Ombrotrophic Peatlands Research Articles

Impact of nutrients on peatland GPP estimations using MODIS time series data

Time series of satellite sensor-derived data can be used in the light use efficiency (LUE) model for gross primary productivity (GPP). The LUE model and a closely related linear regression model were studied at an ombrotrophic peatland in southern Sweden. Eddy covariance and chamber GPP, incoming and reflected photosynthetic photon flux density (PPFD), field-measured spectral reflectance, and data from the Moderate Resolution Imaging Spectroradiometer (MODIS) were used in this study. The chamber and spectral reflectance measurements were made on four experimental treatments: unfertilized control (Ctrl), nitrogen fertilized (N), phosphorus fertilized (P), and nitrogen plus phosphorus fertilized (NP). For Ctrl, a strong linear relationship was found between GPP and the photosynthetically active radiation absorbed by vegetation (APAR) (R2=0.90). The slope coefficient (εs, where s stands for “slope”) for the linear relationship between seasonal time series of GPP and the product of the normalized difference vegetation index (NDVI) and PPFD was used as a proxy for the light use efficiency factor (ε). There were differences in εs depending on the treatments with a significant effect for N compared to Ctrl (ANOVA: p=0.042, Tukey's: p≤0.05). Also, εs was linearly related to the cover degree of vascular plants (R2=0.66). As a sensitivity test, the regression coefficients (εs and intercept) for each treatment were used to model time series of 16-day GPP from the product of MODIS NDVI and PPFD. Seasonal averages of GPP were calculated for 2005, 2006, and 2007, which resulted in up to 19% higher average GPP for the fertilization treatments compared to Ctrl. The main conclusion is that the LUE model and the regression model can be applied in peatlands but also that temporal and spatial changes in ε or the regression coefficients should be considered.

Combining LiDAR and IKONOS Data for Eco‐Hydrological Classification of an Ombrotrophic Peatland

Remote sensing techniques have potential for peatland monitoring, but most previous work has focused on spectral approaches that often result in poor discrimination of cover types and neglect structural information. Peatlands contain structural "microtopes" (e.g., hummocks and hollows) which are linked to hydrology, biodiversity and carbon sequestration, and information on surface structure is thus a useful proxy for peatland condition. The objective of this work was to develop and test a new eco-hydrological mapping technique for ombrotrophic (rain-fed) peatlands using a combined spectral-structural remote sensing approach. The study site was Wedholme Flow, Cumbria, UK. Airborne light dectection and ranging (LiDAR) data were used with IKONOS data in a combined multispectral-structural approach for mapping peatland condition classes. LiDAR data were preprocessed so that spatial estimates of minimum and maximum land surface height, variance and semi-variance (from semi-variogram analysis) were extracted. These were assimilated alongside IKONOS data into a maximum likelihood classification procedure, and thematic outputs were compared. Ecological survey data were used to validate the results. Considerable improvements in thematic separation of peatland classes were achieved when spatially-distributed measurements of LiDAR variance or semi-variance were included. Specifically, the classification accuracy improved from 71.8% (IKONOS data only) to 88.0% when a LiDAR semi-variance product was used. Of note was the improved delineation of management classes (including Eriophorum bog, active raised bog and degraded raised bog). The application of a combined textural-optical approach can improve land cover mapping in areas where reliance on purely spectral discrimination approaches would otherwise result in considerable thematic uncertainty.

Changes in microbial community structure and function following Sphagnum peatland restoration

This study examines the recovery of the microbial compartment following active restoration of a North American ombrotrophic peatland extracted for horticultural peat-based substrates and restored by the Sphagnum moss transfer method. We used phospholipid fatty acids (PLFAs) to portrait the microbial community structure and Community Level Physiological Profiles (CLPP) to describe the functional diversity of the microbial communities. Our results indicate that the PLFA profiles were different between the beginning and the end of the growing season, but that it was impossible to distinguish five different vegetation classes found along the disturbance-recovery gradient on the basis of the microbial community structure. The pH, the cover of mosses, Ledum groenlandicum and Eriophorum vaginatum var. spissum were the best environmental predictors for the PLFA composition. The newly formed peat found in aerobic conditions beneath restored Sphagnum carpets had the highest decomposition capacity, whereas the lowest rates were found in the surface samples of non-restored conditions or in the deepest horizons of the natural samples. A large proportion of the variation in the physiological profiles was explained with variables related to the vegetation cover, the physicochemical environment and the microbial structure of the community, which is very promising for future monitoring studies. Overall, this study demonstrates that the recovery of particular plant groups, namely mosses and shrubs in restored peatlands might be the driver of changes occurring in the structure of the microbial communities in restored peatlands.

Interspecific and geographical differences of plant tissue nutrient concentrations along an environmental gradient in Southern Patagonia, Chile

Foliar nutrient concentrations of South Patagonian ombrotrophic peatland species were analyzed along a gradient of increasing continentality. We paid particular attention to nutrient demands of Sphagnum magellanicum, the dominant constituent of continental raised bogs, and to those of cushion-forming vascular plants such as Astelia pumila, dominating in western hyperoceanic blanket bogs. With exception of one graminoid species, nutrient concentrations in leaf tissues were generally low, but showed considerable variation. Extremely low concentrations were measured in S. magellanicum reflecting the unpolluted, pristine character of the investigated bog ecosystems. Nutrient concentrations in cushion plants showed remarkable variation. While nutrient concentrations in Donatia fascicularis were almost as low as in S. magellanicum, they were significantly higher in A. pumila. Variation in foliar nutrient concentrations was predominantly due to differences between species. Nevertheless, there was a significant shift within species along the considered west-to-east continental gradient. The stronger minerotrophic character of the western cushion bogs was reflected by higher Ca contents. N concentrations increased and P concentrations decreased westward in most species. Consequently, the most noticeable shift was an increasing N:P ratio indicating a higher degree of P limitation towards western cushion dominated blanket bogs.

Differential hydrogen isotopic ratios of Sphagnum and vascular plant biomarkers in ombrotrophic peatlands as a quantitative proxy for precipitation—evaporation balance

We have developed a new approach to quantitatively reconstruct past changes in evaporation based on compound-specific hydrogen isotope ratios of vascular plant and Sphagnum biomarkers in ombrotrophic peatland sediments. We show that the contrast in H isotopic ratios of water available to living Sphagnum (top 20 cm) and in the rooting zone of peatland vascular plants can be used to estimate “ƒ”—the fraction of water remaining after evaporation. Vascular plant leaf waxes record H isotopic ratios of acrotelm water, which carries the D/H ratio signature of precipitation and is little affected by evaporation, whereas the Sphagnum biomarker, C 23 n-alkane, records H isotopic ratios of the water inside its cells and between its leaves, which is strongly affected by evaporation at the bog surface. Evaporation changes can then be deduced by comparing H isotopic ratios of the two types of biomarkers. We calibrated D/H ratios of C 23 n-alkane to source water with lab-grown Sphagnum. We also tested our isotopic model using modern surface samples from 18 ombrotrophic peatlands in the Midwestern United States. Finally, we generated a 3000-year downcore reconstruction from Minden Bog, Michigan, USA. Our new record is consistent with records of other parameters from the same peatland derived from different proxies and allows us to differentiate precipitation supply and evaporative loss.

Laser scanning of fine scale pattern along a hydrological gradient in a peatland ecosystem

Lowland ombrotrophic (rain-fed) peatlands are a declining ecological resource in Europe. Peatlands display characteristic patterns in vegetation and surface topography, linked to ecological function, hydrology, biodiversity and carbon sequestration. Laser scanning provides a means of precisely measuring vegetation pattern in peatlands, and thus holds promise as a tool for monitoring peatland condition. Terrestrial laser scanning (TLS) was used for measurement of vegetation pattern along an eco-hydrological gradient at a UK peatland (Wedholme Flow, Cumbria) at fine grain sizes (<1 cm spatial resolution over 10 m spatial extent). Seven sites were investigated—each showed varying water table and ecological characteristics. TLS data were analysed using semi-variogram analysis which enabled the scale of spatial dependence in vegetation structures to be measured. In addition ecological, hydrological and positional surveys were conducted to elucidate interpretation of spatial patterns. Results show that TLS was able to rapidly measure vegetation patterns associated with eco-hydrological condition classes. Intact sites with hummock-hollow topography showed an isotropic pattern with a grain size or length-scale of 1 m or less (indicated by semi-variogram range). Degraded sites with high shrub cover showed increased sill variance values at larger range distances—typically around 3–4 m. The work presented shows the advantages of TLS methodologies for rapid measurement of 3-D vegetation canopy structure and surface microtopography, at fine spatial scales, in short vegetation. The paper considers how these approaches may be extended to monitoring peatland structure over larger spatial extents from airborne LiDAR systems.

Variations in above- and below-ground vascular plant biomass and water table on a temperate ombrotrophic peatland

In wetland ecosystems, little is known about the relationships between above- and below-ground plant biomass and water table, a primary driver of their distribution in these systems. These relationships can provide a means for estimating belowground stocks over large areas with variable biomass and predicting vascular plant responses to changing water tables resulting from climate change. We measured above- and below-ground vascular plant biomass across species and microtopography (i.e., hummocks and lawns) in a bog in eastern Ontario. We examined the relationships between above- and below-ground vascular plant biomass their variation with water table and species richness. We took 56 cores during a growing season, separating above- and below-ground biomass by species and plant part (small and coarse root, leaf, stem). Hummocks had greater above- and below-ground biomass, and significantly greater aboveground:belowground ratios than lawns. Lawns had a more even distribution of biomass across species than hummocks aboveground, indicating that only a few species (e.g., Vaccinium myrtilloides Michx. and Chamaedaphne calyculata Moench) are able to thrive in the driest bog conditions. Additionally, fewer species contributed to root biomass at depth, suggesting possible resource partitioning among species. Lower water tables lead to greater belowground biomass. Total above- to below-ground plant biomass relationships were strongest when separated by plant species.

Quantitative assessment of precipitation seasonality and summer surface wetness using ombrotrophic sediments from an Arctic Norwegian peatland

Seasonality of precipitation is an important yet elusive climate parameter in paleoclimatological reconstructions. This parameter can be inferred qualitatively from pollen and other paleoecological methods, but is difficult to assess quantitatively. Here, we have assessed seasonality of precipitation and summer surface wetness using compound specific hydrogen and carbon isotope ratios of vascular plant leaf waxes and Sphagnum biomarkers extracted from the sediments of an ombrotrophic peatland, Bøstad Bog, Nordland, Norway. Our reconstructed precipitation seasonality and surface wetness are consistent with regional vegetation reconstructions. During the early Holocene, 11.5–7.5 ka, Fennoscandia experienced a cool, moist climate. The middle Holocene, 7.5–5.5 ka, was warm and dry, transitioning towards cooler and wetter conditions from the mid-Holocene to the present. Changes in seasonality of precipitation during the Holocene show significant coherence with changes in sea surface temperature in the Norwegian Sea, with higher SST corresponding to greater percentage of winter precipitation. Both high SST in the Norwegian Sea and increased moisture delivery to northern Europe during winter are correlated with a strong gradient between the subpolar low and subtropical high over the North Atlantic (positive North Atlantic Oscillation).

Amazonian floodplains harbour minerotrophic and ombrotrophic peatlands

Abstract In tropical lowlands, ecosystems with peat strata are commonly reported from Southeast Asia, but hardly at all from Amazonia. In this paper, we quantify the horizontal distribution of four important plant nutrients (Ca, Mg, K and P) in five peatland sites located in Peruvian Amazonia and the vertical distribution of these nutrients in one of the sites. With this data as well as topography measurements of the peat deposit from one of the sites, we showed that minerotrophic and ombrotrophic peatlands can be detected in Amazonian floodplains. The nutrient-poor ombrotrophic bogs receive nutrients only from atmospheric deposition because of their thick peat layer and convex topography, while the minerotrophic swamps are periodically covered by nutrient-rich floodwater and/or receive nutrient input from surface waters or from groundwater with capillary rise. The existence of such peatlands in the Amazonian lowlands increases the regional habitat diversity and availability of palaeoecological information and probably has implications also for the hydrological dynamics, water quality, and carbon dynamics of the area.

Spatial and temporal variability in CH 4 and N 2O fluxes from a Scottish ombrotrophic peatland: Implications for modelling and up-scaling

Peatlands typically exhibit significant spatial heterogeneity which can lead to large uncertainties when catchment scale greenhouse gas fluxes are extrapolated from chamber measurements (generally <1 m 2). Here we examined the underlying environmental and vegetation characteristics which led to within-site variability in both CH 4 and N 2O emissions and the importance of such variability in up-scaling. We also consider within-site variation in the controls of temporal dynamics. Net annual emissions (and coefficients of variation) for CH 4 and N 2O were 1.06 kg ha −1 y −1 (300%) and 0.02 kg ha −1 y −1 (410%), respectively. The riparian zone was a significant CH 4 hotspot contributing ∼12% of the total catchment emissions whilst covering only ∼0.5% of the catchment area. In contrast to many other studies we found smaller CH 4 emissions and greater uptake in chambers containing either sedges or rushes. We also found clear differences in the drivers of temporal CH 4 dynamics across the site, e.g. water table was important only in chambers which did not contain aerenchymous plants. We suggest that depending on the heterogeneity of the site, flux models could be improved by incorporating a number of spatially distinct sub-models, rather than a single model parameterized using whole-catchment averages.

Plant functional group identity influences short‐term peatland ecosystem carbon flux: evidence from a plant removal experiment

1. Northern hemisphere peatlands are globally important stores of organic soil carbon. We examined effects of plant functional group identity on short-term carbon (C) flux in an ombrotrophic peatland in northern England, UK, by selectively removing one of each of the three dominant plant functional groups (ericoid dwarf-shrubs, graminoids and bryophytes). Carbon dynamics were quantified by a combination of CO(2) flux measurements and (13)CO(2) stable isotope pulse labelling approaches. 2. Significant effects of plant functional group removals on CO(2) fluxes and tracer (13)C uptake and turnover were detected. Removal of ericoid dwarf- shrubs had the greatest influence on gross CO(2) flux, increasing rates of respiration and photosynthesis by > 200% relative to the undisturbed control. After pulse labelling with (13)CO(2), we found that turnover of recent photosynthate, measured as respired (13)CO(2) was also greatest in the absence of dwarf- shrubs. 3. Analysis of (13)C tracer enrichment in leaf tissues from all plant removal treatments showed that the rate of fixation of (13)CO(2) and turnover of (13)C labelled photosynthate in leaf tissue was greatest in graminoids and lowest in bryophytes. Furthermore, graminoid leaf (13)C enrichment was greatest when growing in the absence of dwarf-shrubs, suggesting that the presence of dwarf- shrubs reduced the photosynthetic activity of graminoids. 4. We conclude that plant functional groups differentially influence the uptake and short-term flux of carbon in peatlands, suggesting that changes in the functional composition of vegetation resulting from global change have the potential to alter short-term patterns of carbon exchange in peatland.

Boreal peatland margins as repository sites of long-term natural disturbances of balsam fir/spruce forests

A multidisciplinary, high-resolution paleoecological study (Lepidoptera and plant remains, macroscopic charcoal, pollen) was conducted on a 4000-yr peat monolith extracted from the margin of an ombrotrophic peatland on Anticosti Island (Gulf of St. Lawrence, eastern Canada) to reconstruct the long-term natural disturbances (insect outbreaks, forest fires) of a balsam fir/spruce forest. We hypothesized that an activity of insect defoliators (spruce budworm, hemlock looper) was the main disturbance factor of conifer forests during the Late Holocene. The earliest remains of spruce budworm and hemlock looper were found ca. 3220 and 2350 cal yr BP, respectively. Peaks of insect head capsules occurred from ca. 1640 to ca. 625 cal yr BP. Low balsam fir pollen concentrations during this period suggest a lengthy episode (∼ 1000 yr) of high insect activity, resulting in extensive fir dieback and mortality. The long-term dynamics of the pristine balsam fir/spruce forests were mainly governed by the activity of insect defoliators. The limited extent and possibly the low occurrence of forest fires in the maritime environment of Anticosti Island allowed the development of mature coniferous stands propitious for insect infestations. Insect head capsules appeared to be a useful and effective tool for establishing insect presence and activity during the Holocene.

Arsenic retention and release in ombrotrophic peatlands

Organic matter can play an important role in the mobility and fate of As in the environment, but there is a lack of data on As biogeochemistry in ombrotrophic peatlands. The aim of this study was to investigate As retention and release in atmospherically contaminated ombrotrophic peat soils in the Peak District National Park (UK). Solid phase As concentrations in the peat soils exceed 25 mg kg − 1 . Solid phase As and Fe concentrations are closely correlated at sites where the peat is subjected to drying and oxic conditions. In a wetter zone of the bog, solid phase As and Fe distributions are decoupled, suggesting that As retention in these systems is not solely controlled by the presence of Fe oxides. Comparison of solid phase As and Pb distributions reveals that As has been subjected to post-depositional mobility in areas of water table fluctuation. Conversely, at permanently waterlogged locations As is immobile. Detailed stream water sampling reveals that As is released from the organic-rich uplands soils into the fluvial system. Dissolved As concentrations are highly variable, with values ranging from 0.20 to 7.28 μg l − 1 . Stream water As concentrations are elevated during late summer stormflow periods when there has been re-wetting of the peat after significant water table draw-down. Dissolved As is strongly correlated to dissolved organic carbon under stormflow and baseflow. The results of this study suggest that organic matter plays an important role in As dynamics in ombrotrophic peatlands, but further work is needed to identify the exact As binding and release mechanisms. Drying and re-wetting of ombrotrophic peat soils and associated changes in redox status has the potential to lead to increased As mobility. Further work is needed to provide information on how predicted climate change will influence As cycling at sites containing a legacy of atmospheric contamination.

Modelling the effects of climate change on methane emission from a northern ombrotrophic bog in Canada

Peatlands are a large potential source of methane (CH4) to the atmosphere. In order to investigate the effects of climate change on CH4 emission from northern ombrotrophic peatlands, a simulation model coupling water table dynamics with methane emission was developed for the Mer Bleue Bog in Ontario, Canada. The model was validated against reported values of CH4 flux from field measurements and the model outputs exhibited high sensitivity to acrotelm thickness, leaf area index, transmissivity and slope of water table. With a 2–4°C temperature rise over the 4-year simulation period, the rate of CH4 release dropped significantly to under 0.1 mg m−2 day−1. On the other hand, mean CH4 emission increased by >26-fold when the increase in precipitation was >15%. When looking at the combined effects, the highest CH4 release (13.3 mg m−2 day−1) was attained under the scenario of 2°C temperature rise and 25% precipitation increase. Results obtained in this study highlight the importance of avoiding more extreme climate change, which would otherwise lead to enhanced methane release from peatlands and further atmospheric warming through positive feedback.

Decreased summer water table depth affects peatland vegetation

Climate change can be expected to increase the frequency of summer droughts and associated low water tables in ombrotrophic peatlands. We studied the effects of periodic water table drawdown in a mesocosm experiment. Mesocosms were collected in Southern Sweden, and subsequently brought to an experimental field in the Netherlands. Two water table treatments were applied: one with constant water tables at 5 cm below the moss surface, and one in which the water table was allowed to drop, resulting in water tables fluctuating between 5 and 21 cm below the moss surface. Sphagnum growth, as well as Sphagnum and vascular plant abundance, were assessed for 2 1 2 years. Our results show that the abundance of graminoid species increased most in the constant water table treatment. In contrast, ericoid species cover increased when water tables were allowed to fluctuate. Furthermore, Sphagnum cuspidatum production decreased with fluctuating summer water tables, while Sphagnum magellanicum responded oppositely. From these results we conclude that increased occurrence of periods with low water tables may bring about a shift in dominant Sphagnum species as well as a shift from graminoid to ericoid vascular plant cover, resembling the shift from hollow to lawn or hummock vegetation. The difference in response within functional groups (vascular plants, Sphagnum ) may add to the resilience of the ecosystem. Es wird erwartet, dass die Klimaveränderung zu einer zunehmenden Häufigkeit von Sommertrockenheit und den damit verbundenen niedrigen Wasserständen in Regenwassermooren führt. Wir untersuchten die Auswirkungen einer periodischen Absenkung des Wasserspiegels in einem Mesokosmos-Experiment. Die Mesokosmen wurden in Südschweden gesammelt und anschließend zu einem Experimentierfeld in die Niederlande gebracht. Es wurden zwei Wasserspiegelbehandlungen durchgeführt: Eine mit einem konstanten Wasserstand fünf Zentimeter unterhalb der Moosoberfläche und eine bei der dem Wasserstand erlaubt wurde abzufallen, was zu Wasserständen führte, die zwischen 5 und 21 cm unterhalb der der Moosoberfläche fluktuierten. Das Sphagnum-Wachstum und die Abundanzen von Sphagnum und Gefäßpflanzen wurden über einen Zeitraum von zweieinhalb Jahren beobachtet. Unsere Ergebnisse zeigen, dass die Abundanzen von grasartigen Arten bei konstantem Wasserspiegel am meisten stieg. Im Gegensatz dazu nahm die Deckung der heideartigen Pflanzen zu, wenn dem Wasserspiegel erlaubt wurde zu fluktuieren. Darüber hinaus nahm die Produktion von S. cuspidatum bei fluktuierenden Sommerwasserständen ab, während S. magellanicum entgegengesetzt reagierte. Aus diesen Ergebnissen schließen wir, dass ein zunehmendes Auftreten von Zeiträumen mit niedrigen Wasserstand eine Veränderung bei den dominanten Sphagnumarten, als auch eine Verschiebung in der Deckung von grasartigen zu heideartigen Gefäßpflanzen mit sich bringt, die der Verschiebung von Senken- zu Rasen- oder Hügelvegetation ähnelt. Die Unterschiede in den Reaktionen der funktionalen Gruppen (Gefäßpflanzen, Sphagnum) könnten zu einer Widerstandsfähigkeit des Ökosystems beitragen.

The effect of increased temperature and nitrogen deposition on decomposition in bogs

Despite their low primary production, ombrotrophic peatlands have a considerable potential to store atmospheric carbon as a result of their extremely low litter decomposition rates. Projected changes in temperature and nitrogen (N) deposition may increase decomposition rates by their positive effects on microbial activity and litter quality, which can be expected to result in enhanced mass loss and N release from Sphagnum and vascular plant litter. This is the first study that examines the combined effects of increased temperature and N deposition on decomposition in bogs. We investigated mass loss and N release at four bog sites along a gradient from north Sweden to northeast Germany in which both temperature and N deposition increased from north to south. We performed two litterbag experiments: one reciprocal experiment with Eriophorum vaginatum litter and one experiment using recalcitrant (Sphagnum fuscum) and more degradable (Sphagnum balticum) Sphagnum litter collected from the most northern site. We measured mass loss and N release during two (Sphagnum) and three (E. vaginatum) years. The N concentration and decomposability of the E. vaginatum litter did not differ between the sites. Mass loss from E. vaginatum litter increased over the gradient from north to south, but there was no such effect on Sphagnum litter. N loss of all litter types was affected by collection site, incubation site and time and all interactions between these factors. N release in Sphagnum was positively related to N concentration.We conclude that decomposition of vascular plants and Sphagnum litter is influenced by different environmental drivers, with enhanced temperatures stimulating mass loss of vascular plant litter, but not of Sphagnum. Enhanced N deposition increases Sphagnum litter N loss. As long‐term consequences of climate change will presumably entail a higher vascular plant production, overall litter decomposition rates are likely to increase, especially in combination with increased temperature.

Testate amoebae as palaeohydrological proxies in sürmene ağaçbaşi yaylasi peatland (northeast Turkey)

Testate amoebae are unicellular micro-organisms whose hydrological sensitivity and good preservation in peats make them valuable proxies for past peatland surface wetness, and therefore climate. Previous testate amoebae transfer functions have been spatially restricted with no studies from Asia. To derive a transfer function, a sequence of samples was extracted from an ombrotrophic peatland in Turkey and amoebae counted. The internal structure of the data was explored using principal components analysis and relationships with the environmental data tested by redundancy analyses. Transfer function models were developed using a variety of techniques. As in other regions, depth to water table is the most important control on amoebae community composition. Transfer function performance was initially poor, primarily due to the inclusion of samples from areas of the site that had been heavily affected by peat cutting and had distinctly different amoebae communities. Model performance is improved by selective sample exclusion, reducing jack-knifed root mean square error of prediction to 7.1 cm. The model was tested using an initial palaeoecological data-set. Overlap with the training set was limited, although a hydrological reconstruction using this model produces similar results to a transfer function derived from northern European peatlands. This study provides the first testate amoebae transfer function from Asia and demonstrates that hydrological preferences of many of the key taxa are consistent across a large area of the Northern Hemisphere. The transfer function will allow detailed palaeoclimate reconstruction from this peatland, adding to our knowledge of Holocene climatic change in southwest Asia.

Aromatase inhibitor as neoadjuvant hormone therapy for breast cancer

Methane (CH4) flux into the atmosphere during spring thaw was investigated in a small ombrotrophic peatland (141°48′E, 43°19′N, Japan) using the conventional chamber method. More than 50 chamber deployments on top of the snow cover were carried out and continued for more than 165 h until the surface snow and underlying ice cover on top of the peat layer had thawed completely. Methane emissions were almost absent in the presence of snow cover. At the very moment the surface ice cover thawed, a large CH4 flush (>10 mg CH4 m−2 h−1) was recorded, which was on the same order of magnitude as episodic ebullition previously observed in the high-summer. Gas bubbles trapped in the ice layer on top of the waterlogged peat were preliminarily analyzed for the volumetric percentage in the total ice volume and their gas species compositions. Results showed that the bubbles occupied about 3.2% volume and that the mixing ratio of CH4 in the bubbles was about 20%. The abundance of the bubble-form CH4 was sufficient to explain the observed episodic CH4 release during the thaw. Results of this study show that CH4 emissions during the thaw season have great temporal variability; emission occurs as an episodic release of bubble-form CH4 stored in the frozen layer. The results also imply the possibility that gas-phase CH4 plays an important role, not only during the growing season but also in cold-season CH4 dynamics in northern peatlands.

Spontaneous revegetation of cutwaway peatlands of North America

Modern extraction methods permit peat to be extracted to the minerotrophic layer of ombrotrophic peatlands (bogs). As the environmental conditions of these harvested peatlands are similar to minerotrophic peatlands (fens), such sites should be restored towards a fen system. However, it is not known whether fen species would recolonize such harvested sites on their own. We surveyed vegetation and environmental variables in 28 harvested peatlands with minerotrophic residual peat across Canada and in Minnesota, USA, and compared them to 11 undisturbed fens. Compared to harvested bogs previously studied, the harvested fens sampled in this study revegetated remarkably quickly (50%-70% vegetation cover) when the hydrological conditions were suitable. However, revegetation was less extensive for sites that were still drained (25% vegetation cover). A high water table and a thin layer of residual peat were the most important factors contributing to rapid recolonization rates. Although the harvested fens were rapidly recolonized, species composition was not the same as observed on undisturbed fens. Carex and Sphagnum, dominant in undisturbed fens, generally did not recolonize harvested fens. Thus, whether the goal is to increase species richness or to ensure the return of peat accumulating functions, fen species may have to be actively introduced.

Gradients of continentality and moisture in South Patagonian ombrotrophic peatland vegetation

This study presents the analysis of 381 phytosociological releves describing predominantly ombrotrophic South Patagonian lowland peatland vegetation along a gradient of increasing continentality. Numerical methods such as cluster analysis and detrended correspondence analysis (DCA) were carried out to explore the data set. Cluster analysis resulted in nine vegetation types that were also distinctly separated in DCA ordination. The major floristic coenocline along the first DCA axis reflected a gradient of continentality ranging from pacific blanket bogs dominated by cushion plants toSphagnum-dominated continental raised bogs. Increasing continentality along the first axis was parallel with decreasing peat decomposition and increasing peat depth and acidity. In contrast, floristic variation along the second DCA axis represented a water level gradient. The typical sequence of vegetation types along the hollow-hummock moisture gradient that is well established for north hemispherical peatlands could also be observed inSphagnum-dominated South Patagonian raised bogs with a surprising similarity in floristic and structural features. Concerning the gradient of continentality significant differences in comparison with the northern hemisphere could be established. Most obvious was the dominance of cushion building plants (e.g.Astelia pumila, Donatia fascicularis) in South Patagonian oceanic peatlands, whereas this life form is totally absent from the northern hemisphere. Similar to the continentalSphagnum bogs the cushion plant vegetation of hyperoceanic peatlands exhibited a clear separation along the moisture gradient.