Spatio‐temporal changes in bog pool bottom topography – temperature effect and its influence on pool development: an example from a raised bog in Estonia          下载免费PDF全文

Edgar Karofeld  Hannes Tõnisson 《水文研究》2014,28(3):958-968

Increases in pool water and peat temperature in summer accelerate peat decomposition and production of biogenic gases, which can be trapped in peat pores and cause oscillation of peatland surfaces and the rise of peat from the bottom of bog pools. Associated changes in peat water conductivity, holding capacity and transpiration also affect bog hydrology. Our multi‐year study is the first to show in detail the extent and dynamics of changes in bog pool depth and bottom topography associated with changes in temperature, peat type and other factors. The true seasonal rise of peat from the pool bottom begins once the water temperature at the pool bottom exceeds 13–14 °C, although the speed and extent of the rise depends on peat properties, making the rise more erratic than its subsequent descent. The more rapid descent occurs after the first large drop in the temperature of the pool's surface water at the end of summer, resulting from the combination of reduced methane production and increased gas solubility with less influence by peat properties. Much higher dissolved organic carbon concentrations (216 ± 26 mg l^?1) in the pore water of peat risen from the bottom to the pool surface compared with that in the same type of peat at the pool bottom (62 ± 20 mg l^?1) indicate an acceleration of peat decomposition at the warmer pool surface. We show the extent and character of changes in pool depth and bottom topography and how annual differences relate to temperature. Only a few degrees' increase in pool water temperature could induce the pool bottom to rise faster and more extensively for a longer period and enhance decomposition in the peat at the pool surface. This should be evaluated in greater detail to assess the effects of temperature increase on the carbon budget and hydrology of peatlands. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Climatic influence upon early to mid‐Holocene fire regimes within temperate woodlands: a multi‐proxy reconstruction from the New Forest,southern England          下载免费PDF全文

M. J. GRANT  P. D. M. HUGHES  K. E. BARBER 《第四纪科学杂志》2014,29(2):175-188

A combined pollen, charcoal and climatic record is presented from Cranes Moor, southern England, covering the period c. 10 500–5850 cal a BP. It is shown that the occurrence of burning is closely related to natural processes, including prevailing climatic conditions and vegetation composition. These burning events are often linked to an increase in the summer moisture deficit, implying that the timing of burning events is linked to periods of warmer/drier climate during the Holocene Thermal Maximum (c. 11 000–5000 cal a BP). These events play an important role in the vegetation composition and succession around the site. The nature of the burning recorded at the site shows strong similarities with other records from northern Europe. This study throws caution on suggestions that fire in the Holocene record from areas such as the British Isles is linked only to human activity, and enhances the possibility that natural fire incidence played an important role in natural woodland structure dynamics.  相似文献   

Anisotropy and depth‐related heterogeneity of hydraulic conductivity in a bog peat. I: laboratory measurements     

Clive W. Beckwith  Andrew J. Baird  A. Louise Heathwaite 《水文研究》2003,17(1):89-101

Anisotropy and heterogeneity of hydraulic conductivity (K) are suspected of greatly affecting rates and patterns of ground‐water seepage in peats. A new laboratory method, termed here the modified cube method, was used to measure horizontal and vertical hydraulic conductivity (K_h and K_v) of 400 samples of bog peat. The new method avoids many of the problems associated with existing field and laboratory methods, and is shown to give relatively precise measurements of K. In the majority of samples tested, K_h was much greater than K_v, indicating that the bog peat was strongly anisotropic. Log₁₀K_h, log₁₀K_v, and log₁₀ (K_h/K_v) were found to vary significantly with depth, although none of the relationships was simple. We comment on the scale dependency of our measurements. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Water budget and surface‐layer water storage in a Sphagnum bog in central Sweden     

Erik Kellner  Sven Halldin 《水文研究》2002,16(1):87-103

A water budget was established for the open, undisturbed bog Stormossen, central Sweden, for the growing seasons of 1996 and 1997 as a part of the NOPEX project. The water budget was complemented with data on the spatial variation of groundwater levels and water contents in different microrelief elements (ridge, hollow and ridge margin). The seasonal (24 May to 4 October) rainfall, evaporation and runoff were 200, 256, and 43 mm in 1996, respectively, and 310, 286 and 74 mm in 1997, giving negative budgets of ?99 mm in 1996 and ?50 mm in 1997. Approximately 60% of the total budget was caused by storage changes in the upper 40 cm of the bog and 40% by swelling/shrinking in the layers below. This ‘mire breathing’ must be incorporated in future models of mire‐water dynamics. The water content varied diversely among the different microrelief elements, much depending on the properties of moss and peat together with distance to water table. There also was a strong hysteresis in the relationships between groundwater level and measured volumetric water content, depending partly on pore‐throat effects and partly on swelling/shrinking of the peat matrix. A seasonal variation of volumetric water content in a layer beneath water table was found to be larger than what could be justified by compression alone. We think that probable causes could be methane gas expansion together with temperature effects. The main conclusions of this study were: (i) water‐transport and storage characteristics are distinctly different among hummocks, ridges and hollows, (ii) mire wetness cannot be deduced from groundwater levels only, and (iii) an important part of the total water storage was caused by swelling/shrinking of the peat, not by changes in unsaturated water content. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Hydrological and meteorological data from research catchments at the Marcell Experimental Forest,Minnesota, USA     

Stephen D. Sebestyen  Nina K. Lany  Daniel Tyler Roman  Jacob M. Burdick  Richard L. Kyllander  Elon Sandy Verry  Randall K. Kolka 《水文研究》2021,35(3):e14092

The Marcell Experimental Forest (MEF) in northern Minnesota, USA, with hydrological research and monitoring of peatland catchments in a low-topographic relief landscape, contrasts with the mountainous terrain that typifies most research catchments. Six research catchments were instrumented and hydrological and meteorological monitoring was initiated during 1960. Paired-catchment studies, which started during 1969, have been used to assess land management and environmental change effects on forests, water availability, and biogeochemistry. Over the decades, the research and collaborations have proliferated to include new monitoring and ecosystem experiments. We provide an overview of available datasets and access information for hydrological and meteorological data. Data on streamflow, water table elevation, precipitation, snow, ground frost, air temperature, soil moisture, upland runoff, and water chemistry are discoverable with associated metadata and are archived through several Web-based, community repositories. The research programme is ongoing and we anticipate updates on an annual or more frequent basis. Additionally, we aim to release other physical, chemical, and isotopic measurements associated with long-term catchment monitoring and studies at the MEF.  相似文献   

The impact of ditch blocking on fluvial carbon export from a UK blanket bog          下载免费PDF全文

Christopher D. Evans  Michael Peacock  Sophie M. Green  Joseph Holden  Pippa J. Chapman  Inma Lebron  Nathan Callaghan  Richard Grayson  Andrew J. Baird 《水文研究》2018,32(13):2141-2154

We investigated the effects of ditch blocking on fluvial carbon concentrations and fluxes at a 5‐year, replicated, control‐intervention field experiment on a blanket peatland in North Wales, UK. The site was hydrologically instrumented, and run‐off via open and blocked ditches was analysed for dissolved organic carbon (DOC), particulate organic carbon, dissolved carbon dioxide, and dissolved methane. DOC was also analysed in peat porewater and overland flow. The hillslope experiment was embedded within a paired control‐intervention catchment study, with 3 years of preblocking and 6 years of postblocking data. Results from the hillslope showed large reductions in discharge via blocked ditches, with water partly redirected into hillslope surface and subsurface flows, and partly into remaining open ditches. We observed no impacts of ditch blocking on DOC, particulate organic carbon, dissolved carbon dioxide or methane in ditch waters, DOC in porewaters or overland flow, or stream water DOC at the paired catchment scale. Similar DOC concentrations in ditch water, overland flow, and porewater suggest that diverting flow from the ditch network to surface or subsurface flow had a limited impact on concentrations or fluxes of DOC entering the stream network. The subdued response of fluvial carbon to ditch blocking in our study may be attributable to the relatively low susceptibility of blanket peatlands to drainage, or to physical alterations of the peat since drainage. We conclude that ditch blocking cannot be always be expected to deliver reductions in fluvial carbon loss, or improvements in the quality of drinking water supplies.  相似文献   

Microtopographical and hydrophysical controls on subsurface flow and solute transport: A continuous solute release experiment in a subarctic bog          下载免费PDF全文

Nicole Elizabeth Balliston  Jonathan Stephen Price 《水文研究》2018,32(19):2963-2975

Resource extraction and transportation activities in subarctic Canada can result in the unintentional release of contaminants into the surrounding peatlands. In the event of a release, a thorough understanding of solute transport within the saturated zone is necessary to predict plume fate and the potential impacts on peatland ecosystems. To better characterize contaminant transport in these systems, approximately 13,000 L/day of sodium chloride tracer (200 mg/L) was released into a bog in the James Bay Lowland. The tracer was pumped into a fully penetrating well (1.5 m) between July 5 and August 18, 2015. Horizontal and vertical plume development was measured via in situ specific conductance and water table depth from an adaptive monitoring network. Over the spill period, the bulk of the plume travelled a lateral distance of 100 m in the direction of the slight regional groundwater and topographical slope. The plume shape was irregular and followed the hollows, indicating preferential flow paths due to the site microtopography. Saturated transport of the tracer occurred primarily at ~25 cm below ground surface (bgs), and at a discontinuous high hydraulic conductivity layer ~125 cm bgs due to a complex and heterogeneous vertical hydraulic conductivity profile. Plume measurement was confounded by a large amount of precipitation (233 mm over the study period) that temporarily diluted the tracer in the highly conductive upper peat layer. Longitudinal solute advection can be approximated using local water table information (i.e., depth and gradient); microtopography; and meteorological conditions. Vertical distribution of solute within the peat profile is far more complex due to the heterogeneous subsurface; characterization would be aided by a detailed understanding of the site‐specific peat profile; the degree of decomposition; and the type of contaminant (e.g., reactive/nonreactive). The results of this research highlight the difficulty of tracking a contaminant spill in bogs and provide a benchmark for the characterization of the short‐term fate of a plume in these complex systems.  相似文献   

Bog surface oscillation (mire breathing): A useful measure in raised bog restoration          下载免费PDF全文

Sarah A. Howie  Richard J. Hebda 《水文研究》2018,32(11):1518-1530

Oscillation of the peat surface is an important mechanism for hydrological self‐regulation in bogs. As the water table rises in the wet season, the peat body expands, raising the bog surface and increasing water storage. With seasonal drying, the water table declines, the peat loses volume, and the bog surface drops, thereby keeping Sphagnum mosses in close contact with the water table. The oscillation of surface elevation in a Pacific coastal temperate raised bog was monitored at multiple sites for 4–12 years in 8 different plant communities of both peat‐harvested and unharvested sites to determine how bog surface oscillation relates to site conditions. The multiyear averages of bog surface oscillation for the different sites ranged from 2 to 34 cm (mean: 10.8 cm). In harvested sites, surface oscillation was linked to a larger water level amplitude and a shallower water table. In unharvested sites, a shallow water table was also a strong predictor of surface oscillation, but water level amplitude was negatively correlated to surface oscillation. This discrepancy was attributed to rewetting and regeneration of harvested sites, as well as historic drainage in many of the unharvested sites that reduced the elasticity of the peat. Surface oscillation differed significantly between some of the plant communities, generally between drier and wetter sites. In disturbed bogs, regeneration of a more elastic surface peat can increase the magnitude of peat volume change and bring about the return of self‐regulating mechanisms. Bog surface oscillation may be an important metric for assessing the restoration success or storage capacity of raised bogs in similar climatic settings.  相似文献   

黄县盆地第三纪含煤岩系岩相与沉积环境   总被引：3，自引：0，他引：3  

陈海泓  孙枢 《岩石学报》1988,4(2)

本文根据钻孔岩芯资料对含煤岩系的岩相进行了划分,识别出主要九种岩相类型:小型扇——三角洲砂岩相;河道砂岩相;决口扇细砂岩相;河口坝砂岩相;湖沼黑色泥岩-油页岩相;泛滥平原泥岩相;泥流含砾泥岩相;潟湖泥质灰岩相与潮沼炭质泥岩相。对沉积环境的空间变化与演化进行了分析,并对成煤沼泽的环境背景对煤层、煤质的控制作用做了扼要讨论。最后对整个盆地的演化阶段进行了简要论述。  相似文献   

CLIMATE ENVELOPES OF MIRE COMPLEX TYPES IN FENNOSCANDIA   总被引：1，自引：0，他引：1  

MIIA PARVIAINEN  MISKA LUOTO 《Geografiska Annaler: Series A, Physical Geography》2007,89(2):137-151

Peatlands are characteristic features of the Fennoscandian landscape, about one‐quarter of the land surface being classified as peatland. The aim of this work was to determine the extent to which the distribution of four main mire complex types (aapa mire, blanket bog, palsa mire, raised bog) can be modelled on the basis of climatological parameters. Additionally, the relative importance of different climatological variables in influencing the distribution of different mire complex types was scrutinized using the variation partitioning method. Variation partitioning is a novel statistical approach that provides deeper understanding of the importance of different explanatory variable groups for geographical patterns than traditional regression methods. The variation in the distribution of mire complex types was decomposed into independent and joint effects of temperature, precipitation and spatial variables. The distributional limits of aapa mires, palsa mires and raised bogs were primarily associated with thermal factors, whereas moisture regime also played an obvious role for blanket bogs. A considerable amount of variation in the distribution of mire complex types was accounted for by the joint effects of explanatory variables and may thus be causally related to two or all three groups of variables. Although the present distribution of mire complex types corresponded well to the contemporary climate in Fennoscandia, our results indicate that the climate envelopes of palsa mires are narrow. Thus, they can be expected to be extremely sensitive to changes in future climatic conditions.  相似文献