**6. Research studies having a focus on carbon loss as greenhouse gas emissions**

Peatlands are an important terrestrial carbon sink and any increased microbial activity may result in soil organic matter oxidation, with subsequent CO2 release. Northern peatlands historically have had the benefit of cool to frigid temperatures that limit microbial activity. Low oxygen activity attributed to water saturation further limits mineralization. Climate change may result in warmer soils, with the cavate that the effective length of the increasingly warmer summer interval is also increased. The encroachment of vascular plants will be expected to proceed, leading to a positive feedback on microbial activity. Thus, studies on peatland functioning in higher latitudes and their potential to accelerate climate change are becoming commonplace [14].

In Canada, Dieleman et al. [21] established mesocosms, where peat production of dissolved organic carbon was measured. The production of dissolved organic carbon from peat was estimated to be a function of temperature, CO2 concentration and the influence of the water table, wherein increased temperatures increased the dissolved organic carbon contents, lowered water tables increased decomposition rates and reduced pore water dissolved organic carbon concentrations. In the Alaskan arctic Euskirchen et al. [22] established eddy covariance flux towers across various ecosystems for three years to document peak CO2 uptake patterns. Peak CO2 uptake centered from June to August at a mean of 51 to 95 g C m−2 across the various ecosystems. Warmer spring seasons promoted greater CO2 uptake patterns, whereas warmer late seasons supported greater soil respiration rates, reducing the Net Ecosystem Exchange (NEE).

In Canada, Frolking et al. [23] employed the Holocene Peat Model to simulate the vegetation community composition and the annual net primary productivity. Northern peatlands take up CO2 at rates of 40 to 80 g carbon m−2 yr.−1, with carbon leaching as DOC at rates of 10–20 g DOC m−2 yr.−1. Decomposition was estimated to be 95% of the Net Primary Productivity. Similarly, Frolking et al. [23] observed undisturbed Canadian peatlands and determined that these peatlands were a weak sink for carbon and a moderate source of methane emission. McLoughlin and Webster [24] performed a review of peatland dynamics, primarily within the Hudson Bay Lowlands. Long term carbon accumulation, CO2 sequestration, peat depth and land age were positively correlated. Carbon dioxide sequestration showed the greatest variability, with bogs (−1.7 to 1.5 g carbon m−2 day−1), fens (−4.3 to 1.6 g carbon m−2 day−1), and palsa peat (−0.8 to 1 g carbon m−2 day−1). Methane and evapotranspiration were greater in the wettest ecosystems, with methane emission for bogs (3.3 to 28 mg carbon m−2 day−1), fens (0.1 to 204 mg carbon m−2 day−1), and palsa peat (−1.6 to 24 mg carbon m−2 day−1).

On paludified soils Schneider et al. [25] measured methane (CH4) flux for forest and peatland areas. Open peatlands exhibited a methane emission rate of 21.9 ± 1.6 g m−2 yr.−1 in contrast with forested peatland transition zones (7.9 ± 0.5 g m−2 yr.−1). The forested peatland transition zones demonstrated an inflow of less acidic surface water that supported a higher biological diversity and greater plant productivity. These authors noted that methane emission was more influenced by increased temperatures than the water table depths. In Sweden, Sagerfors et al. [26] established eddy covariance measurements across oligotrophic mires. Based on the vertical exchange of CO2 their sites were a net sink for carbon (55 ± 7 g carbon m−2 yr.−1). The non-growing seasons exhibited a carbon loss; however, the growing season sequestration of carbon more than compensated for the non-growing season carbon loss.

Wickland et al. [27] observed changes in CO2 and methane exchanges on a black spruce (*Picea mariana*) lowland experiencing permafrost melting. Sites were partitioned as peat soils having permafrost, thermokarst wetlands, and thermokarst edges, with thermokarst edges having greater methane emissions. Ernakovich et al. [28] measured greenhouse gas emissions from thawed permafrost with simulated oxic and anoxic redox environments. Carbon dioxide emission was supported by an active microbial community and a labile dissolved organic carbon pool. Increased methane production was related to soils with a labile litter pool. Carbon dioxide emission was 30 to 450 times the methane production in an anoxic soil and carbon dioxide emission was 500 to 2500 times the methane production in an oxic soil.

In Canada, Webster et al. [29] investigated net ecosystem exchange and methane emissions for bogs, nutrient-poor fens, intermediate-rich fens across seven ecozones. During the growing season, the net ecosystem exchange, per season, was −108 ± 41.3 Mt. CO2 and the methane emissions were 4.1 ± 1.5 Mt. CH4. Converting methane to CO2 global warming potential for a 25 to 100-year event, the total sink was −7 ± 77.6 Mt. CO2e. The boreal plain peatlands exhibited the greatest net ecosystem exchange, whereas the boreal shield peatlands exhibited the highest methane emissions. In the discontinuous permafrost zone of western Siberia, Shirokova et al. [30] showed that permafrost thaw supported an increase in soil subsidence and the development of thermokarst lakes. Soil subsidence was related to soil carbon decomposition and mobilization to water resources.

Jackowicz-Korczynski et al. [31] observed methane emission from subarctic Swedish mires. A permafrost free mire having tall graminoid vegetation showed methane emission rates of 6.2 ± 2.6 mg CH4 m−2 hr.−1. The annual emission was 24.5 to 29.5 g CH4 m−2 yr.−1, with most of the emission during the summer months. In Wales (UK), Fenner et al. [32] investigated ombrotrophic peat or acid mires. Artificially enhanced CO2 and warming produced increased concentrations of dissolved organic carbon. Higher concentrations of phenolic compounds were associated with the increase in dissolved organic carbon. The influence of increased temperature promoted microbial activity, whereas increased CO2 content increased the supply of photosynthate to the soil because of greater root exudates. The effect of the temperature and elevated CO2 were to synergistically decrease the C/N of the dissolved organic carbon. In Indonesian tropical peatlands, Uda et al. [33] noted that land drainage influenced CO2 emissions from drained oil palm landscapes.

Aurangojeb et al. [34] contrasted a drained Histosol and an adjacent mineral soil in Sweden, noting that the Histosol N2O emissions were 49.9 ± 3.3 μg N2O m−2 hr.−1, whereas the adjacent mineral soil N2O emission was 8.0 ± 3.3 μg N2O m−2 hr.−1. The N2O difference was attributed to the mineral soil having greater mycorrhizal N demand reducing the N availability. Leifeld et al. [35] investigated four temperate ombrotrophic peatlands across central Europe and determined that ash content is related to land drainage and land management, thus ash may be an indicator of historical decomposition but this protocol should be used only in pristine study areas.

## **7. Peatlands, net primary productivity and climate change**

Net primary production is critical to developing large carbon contents in peatlands. Net primary production is a function of climate, vegetation, topography, the natural of the parent materials, and land use. Investigating Swedish peatlands, Chaudhary et al. [36] investigated drivers of biotic and abiotic peatland dynamics. For patterned ground they noted that plant species, hydrology, nutrient status, plant productivity and decomposition rates vary between hummock and hollow positions. Typically hollows possessed taller productive graminoid species that

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*Soil Genesis of Histosols and Gelisols with a Emphasis on Soil Processes Supporting Carbon…*

showed faster decomposition rates than sphagnum. Hummock positions possessed more shrub species that preferentially lowered the water table. In interior Alaska, O'Donnell et al. [37] studied Gelisols having a 30-day enhanced temperature incubation period, noting that the dissolved organic carbon concentration and its associated aromaticity increased at higher incubation temperatures. At these higher temperatures the dissolved organic materials contained more hydrophobic organic acids, polyphenols, and condensed aromatics and smaller concentrations of lowmolecular weight hydrophilic and aliphatic compounds. Dissolved labile organic materials were preferentially mineralized, with the dominant kinetic controls being

Wang et al. [38] correlated that increased mean annual air temperature was associated with increased active layer thickness. In a Siberian low arctic landscape, Frost et al. [39] documented seasonal and long-term changes to active layer temperatures and noted that vegetation and snow cover were important predictors of active layer thickness. Summer soil temperatures decreased with increasing shrub cover and soil organic matter thickness. Compared with open tundra, mature shrubs depressed summer soil temperatures; however, mature shrubs altered the

In Canada Kroetsch et al. [5], working with the National Wetlands Working Group, noted that peatlands were routinely identified when peat depths exceeded 0.40 meters. Fibrisol, Mesisol and Humisol great groups were partitioned based on rubbed fiber content, von Post scale, pyrophosphate and depth of the surface, middle and bottom tiers. The key diagnostic genetic processes of organic soils included: (i) additions from litter, fine roots, soil organic matter deposition and low molecular weight organic acid exudation from sphagnum, feather mosses and related plant species, (ii) losses attributed to decomposition, (iii) transfers of dissolved organic carbon because of fluctuating water tables, leaching and burrowing organisms, (iv) transformations attributed to soil organic matter decomposition, O2

Glaser et al. [40] observed Hudson Bay Lowlands peatland development from a chronological perspective, relating the length of time for isostatic rebound to elevate the landscape and developing a transect of peatland sites ranging from comparatively younger to older sites. They observed that the resulting transects consisted of a sequence consisting of (i) basal tidal marshes in the youngest sites, (ii) Larix (Larches) dominated swamp forests, (iii) Picea (Spruce) forested bogs, and ending with (iv) non-forested bogs in the oldest sites. This sequence of peatlands was viewed as a predictable vegetation succession influenced by changes in hydrology and other factors derived from continuing isostatic rebound. Conversely, in western Siberia, peatlands demonstrated an increase in carbon accumulation upon transition from the northern region to the southern region [41]. The northern peatlands exhibited a carbon content of 7–35 kg carbon m−2, whereas the southern peatlands exhibited a carbon content range of 43–88 kg carbon m−2. The carbon content was estimated to be a complex function of soil organic matter quality (lignin content) and the predominant vegetation (vascular plants versus bryophytes).

Karofeld et al. [42] noted Estonia's decline of pristine mires and investigated a method for mire reconstruction, involving the removal of oxidized peak layer followed by the spreading of plant fragments to increase the effective development of bryophyte and vascular plants. Along with maintaining the presence of a

highwater table, the reconstruction effort was deemed successful.

insulative snowpack and fostered warmer winter soil temperatures.

*DOI: http://dx.doi.org/10.5772/intechopen.94399*

temperature and substrate lignin contents.

status, nutrient availability, and toxins.

**8. Peatlands and their conservation**

#### *Soil Genesis of Histosols and Gelisols with a Emphasis on Soil Processes Supporting Carbon… DOI: http://dx.doi.org/10.5772/intechopen.94399*

showed faster decomposition rates than sphagnum. Hummock positions possessed more shrub species that preferentially lowered the water table. In interior Alaska, O'Donnell et al. [37] studied Gelisols having a 30-day enhanced temperature incubation period, noting that the dissolved organic carbon concentration and its associated aromaticity increased at higher incubation temperatures. At these higher temperatures the dissolved organic materials contained more hydrophobic organic acids, polyphenols, and condensed aromatics and smaller concentrations of lowmolecular weight hydrophilic and aliphatic compounds. Dissolved labile organic materials were preferentially mineralized, with the dominant kinetic controls being temperature and substrate lignin contents.

Wang et al. [38] correlated that increased mean annual air temperature was associated with increased active layer thickness. In a Siberian low arctic landscape, Frost et al. [39] documented seasonal and long-term changes to active layer temperatures and noted that vegetation and snow cover were important predictors of active layer thickness. Summer soil temperatures decreased with increasing shrub cover and soil organic matter thickness. Compared with open tundra, mature shrubs depressed summer soil temperatures; however, mature shrubs altered the insulative snowpack and fostered warmer winter soil temperatures.

In Canada Kroetsch et al. [5], working with the National Wetlands Working Group, noted that peatlands were routinely identified when peat depths exceeded 0.40 meters. Fibrisol, Mesisol and Humisol great groups were partitioned based on rubbed fiber content, von Post scale, pyrophosphate and depth of the surface, middle and bottom tiers. The key diagnostic genetic processes of organic soils included: (i) additions from litter, fine roots, soil organic matter deposition and low molecular weight organic acid exudation from sphagnum, feather mosses and related plant species, (ii) losses attributed to decomposition, (iii) transfers of dissolved organic carbon because of fluctuating water tables, leaching and burrowing organisms, (iv) transformations attributed to soil organic matter decomposition, O2 status, nutrient availability, and toxins.

Glaser et al. [40] observed Hudson Bay Lowlands peatland development from a chronological perspective, relating the length of time for isostatic rebound to elevate the landscape and developing a transect of peatland sites ranging from comparatively younger to older sites. They observed that the resulting transects consisted of a sequence consisting of (i) basal tidal marshes in the youngest sites, (ii) Larix (Larches) dominated swamp forests, (iii) Picea (Spruce) forested bogs, and ending with (iv) non-forested bogs in the oldest sites. This sequence of peatlands was viewed as a predictable vegetation succession influenced by changes in hydrology and other factors derived from continuing isostatic rebound. Conversely, in western Siberia, peatlands demonstrated an increase in carbon accumulation upon transition from the northern region to the southern region [41]. The northern peatlands exhibited a carbon content of 7–35 kg carbon m−2, whereas the southern peatlands exhibited a carbon content range of 43–88 kg carbon m−2. The carbon content was estimated to be a complex function of soil organic matter quality (lignin content) and the predominant vegetation (vascular plants versus bryophytes).
