Temperate Peatland Research Articles

Ten‐year meteorological record for an upland research catchment near the summit of Snake Pass in the Peak District, UK

High elevation meteorological records are sparse in the United Kingdom, due in part to the logistical challenges of setting up and maintaining monitoring stations. These upland regions are also coincident with peatland landscapes, many of which are at the southern limit of temperate peatlands. Given concerns over the long‐term stability of these landscapes, which are currently at risk due to shifts in climatic zones, we present a 10‐year review of meteorological conditions in an upland peatland catchment in the Peak District, UK, which provides baseline data for assessment of change in this area.

Greenhouse gas emissions in natural and managed peatlands of America: Case studies along a latitudinal gradient

Processes affecting CO2 and CH4 emissions and their budgets have been relatively well studied in northern temperate peatlands, whereas similar studies are almost absent in southern Patagonia and the high-altitude Andean peatlands, both of which are currently under heavy anthropogenic pressure. The objectives of this study were to compare greenhouse gas (GHG) emissions in natural and managed peatlands to examine the effect of management on GHG emissions and identify the environmental parameters affecting them. We analysed CO2, CH4 and N2O emissions related to the physical and chemical conditions of the peat: in a natural and managed transitional bog in Quebec, Canada, a natural páramo and grazed peatland in the Colombian Andes, and a bog and a fen in Tierra del Fuego, Argentina. GHG fluxes were measured using the dark static chamber method. Groundwater table, temperature, O2 content, pH and redox potential were measured from observation wells, soil temperature was measured at four depths, peat samples were analysed for pH, soil organic matter and dry matter content, P, K, Ca, Mg, NH4-N, NO3-N, total N and C. In all regions, human-impacted peatlands showed significantly higher CO2-C, N2O-N and CH4-C emissions than their natural counterparts. The Canadian managed transitional bog showed the highest average CO2-C (575mgCm−2h−1) and N2O-N (0.08mgNm−2h−1) emissions, whereas the Colombian pasture was the largest emitter of CH4-C (2.35mgCm−2h−1). CO2-C emissions were controlled by soil temperature and C content, whereas CH4-C flux was negatively correlated to dissolved oxygen content in peat water, and positively to water table level and soil log (C/NO3-N) ratio. Total Inorganic Nitrogen (TIN), C/N ratio, and soil temperature were the main factors controlling N2O emissions. Intensive peatland management alters the soil C/N balance, and increases and leads to higher variability of GHG emissions. Agricultural activities, especially crop production in peatlands, as well as intensive grazing in mountain peatland pastures, are the main factors increasing GHG emissions in the peatlands studied. Mitigation is possible via regulation of grazing intensity and replacing arable fields with grasslands.

Predicting peatland carbon fluxes from non‐destructive plant traits

Summary Determining the plant traits that best predict carbon (C) storage is increasingly important as global change drivers will affect plant species composition and ecosystem C cycling. Despite the critical role of peatlands in the global C cycle, trait–flux relationships in peatlands are relatively unknown. We assessed the ability of four non‐destructive plant traits to predict carbon dioxide (CO2) and methane (CH4) fluxes over two growing seasons in a temperate peatland in Ontario, Canada. We examined relationships between C‐fluxes and leaf area, leaf persistence (deciduous, evergreen), growth form (woody, herbaceous) and aerenchyma tissue. To explore potential inconsistencies between different scales of data aggregation, traits were analysed at the level of plots, species and microsites. CO2 fluxes showed a positive relationship with leaf area and leaf persistence, and a negative relationship with proportion of woody species. CH4 fluxes showed a positive relationship with aerenchyma and leaf area. The significance of trait–flux relationships differed based on whether data were averaged at the level of plot, species or microsite. We recommend applying leaf area as a non‐destructive trait to other systems where it is not ideal to measure traits destructively. A better understanding of the relationships between above and below‐ground traits is likely needed to further explain variation in ecosystem respiration and CH4 fluxes from plant traits. A lay summary is available for this article.

Effect of temperature and soil organic matter quality on greenhouse-gas production from temperate poor and rich fen soils

Production of carbon dioxide (CO2) and methane (CH4) from peatland soil is controlled by rates of organic matter decomposition; soil organic matter (SOM) decomposition is influenced by the quality of the SOM and the soil temperature. This study determined the effect of increasing temperature and SOM quality on rates of greenhouse-gas production in lab incubations from peat soils formed under different plant functional types found in temperate rich and poor fens of southern Ontario, Canada. Peat derived from different plant functional type (sedge, shrub, and non-vascular vegetation) between the fens was composed of different amounts of SOM, lignin, and cellulose. Rates of CO2 and CH4 production from the lab slurries increased with increasing temperature; however, the relative increases were specific to the vegetation type overlying the soils. Anaerobic to aerobic production ratios ranged from 7% (Chamaedaphne soils) to >30% (Sphagnum soils). Ratios of potential anaerobic production (CO2 to CH4) generally decreased with increasing temperature. The interaction between temperature and SOM quality was demonstrated through the range of Q10 values (1.09–2.38 for CO2; 2.98–21.40 for CH4). These measures were correlated to lignin and cellulose content and the lingo-cellulose index. Results of this study indicate the variability of greenhouse-gas fluxes from peatland soils is influenced by the SOM quality derived from the overlying vegetation. As the climate warms soil temperatures will increase rates of decomposition, and this study will improve models of temperate peatland carbon cycling and can inform land management planning by providing options for minimizing carbon loss.

Carbon Emissions during Wildland Fire on a North American Temperate Peatland

Northern temperate zone (30° to 50° latitude) peatlands store a large proportion of the world’s terrestrial carbon (C) and are subject to high-intensity, stand-replacing wildfires characterized by flaming stage combustion of aboveground vegetation and long-duration smoldering stage combustion of organic soils. Coastal peatlands are a unique region in which long-duration wildfire soil combustion is responsible for the majority of total annual emissions from all wildfires in the North American coastal plain. We developed a new method and approach to estimate aboveground and belowground C emissions from a 2008 peatland wildfire by analyzing vegetation C losses from field surveys of biomass consumption from the fire and soil C losses derived from the Soil Survey Geographic Database, a digital elevation model derived from airborne optical remote-sensing technology and ground elevation surveys using a Global Navigation Satellite System receiver. The approach to estimate belowground C emissions employed pre-fire LI-DAR-derived elevation from ground return points coupled with post-fire survey-grade GPS elevation measurements from co-located ground return points. Aboveground C emission calculations were characterized for litter, shrub foliage and woody biomass, and tree foliage fractions in different vegetation classes, thereby providing detailed emissions sources. The estimate of wildland fire C emissions considered the contribution of hydrologic regime and land management to fire severity and peat burn depth. The peatland wildfire had a mean peat burn depth of 0.42 m and resulted in estimated belowground fire emissions of 9.16 Tg C and aboveground fire emissions of 0.31 Tg C, for total fire emissions of 9.47 Tg C (1 Tg = 1012 grams). The mean belowground C emissions were estimated at 544.43 t C ha−1, and the mean aboveground C emissions were 18.33 t C ha−1 (1 t = 106 grams).

How does elevated ozone reduce methane emissions from peatlands?

The effects of increased tropospheric ozone (O3) pollution levels on methane (CH4) emissions from peatlands, and their underlying mechanisms, remain unclear. In this study, we exposed peatland mesocosms from a temperate wet heath dominated by the sedge Schoenus nigricans and Sphagnum papillosum to four O3 treatments in open-top chambers for 2.5years, to investigate the O3 impacts on CH4 emissions and the processes that underpin these responses. Summer CH4 emissions, were significantly reduced, by 27% over the experiment, due to summer daytime (8hday-1) O3 exposure to non-filtered air (NFA) plus 35ppb O3, but were not significantly affected by year-round, 24hday-1, exposure to NFA plus 10ppb or NFA plus 25ppb O3. There was no evidence that the reduced CH4 emissions in response to elevated summer O3 exposure were caused by reduced plant-derived carbon availability below-ground, because we found no significant effect of high summer O3 exposure on root biomass, pore water dissolved organic carbon concentrations or the contribution of recent photosynthate to CH4 emissions. Our CH4 production potential and CH4 oxidation potential measurements in the different O3 treatments could also not explain the observed CH4 emission responses to O3. However, pore water ammonium concentrations at 20cm depth were consistently reduced during the experiment by elevated summer O3 exposure, and strong positive correlations were observed between CH4 emission and pore water ammonium concentration at three peat depths over the 2.5-year study. Our results therefore imply that elevated regional O3 exposures in summer, but not the small increases in northern hemisphere annual mean background O3 concentrations predicted over this century, may lead to reduced CH4 emissions from temperate peatlands as a consequence of reductions in soil inorganic nitrogen affecting methanogenic and/or methanotrophic activity.

Intermediate-scale community-level flux of CO2 and CH4 in a Minnesota peatland: putting the SPRUCE project in a global context

Peatland measurements of CO2 and CH4 flux were obtained at scales appropriate to the in situ biological community below the tree layer to demonstrate representativeness of the spruce and peatland responses under climatic and environmental change (SPRUCE) experiment. Surface flux measurements were made using dual open-path analyzers over an area of 1.13 m2 in daylight and dark conditions along with associated peat temperatures, water table height, hummock moisture, atmospheric pressure and incident radiation data. Observations from August 2011 through December 2014 demonstrated seasonal trends correlated with temperature as the dominant apparent driving variable. The S1-Bog for the SPRUCE study was found to be representative of temperate peatlands in terms of CO2 and CH4 flux. Maximum net CO2 flux in midsummer showed similar rates of C uptake and loss: daytime surface uptake was −5 to −6 µmol m−2 s−1 and dark period loss rates were 4–5 µmol m−2 s−1 (positive values are carbon lost to the atmosphere). Maximum midsummer CH4-C flux ranged from 0.4 to 0.5 µmol m−2 s−1 and was a factor of 10 lower than dark CO2–C efflux rates. Midwinter conditions produced near-zero flux for both CO2 and CH4 with frozen surfaces. Integrating temperature-dependent models across annual periods showed dark CO2–C and CH4–C flux to be 894 ± 34 and 16 ± 2 gC m−2 y−1, respectively. Net ecosystem exchange of carbon from the shrub-forb-Sphagnum-microbial community (excluding tree contributions) ranged from −3.1 gCO2–C m−2 y−1 in 2013, to C losses from 21 to 65 gCO2–C m−2 y−1 for the other years.

Summer fluxes of methane and carbon dioxide from a pond and floating mat in a continental Canadian peatland

Abstract. Ponds smaller than 10 000 m2 likely account for about one-third of the global lake perimeter. The release of methane (CH4) and carbon dioxide (CO2) from these ponds is often high and significant on the landscape scale. We measured CO2 and CH4 fluxes in a temperate peatland in southern Ontario, Canada, in summer 2014 along a transect from the open water of a small pond (847 m2) towards the surrounding floating mat (5993 m2) and in a peatland reference area. We used a high-frequency closed chamber technique and distinguished between diffusive and ebullitive CH4 fluxes. CH4 fluxes and CH4 bubble frequency increased from a median of 0.14 (0.00 to 0.43) mmol m−2 h−1 and 4 events m−2 h−1 on the open water to a median of 0.80 (0.20 to 14.97) mmol m−2 h−1 and 168 events m−2 h−1 on the floating mat. The mat was a summer hot spot of CH4 emissions. Fluxes were 1 order of magnitude higher than at an adjacent peatland site. During daytime the pond was a net source of CO2 equivalents to the atmosphere amounting to 0.13 (−0.02 to 1.06) g CO2 equivalents m−2 h−1, whereas the adjacent peatland site acted as a sink of −0.78 (−1.54 to 0.29) g CO2 equivalents m−2 h−1. The photosynthetic CO2 uptake on the floating mat did not counterbalance the high CH4 emissions, which turned the floating mat into a strong net source of 0.21 (−0.11 to 2.12) g CO2 equivalents m−2 h−1. This study highlights the large small-scale variability of CH4 fluxes and CH4 bubble frequency at the peatland–pond interface and the importance of the often large ecotone areas surrounding small ponds as a source of greenhouse gases to the atmosphere.

Multiyear greenhouse gas balances at a rewetted temperate peatland.

Drained peat soils are a significant source of greenhouse gas (GHG) emissions to the atmosphere. Rewetting these soils is considered an important climate change mitigation tool to reduce emissions and create suitable conditions for carbon sequestration. Long-term monitoring is essential to capture interannual variations in GHG emissions and associated environmental variables and to reduce the uncertainty linked with GHG emission factor calculations. In this study, we present GHG balances: carbon dioxide (CO2 ), methane (CH4 ) and nitrous oxide (N2 O) calculated for a 5-year period at a rewetted industrial cutaway peatland in Ireland (rewetted 7years prior to the start of the study); and compare the results with an adjacent drained area (2-year data set), and with ten long-term data sets from intact (i.e. undrained) peatlands in temperate and boreal regions. In the rewetted site, CO2 exchange (or net ecosystem exchange (NEE)) was strongly influenced by ecosystem respiration (Reco ) rather than gross primary production (GPP). CH4 emissions were related to soil temperature and either water table level or plant biomass. N2 O emissions were not detected in either drained or rewetted sites. Rewetting reduced CO2 emissions in unvegetated areas by approximately 50%. When upscaled to the ecosystem level, the emission factors (calculated as 5-year mean of annual balances) for the rewetted site were (±SD) -104±80g CO2 -C m-2 yr-1 (i.e. CO2 sink) and 9±2g CH4 -C m-2 yr-1 (i.e. CH4 source). Nearly a decade after rewetting, the GHG balance (100-year global warming potential) had reduced noticeably (i.e. less warming) in comparison with the drained site but was still higher than comparative intact sites. Our results indicate that rewetted sites may be more sensitive to interannual changes in weather conditions than their more resilient intact counterparts and may switch from an annual CO2 sink to a source if triggered by slightly drier conditions.

Temperature the dominant control on the enzyme-latch across a range of temperate peatland types

The large accumulation of carbon in peatlands arises from slow organic matter decomposition where microorganisms and their enzyme activities play a critical role. However, there is a dearth of studies on the natural patterns of peatland microbial enzyme activity and inhibitory phenolic compounds over seasons, and across a range of depths and biogeochemically different peatland types. We report the spatiotemporal patterns for phenol oxidases, phenolics, and a suite of five key hydrolase enzymes at two depths in two ombrotrophic bogs, mineral poor and rich fens, and a forested basin swamp over the growing season. Results obtained using linear fixed and mixed effect models suggest that phenol oxidase activity varies significantly with temperature and, to a lesser extent pH, leading to a breakdown of inhibitory phenolics and increased hydrolase enzyme activity across all peatland types. Overall, enzyme activity decreased significantly with depth and showed significant variation over the course of the growing season with a minimum in the spring and a maximum in the summer and fall. Enzyme activities were generally greatest in the rich fen and lowest in the forested basin swamp with no significant difference between bogs and poor fens. Site-specific factors such as nutrient availability explain deviations from these patterns. Our results illustrate the widespread but conditional applicability of the enzyme-latch mechanism to peatlands and the vulnerability of the peatland soil organic carbon stock to climate warming.

Large interannual variability in net ecosystem carbon dioxide exchange of a disturbed temperate peatland

Peatland ecosystems play an important role in the global carbon (C) cycle as significant C sinks. However, human-induced disturbances can turn these sinks into sources of atmospheric CO2. Long-term measurements are needed to understand seasonal and interannual variability of net ecosystem CO2 exchange (NEE) and effects of hydrological conditions and their disturbances on C fluxes. Continuous eddy-covariance measurements of NEE were conducted between August 2010 and April 2014 at Yenicaga temperate peatland (Turkey), which was drained for agricultural usage and for peat mining until 2009. Annual NEE during the three full years of measurement indicated that the peatland acted as a CO2 source with large interannual variability, at rates of 246, 244 and 663gCm−2yr−1 for 2011, 2012, and 2013 respectively, except for June 2011, and May to July 2012. The emission strengths were comparable to those found for severely disturbed tropical peatlands. The peak CO2 emissions occurred in the dry summer of 2013 when water table level (WTL) was below a threshold value of −60cm and soil water content (SCW) below a threshold value of 70% by volume. Water availability index was found to have a stronger explanatory power for variations in monthly ecosystem respiration (ER) than the traditional water status indicators (SCW and WTL). Air temperature, evapotranspiration and vapor pressure deficient were the most significant variables strongly correlated with NEE and its component fluxes of gross primary production and ER.

Vegetation structure and fire weather influence variation in burn severity and fuel consumption during peatland wildfires

Abstract. Temperate peatland wildfires are of significant environmental concern but information on their environmental effects is lacking. We assessed variation in burn severity and fuel consumption within and between wildfires that burnt British moorlands in 2011 and 2012. We adapted the composite burn index (pCBI) to provide semi-quantitative estimates of burn severity. Pre- and post-fire surface (shrubs and graminoids) and ground (litter, moss, duff) fuel loads associated with large wildfires were assessed using destructive sampling and analysed using a generalised linear mixed model (GLMM). Consumption during wildfires was compared with published estimates of consumption during prescribed burns. Burn severity and fuel consumption were related to fire weather, assessed using the Canadian Fire Weather Index System (FWI System), and pre-fire vegetation type. pCBI varied 1.6 fold between, and up to 1.7 fold within, wildfires. pCBI was higher where moisture codes of the FWI System indicated drier fuels. Spatial variation in pre- and post-fire fuel load accounted for a substantial proportion of the variance in fuel loads. Average surface fuel consumption was a linear function of pre-fire fuel load. Average ground fuel combustion completeness could be predicted by the Buildup Index. Carbon release ranged between 0.36 and 1.00 kg C m−2. The flammability of ground fuel layers may explain the higher C release-rates seen for wildfires in comparison to prescribed burns. Drier moorland community types appear to be at greater risk of severe burns than blanket-bog communities.

Time-scales of hydrological forcing on the geochemistry and bacterial community structure of temperate peat soils.

Peatlands are an important global carbon reservoir. The continued accumulation of carbon in peatlands depends on the persistence of anoxic conditions, in part induced by water saturation, which prevents oxidation of organic matter, and slows down decomposition. Here we investigate how and over what time scales the hydrological regime impacts the geochemistry and the bacterial community structure of temperate peat soils. Peat cores from two sites having contrasting groundwater budgets were subjected to four controlled drought-rewetting cycles. Pore water geochemistry and metagenomic profiling of bacterial communities showed that frequent water table drawdown induced lower concentrations of dissolved carbon, higher concentrations of sulfate and iron and reduced bacterial richness and diversity in the peat soil and water. Short-term drought cycles (3–9 day frequency) resulted in different communities from continuously saturated environments. Furthermore, the site that has more frequently experienced water table drawdown during the last two decades presented the most striking shifts in bacterial community structure, altering biogeochemical functioning of peat soils. Our results suggest that the increase in frequency and duration of drought conditions under changing climatic conditions or water resource use can induce profound changes in bacterial communities, with potentially severe consequences for carbon storage in temperate peatlands.

Soil organic matter characterization of temperate peatland soil with FTIR‐spectroscopy: effects of mire type and drainage intensity

SummaryPeatlands are an important component of the global carbon cycle because they comprise huge amounts of terrestrial carbon (C). Different conditions during peat formation and secondary peat decomposition affect the quantity and composition of soil organic matter (SOM) in peats. There are few comparative studies on the chemical composition of SOM in temperate peatland soil. This study investigates compositional changes of SOM functional groups in peats and corresponding peat‐forming plants by Fourier transform infrared (FTIR) spectroscopy. Three plant samples and 29 peat samples were taken from seven temperate peatland sites with different genesis and land‐use intensity. Site‐specific differences, such as genesis of the peat, were found to be reflected in the FTIR spectra. In general, there was more variation in FTIR spectra in samples from fens than in those from bogs and peat‐forming plants. The samples from fens have a smaller C–H absorption band than those from bogs and plants, which reflects greater biochemical activity in the minerotrophic than ombrotrophic environments. In addition to peat genesis, drainage and secondary peat decomposition also affect SOM composition substantially. The larger amounts of aliphatic compounds in undrained peats could be explained by selective preservation caused by anaerobic conditions. With increasing drainage of the sites, there was a decrease in the C–H absorption that was accompanied by a relative increase in C=O absorption. These changes in absorption intensities reflect the enhanced aerobic decomposition and mineralization that accompanies drainage and land‐use intensity. However, the ‘degree of peat decomposition’, a diagnostic tool used in the field, is not reflected by OM composition determined by FTIR spectroscopy. Our results contribute to further understanding of changes in SOM composition during peat formation and processes of secondary decomposition caused by drainage.

Holocene peatland initiation and carbon storage in temperate peatlands of the Sanjiang Plain, Northeast China

The Sanjiang Plain (SJP) wetland is the largest freshwater marshland in China. Peatlands were initiated early and are widely distributed across the SJP and form a large carbon (C) pool. Consequently, there is a growing interest in understanding past, present, and future peatland dynamics. Most studies on peatland dynamics have been carried out on boreal and subarctic region; however, there are limited data about peatland dynamics on temperate region, such as SJP wetland, which is sensitive to climate change and human disturbance. Here, we presented a data synthesis of basal peat ages, peatland area, and peat C accumulation rate in the SJP to examine Holocene peatland dynamics and climate sensitivity, along with total C storage and their future fate. We show that peatland initiation in the SJP started in the early Holocene, but the most intense period of peatland initiation occurred during the late Holocene, when the climate was colder and drier than the early and mid-Holocene. And the C accumulation rate also continued to increase during the late Holocene. Our results suggest that insolation and monsoon intensity as well as the local topographic characteristics and hydrology during the late Holocene in the SJP might have played an important role in causing the highest rates of peatland initiation and C accumulation. Based on the Second National Wetland Resources Survey data, we estimated that the total peatland covered an area of about 10,520 km2 on the SJP and currently stores ~0.26 Pg C. However, human activities, together with the widespread warming on the SJP over the past 60 years, not only reduce the area of wetlands but also have switched it from being a net C sink to a significant C source.

Assessing CO2 sink/source strength of a degraded temperate peatland: atmospheric and hydrological drivers and responses to extreme events

AbstractMonthly mean sink/source strength pattern of a degraded temperate peatland in northwestern Turkey was quantified using the eddy covariance technique between July 2010 and February 2014. Atmospheric and hydrological drivers and responses to extreme events of sink/source strength were analysed using multiple linear regression models, support vector machine, multilayer perceptron with principal component analysis and multiple comparisons following general linear models. On the basis of the three full‐year measurements, mean annual, growing season and maximum estimates of net ecosystem CO2 exchange (NEE) were −0.22 mg CO2 m−2 s−1, −0.28 mg CO2 m−2 s−1 and −0.11 mg CO2 m−2 s−1 in July, respectively. The main driver of changes in monthly mean NEE pattern was found to be latent heat flux. Independent validation results showed a similar predictive performance (r2 = 74%) of multiple linear regression and support vector machine models as a function of month, total rainfall, water table depth, relative humidity, latent heat, atmospheric water vapour, wind direction and downwelling shortwave radiation. A shift in NEE from a net sink to a net source was observed in response to the deepest and shallowest water table depths due to drought and flooding, respectively. Copyright © 2014 John Wiley & Sons, Ltd.

Ecosystem-atmosphere exchange of CO2 in a temperate herbaceous peatland in the Sanjiang Plain of northeast China

Northern peatlands contain a considerable share of the terrestrial carbon pool, which will be affected by future climatic variability. Using the static chamber technique, we investigated ecosystem respiration and soil respiration over two growing seasons (2012 and 2013) in a Carex lasiocarpa-dominated peatland in the Sanjiang Plain in China. We synchronously monitored the environmental factors controlling CO2 fluxes. Ecosystem respiration during these two growing seasons ranged from 33.3 to 506.7mg CO2–Cm−2h−1. Through step-wise regression, variations in soil temperature at 10cm depth alone explained 73.7% of the observed variance in log10(ER). The mean Q10 values ranged from 2.1 to 2.9 depending on the choice of depth where soil temperature was measured. The Q10 value at the 10cm depth (2.9) appears to be a good representation for herbaceous peatland in the Sanjiang Plain when applying field-estimation based Q10 values to current terrestrial ecosystem models due to the most optimized regression coefficient (63.2%). Soil respiration amounted to 57% of ecosystem respiration and played a major role in peatland carbon balance in our study. Emphasis on ecosystem respiration from temperate peatlands in the Sanjiang Plain will improve our basic understanding of carbon exchange between peatland ecosystem and the atmosphere.

Three decades of vegetation changes in peatlands isolated in an agricultural landscape

AbstractQuestionsWhat vegetation changes occurred over three decades on two large temperate peatlands (1115 ha) isolated in an agricultural landscape and affected by a human‐ignited fire?LocationSouthwest Québec, Canada.MethodsIn 2012, we revisited 103 plots first sampled in 1984–85. Changes in species composition were evaluated using the Sørensen dissimilarity index, in species frequency with Chi‐square goodness‐of‐fit tests, and in species cover using one‐sample t‐tests. Tree encroachment was evaluated using aerial photographs and satellite imagery. We used linear discriminant analyses (LDA) and ANOVA to evaluate the impact of tree encroachment on species composition.ResultsWe found a floristic dissimilarity of 35% between 1984 and 1985 and 2012. Most species whose frequency and mean cover increased were peatland species, while most species with lower frequency and mean cover in 2012 were non‐peatland species. The total area occupied by forest increased from 26% to 51%, an overall gain of 280 ha of forest. The species composition of old and new forests as well as of open sectors was highly distinct, as shown by the LDA that correctly assigned 97% of the sampling plots to these groups. Non‐peatland species were 15 and five times more abundant than peatland species in old and new forests than open habitats, respectively.ConclusionsGradual drying of the peatland margins due to drainage of the surrounding catchment, as well as post‐fire succession are likely the main drivers of the changes observed. Overall, our study showed that peatlands isolated in an anthropogenic landscape are dynamic ecosystems where vegetation communities can experience substantial changes in a short time frame. The broader implication is that peatland conservation in highly modified landscapes must be linked to restoration.

Carbon accumulation of tropical peatlands over millennia: a modeling approach.

Tropical peatlands cover an estimated 440,000 km2 (~10% of global peatland area) and are significant in the global carbon cycle by storing about 40-90 Gt C in peat. Over the past several decades, tropical peatlands have experienced high rates of deforestation and conversion, which is often associated with lowering the water table and peat burning, releasing large amounts of carbon stored in peat to the atmosphere. We present the first model of long-term carbon accumulation in tropical peatlands by modifying the Holocene Peat Model (HPM), which has been successfully applied to northern temperate peatlands. Tropical HPM (HPMTrop) is a one-dimensional, nonlinear, dynamic model with a monthly time step that simulates peat mass remaining in annual peat cohorts over millennia as a balance between monthly vegetation inputs (litter) and monthly decomposition. Key model parameters were based on published data on vegetation characteristics, including net primary production partitioned into leaves, wood, and roots; and initial litter decomposition rates. HPMTrop outputs are generally consistent with field observations from Indonesia. Simulated long-term carbon accumulation rates for 11,000-year-old inland, and 5000-year-old coastal peatlands were about 0.3 and 0.59 Mg C ha(-1) yr(-1), and the resulting peat carbon stocks at the end of the 11,000-year and 5000-year simulations were 3300 and 2900 Mg C ha(-1), respectively. The simulated carbon loss caused by coastal peat swamp forest conversion into oil palm plantation with periodic burning was 1400 Mg C ha(-1) over 100 years, which is equivalent to ~2900 years of C accumulation in a hectare of coastal peatlands.

Effect ofCarex rostrataon seasonal and interannual variability in peatland methane emissions

[1] Peatlands are a large natural source of atmospheric methane (CH4), and the sedge Carex rostrata plays a critical role in the production, oxidation, and transport of CH4 in these systems. This 4 year clipping experiment examined the changes in CH4 emissions from a temperate peatland after removing all aboveground C. rostrata biomass. Methane fluxes, dissolved CH4, and environmental variables were measured during spring, summer, and fall from 2008 to 2011. Clipping and removing the C. rostrata leaves and stems caused an immediate decrease in CH4 emissions that persisted over 4 years of this study. There was a strong seasonal trend in CH4 flux, with the largest treatment effects occurring during the fall months when the sedges were senescing. As expected, there was a strong positive correlation between C. rostrata green-leaf area and CH4 flux, implying that the presence of C. rostrata increases CH4 emissions from this peatland. Large interannual variability in vegetation distribution and biomass, water table depth, and temperature was observed in this study, indicating the importance of multiyear studies for understanding the interactions among these factors to determine how they could be incorporated into biogeochemical models to predict CH4 emissions under changing environmental conditions.