Northern Peatland Ecosystems Research Articles

Challenges and Limitations of Remote Sensing Applications in Northern Peatlands: Present and Future Prospects

This systematic literature review (SLR) provides a comprehensive overview of remote sensing (RS) applications in northern peatlands from 2017 to 2022, utilising various platforms, including in situ, UAV, airborne, and satellite technologies. It addresses the challenges and limitations presented by the sophisticated nature of northern peatland ecosystems. This SLR reveals an in-creased focus on mapping, monitoring, and hydrology but identifies noticeable gaps in peatland degradation research. Despite the benefits of remote sensing, such as extensive spatial coverage and consistent monitoring, challenges persist, including high costs, underexplored areas, and limitations in hyperspectral data application. Fusing remote sensing data with on-site research offers new insights for regional peatland studies. However, challenges arise from issues like the cost of high-resolution data, coverage limitations, and inadequate field validation data in remote areas. This review suggests refining methodologies, validating with high-resolution data, and addressing these limitations for future research.

Repeated fires in forested peatlands in sporadic permafrost zone in Western Canada

Wildfires play a crucial role in northern boreal peatland ecosystems, influencing the functioning of these ecosystems by affecting vegetation composition and biomass, peat accumulation patterns, and soil carbon stocks. Northern peatland ecosystems are under pressure due to climate warming and increasing anthropogenic stress. The frequency and severity of wildfires is predicted to increase in the coming years. Therefore, understanding long-term natural fire dynamics and their effect on peatland functionality will provide crucial information for peatland management and preservation policies. To investigate the long-term fire history of Western Canada and its effect on peat accumulation and vegetation succession, we analyzed macroscopic plant remains and charcoal within peat cores taken from five peatlands in the region. Records of the most recent fire events were derived from fire scars and documented fires in the study area. Regional long-term peatland fire patterns were examined by pooling together macroscopic charcoal records and calculating 100 year moving averages. All studied sites, except the northernmost one, demonstrated repeated fires throughout the past 1500 years, suggesting that fires have been an integral part of the peatland ecosystem in Western Canada. Compiled charcoal records indicated a peak in fire activity, with the highest abundance of charcoal for the period from the 1300s to the 1550s and decreasing fire activity during recent centuries. The clear and consistent post-fire increase in the abundance of Sphagnum mosses suggests a relatively rapid recovery of peatland ecosystems after burning. The regeneration pattern, where pre-fire vegetation repeatedly re-establishes, suggests that from a long-term perspective, fires do not necessarily have a negative effect on peatland functioning and peat accumulation. In conclusion, peatlands could remain as effective carbon sinks if their natural state is secured.

Quantifying wetness variability in aapa mires with Sentinel‐2: towards improved monitoring of an EU priority habitat

AbstractAapa mires are waterlogged northern peatland ecosystems characterized by a patterned surface structure where water‐filled depressions (‘flarks’) alternate with drier hummock strings. As one of the EU Habitat Directive priority habitats, aapa mires are important for biodiversity and carbon cycling, harbouring several red‐listed species and supporting unique species communities. Due to their sensitivity to hydrological disturbances, reliable, up‐to‐date and systematic information on the hydrological condition and responses of mires is crucial and required for multiple purposes ranging from carbon exchange modelling to EU Habitats Directive reporting and conservation and ecosystem restoration planning. Here, we demonstrate the usability of Sentinel‐2 satellite data in a semi‐automatic cloud‐based approach to retrieve large‐scale information on aapa mire hydrological variability. Two satellite‐derived metrics, soil moisture index and the extent of water‐saturated surfaces based on pixel‐wise classification, are used to quantify monthly and interannual wetness variation between 2017 and 2020 across Natura 2000 aapa mires in Finland, including responses to the extreme drought of 2018. The results revealed high temporal variability in wetness, particularly in the southern parts of the aapa mire zone and generally in the late summer months interannually. Observations from the drought summer showed that one third of usually year‐round wet flark surfaces may be exposed to drying during climatic extremes. Responses varied between sites and regions, implicating the significance of environmental factors for drought resistance: some sites maintained high levels of moisture, whereas others lost wet surfaces completely. Our study provides the first comprehensive national‐level representation of seasonal and interannual wetness variability and drought‐sensitivity of pristine aapa mire sites. The approach and methods used here can be directly upscaled outside protected areas and to other EU countries. Thus, they provide a means for harmonized, systematic large‐scale monitoring of this priority habitat, as well as valuable information for other applications supporting peatland conservation and research.

Microbial organic matter reduction regulates methane and carbon dioxide production across an ombrotrophic-minerotrophic peatland gradient

Unraveling the mechanistic controls of methane (CH4) cycling in northern peatland ecosystems is crucial for understanding peatland-climate feedbacks. Growing evidence indicates that the microbial reduction of organic matter as a terminal electron acceptor can be a key regulator of CH4 production in peatlands, but the role of microbial organic matter reduction in different peatlands has not been well explored. Using an electron shuttling capacity assay, we investigated the relationship between the microbial reduction of organic matter and anaerobic CH4 and carbon dioxide (CO2) production in peatland soils in three experiments. In the first experiment, we surveyed the importance of microbial organic matter reduction in six soils representing the ombrotrophic-minerotrophic peatland gradient. In the second experiment, we further explored the reduction of solid-phase organic electron acceptors in a minerotrophic fen and compared these results to previously published values from an ombrotrophic bog (the end members of the initial gradient surveyed). Results from these experiments suggest that microbial organic matter reduction suppresses CH4 production, especially in ombrotrophic peat soils, likely helping to explain low CH4 production in bog-like soils. In contrast, the pool of oxidized organic matter was quickly reduced in minerotrophic peat soils which subsequently exhibited higher rates of CH4 production. In the final experiment, we investigated the effect of temperature on microbial organic matter reduction in the same ombrotrophic bog soil, demonstrating that warmer temperatures resulted in both a faster reduction of solid-phase organic matter and an apparent increase in the size of the organic electron acceptor pool that can be reduced by microbes. Future work should explore the drivers of the observed differences in microbial organic matter reduction in different peatland soils to provide a stronger mechanistic explanation for how this process will regulate peatland greenhouse gas dynamics in the face of global change, including increases in temperature.

Growth of floating hook-moss (Warnstorfia fluitans) differs with nutrient and water flow adjustments in greenhouse and cold room conditions

Floating hook-moss (Warnstorfia fluitans) is a bryophyte growing in northern aquatic and peatland ecosystems. W. fluitans uptakes metals and excessive amounts of nitrogen from wastewater, which suggests that it may have commercial potential for use in phytoremediation. Optimization of growth conditions would allow artificial cultivation of floating hook moss in large quantities for phytoremediation applications. We tested how application of combined nutrient (NPK 7-2-2 ranging from 0.1 to 1 ml per liter of water) and water flow (ranging from 0.15 to 1.9 ml/min) treatments affect growth of W. fluitans in greenhouse conditions. At the end of the experiment, all treatment combinations were subjected to an additional cold room condition at low temperature (0–2 °C) without constant water flow. The moss generally produced biomass in the various treatment combinations. However, contrary to our expectations, we found that increase of nutrients and water flow had a negative effect on the growth of W. fluitans. The highest growth rates in the experiment were detected in the control unit that had no nutrient addition or applied water flow. Our results suggest that cold temperatures are beneficial for W. fluitans growth. Our results show that the commercial production of W. fluitans may not require nutrient or water flow manipulation, at least in the tested scale. Instead, the growth conditions should mimic the natural cold climate conditions of W. fluitans habitats in northern peatlands and/or spring ecosystems.

Draft Metagenome Sequences of the Sphagnum (Peat Moss) Microbiome from Ambient and Warmed Environments across Europe.

ABSTRACTWe present 49 metagenome assemblies of the microbiome associated with Sphagnum (peat moss) collected from ambient, artificially warmed, and geothermally warmed conditions across Europe. These data will enable further research regarding the impact of climate change on plant-microbe symbiosis, ecology, and ecosystem functioning of northern peatland ecosystems.

Mercury dynamics in the pore water of peat columns during experimental freezing and thawing

Biogeochemical processes in northern peatland ecosystems are influenced by seasonal temperature fluctuations that are changing with the climate. Methylmercury (MeHg), commonly produced in peatlands, affects downstream waters; therefore, it is important to understand how temperature transitions affect mercury (Hg) dynamics. We investigated how the freeze-thaw cycle influences belowground peat pore water total Hg (THg), MeHg, and dissolved organic carbon (DOC). Four large, intact peat columns were removed from an ombrotrophic peat bog and experimentally frozen and thawed. Pore water was sampled across seven depths in the peat columns during the freeze-thaw cycle and analyzed for THg, MeHg, and DOC concentrations. Freezing results showed increased concentrations of THg below the ice layers and limited change in MeHg concentrations. During thawing, THg concentrations significantly increased, whereas MeHg concentrations decreased. Limited bromide movement and depth decreases in THg and DOC concentrations were associated with increased bulk density and degree of humification in the peat. The experiment demonstrates the effects of the freeze-thaw cycle on Hg concentrations in northern peatlands. Changes to freeze-thaw cycles with climate change may exacerbate Hg cycling and transport processes in peatland environments.

Structural Variations of Bacterial Community Driven by Sphagnum Microhabitat Differentiation in a Subalpine Peatland.

Sphagnum microbiomes play an important role in the northern peatland ecosystems. However, information about above and belowground microbiomes related to Sphagnum at subtropical area remains largely limited. In this study, microbial communities from Sphagnum palustre peat, S. palustre green part, and S. palustre brown part at the Dajiuhu Peatland, in central China were investigated via 16S rRNA gene amplicon sequencing. Results indicated that Alphaproteobacteria was the dominant class in all samples, and the classes Acidobacteria and Gammaproteobacteria were abundant in S. palustre peat and S. palustre brown part samples, respectively. In contrast, the class Cyanobacteria dominated in S. palustre green part samples. Microhabitat differentiation mainly contributes to structural differences of bacterial microbiome. In the S. palustre peat, microbial communities were significantly shaped by water table and total nitrogen content. Our study is a systematical investigation on above and belowground bacterial microbiome in a subalpine Sphagnum peatland and the results offer new knowledge about the distribution of bacterial microbiome associated with different microhabitats in subtropical area.

High Genetic Potential for Proteolytic Decomposition in Northern Peatland Ecosystems.

Nitrogen (N) is a scarce nutrient commonly limiting primary productivity. Microbial decomposition of complex carbon (C) into small organic molecules (e.g., free amino acids) has been suggested to supplement biologically fixed N in northern peatlands. We evaluated the microbial (fungal, bacterial, and archaeal) genetic potential for organic N depolymerization in peatlands at Marcell Experimental Forest (MEF) in northern Minnesota. We used guided gene assembly to examine the abundance and diversity of protease genes and further compared them to those of N fixation (nifH) genes in shotgun metagenomic data collected across depths and in two distinct peatland environments (bogs and fens). Microbial protease genes greatly outnumbered nifH genes, with the most abundant genes (archaeal M1 and bacterial trypsin [S01]) each containing more sequences than all sequences attributed to nifH Bacterial protease gene assemblies were diverse and abundant across depth profiles, indicating a role for bacteria in releasing free amino acids from peptides through depolymerization of older organic material and contrasting with the paradigm of fungal dominance in depolymerization in forest soils. Although protease gene assemblies for fungi were much less abundant overall than those for bacteria, fungi were prevalent in surface samples and therefore may be vital in degrading large soil polymers from fresh plant inputs during the early stage of depolymerization. In total, we demonstrate that depolymerization enzymes from a diverse suite of microorganisms, including understudied bacterial and archaeal lineages, are prevalent within northern peatlands and likely to influence C and N cycling.IMPORTANCE Nitrogen (N) is a common limitation on primary productivity, and its source remains unresolved in northern peatlands that are vulnerable to environmental change. Decomposition of complex organic matter into free amino acids has been proposed as an important N source, but the genetic potential of microorganisms mediating this process has not been examined. Such information can inform possible responses of northern peatlands to environmental change. We show high genetic potential for microbial production of free amino acids across a range of microbial guilds in northern peatlands. In particular, the abundance and diversity of bacterial genes encoding proteolytic activity suggest a predominant role for bacteria in regulating productivity and contrasts with a paradigm of fungal dominance of organic N decomposition. Our results expand our current understanding of coupled carbon and nitrogen cycles in northern peatlands and indicate that understudied bacterial and archaeal lineages may be central in this ecosystem's response to environmental change.

Modelling Holocene peatland dynamics with an individual-based dynamic vegetation model

Abstract. Dynamic global vegetation models (DGVMs) are designed for the study of past, present and future vegetation patterns together with associated biogeochemical cycles and climate feedbacks. However, most DGVMs do not yet have detailed representations of permafrost and non-permafrost peatlands, which are an important store of carbon, particularly at high latitudes. We demonstrate a new implementation of peatland dynamics in a customized Arctic version of the LPJ-GUESS DGVM, simulating the long-term evolution of selected northern peatland ecosystems and assessing the effect of changing climate on peatland carbon balance. Our approach employs a dynamic multi-layer soil with representation of freeze–thaw processes and litter inputs from a dynamically varying mixture of the main peatland plant functional types: mosses, shrubs and graminoids. The model was calibrated and tested for a sub-Arctic mire in Stordalen, Sweden, and validated at a temperate bog site in Mer Bleue, Canada. A regional evaluation of simulated carbon fluxes, hydrology and vegetation dynamics encompassed additional locations spread across Scandinavia. Simulated peat accumulation was found to be generally consistent with published data and the model was able to capture reported long-term vegetation dynamics, water table position and carbon fluxes. A series of sensitivity experiments were carried out to investigate the vulnerability of high-latitude peatlands to climate change. We found that the Stordalen mire may be expected to sequester more carbon in the first half of the 21st century due to milder and wetter climate conditions, a longer growing season, and the CO2 fertilization effect, turning into a carbon source after mid-century because of higher decomposition rates in response to warming soils.

Continuous Wavelet Analysis for Spectroscopic Determination of Subsurface Moisture and Water-Table Height in Northern Peatland Ecosystems

Climate change is altering the water-table (WT) height and near-surface moisture conditions in northern peatlands, which in turn both increases the susceptibility to fire and reduces the carbon sink capacity of these ecosystems. To further develop remote sensing-based measurements of peatland moisture characteristics, we employed coincident surface reflectance and moisture measurements in two Sphagnum moss-dominated peatland sites. We applied the Mexican hat continuous wavelet transform to the measured spectra to generate wavelet features and coefficients across a range of scales. Overall, wavelet analysis was an improvement over the previously tested spectral indices at both the study sites. Linear mixed effect models for WT height using wavelet features accounted for more of the variance with both an improved marginal $R^{\mathrm { {2}}}$ (29% greater) and a larger conditional $R^{\mathrm { {2}}}$ (21% greater) compared to the best performing spectral index. While spectral indices performed similarly with wavelet coefficients for moisture content measured at 3 cm depth, they performed poorly for volumetric moisture content measured at 7 cm depth. The current study also revealed the advantage of selecting the best subsets of wavelet features based upon genetic algorithm over a more widely used technique that selects features based on correlation scalograms. It also provided new insights into the significance of various spectral regions to detect WT alteration-induced vegetation change.

Fungal Communities in Ancient Peatlands at Sanjiang Plain, China

There is a growing concern that the on-going and future global warming would change the C cycling in northern peatland ecosystems. The peatlands in the Sanjiang plain could be more vulnerable to global warming because they are mainly located at the most southern regions of northern peatlands. Compared with bacteria, fungi are often overlooked; even they also play important roles on the substance circulation in the peatland ecosystems. Accordingly, it is imperative that we deepen our understanding on fungal community structure and diversity in the peatlands. In this study, the relative abundance, distribution, and composition of fungal communities in three different minerotrophic fens distributed in the Sanjiang Plain, was investigated by next-generation sequencing. A total of 533,323 fungal ITS sequences were obtained and these sequences were classified into at least 6 phyla, 21 classes, more than 60 orders and over 200 genera, suggesting a rich fungal community in this ecosystem. The dominated taxa were confirmed to be frequently detected in other northern peatland ecosystems. In comparison with pH, the TC, TN, C/N ratio, and bulk density were determined to be more important environmental parameters shaping fungal community structure. Additionally, for the first time, we found the distribution patterns of several abundant fungal taxa were closely related to the soil age and C accumulation rate.

The Sphagnum microbiome: new insights from an ancient plant lineage.

57 I. 57 II. 58 III. 59 IV. 59 V. 61 VI. 62 63 References 63 SUMMARY: Peat mosses of the genus Sphagnum play a major role in global carbon storage and dominate many northern peatland ecosystems, which are currently being subjected to some of the most rapid climate changes on Earth. A rapidly expanding database indicates that a diverse community of microorganisms is intimately associated with Sphagnum, inhabiting the tissues and surface of the plant. Here we summarize the current state of knowledge regarding the Sphagnum microbiome and provide a perspective for future research directions. Although the majority of the microbiome remains uncultivated and its metabolic capabilities uncharacterized, prokaryotes and fungi have the potential to act as mutualists, symbionts, or antagonists of Sphagnum. For example, methanotrophic and nitrogen-fixing bacteria may benefit the plant host by providing up to 20-30% of Sphagnum carbon and nitrogen, respectively. Next-generation sequencing approaches have enabled the detailed characterization of microbiome community composition in peat mosses. However, as with other ecologically or economically important plants, our knowledge of Sphagnum-microbiome associations is in its infancy. In order to attain a predictive understanding of the role of the microbiome in Sphagnum productivity and ecosystem function, the mechanisms of plant-microbiome interactions and the metabolic potential of constituent microbial populations must be revealed.

Dissimilar bacterial and fungal decomposer communities across rich to poor fen peatlands exhibit functional redundancy

Haynes, K. M., Preston, M. D., McLaughlin, J. W., Webster, K. and Basiliko, N. 2015. Dissimilar bacterial and fungal decomposer communities across rich to poor fen peatlands exhibit functional redundancy. Can. J. Soil Sci. 95: 219–230. Climatic and environmental changes can lead to shifts in the dominant vegetation communities present in northern peatland ecosystems, including from Sphagnum- to vascular-dominated systems. Such shifts in vegetation result in changes to the chemical quality of carbon substrates for soil microbial decomposers, with leaves and roots deposited in the peat surface and subsurface that potentially decompose faster. This study characterized the bacterial and fungal communities present along a nutrient gradient ranging from rich to poor fen peatlands and assessed the metabolic potential of these communities to mineralize a variety of organic matter substrates of varying chemical complexity using substrate-induced respiration (SIR) assays. Distinct microbial communities existed between rich, intermediate and poor fens, but SIR in each of the three sites exhibited the same pattern of carbon mineralization, providing support for the concept of functional redundancy, at least under standardized in vitro conditions. Preferential mineralization of simple organic substrates in the rich fen and complex compounds in the poor fen was not observed. Similarly, no preference was given to “native” organic matter extracts derived from each fen, with microbial communities opting for the most bioavailable substrate. This study suggests that soil bacteria and fungi might be able to respond relatively rapidly to shifts in vegetation communities and subsequent changes in the quality of carbon substrate additions to peatlands associated with environmental and climatic change.

Spectral detection of near-surface moisture content and water-table position in northern peatland ecosystems

Wildland fire occurrence has been increasing in peatland ecosystems during recent decades. As such, there is a need for broadly applicable tools to detect and monitor controls on combustion such as surface peat moisture and water-table position. A field portable spectroradiometer was used to measure surface reflectance of two Sphagnum moss-dominated peatland experiments, one being an experimental study utilizing a factorial experiment of vegetation and water-table manipulations and the other being a field site located in the Upper Peninsula of Michigan that is broadly representative of northern peatland ecosystems. Relationships were developed correlating spectral indices to surface moisture as well as water-table position using the surface reflectance data. Spectral convolutions, or integrations of the hyperspectral data with the relative spectral response curves of multispectral sensors, were also applied to represent spectral sensitivity of commonly used Earth observing sensors. Band ratios previously used to monitor surface moisture with these sensors were assessed. Strong relationships with surface moisture and water-table position are evident for both the narrow-band indices as well as broad-band indices. This study also revealed a dependence of spectral relationships on changes in vegetation cover, particularly ericoid shrubs, within the vegetation manipulation experiment.

Phenology and its role in carbon dioxide exchange processes in northern peatlands

AbstractEcosystem phenology plays an important role in carbon exchange processes and can be derived from continuous records of carbon dioxide (CO2) exchange data. In this study we examined the potential use of phenological indices for characterizing cumulative annual CO2 exchange in four contrasting northern peatland ecosystems. We used the approach of Jonsson and Eklundh (2004) to derive a set of phenological indices based on the daily time series of gross primary production (GPP), ecosystem respiration (Re), and net ecosystem production (NEP) measured in the four peatland sites. The main objectives of this study were (a) to examine the variation in phenological indices across sites and (b) to determine the relationships among phenological indices, environmental conditions, and cumulative annual CO2 exchange. The phenological index used to define the “start of the growing season” showed good potential for differentiation among sites based on their average annual site GPP. Sites with earlier growing seasons had the highest average annual site GPP. The “peak CO2 exchange rate” phenological index performed best in reflecting variations among sites and for estimating annual values of GPP, Re, and NEP (Pearson correlation coefficients ranged between 0.77 and 0.99, p < 0.05 for all.). The phenological indices and annual GPP, Re, and NEP were sensitive to winter (January–March) and summer (July–September) temperature and precipitation, but correlations, though significant, were weak.

A satellite data driven biophysical modeling approach for estimating northern peatland and tundra CO<sub>2</sub> and CH<sub>4</sub> fluxes

Abstract. The northern terrestrial net ecosystem carbon balance (NECB) is contingent on inputs from vegetation gross primary productivity (GPP) to offset the ecosystem respiration (Reco) of carbon dioxide (CO2) and methane (CH4) emissions, but an effective framework to monitor the regional Arctic NECB is lacking. We modified a terrestrial carbon flux (TCF) model developed for satellite remote sensing applications to evaluate wetland CO2 and CH4 fluxes over pan-Arctic eddy covariance (EC) flux tower sites. The TCF model estimates GPP, CO2 and CH4 emissions using in situ or remote sensing and reanalysis-based climate data as inputs. The TCF model simulations using in situ data explained > 70% of the r2 variability in the 8 day cumulative EC measured fluxes. Model simulations using coarser satellite (MODIS) and reanalysis (MERRA) records accounted for approximately 69% and 75% of the respective r2 variability in the tower CO2 and CH4 records, with corresponding RMSE uncertainties of ≤ 1.3 g C m−2 d−1 (CO2) and 18.2 mg C m−2 d−1 (CH4). Although the estimated annual CH4 emissions were small (< 18 g C m−2 yr−1) relative to Reco (> 180 g C m−2 yr−1), they reduced the across-site NECB by 23% and contributed to a global warming potential of approximately 165 ± 128 g CO2eq m−2 yr−1 when considered over a 100 year time span. This model evaluation indicates a strong potential for using the TCF model approach to document landscape-scale variability in CO2 and CH4 fluxes, and to estimate the NECB for northern peatland and tundra ecosystems.

Responses of carbon dioxide flux and plant biomass to water table drawdown in a treed peatland in northern Alberta: a climate change perspective

Abstract. Northern peatland ecosystems represent large carbon (C) stocks that are susceptible to changes such as accelerated mineralization due to water table lowering expected under a climate change scenario. During the growing seasons (1 May to 31 October) of 2011 and 2012 we monitored CO2 fluxes and plant biomass along a microtopographic gradient (hummocks-hollows) in an undisturbed dry continental boreal treed bog (control) and a nearby site that was drained (drained) in 2001. Ten years of drainage in the bog significantly increased coverage of shrubs at hummocks and lichens at hollows. Considering measured hummock coverage and including tree incremental growth, we estimate that the control site was a sink of −92 in 2011 and −70 g C m−2 in 2012, while the drained site was a source of 27 and 23 g C m−2 over the same years. We infer that, drainage-induced changes in vegetation growth led to increased biomass to counteract a portion of soil carbon losses. These results suggest that spatial variability (microtopography) and changes in vegetation community in boreal peatlands will affect how these ecosystems respond to lowered water table potentially induced by climate change.

Maintaining northern peatland ecosystems in a changing climate: effects of soil moisture, drainage and drain blocking on craneflies

AbstractThe capacity of peatlands in the northern hemisphere to provide carbon storage, maintain water quality and support northern biodiversity is threatened by a combination of climate change and inappropriate land management. Historical drainage and increasing temperatures threaten the maintenance of the high water tables required for effective peatland functioning, and there is an urgent need to develop appropriate adaptation strategies. Here we use a large‐scale replicated experimental design to test the effects of artificial drainage and drain blocking upon soil moisture and cranefly (Diptera: Tipulidae) abundance. Craneflies constitute a key component of peatland biological communities; they are important herbivores and a major prey item for breeding birds. However, they are also susceptible to drought, so are at risk from future climate change. We found that cranefly abundance increased with soil moisture, in a wedge‐shaped relationship; high soil moisture is a necessary condition for high cranefly abundance. Blocking drains increased both soil moisture (by 0.06 m3 m−3 in 2009 and 0.23 m3 m−3 in 2010) and cranefly abundance (1.3‐fold in 2009, 4.5‐fold in 2010), but the strength and significance of the effects varied between years. The benefits of restoring ecosystem moisture levels are likely to be greatest during dry years and at dry sites. This study provides some of the first evidence that adaptation management can potentially reduce some of the negative effects of climate change on vulnerable peatland systems. Management to maintain or increase soil moisture in peatlands can therefore be expected to increase populations of craneflies and their avian predators (which are of conservation and economic interest), but also increase the resilience of the ecosystem to future warming and increasingly frequent droughts, and improve carbon storage and water quality.

Contrasting responses of growing season ecosystem CO2exchange to variation in temperature and water table depth in two peatlands in northern Alberta, Canada

[1] The large belowground carbon stocks in northern peatland ecosystems are potentially susceptible to release because of the expected differential responses of photosynthesis and respiration to climate change. This study compared net ecosystem CO2 exchange (NEE) measured using the eddy covariance technique at two peatland sites in northern Alberta, Canada, over three growing seasons (May–October). We observed distinct differences between the poor fen (Sphagnum moss dominated) and extreme-rich fen (Carex sedge dominated) sites for their responses of NEE to interannual variation in temperature and water table depth. The rates of growing season cumulative NEE at the poor fen were very similar among the three study years with an average (± standard deviation) of −110.1 ± 0.5 g C m−2 period−1. By contrast, the growing season cumulative NEE at the extreme-rich fen varied substantially among years (−34.5, −153.5, and −41.8 g C m−2 period−1 in 2004, 2005, and 2006, respectively), and net uptake of CO2 was lower (on average) than at the poor fen. Consistent with the eddy covariance measurements, analysis of 210Pb-dated peat cores also showed higher recent net rates of carbon accumulation in the poor fen than in the rich fen. Warm spring temperatures and sufficient water availability during the growing season resulted in the highest-magnitude ecosystem photosynthesis and NEE at the extreme-rich fen in 2005. Cool spring temperatures limited photosynthesis at the extreme-rich fen in 2004, while reduced water availability (lower water table) in 2006 constrained photosynthetic capacity relative to 2005, despite the warmer spring and summer temperatures in 2006. The combination of contrasting plant functional types and different peat water table features at our two study sites meant that the poor fen showed a reduced response of ecosystem CO2 exchange to environmental variation compared to the extreme-rich fen.