No description available.

No description available.

In its industrial heyday, Thorne Moors was the most extensive commercial peat operation in Britain. It became closely tied to nearby Hatfield Moors, and at both the methods of exploitation were essentially the same. Although much of Thorne Moors is situated in Yorkshire, the eastern extent lies in Lincolnshire. Recognizable differences in scale and methodology existed between the Yorkshire and Lincolnshire parts. After regional drainage in the 1620-30s, there was increased trade in the peat of Thorne Moors along the River Don. A succession of uses included unrefined and refined fuel, products from carbonization and distillation, and moss litter for working horses. From the mid-19th century, companies were formed to exploit the new uses, especially moss litter, and export became increasingly focused on railways. In 1896, the British Moss Litter Co. Ltd was set up (restructured 1899) to assume the Thorne/Hatfield interests of several smaller companies, including the Anglo-Dutch Griendtsveen Moss Litter Co. Ltd. The British Moss Litter Co. was acquired by Fisons Ltd in 1963. Following a contextual history, descriptions are given of both muscle-powered peat winning and transportation methodologies. These comprise exploitation in the 17th and 18th centuries, an examination of the 19th century writings of William Casson, and written allusions spanning 1863-1963. Information is imparted on the Griendtsveen Moss Litter Co. In addition to creating a 'Dutch' peat canal system, this company introduced an immigrant Dutch workforce, proficient in their native methods and intended inter alia to retrain local workers looking for employment with Griendtsveen. Dutch methodology persisted alongside the local methods for c.60 years. Accounts are also presented of the evolutionary limit of indigenous peat winning, and the use of narrow gauge railways. Finally the transition to mechanisation of peat cutting and narrow gauge haulage is outlined.

Les écosystèmes aquatiques sont de plus en plus reconnus pour leur rôle dans les cycles biogéochimiques locaux et globaux en raison de leur grand potentiel réactif. Les tourbières sont quant à elles des environnements relativement stables, mais qui participent aussi largement aux cycles biogéochimiques car elles accumulent de grandes quantités de carbone (C) et d’autres éléments dans leurs sols. À l’intérieur de certaines tourbières tempérées, de petites étendues d’eau se développent par la décomposition de la matière organique qui compose leur matrice, mais de larges pans de leur fonctionnement biogéochimique sont ignorés. La structure et la géographie de ces mares de tourbières, particulièrement l’interface eau-tourbe qui les caractérise, pourraient d’ailleurs en faire des écosystèmes d’un dynamisme peu commun. Le but de cette thèse est de déterminer en quoi la géographie particulière des mares de tourbières, à commencer par celle des régions tempérées, influence leurs patrons et processus biogéochimiques. Les résultats démontrent que les mares de tourbières sont des écosystèmes sans commune mesure parmi les milieux aquatiques. Les mares sont biogéochimiquement distinctes des autres milieux lentiques en raison de la structure du paysage qui les entoure, faisant d’elles des environnements où les concentrations en C organique dissous (DOC) sont plusieurs fois plus élevées et où le pH est 100 fois plus acide que dans les lacs. La biogéochimie des mares est par contre variable dans le temps et l’espace en fonction de paramètres morphologiques et climatiques. Par exemple, les concentrations en DOC sont plus élevées dans les mares les moins profondes et sous un climat moins humide, mais ces concentrations fluctuent rapidement au cours des saisons en fonction de variations météorologiques, faisant d’elles des sentinelles climatiques. Les patrons biogéochimiques observés dans les mares de tourbières semblent tirer leur origine de leur structure plutôt que d’une influence allochtone à plus grande échelle comme c’est le cas pour la plupart des lacs. Une expérience menée dans une tourbière ombrotrophe du sud du Québec montre ainsi que les processus de décomposition de la matière organique qui caractérisent les mares de tourbières varient spatialement en fonction de la profondeur des mares et de la composition chimique du matériel à décomposer. Au final, les résultats de la thèse démontrent que les patrons et processus biogéochimiques observés dans les mares de tourbières tempérées sont effectivement dirigés par leur géographie particulière, où les mécanismes fonctionnels sont en partie dictés par l’interface eau-tourbe. / Aquatic ecosystems are increasingly recognized for their contribution to local and global biogeochemical cycles because of their high reactivity potential. Peatlands are relatively stable ecosystems but that nonetheless play a large role in biogeochemical cycles because they sequester large amounts of carbon (C) and other elements. Within temperate peatlands, waterbodies may develop by the decomposition of the organic matter that forms the soil but their biogeochemical functioning remain largely ignored. Their structure and their geography, especially the water-peat interface, may thus make peatland pools ecosystems that are more dynamic than other aquatic environments. The goal of this thesis is to determine how the geography of temperate peatland pools influences their biogeochemical patterns and processes. Results show that peatland pools are biogeochemically distinct from other aquatic environments because of the structure of the landscape in which they develop, with dissolved organic C (DOC) concentrations being severalfold higher and pH being 100-fold more acidic than lakes. The biogeochemistry of peatland pools is, however, variable in both space and time in relation to morphological and climatic parameters. For example, DOC concentrations are higher in shallower pools and in arid climates, but these concentrations rapidly vary within and across seasons in relation to changes in temperatures and precipitation, highlighting their potential to act as climate sentinel. The observed biogeochemical patterns in peatland pools originate from their internal structure rather than from a broader-scale allochthonous influence like lakes. The influence of pool internal structure was revealed in an experiment we conducted in an ombrotrophic peatland of southern Québec that showed that organic matter decomposition processes vary spatially in relation to pool depth and to the chemical composition of the organic matter. Overall, the results demonstrate that temperate peatland pool biogeochemical patterns and processes are indeed controlled by their unique geography, and where functional mechanisms are partly driven by the water-peat interface.

As they are not only the home of many threatened species, but also one of the main actors in the global carbon cycle, peatlands are highly valuable ecosystems. Human disturbance, in particular drainage for forestry and agriculture, has substantially changed the state of the world’s peatlands and will continue to do so. Lowering the water table by drainage has many hydrological and biological effects, including an increased growth of trees and shrubs as well as reduced growth of the key peat moss genus Sphagnum, leading to peat degradation and release of carbon dioxide. The effects of drainage are sometimes used as predictions for how peatlands will respond to climate change, and undrained mires are thus expected to become more like drained ones in the future. The accuracy of that assumption has, to my knowledge, not been tested on a large scale. Here, I use data from two Swedish national monitoring programs to analyze how the vegetation on drained and undrained mires has changed in recent decades. The results showed an increased tree growth but a decreased establishment of new trees on both drained and undrained mires, implying that contrary to common belief there is no current large-scale afforestation of open mires in Sweden. Sphagnum had, surprisingly, increased on both drained and undrained mires, while other functional groups showed varying results. The tree growth rate was faster on drained mires, but in most other analyses the response to time did not differ depending on drainage regime. Thereby, this study found limited support for the hypothesis that undrained mires are becoming more like drained mires with climate change.

The role of Eriophorum vaginatum in carbon dioxide (CO 2) and methane (CH4) dynamics of two restored peatlands in eastern Canada was examined. Sites were established in Riviere-du-Loup, Quebec from May to October of 1999 and 2000, and Shippagan, New Brunswick from May to October of 2001. / CH4 emissions from E. vaginatum collars were positively related to maximum photosynthesis in 1999 and 2001, when the water table was close to the surface. CH4 emissions were also positively related to end of season above ground plant biomass at both sites. CH4 emissions from E. vaginatum collars ranged from -0.015 to 14.7 mg CH4-C m-2 h-1 at Riviere-du-Loup and -0.15 to 5.4 mg CH4-C m -2 h-1 at Shippagan. It is likely that E. vaginatum provides substrate for methanogenesis through plant production and acts as a conduit transporting CH4 to the atmosphere. / Patterns of NEE from E. vaginatum depended on site-specific and year-specific conditions. E. vaginatum was a net sink for CO2 at high and low light levels at Shippagan, and a net source of CO2 at low light levels at Riviere-du-Loup.

No description available.

Dans l’éventualité où l’important réservoir de carbone que représentent les tourbières venait à être déstabilisé, les impacts sur le climat planétaire pourraient être majeurs. Pourtant, les facteurs influençant les taux d’accumulation de carbone à l’échelle décennale et centennale dans les tourbières n’ont pas clairement été déterminés et les dynamiques passées et contemporaines en matière d’accumulation de carbone ont rarement été comparées pour le même site d’étude. Ce projet visait à (1) reconstruire à l’échelle fine (cm) les taux d’accumulation de carbone pour la tourbière Degerö Stormyr (Suède), (2) identifier les principaux facteurs influençant ces taux d’accumulation et (3) comparer les taux reconstruits aux flux de carbone contemporains mesurés sur le site. Deux approches méthodologiques complémentaires ont été employées : les reconstructions paléoécologiques et la modélisation. Les principales conclusions de ce mémoire sont les suivantes : (1) les taux apparents d’accumulation de carbone sont principalement liés aux conditions hydroclimatiques dans l’acrotelme, mais sont influencés par la composition végétale de la tourbe dans le catotelme. (2) Les taux réels d’accumulation de carbone pour la période récente (≈ 130 dernières années) sont semblables au bilan écosystémique net de carbone mesuré sur le site. (3) La comparaison entre les dynamiques récentes et à plus long terme suggère que Degerö Stormyr a séquestré davantage de carbone au cours des dernières décennies. Les résultats de ce mémoire soulignent l’importance d’étudier les facteurs influençant les taux d’accumulation de carbone pour différentes échelles temporelles et suggèrent que l’accent doit être mis sur l’accumulation de carbone à l’échelle décennale et centennale. / In the event that the important carbon reservoir sequestered in peatlands were to be destabilized, the impacts on global climate could be major. However, the factors influencing carbon accumulation rates at decadal and centennial scale in peatlands have not yet been clearly identified and past and contemporary carbon accumulation dynamics of the same study site have rarely been compared. This project aimed to (1) reconstruct fine scale (cm) carbon accumulation rates for the Degerö Stormyr peatland (Sweden), (2) identify the key factors influencing accumulation rates and (3) compare the reconstructed rates to modern carbon fluxes measured at the site. Two complementary methodological approaches were used: paleoecological reconstructions and modelling. The main conclusions of this thesis are that: (1) Apparent rates of carbon accumulation are mainly related to hydroclimatic conditions in the acrotelm, but are influenced by the vegetation composition of the peat in the catotelm. (2) True rates of carbon accumulation for the recent period (≈ last 130 years) are similar to the net ecosystem carbon balance measured on site. (3) The comparison between recent and long-term carbon accumulation dynamics suggests that Degerö Stormyr has sequestered more carbon over the past decades. The results of this thesis highlight the importance of studying factors influencing carbon accumulation rates at different time scales and suggest that emphasis should be placed on decadal and centennial scales.

Les forêts d’Écouves (Basse-Normandie) et de Slieveanorra (Irlande du Nord) sont ponctuées de milieux tourbeux. La thèse retrace les trajectoires historiques de ces deux sites, aux changements paradigmatiques synchrones et en étudie, par enquêtes, les représentations et la gestion.Les résultats montrent le poids du sociosystème dans la naissance et le devenir des tourbières intraforestières, mais les systèmes de représentations et pratiques de gestion de ces turfi-sylvosystèmes diffèrent.De la moitié du 19e siècle au milieu du 20e, le bois de Goult était un taillis de feuillus dégradé, ponctué de milieux tourbeux, dévalorisés, voire dangereux. Des tourbières de couverture et des landes tourbeuses pâturées et exploitées extensivement par les paysans locaux caractérisaient les milieux occupés par l’actuelle forêt de Slieveanorra.Durant la période 1950-1980, le « tout boisement » valorisa ces terres marginales par la sylviculture de bois exotiques. Le bois de Goult, domanialisé en 1955, fut reboisé et les zones humides, plantées en épicéas de Sitka (Picea Sitchensis). La forêt de Slieveanorra fut créée de toutes pièces, à partir de 1955 aussi, avec l’acquisition des terres par le ministère de l’Agriculture.À la fin des années 1980, des mesures de gestion conservatoire se multiplient. Interventionnistes en forêt d’Écouves, elles sont plus légères en forêt de Slieveanorra où l’on protège et gère a minima les espaces non boisés. Les Normands, influencés par la communication du PNR Normandie-Maine et de l’ONF, connaissent bien le milieu-tourbière et ses attraits naturalistes tandis que les Nord-irlandais connaissent mieux le produit-tourbe, qu’ils craignent de voir disparaître. / Écouves (Basse-Normandie, France) and Slieveanorra (Northern Ireland) forests are punctuated with peatlands. The thesis relates historical trajectories of these two sites, which experienced synchronic paradigmatic changes, and conducts surveys on representations and management.Results show that the sociosystem weights on the birth and future of intraforest peatlands, but representations and management practices of these turfi-sylvosystems are different.From the beginning of the 19th century to the middle of the 20th, the wood of Goult was a ruined broadleaved coppice, punctuated with depreciate, indeed dangerous, peatlands. The current Slieveanorra forest was occupied with extensively grazed and exploited blanket bogs and peaty heaths.Between 1950 and 1980, the “all-afforestation” policy developed these marginal lands with exotic coniferous trees plantations. The wood of Goult, state-owned in 1955, was replanted and peatlands were afforested with Sitka Spruce (Picea sitchensis). Slieveanorra forest was built, from 1955 too, with land purchasing by the department of Agriculture.Since the end of the 1980’s, conservation measures have grown in number. In the forest of Écouves, they are interventionists whereas in Slieveanorra forest, they are lighter; open spaces are protected and managed at least. Normans are influenced by the PNR Normandie-Maine and ONF communication and know the environment-bog and his naturalists qualities well whereas Northern Irish know the product-turf better, which they don’t want to see disappear.

A static chamber technique was used to measure methane emissions in July and August, 1995 from peatland sites in the Fort Simpson area, Northwest Territories, at the southern fringe of the discontinuous permafrost zone. Sites were classified ecologically and geomorphologically, and water table and temperature regimes were monitored. / Methane emissions ranged from $-$3.3 to 1144.2 mg/m$ sp2 cdot$d, from raised frozen sites to pond sites, respectively, similar to emissions recorded from other boreal regions. Water table was the strongest predictor of CH$ sb4$ emission. Although peat temperature is significantly correlated to methane flux, it did not significantly improve the flux-water table relationship. Methane storage within the saturated portion of the peat profile ranged from 0.2 to 4.2 g/m$ sp2$ over depths ranging from 30 to 76 cm, and did not play a large role in surficial emissions. The zone immediately above and below the water table appears to regulate methane diffusion to the surface. Residence times (storage/flux) ranged from 12 to 30 days in poor fens, and from 6 to 5789 days in fens. / Ranges and mean fluxes of methane were determined according to landform and water table position. Based on the geomorphology of the area, overall flux determined for the Fort Simpson area, map NTS 95H, NW1/4, is estimated to be 19 mg/m$ sp2 cdot$d.