are poorly constrained. Here we combine monitoring of environmental parameters and greenhouse gas fluxes with monthly records of microbial phospholipid fatty acid (PLFAs) δ13C values to probe changes in microbial community and biogeochemistry in response to hydrological changes in a monsoon influenced subtropical wetland from central China. Our results show that water table depth is a key factor controlling the microbial community structure, with Gram-negative bacteria and actinobacteria increasing and fungi decreasing during dry and low water table periods. Meanwhile, the δ13C values of specific PLFAs decreased up to 12‰ during dry compared to wet periods. The extent of depletion varied, but PLFAs from Gram-negative bacteria were most depleted in 13C, indicative for a rapid increase in methanotrophy (methane consumption) during these dry periods. Furthermore, the methane emission of the wetland was drastically reduced and even had negative flux values during dry periods, suggesting that the increased methanotrophy led to a reduced methane flux and a temporary shift of the wetland from a methane source to a methane sink. Our results indicate that short-term hydrological variations lead to a rapid response in microbial community and carbon metabolic activity that directly influences wetland carbon dynamics and greenhouse gas emissions.

Indicator for peat natural recovery in Sebangau National Park in Central Kalimantan, Indonesia

Most of the existing peatland area in Indonesia is degraded mainly due to human activities. This, in association with the construction of drainage canals, resulted in a lower water table compared to its natural condition, causing many changes. Although the criteria for damage and recovery have already been articulated into several existing regulations, yet the indicators for recovery have not been widely studied. For effective restoration, managers need to have basic data related to the initial condition of damaged areas or at least have data on areas that are able to recover naturally without human assistance. Random sampling was used to collect field data on vegetation structure and composition, including direct interviews with the resource persons. Observations made in several locations within the Sebangau National Park indicated that some areas are recovering naturally and relatively fast, although some are not. During 2017 forest fires, only 98.03 ha or burned areas were recorded. This can be seen from the species composition and the vegetation structure covering the studied area. Conditions in the field indicate that all peat forests have been fragmented through the existence of canals which are used for various activities.

Holocene coastal environmental changes inferred by multi-proxy analysis from Lago Formoso sediments in Maranhão State, northeastern Brazil

Little is known about the history of the coastal environment in the northern part of northeastern Brazil and the role of sea level and climate change, as well as the human impact during the past. In order to shed more light on coastal ecosystem dynamics and its influencing factors, a 300 cm long sediment core has been taken from Lago Formoso (LF), located around 150 km distance from the present-day coast in Maranhão State. The core has been radiocarbon dated and analyzed by pollen, spores, charcoal, X-Ray Fluorescence (XRF), X-ray Powder Diffraction (XRPD), LOI, and sedimentary characteristics. During the period from 7520 to 6230 cal yr BP occurred a dominance of mangrove vegetation, and a high relative sea level (RSL), indicating that the coast of the Atlantic Ocean was very close to the study area. The following period is characterized by an increased input of marine sediment into LF and vegetational succession, indicating a highstand of RSL between 5500 and 5020 cal yr BP. From 5020 to 2580 cal yr BP, dominant sandy sediments show chemical and mineralogical characteristic typical of continental sources. The study area was represented mainly by herbaceous and arboreal vegetation, while mangroves were absent, indicating an RSL decrease. The period between 2580 and 1350 cal yr BP is marked by the lower water table and the stronger presence of rainforest vegetation, and an increasing presence of palm trees, indicating the beginning of the human settlement. The last period, after 1350 cal yr BP, is marked by an even stronger anthropogenic influence in the study area, as the records of the stilt-house settlements also evidence it. These records together with others from the same region are the only evidence of stilts-houses from the pre-colonial period in South America.

Managing water table depth thresholds for potato subirrigation

Subirrigation requires precise control of the water table level to provide adequate soil water content (SWC) for promoting plant growth. Optimizing water table level management has been shown to improve soil aeration, reduce N-leaching, and reduce risk of crop losses. The objectives of this study were to: i) assess if water table level and N-fertilizer rate impact potato growth, root development, plant N uptake, or tuber yield; and ii) estimate the optimum water table level threshold that provides sufficient soil upward water flux to meet plant water requirements. The study was conducted in 2013 and 2014 in Hastings, FL, USA. Water table level was automatically controlled in three independent irrigation zones of 1.4 ha at 36, 54, and 71 cm from the top of the hilled row, termed as high (HWT), medium (MWT), and low (LWT) water table treatments, respectively, and SWC measured at 22 cm depth was used as covariate to compare treatments. A randomized complete block with three replications was used to evaluate potato cultivars ‘Atlantic’ and ‘FL1867′ under 0, 112, 224, and 336 kg ha−1 of N-fertilizer within water table treatments. Marketable yield in 2013 was lower than 2014, owing to the high precipitation (421 mm) during tuber bulking that led to high SWC and tuber decay. Total and marketable tuber yields were maximized when N fertilizer rates ranged from 243 to 336 kg ha−1. The highest yield and proportion of large tubers occurred when SWC at 22 cm ranged from 0.13 to 0.16 m3 m−3. The HWT significantly limited root length, diameter, and surface area, compared to the LWT. In 2014, variation of SWC at 22 cm depth had little effect on tuber yield. The HWT was not detrimental to tuber yield, but rather it compounded the negative effect that high precipitation rate had on fluctuating SWC in the root zone, resulting in reduced yield and tuber quality. Optimal SWC in the root zone can be achieved by adjusting the water table level and upward soil water flux throughout the season, according to the crop evapotranspiration for each crop stage, which reduces irrigation water requirements and minimizes the risks of soil water saturation and tuber yield losses.

Drainage increases species richness and density of soil macro-invertebrates in the Zoige peatland of eastern Tibetan Plateau

Soil macro-invertebrates play an important role in the decomposition process of soil organic matter. As the world’s largest alpine peatland, the Zoige peatland on the eastern Tibetan Plateau is experiencing the decline in water table level primarily because of historic drainage. However, little is known about the responses of soil macro-invertebrate communities to water table decline. To address this issue, we established a field drainage experimental platform in 2013, which consists of low (50 cm deep drainage ditch) and intermediate (20 cm deep drainage ditch) water table level treatments, and the ambient (no drainage ditch) plots. In July (warm season) and November (cold season) of 2019, we examined the species composition, richness, densities and the vertical distribution of soil macro-invertebrates. Results showed that the species composition differed significantly among treatments. Species richness and densities of overall and different trophic groups (i.e., detritivores, herbivores and predators) of soil macro-invertebrates were significantly higher in the drained treatments compared to the ambient plots. Moreover, soil macro-invertebrates moved down to deeper soil layers in the low water table treatments compared to the ambient plots. In addition, sampling season (warm vs. cold) did not affect the responses of soil macro-invertebrates to water table decline. These results indicate that soil macro-invertebrate community is sensitive to water table decline in the Zoige peatland. Given the recognized importance of soil fauna to ecosystem functioning, more attention should be paid to the conservation of peatlands.

Numerical Assessments of Excess Ice Impacts on Permafrost and Greenhouse Gases in a Siberian Tundra Site Under a Warming Climate

Excess ice that exists in forms such as ice lenses and wedges in permafrost soils is vulnerable to climate warming. Here, we incorporated a simple representation of excess ice in a coupled hydrological and biogeochemical model (CHANGE) to assess how excess ice affects permafrost thaw and associated hydrologic responses, and possible impacts on carbon dioxide and methane (CH4) fluxes. The model was used to simulate a moss-covered tundra site in northeastern Siberia with various vertical initializations of excess ice under a future warming climate scenario. Simulations revealed that the warming climate induced deepening of the active layer thickness (ALT) and higher vegetation productivity and heterotrophic respiration from permafrost soil. Meanwhile, excess ice temporarily constrained ALT deepening and thermally stabilized permafrost because of the highest latent heat effect obtained under these conditions. These effects were large under conditions of high excess ice content distributed in deeper soil layers, especially when covered by moss and thinner snow. Once ALT reached to the layer of excess ice, it was abruptly melted, leading to ground surface subsidence over 15–20 years. The excess ice meltwater caused deeper soil to wet and contributed to talik formation. The anaerobic wet condition was effective to high CH4emissions. However, as the excess ice meltwater was connected to the subsurface flow, the resultant lower water table limited the CH4efflux. These results provide insights for interactions between warming climate, permafrost excess ice, and carbon and CH4fluxes in well-drained conditions.

A rapid sediment pulse induced by glacial melting during the MIS 8/7e transition buried well‐developed karst in the Railton Valley, Tasmania, Australia

Recent catastrophic sinkhole collapse caused by regional water table lowering induced by quarrying has led to the partial exhumation and reactivation of a buried karst cave system in the floor of the Railton Valley in the lowlands of northern Tasmania, Australia, and widespread sinkhole development. Extensive silty sediments exposed in sinkholes, OSL dated to approximately 237 ka, are interpreted to be lacustrine deposits derived from rapidly deposited glacial outwash. The silty sediments have mineralogy consistent with derivation from a source in the upper Mersey catchment rather than locally and are interpreted to be the product of rapid melting of the Mersey Valley glacier during the MIS 8/7e transition. Thick Last Glacial alluvial fan and Holocene flood‐plain deposits mantle the lacustrine sediments. Exposures of glacial erratics and weathered till in streambeds provide further evidence that the valley was impacted by earlier Pleistocene glaciations.

Ecohydrological interactions in a boreal fen–swamp complex, Alberta, Canada

AbstractThe Western Boreal Plain (WBP) comprises a diverse array of wetland types; however, swamps are understudied in the WBP relative to other wetlands, despite their ubiquity. We apply an ecohydrological and GIS‐based research approach at a fen–swamp complex in the WBP to characterize the ecohydrological properties of the varying wetland types and relate these interactions to the hydrologic function of the watershed. In this study, we evaluate 3 years of hydrological monitoring data, with additional hydrochemical, vegetation and remote sensing data. In our analyses, we identified five land types: fen, flat peat swamp and peat margin swamp (peatlands), mineral swamp and upland. Flat peat swamp was distinguished from fen using Ducks Unlimited criteria, stating fens cannot have trees >10 m in height. Little difference in water table variability, groundwater connectivity, vegetation composition and water chemistry were found between flat peat swamp and fen, suggesting that for all practical purposes, they can be considered a single unit and tree height alone cannot be used to differentiate these peatland types. In contrast, peat margin swamps exhibited lower and more variable water tables and consistent downward hydraulic gradients and comprised a mixture of peatland and upland vegetation. Peat margin swamps, however, exhibited similar porewater pH, electrical conductivity and base cation concentrations as upland, flat peat swamp and fen, suggesting that they are well connected hydrologically. Peat margin swamps were also found to modulate subsurface water movement between fen and upland (via reduced transmissivity from lower water tables) and therefore act as distinct ecohydrological units.

Quaternary diatoms and palaeoenvironments of the Koora Plain, southern Kenya rift

The Koora Basin (south Kenya Rift) preserves a continental, tropical, one-million-year record of environmental change driven by global climate, regional tectonism and volcanism. Diatom-based reconstructions from Olorgesailie Drilling Project (ODP) cores indicate lakes that expanded and contracted with conductivities ranging between ∼200 and > 25,000 μS.cm−1 and pH of 7.9–11.2. Benthic and planktonic diatoms document mostly shallow fresh water between 1 Ma and 870 ka with deeper freshwater lakes from 870 to 470 ka. After the Mid-Brunhes Event at about 430 ka, diatoms record many transgression-regression cycles with both freshwater and saline-alkaline lakes present. Palaeosols also indicate episodes of desiccation and lower water tables. Carbonates and zeolites are present in younger sediments, especially after 400 ka. Many high-lake-level stages correlate with low values in ocean benthic δ18O stack data. Most, but not all, low lake levels occurred during higher δ18O MIS intervals, suggesting tectonic and/or volcanic events, in addition to climatic forcing, influenced the drainage, outlet heights and accommodation space.The 870–470 ka period of deeper freshwater lakes at Koora correlates well with the neighbouring Lake Magadi pollen record that suggests generally wetter conditions at this time. Wet-dry cycles after 470 ka at Koora developed when the Magadi record indicates a change towards drier conditions, but with many wetter intervals. High lake level periods at Koora also correlate with phases of diatom-inferred flooding at Magadi. Outcrops north of Koora also document several large lakes during deposition of parts of the Olorgesailie Formation prior to ∼500 ka. The Koora environmental history helps to fill an environmental gap (500–320 ka) encompassing critical changes in hominin lithic technology caused by a hiatus at Olorgesailie. During the first part of this interval (470–390 ka), Koora was occupied by a shallow alkaline lake, suggesting relatively dry conditions. The second part (390–320 ka) was characterised by fluctuating deeper lakes that imply greater variability and wetter conditions. Subsequently, both the Olorgesailie and Koora records indicate variable environments.

A Case Study of a Large Unstable Mass Stabilization: “El Portalet” Pass at the Central Spanish Pyrenees

This case study presents the engineering approach conducted for stabilizing a landslide that occurred at “El Portalet” Pass in the Central Spanish Pyrenees activated due to the construction of a parking lot. Unlike common slope stabilization cases, measures projected here were aimed at slowing and controlling the landslide, and not completely stopping the movement. This decision was taken due to the slow movement of the landslide and the large unstable mass involved. The degree of success of the stabilization measures was assessed by stability analyses and data obtained from different geotechnical investigations and satellite survey techniques such as GB-SAR and DinSAR conducted by different authors in the area under study. The water table was found to be a critical factor in the landslide’s stability, and the tendency of the unstable slope for null movement (total stability) was related to the water table lowering process, which needs more than 10 years to occur due to regional and climatic issues. Results showed a good performance of the stabilization measures to control the landslide, demonstrating the effectiveness of the approach followed, and which became an example of a good response to the classical engineering duality cost–safety.

Greenhouse Gas Balance of Sphagnum Farming on Highly Decomposed Peat at Former Peat Extraction Sites

For two years, we quantified the exchange of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) at two different large-scale Sphagnum farming sites. At both, peat extraction left a shallow layer of highly decomposed peat and low hydraulic conductivities. One site was characterized by preceding multi-annual inundation and irrigated by ditches, while the other one was inoculated directly after peat extraction and irrigated by ditches and drip irrigation. Further, GHG emissions from an irrigation polder and the effect of harvesting Sphagnum donor material at a near-natural reference site were determined. GHG mitigation potentials lag behind the results of less decomposed sites, although our results were also affected by the extraordinary hot and dry summer 2018. CO2 exchanges ranged between -0.6 and 2.2 t CO2-C ha−1 y−1 and were mainly influenced by low water table depths. CH4 emissions were low with the exception of plots with higher Eriophorum covers, while fluctuating water tables and poorly developing plant covers led to considerable N2O emissions at the ditch irrigation site. The removal of the upper vegetation at the near-natural site resulted in increased CH4 emissions and, on average, lowered CO2 emissions. Overall, best plant growth and lowest GHG emissions were measured at the previously inundated site. At the other site, drip irrigation provided more favourable conditions than ditch irrigation. The size of the area needed for water management (ditches, polders) strongly affected the areal GHG balances. We conclude that Sphagnum farming on highly decomposed peat is possible but requires elaborate water management.

History of Mid- and Late Holocene Palaeofloods in the Yangtze Coastal Lowlands, East China: Evaluation of Non-Pollen Palynomorph Evidence, Review and Synthesis

The surface of the lowland deltaic plain around Taihu (Lake Tai), south of the Yangtze river mouth in eastern China, lies near sea level and until recent drainage and development by human societies was mostly covered by wetlands of various types. It was created by regular overbank flooding, mainly from the Yangtze, and the deposition of mostly mineral sediments over the several millennia since sea level regained its current altitude in the early mid-Holocene and progradation of the Yangtze delta began. Fluvial activity has therefore been the dominant influence on sedimentation in the Taihu lowlands, and in the lower Yangtze valley generally, and has determined the character of the mainly inorganic sediment sequences that have accumulated there, with autochthonous deposition of organic sediments within the local wetland plant communities playing a minor role. The presence of both clastic flood horizons and peat layers within the deposits of the Taihu plain attests to great variability in the magnitude of fluvial input from the Yangtze, with repeated extreme floods occurring at some periods, but with periods when the growth of peat layers shows low water tables, little exogenic sediment input and so little fluvial influence. We have examined the published evidence for these different depositional environments in the lower Yangtze and the Taihu plain during the Holocene, comparing the flood history with the middle and upper reaches of the Yangtze catchment. Discrete phases of high or low flooding influence are recognised, and these correspond with large-scale Holocene climate history. Intensified human land use in recent millennia has complicated this relationship, amplifying the flooding signal. Our palynological research shows that algal microfossil type and abundance is a useful proxy for changing water depth and quality in the aquatic environments of the Holocene Taihu wetlands, and can recognise flooding events that are not registered in the floodplain lithological sequences.

Optimizing fen peatland water‐table depth for romaine lettuce growth to reduce peat wastage under future climate warming

SummaryForty percentage of UK peatlands have been drained for agricultural use, which has caused serious peat wastage and associated greenhouse gas emissions (carbon dioxide (CO2) and methane (CH4)). In this study, we evaluated potential trade‐offs between water‐table management practices for minimizing peat wastage and greenhouse gas emissions, while seeking to sustain romaine lettuce production: one of the most economically relevant crop in the East Anglian Fenlands. In a controlled environment experiment, we measured lettuce yield, CO2, CH4 fluxes and dissolved organic carbon (DOC) released from an agricultural fen soil at two temperatures (ambient and +2°C) and three water‐table levels (−30 cm, −40 cm and −50 cm below the surface). We showed that increasing the water table from the currently used field level of −50 cm to −40 cm and −30 cm reduced CO2 emissions, did not affect CH4 fluxes, but significantly reduced yield and increased DOC leaching. Warming of 2°C increased both lettuce yield (fresh leaf biomass) and peat decomposition through the loss of carbon as CO2 and DOC. However, there was no difference in the dry leaf biomass between the intermediate (−40 cm) and the low (−50 cm) water table, suggesting that romaine lettuce grown at this higher water level should have similar energetic value as the crop cultivated at −50 cm, representing a possible compromise to decrease peat oxidation and maintain agricultural production.

Water and Sediment Bacterial Communities in a Small Mediterranean, Oxygen-Stratified, Saline Lake (Lake Alboraj, SE Spain)

Lake Alboraj, located in southeast Spain, was declared natural Microreserve and included into European Natura-2000 Network due to its contribution to environmental heritage. Unfortunately, the ecological status of the lake has changed dramatically, mainly due to the lowering of water table caused by groundwater abstractions for irrigation. It is a permanent small karstic lake whose surface has reduced in the last decades to nearly the third part of its historical water level. The water column shows a marked seasonal oxycline, that splits an aerobic upper layer (epilimnion) from an anaerobic layer below (hypolimnion). Sequencing 16S rRNA gene amplicons and applying chemical tools at epilimnion, hypolimnion and sediment, showed a clear gradient in the bacterial community structure, which support the co-existence of assimilatory and dissimilatory microbial mediated reactions. Results allows to infer that microbial stratification could provide various physical and chemical environments at different depths in the water column related to biogeochemical reactions providing N-S-C- recycling processes.

Lowered water table causes species substitution while nitrogen amendment causes species loss in alpine wetland microbial communities

Alpine wetlands are hotspots of carbon (C) storage and methane emission, and they could be key contributors to global warming. In recent years, rapid warming has lowered the water table in alpine wetlands on the Tibetan Plateau, concurrent with intensified nitrogen (N) deposition via anthropogenic activities. We carried out a field experiment to investigate the ecological impacts of these two factors on soil bacterial and functional communities, which are essential drivers of greenhouse gas emissions. Nitrogen amendment alone decreased the phylogenetic alpha-diversity of bacterial communities which could be offset by lowered water table. In contrast, microbial functional alpha-diversity, revealed by a high-throughput microarray, remained unchanged. Both bacterial and functional beta-diversity responded to lowered water table, but only bacterial community responded to N amendment. The alpha-Proteobacteria, beta-Proteobacteria, and Bacteroidetes were the major responsive bacterial lineages, and C degradation, methanogenesis, alkaline shock, and phosphorus oxidation were the major responsive functional processes. Partitioning analysis revealed that N amendment changed bacterial community structure mainly via species loss processes but did not affect bacterial functional communities, with soil pH and ammonium as the key factors influencing changes in bacterial community structure. Conversely, lowered water table altered bacterial and functional communities through species substitution processes linked to soil pH and soil moisture. According to our results, the response mechanisms of microbial communities to lowered water table and N amendment are fundamentally different in alpine wetlands.

Paleoenvironmental analysis of wet meadow in the Deseado Massif: Implications for the Holocene occupation of Argentinian Patagonia

Paleoenvironmental data from wet-meadow environments in the arid-semiarid region of Patagonia are still incipient and the paleoenvironmental records came from pollen sequences of caves and rockshelters. The main reasons to study wetland records are their undisturbed (by humans) sedimentologic continuity, in contrast to deposits in rock shelters and caves; and their regional presentation of environmental changes that can be compared to archeological data. The aim of this paper is to evaluate the past hydrological dynamic of a wet-meadow from Deseado Massif and its relationship with the human occupation. For this purpose, we present the results of the sediment and pollen analysis of Mallín La Primavera wet-meadow that provide a sequence starting in the mid-Holocene. The results indicate a lower water table in the mallín prior to 6900 cal yr BP. Sediment analysis indicates low energy sedimentation environment with flood events and very low energy streams. Human occupational data show chronological discontinuities in mid-Holocene in several regions of Patagonia and the southern cone. In the studied region, two chronological hiatuses (7828–6434 cal yr BP and 3005–2710 cal yr BP) where recognized that appear to correlate with shrub steppes, indicating dry conditions. These conditions may explain the lack of archeological radiocarbon dates in the area during this period. The integration of sediment and pollen results from the Deseado Massif indicates dry and windy conditions for the middle Holocene. The lack of archeological radiocarbon dates would have been influenced by the loss of moisture in water sources such as springs and their associated wet meadows ( mallines).

A comparison of plant communities and water chemistry at Sandhill Wetland to natural Albertan peatlands and marshes

Plant communities and water chemistry properties were characterized at Sandhill Wetland; an experimental reclamation site constructed above a backfilled open pit mine in northeastern Alberta, Canada. Observations from the reclamation site were compared to 12 mature reference wetlands (10 fens and 2 marshes) to determine the type of natural wetland the site most closely resembles at its current successional stage. From this survey of 20 research plots distributed across Sandhill Wetland, 44 plant species were encountered (35 vascular plants and 9 bryophytes). Using multivariate approaches, diversity indices, and coefficient of conservatism values, results indicate areas with water levels above the soil surface at Sandhill Wetland are most comparable to regional marshes, with Typha latifolia and Carex aquatilis exhibiting the highest cover. Across the wetland periphery where water levels are several centimeters below the soil surface, plant communities were quite dissimilar from the reference sites and dominated by the grass Calamagrostis canadensis. Based on principle components analysis, we show water chemistry at Sandhill Wetland is in a state that is between marshes and saline fens. Sandhill Wetland overall possesses a unique set of structural and chemical features in the sixth year of development. In areas where water levels are above the soil surface there is potential for development into a slightly brackish marsh analogue. The successional trajectory of low water table position areas is somewhat uncertain as the wetland periphery exhibited mixed characteristics resembling those of wet meadow, riparian, and upland environments, which we did not survey.

Drivers controlling spatial and temporal variation of microbial properties and dissolved organic forms (DOC and DON) in fen soils with persistently low water tables

Factors controlling dissolved organic carbon (DOC) and nitrogen (DON) production in degraded fen peatlands remains largely equivocal. Thus, the purpose of this research was to determine whether short-term changes in DOC and DON content and microbial properties are related to variations in weather conditions, soil properties and human activity. The study was conducted in May and September 2017–2019 to determine the seasonal variations in the abovementioned parameters in soil layers (0–30 cm) of a long-term agricultural peatland additionally affected by open-pit mining. We found that the most critical environmental factors that shape microbial community structure and activity are air temperature and precipitation, which explained 59.9% of the variability. Air temperature was also the most important explanatory factors for DOC and DON variation, which explained 18.9% of the total variability. Moreover, in the case of DOC and DON production, significant positive correlations with soil organic carbon content (DOC r = 0.46, p < 0.01; DON r = 0.54, p < 0.001) was found. The potential impact of open-pit mines on the DOC and DON production was not confirmed, as there was no significant difference between sites located in the depression cones (caused by lignite mining) and those sites affected exclusively by agriculture drainage. This work hopes to contribute towards a deeper understanding of the variables and dependencies that affect the production of labile organic forms in degraded fen peatland soils in the temperate climate zone.

Water Table Fluctuation in Peatlands Facilitates Fungal Proliferation, Impedes Sphagnum Growth and Accelerates Decomposition

Northern peatlands are substantial carbon sinks because organic matter in peat is highly stable due to the low rate of decomposition. Waterlogged anaerobic conditions induce accumulation of Sphagnum-derived phenolic compounds that inhibit peat organic matter decomposition, a mechanism referred to as the “enzymic latch”. Recent studies have predicted that the water table in northern peatlands may become unstable. We observed that such unstable water table levels can impede the development of Sphagnum mosses. In this study, we determined the effects of low and high frequency water table fluctuation regimes on Sphagnum growth and peat organic matter decomposition, by conducting a year-long mesocosm experiment. In addition, we conducted a molecular analysis to examine changes in abundance of fungal community which may play a key role in the decomposition of organic matter in peatlands. We found that rapid water table fluctuation inhibited the growth of Sphagnum due to fungal infection but stimulated decomposition of organic matter that may dramatically destabilize peatland carbon storage. Increased pH, induced by the fluctuation, may contribute to the enhanced activity of hydrolases in peat. We demonstrated that the water table fluctuation in peatlands impeded Sphagnum growth and accelerates decomposition due to fungal proliferation. Thus, we suggested that understanding the microbial community in the northern peatlands is essential for elucidating the possible changes in carbon cycle of peatland under the changing world.