Water Table Drawdown Research Articles

Carbon balance of a Finnish bog: temporal variability and limiting factors based on 6 years of eddy-covariance data

Abstract. 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 g C m−2 was observed, which partitions into mean total respiration (Re) of 167 ± 33 (interannual range 146–197) g C m−2 and mean gross primary production (GPP) of 228 ± 46 (interannual range 193–257) g C m−2, while the corresponding FCH4 amounts to 7.1 ± 0.7 (interannual range 6.4–8.4) g C m−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 g C m−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 g C m−2 in 2011 due to elevated Re, and by about 40 g C m−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.

Modelling Shallow Groundwater Evaporation Rates from a Large Tank Experiment

A large tank (1.4 m x 4.0 m x 1.3 m) filled with medium-coarse sand was employed to measure evaporation rates from shallow groundwater at controlled laboratory conditions, to determine drivers and mechanisms. To monitor the groundwater level drawdown 12 piezometers were installed in a semi regular grid and equipped with high precision water level, temperature, and electrical conductivity (EC) probes. In each piezometer, 6 micro sampling ports were installed every 10 cm to capture vertical salinity gradients. Moreover, the soil water content, temperature and EC were measured in the unsaturated zone using TDR probes placed at 5, 20 and 40 cm depth. The monitoring started in February 2020 and lasted for 4 months until the groundwater drawdown became residual. To model the groundwater heads, temperature, and salinity variations SEAWAT 4.0 was employed. The calibrated model was then used to obtain the unknown parameters, such as: maximum evaporation rates (1.5-4.4 mm/d), extinction depth (0.90 m), mineral dissolution (5.0e-9 g/d) and evaporation concentration (0.35 g/L). Despite the drawdown was uniformly distributed, the increase of groundwater salinity was rather uneven, while the temperature increase mimicked the atmospheric temperature increase. The initial groundwater salinity and the small changes in the evaporation rate controlled the evapoconcentration process in groundwater, while the effective porosity was the most sensitive parameter. This study demonstrates that shallow groundwater evaporation from sandy soils can produce homogeneous water table drawdown but appreciable differences in the distribution of groundwater salinity.

Responses of leaf carbon, nitrogen, and phosphorus stoichiometry of Carex muliensis to water table drawdown in an alpine marsh on the Ruoergai Plateau, China.

Based on a field water table drawdown manipulation platform of Naleqiao marsh on the Rueorgai Plateau, we lifted in situ soil block of 1 m×1 m by 20 cm for simulating water table decline, and analyzed the response of carbon, nitrogen, and phosphorus stoichiometry in the wetland species Carex muliensis from June to September 2020. The results showed that there was no significant difference in leaf C content during the whole growing season, while N and P content gra-dually decreased along the growing season. After the drawdown of water table, the C content in leaves during the growing season was not consistent. Water table drawdown increased leaf C content in the early and middle growth stages, but changed little in the peak growth stage. Water table drawdown significantly increased leaf N content, while significantly decreased leaf P content. C:N, C:P, and N:P for leaves all increased along the whole growing period. The relative growth rate of C. muliensis was positively correlated with leaf C:N, but negatively correlated with leaf C:P and N:P. Water table drawdown significantly decreased leaf C:N, while significantly increased leaf C:P and N:P, which significantly reduced the relative growth rate of C. muliensis. The decrease of foliar P content induced by water table drawdown was the main regulating factor for the decrease of single leaf weight and specific leaf weight.

How do water table drawdown, duration of drainage, and warming influence greenhouse gas emissions from drained peatlands of the Zoige Plateau?

AbstractAlpine peatlands on the Qinghai‐Tibet Plateau are an important soil carbon pool and are extremely sensitive to global change. Duration of drainage and water table drawdown accelerate peatland degradation because the soil changes from an anaerobic to aerobic environment, and climate warming exacerbates this shift. The objective of the present study was to evaluate the effects of drainage on microbial characteristics and greenhouse gas (GHG) emissions, as well as identify the factors mediating those effects. This study also analyzed whether warming increases the variability of GHG emissions. Watertable drawdown exerted greater influence on microbial communities than duration of drainage did. Watertable drawdown significantly increased the relative abundances of Proteobacteria, Acidobacteria, Actinobacteria, and Basidiomycota, and changes in soil microbiota correlated with differences in GHG emissions across three water‐table treatments. Longer drainage was associated with lower GHG emission; watertable drawdown decreased emissions of CO2 and CH4, but increased emission of N2O. In addition, high temperature increased CO2 emission by 75% and N2O emission by 42%, without significantly affecting CH4 emission. Structural equation modelling showed that microbes, especially prokaryotes (r = 0.79, p < 0.05 for all), were the primary factor affecting GHG emissions from drained peatlands. Overall, this study indicates that the watertable exerts a greater effect on GHG emissions than duration of drainage, and that warming increases variability of GHG emissions.

Elevated salinity and water table drawdown significantly affect greenhouse gas emissions in soils from contrasting land-use practices in the prairie pothole region

Land-use practices can alter shallow groundwater and salinity, further impacting greenhouse gas (GHG) emissions, particularly in the hydrologically dynamic riparian zones of wetlands. Emissions of CO2, CH4, and N2O were estimated in soil cores collected from two prairie pothole region (PPR) sites with three adjacent land-use practices (i.e., annual crop = AC, pasture = PA, and short rotation willow = SRW) and treated with declining water table depths (2 to 26 cm), and salinity (S0 = control, S1 = 6 mS cm−1, and S2 = 12 mS cm−1) in a microcosm experiment. Land-use practices significantly (p < 0.001) affected GHG emissions in soils from both sites in the order of PA > AC = SRW. Compared to the control, emissions of CO2 and CH4 were significantly lower under higher salinity treatments (i.e., S1 and S2), while N2O was significantly higher (p < 0.05). Emissions under declining groundwater table depths were significantly (p < 0.001) variable and specific to each gas, indicating the impacts of shifted soil moisture regime. Overall, the CO2 and CH4 emissions increased up to week four and then decreased with declining water table depths, whereas N2O emission increased up to a maximum at week six. The soils from SRW had considerably lower global warming potential compared to AC and PA. Groundwater salinity in soils from contrasting land-use in the PPR has significant impacts on GHG emissions with potential for crucial climate feedback; however, the magnitude and direction of the impacts depend on hydrology.

Tradeoff of CO2 and CH4 emissions from global peatlands under water-table drawdown

Water-table drawdown across peatlands increases carbon dioxide (CO2) and reduces methane (CH4) emissions. The net climatic effect remains unclear. Based on global observations from 130 sites, we found a positive (warming) net climate effect of water-table drawdown. Using a machine-learning-based upscaling approach, we predict that peatland water-table drawdown driven by climate drying and human activities will increase CO2 emissions by 1.13 (95% interval: 0.88–1.50) Gt yr−1 and reduce CH4 by 0.26 (0.14–0.52) GtCO2-eq yr−1, resulting in a net increase of greenhouse gas of 0.86 (0.36–1.36) GtCO2-eq yr−1 by the end of the twenty-first century under the RCP8.5 climate scenario. This drops to 0.73 (0.2–1.2) GtCO2-eq yr−1 under RCP2.6. Our results point to an urgent need to preserve pristine and rehabilitate drained peatlands to decelerate the positive feedback among water-table drawdown, increased greenhouse gas emissions and climate warming.

Groundwater potential recharge areas delineation using groundwater potential recharge index (GPRI) within arid areas: Ghomrassen, south Tunisia

The Ghomrassen region is located in southern Tunisia, which is an arid area where the annual rainfall does not exceed 150 mm. This region suffers from water table drawdown and scarcity of surface water. Groundwater is of strategic importance to meet the population and economic needs. Groundwater recharge estimation and fundamental controlling factors assessment were utmost importance solutions for sustainable groundwater management and groundwater protect. This study aims to assess the main factors controlling groundwater recharge and delineate potential recharge area of Ghomrassen aquifer. To achieve this objective, a groundwater potential recharge index (GPRI) was computed using five parameters such as soil lithology, land use/cover, lineament density, slope, and drainage density. For each parameter a score and weight were assigned and thematic maps were developed. The results indicate that about 35% of the study area is designated as excellent potential recharge, whereas 18% of study shows a moderate recharge and lower potential recharge covers 47% of study area. A potential groundwater recharge of Ghomrassen aquifer was estimated is about 5.4 Mm3.y−1. The results show that the most favorable areas for recharging are the upstream part formed by fractured and fissured rocks and the central part of the Ghomrassen basin formed by recent alluvium. The presented GPRI methodology can be helpful for the planning of various water projects locations of artificial recharge structures and wells establishment.

Numerical Simulation of Water Table Drawdown due to Groundwater Pumping in a Contaminated Aquifer System at a Shooting Test Site, Pocheon, Korea

Numerical Simulation of Water Table Drawdown due to Groundwater Pumping in a Contaminated Aquifer System at a Shooting Test Site, Pocheon, Korea

Spatio-temporal analysis of nitrates and piezometric levels in groundwater using geostatistical approach: case study of the Eastern Mitidja Plain, North of Algeria

The groundwater quality in the Mitidja plain has known an important deterioration during the last decades due to uncontrolled industrial waste discharges, intensive use of chemical fertilizers in agriculture, and an intense exploitation of groundwater resources. In this paper, we are interested in the Eastern part of the Mitidja plain, which covers an area of 495.52 km2. This study area is characterized by its industrial and agricultural vocation, thereby the problem of groundwater pollution. The study will focus on the fluctuation of the groundwater table, and the interpretation of the water quality analysis result made by ANRH (National Water Resources Agency), during the period between 2006 and 2016. The last ones have been geostatistically approached. This allowed us to carry out a GIS-assisted mapping of the nitrate concentrations in the aquifer and to draw up an exhaustive report on the current state of the relationship between the fluctuation of water table and the nitrate concentration rates, also the spatial and temporal evolution of the aquifer. As a result, the geostatistical approach gave us the possibility to draw up Kriging maps of the nitrate level spatial distribution for the two field monitoring campaigns: 2006 and 2016 as well as groundwater fluctuation maps for the periods under consideration. The obtained result reveals that 72% of the sample’s points have nitrate concentrations higher than 50 mg/l in rainy period in the 2 years 2006 and 2016. As for the dry period, the results show that more than 54% in 2006 and more than 81% in 2016 of the water samples analyzed are contaminated (exceeding the WHO’s recommendation). A significant water table drawdown, between 2006 and 2016, is highlighted, which reached an average of around 23 m in low water and 26 m in rainy period (case of drilling F1003). This drop in the water table level can be explained by overexploitation of the groundwater caused by intensive pumping for irrigation, industry, and water supply, due essentially to the increasing scarcity of rainfall, which is a consequence of climate change, which has become increasingly prevalent over the last three decades. Given the upward trend in nitrate levels in recent years, there is a significant risk that nitrate levels will far exceed the 50 mg/l threshold recommended by the WHO in the next 10 years. It is therefore imperative to remedy this through the control of industrial discharges and the extension at the level of the agricultural community regarding the intensive use of chemical fertilizers and (in particular nitrogen) and groundwater (by controlling the pumping).

Deformation characteristics, mechanisms, and influencing factors of hydrodynamic pressure landslides in the Three Gorges Reservoir: a case study and model test study

Hydrodynamic Pressure landslides are the most typical landslides affected by the water level in the Three Gorges Reservoir. These types of landslides are large and cause severe deformation. Therefore, they may significantly affect the safe operation of the Three Gorges Reservoir once losing stability. Taking the Shuping landslide in the Three Gorges Reservoir as a typical case, this study explored the deformation characteristics and influencing factors of the Hydrodynamic Pressure landslide using monitoring data of its surface deformation, 17 years of GPS displacement data, automatic displacement metre of surface cracks, and groundwater level. To determine the deformation mechanism of the Hydrodynamic Pressure landslide, the model of Hydrodynamic Pressure landslide was designed and carried out to simulate the fluctuation of reservoir water level. The results showed that the hydrodynamic pressure landslides deformation was mainly affected by the overall deformation of the front edge of the landslide, and the amount of deformation was relatively large. The back part of the landslide mainly encountered tensile deformation. The Hydrodynamic Pressure landslides are a typical retrogressive deformation. The deformation of Hydrodynamic Pressure landslide was affected by the periodic change in the reservoir water level and the overall deformation trend is increasing. The intrinsic factor influencing the deformation of the hydrodynamic pressure landslide is the low permeability coefficient of the sliding mass, and the extrinsic factor is the drawdown of the reservoir water level. When the reservoir water table drawdown occurred, there was a noticeable water level difference with the underground water level in the landslide mass and generated hydrodynamic pressure. The Hydrodynamic Pressure landslide model results showed that the pore-water pressure, effective stress, and groundwater level in the landslide were consistent with the reservoir water level but with noticeable hysteresis. The key hydrodynamic factor for the deformation of this type of landslide was the hydrodynamic pressure towards the outside of the slope, formed when the reservoir water level dropped. Moreover, it was found that the faster reservoir water-level drawdown rates led to an increased influence on the stability of the landslide.

An Optimal Socialist Cooperative Game Theory Model in Agricultural Sector (Case Study: Dezful-Andimeshk Plain)

The increase in exploitation from aquifers in an unbalanced way to meet the growing demands of agriculture has led to a decrease in the groundwater levels and as a result, an increase in the cumulative groundwater-reservoir deficit. In the long run, this will also reduce profits from agriculture due to declining water table levels and rising water extraction costs. In this article, is proposed the application of a socialist cooperative game for propensity to cooperate and improve agriculture's cumulative net benefit and stimulate the balanced use of groundwater. The purpose of this approach is to prevent groundwater level drawdown and compensate for part of the groundwater-reservoir deficit in the Dezful-Andimeshk plain, southwest of Iran. In this study, the consumer behavior, as one of the main factors in groundwater resources management has been investigated. This method has been derived from the socialist cooperative game theory, taking the consumer as an effective factor on water table drawdown, and envisioned in the form of an eco-socialism model. Results revealed that maximum water table drawdown will be reduced by 21%, and as a result, 16 million cubic meters (MCM) of groundwater reservoir deficit will be compensated and the net benefit from agricultural activities will also increase by 26%.

Dewatering System Control by MATLAB Software

The aim was to design a MATLAB program to calculate the phreatic surface of the multi-well system and present the graphical shape of the water table drawdown induced by water extraction. Dupuit’s assumption is the base for representing the dewatering curve. The program will offer the volume of water to be extracted, the total number of wells, and the spacing between them as well as the expected settlement of soil surrounding the dewatering foundation pit. The dewatering well arrangement is required in execution works, and it needs more attention due to the settlement produced from increasing effective stress.

Impacts of longwall mining speeds on permeability of weakly cemented strata and subsurface watertable: a case study

The negative impacts of underground longwall coal mining on water resources and ecological environment are associated with changing overburden permeability and subsurface watertable. For weakly cemented strata characterized by short diagenesis, low strength, easy swelling and mudding with water, overburden permeability and subsurface watertable are highly sensitive to the advancing speed of the longwall. In this paper, the longwall panel 21103 in Yili No.4 Coal Mine, Xinjiang, China, where weakly cemented strata exist in Jurassic and Palaeogene systems, was taken as the case to study the response of overburden permeability and subsurface watertable to different advancing speeds. Results show that there is a butterfly-shaped permeability-increasing area comprised of a trapezoid and double V-shaped subareas in overburden. Generally, the permeability curves of aquiclude are of double peaks. In shallow aquifer, there is an exponential decline in the maximum drawdown of watertable, while a linear decline in lateral influence range as the speed goes up. If constrained by the ultimate watertable drawdown still being able to sustain the regular growth of vegetative covers, the optimal minimum advancing speed of panel 21103 is determined as 8 m/d, which is demonstrated by field verification.

A comparison of porewater chemistry between intact, afforested and restored raised and blanket bogs

Afforestation is a significant cause of global peatland degradation. In some regions, afforested bogs are now undergoing clear-felling and restoration, often known as forest-to-bog restoration. We studied differences in water-table depth (WTD) and porewater chemistry between intact, afforested, and restored bogs at a raised bog and blanket bog location. Solute concentrations and principal component analysis suggested that water-table drawdown and higher electrical conductivity (EC) and ammonium (NH4-N) concentrations were associated with afforestation. In contrast, higher dissolved organic carbon (DOC) and phosphate (PO4-P) concentrations were associated with deforestation. Drying-rewetting cycles influenced seasonal variability in solute concentrations, particularly in shallower porewater at the raised bog location. WTD was significantly deeper in the oldest raised bog restoration site (~9 years post-restoration) than the intact bog (mean difference = 6.2 cm). However, WTD in the oldest blanket bog restoration site (~17 years post-restoration), where furrows had been blocked, was comparable to the intact bog (mean difference = 1.2 cm). When averaged for all porewater depths, NH4-N concentrations were significantly higher in the afforested than the intact sites (mean difference = 0.77 mg L−1) whereas significant differences between the oldest restoration sites and the intact sites included higher PO4-P (mean difference = 70 μg L−1) in the raised bog and higher DOC (mean difference = 5.6 mg L−1), EC (mean difference = 19 μS cm−1) and lower SUVA254 (mean difference = 0.13 L mg−1 m−1) in the blanket bog. Results indicate felled waste (brash) may be a significant source of soluble C and PO4-P. Mean porewater PO4-P concentrations were between two and five times higher in furrows and drains in which brash had accumulated compared to other locations in the same sites where brash had not accumulated. Creating and maintaining brash-free buffer zones may therefore minimise freshwater impacts.

Temperate mire fluctuations from carbon sink to carbon source following changes in water table

The generally-accepted paradigm of wetland response to climate change is that water table drawdown and higher temperatures will cause wetlands to switch from a sink to a source of atmospheric carbon. However, it is hard to find a multi-year, ecosystem scale dataset representative of an undisturbed wetland that clearly demonstrates this paradigm on an annual total basis. Here we provide strong empirical confirmation of the above scenario based on six years of continuous eddy-covariance CO2 and CH4 flux measurements in Biebrza Valley, north-eastern Poland. In wet years the mire was a significant sink of atmospheric carbon (down to −270 ± 70 gC-CO2 m−2 yr−1 against +21.8 ± 3.4 gC-CH4 m−2 yr−1 in 2013) whereas in dry years it constituted a substantial carbon source (releasing up to +130 ± 70 gC-CO2 m−2 yr−1 and +2.6 ± 1.4 gC-CH4 m−2 yr−1 in 2015). Our findings demonstrate that the scenario of positive feedback between wetland carbon release and the present climate change trajectory is realistic and support the need of natural wetland preservation or rewetting. Our findings also indicate that conclusions drawn regarding a wetland's response to changing climate can depend strongly on the chosen period of analysis.

Water table drawdown increases plant biodiversity and soil polyphenol in the Zoige Plateau

Water table drawdown accelerates peatland degradation and carbon loss from peatland, but phenolic compounds—the concentration and composition of which are determined by vegetation community composition—can slow down carbon loss. However, the response of phenolic compounds to water table drawdown is not clear. We aimed to clarify how water table drawdown influence soil phenolic compounds composition by detecting them at peatlands with different water table. Our results showed that water table drawdown changed plant biodiversity and altered the structure of phenolic compounds. Plant biodiversity, richness, evenness, areal coverage, and aboveground biomass all significantly increased with the water table drawdown. Phenolic compounds transferred from monophenol to polyphenol with the water table drawdown. The concentration of water-soluble phenols also increased with the water table drawdown due to the hydrophilic nature of polyphenol compounds. In addition, the concentration of water-soluble phenols was positively correlated with total vegetation coverage and richness. We concluded that water table drawdown accelerates change in the vegetation community, alters the structure of phenolic compounds and increased the concentration of water-soluble phenols, which could play an important role in carbon output from peatlands.

The impact of groundwater drawdown and vacuum pressure on sinkhole development. Physical laboratory models

A considerable proportion of the damaging sinkholes worldwide correspond to human-induced subsidence events related to groundwater withdrawal and the associated water-table decline (e.g. aquifer overexploitation, dewatering for mining). Buoyancy loss in pre-existing cavity roofs is generally claimed to be the main underlying physical mechanism. It has been also postulated that rapid water-table drawdowns may create a vacuum effect in the subsurface and contribute to enhance sinkhole activity in karstic terrains with a low effective porosity cover. Our laboratory physical model explores the role played by vacuum pressure induced water-table drops with different magnitudes and rates on sinkhole development, simulating an invariable mantled karst comprising cavernous bedrock and a low-permeability cover. The multiple tests performed include real-time monitoring of the water level drawdown (magnitude, duration, rate), the negative air pressures in the bedrock cavity and the cover, and several features of the subsidence phenomena (deformation style, size, magnitude, rate). The main findings derived from the test results include: (1) Vacuum pressure may trigger the development of cover collapse sinkholes in areas with low-permeability covers. (2) Different water-table decline patterns (magnitude, duration, rate) may result in different subsidence styles or rheological behaviours: sagging versus collapse. (3) Ground fissuring, frequently related to extension at the margin of sagging depressions, may cancel or significantly diminish the vacuum effect. (4) An overall direct relationship between the water-table decline rate and the subsidence rate. Some possible strategies are proposed to ameliorate the adverse effect of the negative air pressure on sinkhole hazard, which most probably has a local impact restricted by the concurrence of rapid water drawdowns and low-permeability covers.

Shallow peat is most vulnerable to high peat burn severity during wildfire

Peatlands typically act as carbon sinks, however, increasing wildfire severity and annual area burned may challenge this carbon sink status. Whilst most peat resistance to wildfire and drought research is based on deep peatlands that rarely lose their water table below the peat profile, shallow peatlands and peat deposits may be most vulnerable to high peat burn severity and extensive carbon loss. To examine the role of pre-fire peat depth on peat burn severity, we measured the depth of burn (DOB) in peat of varying depths (0.1–1.6 m) within a rock barrens landscape. We found that DOB (0–0.4 m) decreased with increasing pre-fire peat depth, and that there was a strong correlation between the percent of the profile that burned and pre-fire peat depth. Breakpoint analysis indicates a threshold depth of 0.66 m where deeper peat deposits experienced little impact of wildfire, whereas shallower peat typically experienced high peat burn severity (median percent burned = 2.2 and 65.1, respectively). This threshold also corresponded to the loss of the water table in some nearby unburned peatlands, where water table drawdown rates were greater in shallower peat. We suggest that peat depth may control peat burn severity through feedbacks that regulate water table drawdown. As such, we argue that the identification of a critical peat depth threshold could have important implications for wildfire management and peatland restoration aiming to protect vulnerable carbon stores.

Recovery of fen peatland microbiomes and predicted functional profiles after rewetting.

Many of the world's peatlands have been affected by water table drawdown and subsequent loss of organic matter. Rewetting has been proposed as a measure to restore peatland functioning and to halt carbon loss, but its effectiveness is subject to debate. An important prerequisite for peatland recovery is a return of typical microbial communities, which drive key processes. To evaluate the effect of rewetting, we investigated 13 fen peatland areas across a wide (>1500 km) longitudinal gradient in Europe, in which we compared microbial communities between drained, undrained, and rewetted sites. There was a clear difference in microbial communities between drained and undrained fens, regardless of location. Community recovery upon rewetting was substantial in the majority of sites, and predictive functional profiling suggested a concomitant recovery of biogeochemical peatland functioning. However, communities in rewetted sites were only similar to those of undrained sites when soil organic matter quality (as expressed by cellulose fractions) and quantity were still sufficiently high. We estimate that a minimum organic matter content of ca. 70% is required to enable microbial recovery. We conclude that peatland recovery after rewetting is conditional on the level of drainage-induced degradation: severely altered physicochemical peat properties may preclude complete recovery for decades.

Variation in the Soil Prokaryotic Community Under Simulated Warming and Rainfall Reduction in Different Water Table Peatlands of the Zoige Plateau.

Climate change and water table drawdown impact the community structure and diversity of peatland soil prokaryotes. Nonetheless, how soil prokaryotes of different water tables respond to climate change remains largely unknown. This study used 16S rRNA gene sequencing to evaluate the variation in soil prokaryotes under scenarios of warming, rainfall reduction, and their combination in different water table peatlands on the Zoige Plateau in China. Stimulated climate change affected some of the diversity indexes and relative abundances of soil prokaryotes in three water table peatlands. Additionally, those from the dry-rewetting event peatland had the most dominant phyla (genera) that showed significant changes in a relative abundance due to the simulated climate change treatments. Regarding functional microbial groups of carbon and nitrogen cycling, simulated climate change did not affect the abundances of the Euryarchaeota, Proteobacteria, Verrucomicrobia, and Methanobacterium in three water table peatlands, except NC10 and Nitrospirae. Redundancy analysis showed that the prokaryotic community variation was primary impacted by site properties of the different water table peatlands rather than the simulated climate change treatments. Moreover, the water table, total carbon, total nitrogen, and soil pH were the primary factors for the overall variation in the soil prokaryotic structure. This study provides a theoretical guidance for management strategies in the Zoige peatland, under climate change scenarios. More attention should be given to the interactive effects of peatland water table drawdown and simulated climate changes for better restorative efforts in water table drawdown, rather than simply adapting to climate change.