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Article

Peat Formation in Rewetted Fens as Reflected by Saturated n-Alkyl Acid Concentrations and Patterns

by
Gerald Jandl
1,
Wakene Negassa
2,
Kai-Uwe Eckhardt
1 and
Peter Leinweber
1,*
1
Faculty of Agricultural and Environmental Sciences, Soil Science, University of Rostock, 18051 Rostock, Germany
2
The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, UK
*
Author to whom correspondence should be addressed.
Land 2023, 12(9), 1768; https://0-doi-org.brum.beds.ac.uk/10.3390/land12091768
Submission received: 11 July 2023 / Revised: 1 September 2023 / Accepted: 8 September 2023 / Published: 12 September 2023
(This article belongs to the Special Issue Peatland Ecosystem II)
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Abstract

:
The conversion of cultivated fen peat soils into rewetted soils can mitigate global climate change. Specifically, carbon in newly formed peat can store atmospheric CO2 for a long time in soil, but alterations in the quality of soil organic matter are not well known. To shed light on the complex processes of peat degradation or new formation under dry or rewetting conditions, we investigated and quantified saturated n-alkyl acids as an indicator compound class of peatlands response to the contrasting management practices. The concentrations of saturated n-alkyl acids from two soil layers of the drained and rewetted were determined in two soil layers of drained and rewetted fenland types such as Alder Carr forest, coastal peatland, and percolation mire. The analytical methods were solvent extraction, methylation with tetramethylammonium hydroxide, and gas chromatography/mass spectrometry. The saturated n-alkyl acid distribution pattern showed that the concentrations of long C-chain lengths were larger by factors of up to 28 relative to the short C-chain lengths. The effect of rewetting was reflected by the ratios of the summed concentrations of long (n-C21:0 to n-C34:0) to short (n-C10:0 to n-C20:0) C-chain saturated n-alkyl acids for drained and rewetted peat soil samples. These ratios were consistently lower in samples from the rewetted sites, indicating a higher input of microbial bio- and necromass to soil organic matter, likely from algae and anaerobic bacteria, under rewetting. The results suggest that the enrichment of microbial biomass and necromass in rewetted soils may be an important contributor to the formation of new peat in fenlands, irrespective of fenland type.

1. Introduction

The earth’s surface is covered by about 6–7% wetlands, of which 50 to 70% are peatlands, and they store about 50% of the global soil carbon (C) stocks [1,2,3,4,5,6]. The reductive conditions of peatlands slow down the mineralization of vegetation residues and soil organic matter (SOM), resulting in substantial C-stock accumulation. Because of the high organic C content of peatlands and their associated high fertility, these soils have been used for agriculture, forestry, peat extraction, and other destructive land uses. Preconditions for these land uses were drainage and lowering the water table, which resulted in the overall extreme degradation of 50 to 80% of the historic peatlands in North America and Europe [6,7,8,9]. Various approaches have been used to understand the influences of different management practices on soil organic matter chemistry in peatlands. For instance, a drainage effect was described by comparing a somewhat higher-elevated and, therefore, better-drained bog with the surrounding peatlands in Ontario, revealing a slower carbon accumulation rate in the former [10]. Furthermore, differences in the chemical composition of peat in natural and drained Finnish bogs revealed that the largest influence of drainage was induced by aerobic decomposition, with a decreased abundance of Sphagnum-derived phenols and simple polysaccharides and an accumulation of macromolecular polysaccharides [11]. This publication also reported vegetation change after drainage from Sphagnum to Pinus sylvestris, resulting in an increased abundance of, e.g., lipids.
In Germany, about 98% of the 12,800 km2 of peatlands have been drained to enable various land uses [12,13]. Drained bog and fen peats under grassland use in Germany showed a modified chemical composition, such as higher proportions of proteins and lipids in the stronger degraded topsoils and lower proportions of carbohydrates and aromatics in the rather “native” subsoils, as determined by standard 13C nuclear magnetic resonance (NMR) spectroscopy [14].
Rewetting of drained peatland has been described as a peatland restoration technique to enhance SOM accumulation [15] in order to reverse the previous destructive land use. Therefore, rewetting drained and degraded peatlands has been at the top of the nature and biodiversity conservation agenda in most European countries for the last two decades. Accordingly, about 297,64 km2 of drained and degraded peatlands were rewetted in Mecklenburg–West Pomerania, northeastern Germany, between 2000 and 2008 [16]. Recent studies indicated that the contribution of rewetting to enhance soil carbon sequestration and restoration depends on historical and current land use, degree of degradation stages at the inception of rewetting, rewetting intensity, and groundwater dynamics across different seasons within a year [17,18,19]. Carbon sequestration in rewetted peatlands also depends on a net primary production that exceeds the organic matter mineralization, the stage of humification, and the chemical composition of the peat [20,21]. While experimental evidence exists for an annual accumulation of about 2 kg C m−2 during 20 years of land cover change towards a rewetted status of a fen peatland [22], the chemical background for this accumulation at the molecular level is largely unknown.
Aliphatic lipids were used as indicator substances for SOM stabilization and C sequestration in long-term experiments [23,24,25,26] and for estimating the contribution of primary organic matter to the fatty acid pool in agricultural soils [27]. Therefore, lipid studies seem to be a promising approach to describing vegetation and SOM quality changes after rewetting drained peatlands. For instance, various marsh plant species differed in maxima of long-chain n-alkanes and of n-alkan-2-ones, which allowed deducing the source of these compounds in Sphagnum peat occurring in raised bogs [28].
Increasing wetness along a hydrological gradient of raising water levels from 23.4 cm to 10.5, 7.5, and 3.0 cm below the surface altered the Sphagnum lipid composition in the Erxianyan peatland (China), as reflected by increased n-C23/n-C25 alkane ratios and decreased average chain length (ACL) values of n-alkanoic acids and other homologues [29]. Recently, the concentration, molecular compositions, and functional groups of SOM were investigated in drained and rewetted percolation mires, forests, and coastal peatlands by classic chemical analyses, pyrolysis-field ionization mass spectrometry (Py-FIMS), and carbon and nitrogen K-edge X-ray near-edge absorption structure (XANES) spectroscopy in conjunction [18]. The study revealed more abundant Py-FIMS signals of rather labile compound classes (carbohydrates, phenols, lignin monomers, amino acids, peptides, and amino sugars) and of some stable compounds (lignin dimers, heterocyclic nitrogen compounds, and nitriles) at the surface compared to the subsurface layers of all the drained and rewetted sites. The subsurface layers were generally enriched in exclusively stable compound classes such as lipids (alkanes, alkenes, n-alkyl acids, and n-alkyl esters) and suberin building blocks [18]. Except for the few cited studies [28,29], the effect of peat drainage and rewetting on potentially stable lipids is largely under-researched.
Therefore, the objectives of the present study are (i) to determine the concentrations for establishing the distribution pattern of saturated n-alkyl acids and (ii) to evaluate sources of newly formed peat in rewetted fenlands. We hypothesize that concentrations of saturated n-alkyl acids and their distribution pattern can indicate sources of SOM in peatlands, whereby higher concentrations of distinguished saturated n-alkyl acids may have originated from species (plants and/or lower organisms) that are supported by moist soil conditions.

2. Materials and Methods

2.1. Study Sites and Sampling

The study sites were all fen peatlands and have been described in detail in previous publications [30,31]. In brief, we collected samples in October 2017 from drained and rewetted peatlands of percolation mires, Alder Carr, and coastal peatlands in Mecklenburg–West Pomerania, northeastern Germany. These study sites were chosen because they represent the most important fenland types in northeastern Germany, and because large areas of these fenland types have been systematically rewetted since the late 1990s. This situation enabled us to select nearby pairs of sampling sites that are either drained or rewetted, thus showing remarkable similarity in almost all other site characteristics.
The drainage started for the Alder Carr peatlands in 1786, the coastal peatland in 1850, and the percolation mire in the 1970s [31]. The rewetting by passively rising water tables and closing the drainage ditches started in parts of the drained coastal peatland, forest peatland, and percolation mire in 1993, 1998, and 1999, respectively. In addition to the described rewetting technique, occasionally the percolation mire and coastal peatland were flooded by the nearby Trebel river and brackish Baltic Sea, respectively. During soil sampling, the drained coastal peatland and percolation mire were used for grazing and pasture production, respectively, whereas the drained and rewetted forest peatland were used for logging. The rewetted coastal peatland and rewetted percolation mire were under natural conservation. Detailed information on the water table, peat depth, georeferences of sampling sites, altitude, dominant plant species, mean annual temperature, and precipitation is compiled in Table 1. The soil orders of the sites under study are all Histosols. Soil samples were obtained in three replicates from an upper soil layer of 0–10 cm (except the rewetted percolation mire, sampled at 0–20 cm because of complete saturation), and deeper in the soil profile at 40–60 cm (except the rewetted coastal peatland sampled at 20–30 cm). Sampling depth at the rewetted coastal peatland was different from the other sites because we found continuous peat only down to 30 cm, below which a different substrate (no peat but a mud-like marine sediment) occurred. Samples were placed in inert, closed plastic bags and transported in a cool box to the lab. Thus, we tried to maintain the moisture and redox status to avoid microbial organic matter transformations. Subsamples were dried quickly at 35 °C in an oven with circulating air. Dry samples were sieved < 2 mm and used for subsequent analyses.

2.2. Analytical Methods

The soil pH value is determined electrometrically in a 1:2.5 dry soil: 0.01 M CaCl2 solution mixture at room temperature. The total nitrogen and carbon contents of the samples were determined by a dry combustion method with a vario EL cube CNS elemental analyzer (Elementar Analysensysteme GmbH, Hanau, Germany). The SOM was determined by the loss-on-ignition method at 550 °C for 4 h [32].
To determine the saturated n-alkyl acids, about 8 to 71 g of peat samples were Soxhlet-extracted for 24 h using 100 mL dichloromethane/acetone (9:1 v:v) [33]. The volume-reduced extract of 1 mL was methylated in silanized glass vials (4 mL) by adding 50 µL of a 25% (by weight) tetramethylammonium hydroxide/methanol solution followed by ultrasonication in the bath RK 52H (Bandelin, Berlin, Germany) for 15 min [34].
Components of the extracted lipids were separated on a gas chromatograph, Thermo Fisher Trace 1310, equipped with a 60 m BP5 column (0.25 mm i.d., 0.25 µm coating). For each GC-MS run, 1 µL of the derivatized extract was injected at an injector temperature of 300 °C. The carrier gas helium 5.0 was set up with a constant flow of 1 mL min−1. Following split injection up to 45 s (splitless), the split ratio was 1:100 from 45 s up to 90 s and 1:5 from 90 s on. The temperature program was 5 min at 100 °C, subsequently heated at a rate of 5 K min−1 to 280 °C, with a total measurement time of 120 min. The GC was connected to a Thermo Scientific DFS magnetic sector MS. Conditions for mass spectrometric detection in the electron impact mode were 4.7 kV accelerating voltage, 70 eV electron energy, 1.2 kV multiplier voltage, m/z 48–600 mass range, 0.5 s (mass decade)−1 scan rate, and 0.6 s interscan time. A standard mixture was used to quantify the saturated n-alkyl acids (Promochem, Germany). For a more detailed description of this method, see reference [34].

3. Results

The soil pH was in the range of 3.8 to 6.0 and revealed lower pH values for drained Alder Carr forest (pH 4.2 and 4.9) and coastal peatlands (pH 3.8 and 3.9) than for the other peatland sites and soil layers (Table 2). The highest pH value was determined for rewetted coastal peatland (pH 6.0) at the soil layer of 20–30 cm, followed by both soil layers of the drained (pH 4.9 and 5.2) and rewetted (pH 5.4 and 5.4) percolation mire and rewetted Alder Carr forest peatland (pH 5.1 and 5.1).
In general, the saturated n-alkyl acids of all sites and soil layers have a bimodal distribution pattern with a short C-chain range from n-C10:0 to n-C20:0, always maximized at n-C16:0, and a long C-chain range from n-C21:0 to n-C34:0 (Figure 1). The latter range shows a concentration maximum mostly at n-C28:0; however, the maximum abundance also appeared at n-C26:0 (coastal peatland, rewetted, upper soil layer; and percolation mire, dried, lower soil layer) and at n-C24:0 in some samples (coastal peatland, rewetted, lower soil layer). Furthermore, the odd-numbered C-chain lengths were always less abundant than the neighboring even-numbered C-chain-length saturated n-alkyl acids.
In the Alder Carr forest, the summed concentrations of saturated n-alkyl acids (0–10 cm: 51.1 µg g−1 vs. 40–60 cm: 501 µg g−1) and the concentrations of long C-chain lengths acids (0–10 cm: 42.5 µg g−1 vs. 40–60 cm: 433 µg g−1) were larger than those in the lower soil layer at the drained site. This disagreed with the rewetted site, which had summed concentrations lower by factor 2.1 at the 40–60 cm soil layer, and for the long C-chain lengths lower by factor 2.4 compared to the upper soil layer (Table 3). Furthermore, the maximum of the long C-chain saturated n-alkyl acids was always higher compared to the short C-chain saturated n-alkyl acids, except for the lower soil layer of the rewetted site (Figure 1). In the coastal peatland site, higher summed concentrations of saturated n-alkyl acids were determined in the upper soil layer of the dried and the rewetted sites when compared to their corresponding lower layers (Table 3). As described for the Alder Carr site, the maximum of the long C-chain saturated n-alkyl acids was higher than the short C-chain saturated n-alkyl acids, except for the lower soil layer of the rewetted site (Figure 1). The percolation mire showed clear enrichments of saturated n-alkyl acids in the lower soil layer at both sites. Moreover, an apparent accumulation and a maximum of long C-chain saturated n-alkyl acids were determined at both sites and soil layers (Table 3, Figure 1).
In all investigated sites and soil layers, generally, longer C-chain than short C-chain saturated n-alkyl acids were determined, larger by factors from 1.6 (CW 20–30 cm) to 28.4 (CD 40–60 cm) (Table 3). The ratio of the summed concentrations of long (n-C21:0 to n-C34:0) to short (n-C10:0 to n-C20:0) C-chain saturated n-alkyl acids showed that every rewetted sample had a lower ratio compared to its corresponding drained sample (Figure 2. This factor, representing enrichments of short C-chain saturated n-alkyl acids, was most pronounced at the upper (f = 6.4) and deeper soil layers (f = 17.9) of the coastal peatland and less pronounced for the other sample pairs (Figure 2). A two-way ANOVA of the ratio of long- to short-chain alkyl acids with the factors “site” and “rewetting” showed the influence of rewetting at p = 0.0554.

4. Discussion

The low pH values of all drained peatlands at both soil depths can be explained by the high contents of organic acids released by the partial decomposition of plant material [13]. Low pH values from 3.8 to 5.4 can influence microbial community structure, biochemical activities, and SOM mineralization in peatlands [35]. The slightly higher pH values (pH 6.0), especially in the lower soil layer (20–30 cm) of rewetted sites, can originate from occasional flooding by the Baltic Sea and the leaching of basic cations into the lower soil layer (coastal peatland). Furthermore, the wetter conditions promoted snails, remnants of which observed at all the rewetted sites during sampling.
The often described bimodal distribution pattern of saturated n-alkyl acids in agricultural soils, e.g., [27,34,36,37], induced by the input of plant material, soil organisms, and organic fertilizers [27], is less pronounced in peat soils because of high concentrations of long C-chain length saturated n-alkyl acids. This finding for the peats under study agreed with analyses of Sphagnum-dominated peat [38] and of various peat types from Sphagnum, Carex, Bryales, and Carex-Bryales [39]. The determined maxima in the long C-chain length range at n-C24:0, n-C26:0, and n-C28:0 in the present study (Figure 1) agreed with C-chain length maxima at n-C24:0 and n-C26:0 in Sphagnum peat [38,39]. Other peat-forming plants and vegetation showed similar chain-length maxima of saturated n-alkyl acids: Carex at n-C26:0, Bryales at n-C24:0 and n-C26:0, and mixed vegetation of Carex-Bryales at n-C24:0, n-C26:0, and n-C28:0 [39].
The generally higher concentrations of long-chain than short C-chain saturated n-alkyl acids (Table 3) disagree with the described higher content of short C-chain than long C-chain saturated n-alkyl acids in a Sphagnum peatland [29]. This can be explained by the input of vegetation other than Sphagnum in the drained and rewetted peatlands under study (Table 1). In a previous study, long C-chain saturated n-alkyl acid concentrations decreased when wetness increased in a Sphagnum peatland in central China [29]. This indicates a tendency towards shorter C-chain length and reduced concentrations of the long C-chain saturated n-alkyl acids when peat soils become wetter. In the present data set, this tendency is consistent with the lower ratio of long to short C-chain length of saturated n-alkyl acids in the rewetted soil samples (Figure 2). The latter appears important because this ratio is the first chemical parameter consistently reflecting rewetting. Other previously published data on the bulk chemical composition of SOM [18] and colloidal organic matter [40], and the speciation of phosphorus [41] and sulfur compounds [42] showed similar trends for the rewetted sites but not throughout all sample pairs. Therefore, the rewetting effect on the chain-length distribution of saturated n-alkyl acids is stronger than other disturbing effects, such as peatland genesis and land cover, management history, or current vegetation. In general, the newly detected lower ratios of the long to short C-chain length saturated n-alkyl acid concentrations in all rewetted samples can be explained by larger inputs from microbes with mostly short C-chain lengths relative to the inputs from plants with dominant long C-chain length saturated n-alkyl acids [27]. In this line of argumentation, reference [31] also reported consistently larger abundances of anaerobic bacteria at the rewetted sites compared to the drained sites of the study area in northeastern Germany.
Consequently, it could be possible that anaerobic microbes are richer in lipids than aerobic microbes and/or that quantitatively more microbes exist in the rewetted samples. The latter explanation is supported by various publications that reported larger microbial biomass C in pristine, less degraded, and restored wetland soils than in their drained and more degraded counterparts. Examples are temperate fen peat soils [43], tropical swamps [44,45], restored coastal wetlands [46], and restored wetlands soils in the Yellow River Delta of China [47]. Furthermore, algae are likely substantial contributors to the lipid fraction at the rewetted sites, as concluded in [48], especially of short C-chain aliphatic lipids [49]. Green algae form a significant proportion of the net primary production in naturally wet and rewetted ombrotrophic peatlands [50]. Although algae appear nearly exclusively at the sunlight-exposed soil surfaces or upper layers, their necromass may have gradually decomposed deeper in the soil profiles due to raising of the moist surface through relatively undecomposed plant residues. For instance, this new fen peat formation was quantified at 2.12 kg C m−2 in the 20 years after rewetting the percolation mire, equaling an average annual uptake of ~0.4 kg CO2 m−2 [22]. To the best of our knowledge, our study for the first time emphasizes the possible role of algae in the peat formation under rewetting and its chemical composition in rewetted fens.
A shortcoming of the study is the restriction on fatty acids as only one, though the most abundant, compound class of lipids. Therefore, for forthcoming studies, it is desirable to investigate other compound classes in lipids such as alkanes, alkenes, alkanoles, unsaturated, and branched fatty acids [24,25,26]. Furthermore, we could not directly show the contribution of microbial necromass to the soil lipid fraction, which would require direct analyses of microbes. Finally, forthcoming studies should involve a wider geographical distribution of pairs of drained and rewetted peat soils to obtain the possibility of generalizing the present findings.

5. Conclusions

(1) The methodological approach was well suited to determining the concentrations of saturated n-alkyl acids and establishing the distribution pattern as a hint to the origin of newly formed peat.
(2) Disclosing the enrichment of shorter-chain saturated n-alkyl acids relative to longer chain length consistently at all rewetted sites is an advantage versus the previous peat investigations with pyrolysis-field ionization mass spectrometry and synchrotron-based X-ray absorption near-edge spectroscopy. These methods reflected the disturbing effects of site properties other than drainage versus rewetting on the organic matter composition.
(3) The consistently lower ratios of long C-chain to short C-chain saturated n-alkyl acids in the rewetted sites are a new finding consistent throughout all sample pairs under study. Although the processes behind this effect remain unclear, the relative enrichment of the shorter C-chain n-alkyl acids probably originate from anaerobic microorganisms, as described by microbial biomass analyses from various restoration studies worldwide.
(4) Therefore, it is concluded that cell wall constituents of microbial biomass and necromass, including algae, are an important source of newly formed peat, contributing to peat enrichment in rewetted fens in addition to vast amounts of relatively undecomposed plant remnants. The logical next step is to research the stability and conservation of these microbial bio- and necromass constituents.
(5) Finally, the present study demonstrates the indicator value of saturated n-alkyl acids and their chain-length distribution pattern for the imprint of peatland use and ecological effects on soil carbon storage under the influence of human activities to mitigate global climate change.

Author Contributions

Methodology, data curation, writing—original draft preparation: G.J.; investigation, writing—review and editing: W.N.; methodology, investigation, data curation, writing—review and editing: K.-U.E.; project administration, funding acquisition, writing—review and editing: P.L. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the European Social Fund (ESF) and the Ministry of Education, Science and Culture of Mecklenburg–Western Pomerania in the WETSCAPES project (ESF/14-BM-A55-0029/16-64160025).

Data Availability Statement

All data related to this study are included in the Tables and Figures of the manuscript or in the papers cited.

Acknowledgments

We are grateful to Christel Baum, Soil Science, University of Rostock, for helpful comments.

Conflicts of Interest

The authors declare no conflict of interest.

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Land 12 01768 g001
Figure 1. Summed concentrations and distribution patterns of saturated n-alkyl acids (in µg g−1) in the C-chain range from n-C10:0 to n-C34:0, and the concentrations of organic C (Corg), proportion of the summed saturated n-alkyl acids (in % of Corg) in an upper and a lower soil layer of drained and rewetted peat under Alder Carr forest, coastal peatland, and percolation mire.
Figure 1. Summed concentrations and distribution patterns of saturated n-alkyl acids (in µg g−1) in the C-chain range from n-C10:0 to n-C34:0, and the concentrations of organic C (Corg), proportion of the summed saturated n-alkyl acids (in % of Corg) in an upper and a lower soil layer of drained and rewetted peat under Alder Carr forest, coastal peatland, and percolation mire.
Land 12 01768 g001
Land 12 01768 g002
Figure 2. Ratio of the summed concentrations of long (n-C21:0 to n-C34:0) to short (n-C10:0 to n-C20:0) C-chain saturated n-alkyl acids) (in µg g−1), each in drained and rewetted peatland under Alder Carr forest (AD and AW), coastal peatland (CD and CW), and percolation mire (PD and PW) in an upper and a lower soil layer.
Figure 2. Ratio of the summed concentrations of long (n-C21:0 to n-C34:0) to short (n-C10:0 to n-C20:0) C-chain saturated n-alkyl acids) (in µg g−1), each in drained and rewetted peatland under Alder Carr forest (AD and AW), coastal peatland (CD and CW), and percolation mire (PD and PW) in an upper and a lower soil layer.
Land 12 01768 g002
Table 1. Detailed information on the study sites: drained Alder Carr forest peatland (AD), rewetted Alder Carr forest peatland (AW), drained coastal peatland (CD), rewetted coastal peatland (CW), drained percolation mire (PD), and rewetted percolation mire (PD). Data were published for these test sites by [18].
Table 1. Detailed information on the study sites: drained Alder Carr forest peatland (AD), rewetted Alder Carr forest peatland (AW), drained coastal peatland (CD), rewetted coastal peatland (CW), drained percolation mire (PD), and rewetted percolation mire (PD). Data were published for these test sites by [18].
Peatland TypesWater Table
(cm)		Depth
(m)		Georeference
(N, E)		Altitude
(m)		Dominant Plant SpeciesMean Temp.
(°C)		Annual Rainfall
(mm)
AD−700.654.1349, 12.512739.00Alnus glatinosa, Fraxinus excelsior8.1571
AW+15>154.1271, 12.485310.00Alnus glatinosa8.1571
CD−700.754.1578, 13.38590.25Deschampsia cespitosa, Calamagrostis epigejos8.2557
CW−50.354.1576, 13.38930.45Agrostis stolomifera, Elymus repens8.2557
PD−70654.1316, 12.62892.25Ranunculus repens, Deschampsia cespitosa,8.2568
PW+5–10654.1011, 12.73951.25Carex acutiformes, Carex rostrata8.2522
Table 2. Peat layers, their acronyms, soil organic matter (SOM), total organic C concentration, C:N ratio, and the pH value of drained and the corresponding rewetted peatland under Alder Carr forest (AD and AW), coastal meadow (CD and CW), and percolation mire (PD and PW) in an upper and lower soil layer (Data were published before for these test sites in [18]. The standard error of the means is given in parentheses.
Table 2. Peat layers, their acronyms, soil organic matter (SOM), total organic C concentration, C:N ratio, and the pH value of drained and the corresponding rewetted peatland under Alder Carr forest (AD and AW), coastal meadow (CD and CW), and percolation mire (PD and PW) in an upper and lower soil layer (Data were published before for these test sites in [18]. The standard error of the means is given in parentheses.
SiteLayer (cm)AcronymSOM
(g kg−1)		C
(g kg−1)		N
(g kg−1)		C:NpH Value
Alder Carr forest drained0–10AD 0–10291 (27)164 (3)13 (0.27)13 (0.12)4.2 (0.23)
40–60AD 40–60338 (29)171 (67)13 (4.62)13 (0.46)4.9 (0.02)
Alder Carr forest rewetted0–20AW 0–20676 (17)340 (20)28 (1.47)12 (0.22)5.1 (0.16)
40–60AW 40–60762 (9)410 (9)27 (0.70)15 (0.64)5.1 (0.09)
Coastal peatland drained0–10CD 0–10415 (10)217 (27)16 (2.00)14 (0.03)3.8 (0.14)
40–60CD 40–60769 (67)443 (2)17 (0.31)26 (0.79)3.9 (0.05)
Coastal peatland rewetted0–10CW 0–10487 (72)314 (38)18 (1.39)18 (0.76)4.7 (0.08)
20–30CW 20–30224 (57)128 (41)7 (2.60)22 (3.61)6.0 (2.39)
Percolation mire drained0–10PD 0–10754 (8)373 (1.16)34 (0.14)11 (0.03)4.9 (0.12)
40–60PD 40–60863 (3)432 (30)29 (1.95)15 (2.00)5.2 (0.13)
Percolation mire rewetted0–20PW 0–20658 (34)311 (46)26 (3.48)12 (0.32)5.4 (0.19)
40–60PW 40–60866 (2)446 (21)29 (0.72)16 (0.39)5.4 (0.03)
Table 3. Concentrations of summed saturated n-alkyl acids (in µg g−1) ranging from n-C10:0 to n-C34:0, subdivided into the short C-chain range (n-C10:0 to n-C20:0) and the long C-chain range (n-C21:0 to n-C34:0) in drained and the corresponding rewetted fens under Alder Carr forest (AD and AW), in a coastal peatland (CD and CW), and a percolation mire (PD and PW) at two depths.
Table 3. Concentrations of summed saturated n-alkyl acids (in µg g−1) ranging from n-C10:0 to n-C34:0, subdivided into the short C-chain range (n-C10:0 to n-C20:0) and the long C-chain range (n-C21:0 to n-C34:0) in drained and the corresponding rewetted fens under Alder Carr forest (AD and AW), in a coastal peatland (CD and CW), and a percolation mire (PD and PW) at two depths.
Site, Sam-
Pling Depth		n-C10:0 to n-C34:0Long C-Chain
n-C21:0 to n-C34:0		Short C-Chain
n-C10:0 to n-C20:0
AD 0–10 cm51.142.58.6
AW 0–20 cm256.9211.045.8
AD 40–60 cm501.0432.968.1
AW 40–60 cm121.086.734.3
CD 0–10 cm369.0353.815.2
CW 0–10 cm188.4147.740.8
CD 40–60 cm117.8113.84.0
CW 20–30 cm50.430.919.5
PD 0–10 cm384.2340.943.3
PW 0–20 cm315.1268.746.5
PD 40–60 cm537.8502.535.4
PW 40–60 cm888.9827.861.0
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Jandl, G.; Negassa, W.; Eckhardt, K.-U.; Leinweber, P. Peat Formation in Rewetted Fens as Reflected by Saturated n-Alkyl Acid Concentrations and Patterns. Land 2023, 12, 1768. https://0-doi-org.brum.beds.ac.uk/10.3390/land12091768

AMA Style

Jandl G, Negassa W, Eckhardt K-U, Leinweber P. Peat Formation in Rewetted Fens as Reflected by Saturated n-Alkyl Acid Concentrations and Patterns. Land. 2023; 12(9):1768. https://0-doi-org.brum.beds.ac.uk/10.3390/land12091768

Chicago/Turabian Style

Jandl, Gerald, Wakene Negassa, Kai-Uwe Eckhardt, and Peter Leinweber. 2023. "Peat Formation in Rewetted Fens as Reflected by Saturated n-Alkyl Acid Concentrations and Patterns" Land 12, no. 9: 1768. https://0-doi-org.brum.beds.ac.uk/10.3390/land12091768

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