Peatland Systems Research Articles

Role of recent climate change on carbon sequestration in peatland systems

This paper provides information on the impact of recent climate change on carbon sequestration in peatland systems in South West England. This is important because peatlands have the potential to sequester and hold large quantities of anthropogenically released CO2. This paper investigates whether there has been a reduction in the strength of carbon sinks in a valley mire and blanket bog, which occur on the limits of the biogeographical envelop for peatlands in Britain. Past rates of carbon accumulation were calculated from peat depth and the sequential analysis of peat age, bulk density and carbon content from cores taken from valley mire and blanket bog. At the valley mire site contemporary net ecosystem carbon balance (NECB) was calculated by measuring inputs to the peat body, via net primary productivity (NPP), of Sphagna. Losses of C from the peat body were calculated by measuring CH4, and aquatic carbon, calculated from catchment export of particulate and dissolved organic carbon. The study found similar mean rates of carbon accumulation since 1850 of 11.26 t ± 0.68 t CO2e ha−1 yr−1 (307 g C m−2 yr−1) in valley mire and 11.77 t ± 0.88 t CO2e ha−1 yr−1 (321 g C m−2 yr−1) in blanket bog. The mean present-day CO2 sequestration rate for Sphagna on valley mire was calculated to be 9.13 t ± 0.98 t CO2e ha−1 yr−1 (249 g C m−2 yr−1). Both past and contemporary rates of CO2 sequestration were found to be at the maxima of those reported for temperate peatlands. NPP was found to vary according to microform with higher rates of carbon sequestration found in lawn and hummock microforms compared with pools. Our work suggests that recent changes in the climate appear to have had limited impact on the strength of peatland carbon sinks in South West England.

Hydrologic function of a moderate-rich fen watershed in the Athabasca Oil Sands Region of the Western Boreal Plain, northern Alberta

Peatlands are a dominant land feature in the Athabasca Oil Sands Region (AOSR) of the Western Boreal Plain (WBP), comprising >50% of the total land area, many of which are moderate-rich fens. The carbon stocks of moderate-rich fens in the WBP are susceptible to degradation through anthropogenic- and climate-related factors, yet, few studies have aimed to understand their hydrologic function. This study, located in a meltwater channel belt characterized by relatively thin outwash sand and gravel (∼6 m) underlying the peat, provides the first hydrological assessment of a moderate-rich fen in the AOSR. The lithology, hydrological function and groundwater geochemistry all point to the dominance of a local flow system supplying groundwater to the fen areas, evidenced by a thick (∼16 m) and shallow (∼7 m below ground surface) aquitard underlying the outwash, restricting hydrological connectivity between the fen and underlying regional aquifers. Vertical hydraulic gradients between the peat and underlying outwash aquifer, and horizontal hydraulic gradients between the fen and upland varied in response to both short-term and seasonal precipitation trends. Groundwater discharge to the fen was enhanced during wet periods characterized by high rainfall. Conversely, flow reversals (groundwater recharge; fen to underlying aquifer and upland), and subsequently, enhanced fen water table drawdown persisted during extended dry periods. This local groundwater flow-system influences recharge/discharge patterns at Poplar Fen, with hydraulic head in the underlying outwash aquifer highly susceptible to fluctuations in the presence and absence of precipitation-driven recharge from adjacent uplands. Moderate-rich fens similar to that studied here will likely become more susceptible to drying in the future due to a changing climate, leading to enhanced water table drawdown, peat oxidation and subsequent decomposition, vulnerability to wildfire, and seral succession to a more ombrogenous peatland system.

Hydrology-driven environmental variability determines abiotic characteristics and Oribatida diversity patterns in a Sphagnum peatland system.

We investigated oribatid mite communities in a Sphagnum-dominated boreal peatland system characterised by a mosaic of oligotrophic and meso-eutrophic areas. We aimed to determine the relative importance of environmental factors (pH, Sphagnum nutrient content, water table level, diversity of vascular plants and bryophytes in the surrounding plant community) and spatial variation in influencing abundance, diversity and community composition of aquatic and terrestrial oribatid mites. Among environmental variables, water table level (micro-topography), pH, and K in Sphagnum tissues were the main predictors of Oribatida community structure. Aquatic species were associated with pools; two terrestrial species-Hoplophthiracarus illinoisensis and Nothrus pratensis-were associated with oligotrophic hummocks; the rest of terrestrial species were associated with dryer mesotrophic and eutrophic habitats. Low water table depth (hummocks), high local plant diversity, and high P in Sphagnum tissues were predictors of high abundance of terrestrial Oribatida. Species richness of terrestrial Oribatida was linked with low water table and high plant diversity. For aquatic Oribatida abundance, water table depth was the single most important predictor variable. Plot trophic class (its status on the peatland poor-rich gradient assigned based on plant indicator species) was also a significant predictor of terrestrial Oribatida abundance, richness, and community structure. Spatial structuring was important for terrestrial Oribatida community composition, weak (P < 0.10) for terrestrial Oribatida abundance and richness, and not significant for aquatic Oribatida.

Paleoecological assessment of cladoceran community dynamics in two subarctic peatlands

Crustacean community structure and dynamics are very well studied in lakes, rivers and oceanic systems but wetlands, where moisture conditions fluctuate, have not received equal attention in research. For example, cladoceran communities in peatland systems in the subarctic region have not been fully investigated. We used paleolimnological and paleoecological methods to study plant and cladoceran assemblages and the community dynamics in two subarctic peatlands, which differ in their hydrological characteristics. At the first site, Iitto, river floods introduce planktonic species to fen pools and the steep topography of the catchment induces rapid but relatively short flooding periods. Fluctuating environmental conditions result in a high amount of cladoceran resting stages in the samples. At the other site, Kaamanen, the cladoceran assemblage goes through clear directional changes, which could be attributed to changes in fen hydrology and ultimately to climatic changes during the past two millennia.

Near surface geophysical analysis of the Navamuño depression (Sierra de Béjar, Iberian Central System): Geometry, sedimentary infill and genetic implications of tectonic and glacial footprint

The geometric and genetic characterization of the Navamuño depression peatland system (Iberian Central System) is presented here using results from a geophysical survey. This depression is a ~30 ha pseudo-endorheic flat basin over granitic bedrock. Three geophysical techniques were used to map the subsurface geology, and identify and describe the infill sequence: shallow seismic refraction (SR), Magnetic Resonance Sounding (MRS) and electrical resistivity measurements (VES and ERT). The three main geoelectrical layers (G1, G2, G3) identified in previous research, have also been identified in the present work. Using the data obtained in this new research we have been able to analyse these three geological layers in detail and reinterpret them. They can be grouped genetically into two sedimentary units: an ancient sedimentary body (G3), of unknown age and type, beneath an Upper Pleistocene (G2) and Holocene (G1) sedimentary infill. The facies distribution and geometry of the Upper Pleistocene was examined using the Sequence Stratigraphy method, revealing that the Navamuño depression was an ice-dammed in the last glacial cycle resulting in glaciolacustrine sedimentation. A highly permeable sedimentary layer or regolith exists beneath the glaciolacustrine deposits. Below 40 m depth, water content falls dramatically down to a depth of 80 m where unweathered bedrock may be present. The information obtained from geophysical, geological and geomorphological studies carried out in this research, enabled us to consider various hypotheses as to the origin of this depression. According to these data, the Navamuño depression may be explained as the result of a transtensional process from the Puerto de Navamuño strike-slip fault during the reactivation of the Iberian Central System (Paleogene-Lower Miocene, Alpine orogeny), and can be correlated with the pull-apart type basins described in these areas. The neotectonic activity of this fault and the ice-dammed processes in these areas during the Last Glacial Cycle (MIS2) were the main causes of recent sedimentary infill in this depression.

Precipitation frequency alters peatland ecosystem structure and CO2 exchange: Contrasting effects on moss, sedge, and shrub communities.

Climate projections forecast a redistribution of seasonal precipitation for much of the globe into fewer, larger events spaced between longer dry periods, with negligible changes in seasonal rainfall totals. This intensification of the rainfall regime is expected to alter near-surface water availability, which will affect plant performance and carbon uptake. This could be especially important in peatland systems, where large stores of carbon are tightly coupled to water surpluses limiting decomposition. Here, we examined the role of precipitation frequency on vegetation growth and carbon dioxide (CO2 ) balances for communities dominated by a Sphagnum moss, a sedge, and an ericaceous shrub in a cool temperate poor fen. Field plots and laboratory monoliths received one of three rainfall frequency treatments, ranging from one event every three days to one event every 14days, while total rain delivered in a two-week cycle and the entire season to each treatment remained the same. Separating incident rain into fewer but larger events increased vascular cover in all peatland communities: vascular plant cover increased 6× in the moss-dominated plots, nearly doubled in the sedge plots, and tripled in the shrub plots in Low-Frequency relative to High-Frequency treatments. Gross ecosystem productivity was lowest in moss communities receiving low-frequency rain, but higher in sedge and shrub communities under the same conditions. Net ecosystem exchange followed this pattern: fewer events with longer dry periods increased CO2 flux to the atmosphere from the moss while vascular plant-dominated communities became more of a sink for CO2 . Results of this study suggest that changes to rainfall frequency already occurring and predicted to continue will lead to increased vascular plant cover in peatlands and will impact their carbon-sink function.

Congo Basin peatlands: threats and conservation priorities

The recent publication of the first spatially explicit map of peatlands in the Cuvette Centrale, central Congo Basin, reveals it to be the most extensive tropical peatland complex, at ca. 145,500 km2. With an estimated 30.6 Pg of carbon stored in these peatlands, there are now questions about whether these carbon stocks are under threat and, if so, what can be done to protect them. Here, we analyse the potential threats to Congo Basin peat carbon stocks and identify knowledge gaps in relation to these threats, and to how the peatland systems might respond. Climate change emerges as a particularly pressing concern, given its potential to destabilise carbon stocks across the whole area. Socio-economic developments are increasing across central Africa and, whilst much of the peatland area is protected on paper by some form of conservation designation, the potential exists for hydrocarbon exploration, logging, plantations and other forms of disturbance to significantly damage the peatland ecosystems. The low level of human intervention at present suggests that the opportunity still exists to protect the peatlands in a largely intact state, possibly drawing on climate change mitigation funding, which can be used not only to protect the peat carbon pool but also to improve the livelihoods of people living in and around these peatlands.

Synchrotron infrared microspectroscopy reveals the response of Sphagnum cell wall material to its aqueous chemical environment

Environmental contextSphagnum moss is a widespread species in peatlands globally and responsible for a large fraction of carbon storage in these systems. We used synchrotron infrared microspectroscopy to characterise the acid-base properties of Sphagnum moss and the conditions under which calcium uptake can occur (essential for plant tissue integrity). The work allows a chemical model for Sphagnum distribution in the landscape to be proposed. AbstractSphagnum is one the major moss types responsible for the deposition of organic soils in peatland systems. The cell walls of this moss have a high proportion of carboxylated polysaccharides (polygalacturonic acids), which act as ion exchangers and are likely to be important for the structural integrity of the cell walls. We used synchrotron light source infrared microspectroscopy to characterise the acid-base and calcium complexation properties of the cell walls of Sphagnum cristatum stems, using freshly sectioned tissue confined in a flowing liquid cell with both normal water and D2O media. The Fourier transform infrared spectra of acid and base forms are consistent with those expected for protonated and deprotonated aliphatic carboxylic acids (such as uronic acids). Spectral deconvolution shows that the dominant aliphatic carboxylic groups in this material behave as a monoprotic acid (pKa=4.97–6.04). The cell wall material shows a high affinity for calcium, with a binding constant (K) in the range 103.9–104.7 (1:1 complex). The chemical complexation model developed here allows for the prediction of the chemical environment (e.g. pH, ionic content) under which Ca2+ uptake can occur, and provides an improved understanding for the observed distribution of Sphagnum in the landscape.

Pure and mixed litters of Sphagnum and Carex exhibit a home-field advantage in Boreal peatlands

The notion that plants are tightly coupled to their belowground environment so that decomposition occurs faster in their place of origin is now a widely tested hypothesis known as the home-field advantage (HFA). Microbial adaptation to the most prevalent plant litter is the hypothesis proposed to explain decomposition results in a number of HFA studies but fails to corroborate results of many others, highlighting the need for a more comprehensive understanding of decomposition dynamics at local scales. Boreal peatlands are important ecosystems for carbon storage that are expected to be significantly affected by climate change, thus understanding decomposition dynamics in Boreal peatland systems is of global relevance. We performed a reciprocal transplant experiment using pure and mixed litters of two dominant peatland plant types (Sphagnum moss and Carex sedge) present in differing densities at two sites differing in nutrient status in a Boreal peatland complex. Aboveground (temperature, relative humidity) and belowground (pH, moisture, available nitrogen) environmental characteristics were measured, and initial litter quality (C, N, S) was assessed with decomposition (mass loss) quantified after one year. We use linked HFA equations that help account for differences in litter quality and site conditions. While Carex lost greater overall mass than Sphagnum, both Carex and Sphagnum demonstrate a HFA, but only where they were the dominant plant of each site. This result held for both pure and mixed litters, suggesting microbial specificity to the most prevalent plant type, yet mixed litters moderated the strength of the HFA. While our results provide novel insights to plant-soil linkages and mixed litter interactions in Boreal peatlands, mechanisms underpinning microbial specificity to plant litter in these ecosystems requires further investigation.

Gaseous mercury fluxes in peatlands and the potential influence of climate change

Climate change has the potential to significantly impact the stability of large stocks of mercury (Hg) stored in peatland systems due to increasing temperatures, altered water table regimes and subsequent shifts in vascular plant communities. However, the Hg exchange dynamics between the atmosphere and peatlands are not well understood. At the PEATcosm Mesocosm Facility in Houghton, Michigan, total gaseous Hg (TGM) fluxes were monitored in a subset of 1-m3 peat monoliths with altered water table positions (high and low) and vascular plant functional groups (sedge only, Ericaceae only or unmanipulated control) above the Sphagnum moss layer. At the SPRUCE bog in north-central Minnesota, TGM fluxes were measured from plots subjected to deep peat soil warming (up to +9 °C above ambient at a depth of 2 m). At PEATcosm, the strongest depositional trend was observed with the Low WT – sedge only treatment mesocosms with a mean TGM flux of −73.7 ± 6.3 ng m−2 d−1, likely due to shuttling of Hg to the peat at depth by aerenchymous tissues. The highest total leaf surface and tissue Hg concentrations were observed with the Ericaceae shrubs. A negative correlation between TGM flux and Ericaceae total leaf surface area suggests an influence of shrubs in controlling Hg exchange through stomatal uptake, surface sorption and potentially, peat shading. Surface peat total Hg concentrations are highest in treatments with greatest deposition suggesting deposition controls Hg accumulation in surface peat. Fluxes in the SPRUCE plots ranged from −45.9 ± 93.8 ng m−2 d−1 prior to the implementation of the deep warming treatments to −1.41 ± 27.1 ng m−2 d−1 once warming targets were achieved at depth and +10.2 ± 44.6 ng m−2 d−1 following prolonged deep soil warming. While these intervals did not differ significantly, a significant positive increase in the slope of the regression between flux and surface temperature was observed across the pre-treatment and warming periods. Shifts in vascular vegetation cover and peat warming as a result of climate change may significantly affect the dynamics of TGM fluxes between peatlands and the atmosphere.

Peatlands and Global Change: Response and Resilience

Peatlands are wetland ecosystems that accumulate dead organic matter (i.e., peat) when plant litter production outpaces peat decay, usually under conditions of frequent or continuous waterlogging. Collectively, global peatlands store vast amounts of carbon (C), equaling if not exceeding the amount of C in the Earth's vegetation; they also encompass a remarkable diversity of forms, from the frozen palsa mires of the northern subarctic to the lush swamp forests of the tropics, each with their own characteristic range of fauna and flora. In this review we explain what peatlands are, how they form, and the contribution that peatland science can make to our understanding of global change. We explore the variety in formation, shape, vegetation type, and chemistry of peatlands across the globe and stress the fundamental features that are common to all peat-forming ecosystems. We consider the impacts that past, present, and future environmental changes, including anthropogenic disturbances, have had and will have on peatland systems, particularly in terms of their important roles in C storage and the provision of ecosystem services. The most widespread uses of peatlands today are for forestry and agriculture, both of which require drainage that results in globally significant emissions of carbon dioxide (CO2), a greenhouse gas (GHG). Climatic drying and drainage also increase the risk of peat fires, which are a further source of GHG emissions [CO2 and methane (CH4)] to the atmosphere, as well as causing negative human health and socioeconomic impacts. We conclude our review by explaining the roles that paleoecological, experimental, and modeling studies can play in allowing us to build a more secure understanding of how peatlands function, how they will respond to future climate- and land-management-related disturbances, and how best we can improve their resilience in a changing world.

Land-use intensity and host plant simultaneously shape the composition of arbuscular mycorrhizal fungal communities in a Mediterranean drained peatland.

Land-use change is known to be a major threat to biodiversity and ecosystem services in Mediterranean areas. However, the potential for different host plants to modulate the effect of land-use intensification on community composition of arbuscular mycorrhizal fungi (AMF) is still poorly understood. To test the hypothesis that low land-use intensity promotes AMF diversity at different taxonomic scales and to determine whether any response is dependent upon host plant species identity, we characterised AMF communities in the roots of 10 plant species across four land use types of differing intensity in a Mediterranean peatland system. AMF were identified using 454 pyrosequencing. This revealed an overall low level of AMF richness in the peaty soils; lowest AMF richness in the intense cropping system at both virtual taxa and family level; strong modulation by the host plant of the impact of land-use intensification on AMF communities at the virtual taxa level; and a significant effect of land-use intensification on AMF communities at the family level. These findings have implications for understanding ecosystem stability and productivity and should be considered when developing soil-improvement strategies in fragile ecosystems, such as Mediterranean peatlands.

Twelve year interannual and seasonal variability of stream carbon export from a boreal peatland catchment

AbstractUnderstanding stream carbon export dynamics is needed to accurately predict how the carbon balance of peatland catchments will respond to climatic and environmental change. We used a 12 year record (2003–2014) of continuous streamflow and manual spot measurements of total organic carbon (TOC), dissolved inorganic carbon (DIC), methane (CH4), and organic carbon quality (carbon‐specific ultraviolet absorbance at 254 nm per dissolved organic carbon) to assess interannual and seasonal variability in stream carbon export for a peatland catchment (70% mire and 30% forest cover) in northern Sweden. Mean annual total carbon export for the 12 year period was 12.2 gCm−2 yr−1, but individual years ranged between 6 and 18 gCm−2 yr−1. TOC, which was primarily composed of dissolved organic carbon (&gt;99%), was the dominant form of carbon being exported, comprising 63% to 79% of total annual exports, and DIC contributed between 19% and 33%. CH4 made up less than 5% of total export. When compared to previously published annual net ecosystem exchange (NEE) for the studied peatland system, stream carbon export typically accounted for 12 to 50% of NEE for most years. However, in 2006 stream carbon export accounted for 63 to 90% (estimated uncertainty range) of NEE due to a dry summer which suppressed NEE, followed by a wet autumn that resulted in considerable stream export. Runoff exerted a primary control on stream carbon export from this catchment; however, our findings suggest that seasonal variations in biologic and hydrologic processes responsible for production and transport of carbon within the peatland were secondary influences on stream carbon export. Consideration of these seasonal dynamics is needed when predicting stream carbon export response to environmental change.

Water‐table‐dependent hydrological changes following peatland forestry drainage and restoration: Analysis of restoration success

AbstractA before‐after‐control approach was used to analyze the impact of peatland restoration on hydrology, based on high temporal resolution water‐table (WT) data from 43 boreal peatlands representative of a south‐boreal to north‐boreal climate gradient. During the study, 24 forestry drained sites were restored and 19 pristine peatlands used as control sites. Different approaches were developed and used to analyze WT changes (mean WT position, WT fluctuation, WT hydrograph, recession, and storage characteristics). Restoration increased WT in most cases but particularly in spruce mires, followed by pine mires and fens. Before restoration, the WT fluctuation (WTF) was large, indicating peat temporary storage gain (SG). After restoration, the WT hydrograph recession limb slopes and SG coefficients (Rc) declined significantly. Drainage or restoration did not significantly affect mean diurnal WT fluctuations, used here as a proxy for evapotranspiration. Overall, the changes in WT characteristics following restoration indicated creation of favorable hydrological conditions for recovery of functional peatland ecosystems in previously degraded peatland sites. This was supported by calculation of bryophyte species abundance thresholds for WT. These results can be used to optimize restoration efforts in different peatland systems and as a qualitative conceptual basis for future restoration operations.

Variations in dissolved organic carbon concentrations across peatland hillslopes

Peatlands are important terrestrial carbon stores and dissolved organic carbon (DOC) is one of the most important contributors to carbon budgets in peatland systems. Many studies have investigated factors affecting DOC concentration in peatland systems, yet hillslope position has been thus far overlooked as a variable that could influence DOC cycling. This study investigates the importance of hillslope position with regard to DOC cycling. Two upland peat hillslopes were studied in the Peak District, UK, to determine what impact, if any, hillslope position had upon DOC concentration. Hillslope position was found to be a significant factor affecting variation in soil pore water DOC concentration, with bottom-slope positions having significantly lower DOC concentrations than up-slope because of dilution of DOC as water moves down-slope and is flushed out of the system via lateral throughflow. Water table drawdown on steeper mid-slopes increased DOC concentrations through increased DOC production and extended residence times allowing a build-up of humic-rich DOC compounds. Hillslope position did not significantly affect DOC concentrations in surface runoff water because of the dilution of near-surface soil pore water by precipitation inputs, while stream water had similar water chemistry properties to soil pore water under low-flow conditions.

Long-term agricultural drainage stimulates CH4 emissions from ditches through increased substrate availability in a boreal peatland

Peatlands have been widely developed for pasture usage through drainage and with the introduction of forage grasses; however, the effects of drainage and plant community change on methane (CH4) emission have not yet been well addressed. In this study, CH4 emissions, environmental factors, and dissolved organic carbon (DOC) in the soil pore water were investigated across a disturbance gradient (i.e., the natural peatlands, the drained peatlands, and an abandoned peatland pasture). Our results show that in addition to temperature and water table, the substrate availability (DOC as a proxy) is also an important regulator of CH4 emission. For example, DOC, peat temperature at 5cm depth (T5), and water table depth (WTD) jointly explained 53% of the temporal variance in the log-transformed CH4 flux for the hollows. Also, DOC was observed to be significantly correlated with the log-transformed CH4 flux for each land form. After the data were split into wet and dry seasons based on the water table, we observed that the T5 was the main driver of the CH4 flux during the wet season (R2=0.13), while WTD replaced it during the dry season (R2=0.23) for the general peatland system (i.e., all plots taken together). For the hummocks, both T5 and WTD together explained 31% of the variance in the log-transformed CH4 flux during the wet season, and peat temperature at 20cm depth explained 16% of the variance in the log-transformed CH4 flux during the dry season, while neither T5 nor WTD was correlated with the log-transformed CH4 flux across the whole season. These results imply that the relationships between environmental factors and CH4 flux depend on the water table and land forms. Our results indicate that water table drawdown is the main driver of the CH4 emission decrease at the non-inundated sites, and it explained 72% of the variance in seasonal mean CH4 emission among sites. The drainage ditches of the drained peatlands and the abandoned pasture, in spite of covering only ∼5% of the land area, contributed 15% and 32% of the CH4 emission of the land use type, respectively, and therefore represent a “hot spot” of CH4 emissions. High CH4 emission rates from the ditches, especially of the abandoned pasture, can be attributed to the higher production and export of DOC as a result of the rigorous vegetation growth. Spatially weighted CH4 emissions from May to October were1.87±0.68g CH4m−2 for the natural peatlands, 1.08±0.35g CH4m−2 for the drained peatlands, and 1.40±0.28g CH4m−2 for the abandoned pasture. Our results suggest that it is critical to measure the CH4 emission from the drainage ditches, where fresher substrate with a higher quality is transferred from the vegetated portion of the drained peatlands, in order to accurately evaluate the effects of agricultural development on the CH4 emissions in boreal peatlands.

Imaging tropical peatlands in Indonesia using ground-penetrating radar (GPR) and electrical resistivity imaging (ERI): implications for carbon stock estimates and peat soil characterization

Abstract. Current estimates of carbon (C) storage in peatland systems worldwide indicate that tropical peatlands comprise about 15% of the global peat carbon pool. Such estimates are uncertain due to data gaps regarding organic peat soil thickness, volume and C content. We combined a set of indirect geophysical methods (ground-penetrating radar, GPR, and electrical resistivity imaging, ERI) with direct observations using core sampling and C analysis to determine how geophysical imaging may enhance traditional coring methods for estimating peat thickness and C storage in a tropical peatland system in West Kalimantan, Indonesia. Both GPR and ERI methods demonstrated their capability to estimate peat thickness in tropical peat soils at a spatial resolution not feasible with traditional coring methods. GPR is able to capture peat thickness variability at centimeter-scale vertical resolution, although peat thickness determination was difficult for peat columns exceeding 5 m in the areas studied, due to signal attenuation associated with thick clay-rich transitional horizons at the peat–mineral soil interface. ERI methods were more successful for imaging deeper peatlands with thick organomineral layers between peat and underlying mineral soil. Results obtained using GPR methods indicate less than 3% variation in peat thickness (when compared to coring methods) over low peat–mineral soil interface gradients (i.e., below 0.02°) and show substantial impacts in C storage estimates (i.e., up to 37 MgC ha−1 even for transects showing a difference between GPR and coring estimates of 0.07 m in average peat thickness). The geophysical data also provide information on peat matrix attributes such as thickness of organomineral horizons between peat and underlying substrate, the presence of buried wood, buttressed trees or tip-up pools and soil type. The use of GPR and ERI methods to image peat profiles at high resolution can be used to further constrain quantification of peat C pools and inform responsible peatland management in Indonesia and elsewhere in the tropics.

CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; fluxes and ecosystem dynamics at five European treeless peatlands – merging data and process oriented modeling

Abstract. The carbon dioxide (CO2) exchange of five different peatland systems across Europe with a wide gradient in land use intensity, water table depth, soil fertility and climate was simulated with the process oriented CoupModel. The aim of the study was to find out whether CO2 fluxes, measured at different sites, can be explained by common processes and parameters or to what extend a site specific configuration is needed. The model was calibrated to fit measured CO2 fluxes, soil temperature, snow depth and leaf area index (LAI) and resulting differences in model parameters were analyzed. Finding site independent model parameters would mean that differences in the measured fluxes could be explained solely by model input data: water table, meteorological data, management and soil inventory data. Seasonal variability in the major fluxes was well captured, when a site independent configuration was utilized for most of the parameters. Parameters that differed between sites included the rate of soil organic decomposition, photosynthetic efficiency, and regulation of the mobile carbon (C) pool from senescence to shooting in the next year. The largest difference between sites was the rate coefficient for heterotrophic respiration. Setting it to a common value would lead to underestimation of mean total respiration by a factor of 2.8 up to an overestimation by a factor of 4. Despite testing a wide range of different responses to soil water and temperature, rate coefficients for heterotrophic respiration were consistently the lowest on formerly drained sites and the highest on the managed sites. Substrate decomposability, pH and vegetation characteristics are possible explanations for the differences in decomposition rates. Specific parameter values for the timing of plant shooting and senescence, the photosynthesis response to temperature, litter fall and plant respiration rates, leaf morphology and allocation fractions of new assimilates, were not needed, even though the gradient in site latitude ranged from 48° N (southern Germany) to 68° N (northern Finland) differed largely in their vegetation. This was also true for common parameters defining the moisture and temperature response for decomposition, leading to the conclusion that a site specific interpretation of these processes is not necessary. In contrast, the rate of soil organic decomposition, photosynthetic efficiency, and the regulation of the mobile carbon pool need to be estimated from available information on specific soil conditions, vegetation and management of the ecosystems, to be able to describe CO2 fluxes under different conditions.

Scandium in the coals of Northern Asia (Siberia, the Russian Far East, Mongolia, and Kazakhstan)

We present new original data on the geochemistry of scandium in the coals of Asian Russia, Mongolia, and Kazakhstan. In general, the studied coals are enriched in Sc as compared with the average coals worldwide. Coal deposits with abnormally high, up to commercial, Sc contents were detected in different parts of the study area. The factors for the accumulation of Sc in coals have been identified. The Sc contents of the coals depend on the petrologic composition of coal basins (composition of rocks in their framing) and the facies conditions of coal accumulation. We have established the redistribution and partial removal of Sc from a coal seam during coal metamorphism. The distribution of Sc in deposits and coal seams indicates the predominantly hydrogenic mechanism of its anomalous concentration in coals and peats. The accumulation of Sc in the coals and peats is attributed to its leaching out of the coal-bearing rocks and redeposition in a coal (peat) layer with groundwater and underground water enriched in organic acids. The enrichment of coals with Sc requires conditions for the formation of Sc-enriched coal-bearing rocks and conditions for its leaching and transport to the coal seam. Such conditions can be found in the present-day peatland systems of West Siberia and, probably, in ancient basins of peat (coal) accumulation.

Spectral monitoring of moorland plant phenology to identify a temporal window for hyperspectral remote sensing of peatland

Recognising the importance of the timing of image acquisition on the spectral response in remote sensing of vegetated ecosystems is essential. This study used full wavelength, 350–2500nm, field spectroscopy to establish a spectral library of phenological change for key moorland species, and to investigate suitable temporal windows for monitoring upland peatland systems. Spectral responses over two consecutive growing seasons were recorded at single species plots for key moorland species and species sown to restore eroding peat. This was related to phenological change using narrowband vegetation indices (Red Edge Position, Photochemical Reflectance Index, Plant Senescence Reflection Index and Cellulose Absorption Index); that capture green-up and senescence related changes in absorption features in the visible to near infrared and the shortwave infrared. The selection of indices was confirmed by identifying the regions of maximum variation in the captured reflectance across the full spectrum. The indices show change in the degree of variation between species occurring from April to September, measured for plant functional types. A discriminant function analysis between indices and plant functional types determines how well each index was able to differentiate between the plant functional groups for each month. It identifies April and July as the two months where the species are most separable. What is presented here is not one single recommendation for the optimal temporal window for operational monitoring, but a fuller understanding of how the spectral response changes with the phenological cycle, including recommendations for what indices are important throughout the year.