Modelling long-term alluvial-peatland dynamics in temperate river floodplains

Peat growth is a frequent phenomenon in European river valleys. The presence of peat in the floodplain stratigraphy makes them hotspots of carbon storage. The long-term dynamics of alluvial peatlands are complex due to interactions between the peat and the local river network, and as a result, alluvial-peatland development in relation to both regional and local conditions is not well understood. In this study, a new modelling framework is presented to simulate long-term peatland development in river floodplains by coupling a river basin hydrology model (STREAM – Spatial Tools for River basins and Environment and Analysis of Management options) with a local peat growth model (modified version of DigiBog). The model is applied to two lowland rivers in northern Belgium, located in the European loess (Dijle (Dyle) River) and sand (Grote Nete River) belts. Parameter sensitivity analysis and scenario analysis are used to study the relative importance of internal processes and environmental conditions on peatland development. The simulation results demonstrate that the peat thickness is largely determined by the spacing and mobility of the local river channel(s) rather than by channel characteristics or peat properties. In contrast, changes in regional conditions such as climate and land cover across the upstream river basin have been shown to influence the river hydrograph but have a limited effect on peat growth. These results demonstrate that alluvial-peatland development is strongly determined by the geomorphic boundary conditions set by the river network and as such models must account for river channel dynamics to adequately simulate peatland development trajectories in valley environments.

Modelling long-term alluvial peatland dynamics in temperate river floodplains

Peat growth is a frequent phenomenon in European river valleys. The presence of peat in the floodplain stratigraphy makes them hotspots of carbon storage. The long-term dynamics of alluvial peatlands are complex due to interactions between the peat and the local river network, and as a result, alluvial peatland development in relation to both regional and local conditions is not well understood. In this study, a new modelling framework is presented to simulate long-term peatland development in river floodplains by coupling a river basin hydrology model (STREAM) with a local peat growth model (modified version of Digibog). The model is applied to two lowland rivers in northern Belgium, located in the European loess (Dijle river) and sand (Grote Nete river) belts. Parameter sensitivity analysis and scenario analysis are used to study the relative importance of internal processes and environmental conditions on peatland development. The simulation results demonstrate that the peat thickness is largely determined by the spacing and mobility of the local river channel(s) rather than by channel characteristics or peat properties. In contrast, changes in regional conditions such as climate and land cover across the upstream river basin showed to influence the river hydrograph, but have a limited effect on peat growth. These results demonstrate that alluvial peatland development is strongly determined by the geomorphic boundary conditions set by the river network and as such models must account for river channel dynamics to adequately simulate peatland development trajectories in valley environments.

Modelling peatland development in temperate alluvial environments

<p>It is well known that C accumulation rates are much higher when focusing on short-term measurement periods in areas with active peat growth when compared to the net C storage at longer timescales as obtained from palaeo-studies. When selecting effective management options that aim to sustain or increase rates of peat development and, hence, C sequestration, a detailed insight into the factors controlling C storage in peatlands at longer timescales is therefore required. Several peatland models have been developed to simulate long-term peatland development and such models thus can be a useful tool to evaluate the effect of environmental changes and management on peatland dynamics at centennial to millennial scales. Many of these models assume the peat to form in a geomorphically stable environment. However, for river floodplains these assumptions cannot always be made. In temperate Europe for example, many river floodplains have known phases of active peat growth throughout the Holocene, influenced by the local geomorphic dynamics of the river channel(s) and associated sediment dynamics. In addition, many restoration efforts in floodplain environments are accompanied by allowing the river channel(s) to behave more freely, with increased meandering and more natural channel dynamics. As these dynamics are currently lacking in peatland models, a detailed assessment of the interactions between river channel(s) and the adjacent peatland in terms of long-term peat growth and carbon accumulation remains difficult.</p><p>Here, we developed a new peatland model, specifically designed for alluvial environments, by modifying an existing local peat growth model (1D version of Digibog), coupled with a raster-based river basin hydrology model (STREAM). This model allows to assess the effect of changes in both the river hydrology and local river channel properties on alluvial peatland development and the associated carbon dynamics. The model was applied at two contrasting lowland river basins in northern Belgium, located in the European loess (Dijle river) and sand (Grote Nete river) belts. Local peat growth was simulated at an annual resolution over a period of 10,000 years under a range of climate and land cover scenarios, as well as varying river channel characteristics (number of channels, channel dimensions, channel roughness and channel slope).</p><p>The results demonstrate that changes in river discharge through regional climate or land cover changes have a negligible effect on the floodplain peat growth as these changes mostly affect the magnitude of peak discharges. In contrast, the configuration of the local river network such as the number of river channels and their position relative to the peatland surface show to have a strong effect on the equilibrium peat thickness. Especially the number of drainage channels strongly affects the peat thickness with a fourfold reduction in number of channels leading to a threefold increase in simulated peat thickness. This demonstrates that limiting the number of drainage channels in a floodplain and raising the elevation of the channel bed can be effective strategies in stimulating floodplain peat formation and allow to quantify the long-term carbon sequestration potential of these different management practices.</p>

A multi-proxy reconstruction of peatland development and regional vegetation changes in subarctic NE Fennoscandia (the Republic of Karelia, Russia) during the Holocene

A better understanding of past long-term environmental changes in the subarctic region is crucial for mitigation of the possible negative effects of climate warming in this vulnerable region. This study provides a new multi-proxy reconstruction of regional vegetation changes and peatland development for north-eastern Fennoscandia (Russia) during most of the Holocene. To that purpose, we performed plant macrofossil, pollen, testate amoebae, peat humification, loss on ignition and radiocarbon analyses of the peat deposits from a mire around Vodoprovodnoe Lake (the Kindo Peninsula, the Republic of Karelia). Our data indicate that the peat deposits started accumulating before 9147 ± 182 cal. yr. BP. The vegetation cover in the area was mainly typical for the northern taiga zone, except for the period ~7800–5600 cal. yr. BP, when it generally resembled the middle taiga zone. The vegetation cover and peatland were greatly affected by reoccurring fires, which can be partly related to human activity. These events were associated with an increased proportion of birch in the vegetation cover (as a pioneer species) and/or water level decreases. By 600 cal. yr. BP, the peatland and the surrounding vegetation reached its current state and only minor changes had been recorded since that time. Overall, our results suggest a considerable and unexpected role of fires in the postglacial dynamics of subarctic peatlands.

Carbon accumulation in peatlands along a boreal to subarctic transect in eastern Canada

In this study, we investigated the links between peat carbon accumulation and past ecological and hydrological conditions in three peatlands (Bouleau, Mista, Auassat) which developed along a South-North transect within a watershed encompassing the boreal and subarctic domain in Eastern Canada. Peatland development and long-term apparent rates of carbon accumulation (LORCA) were asynchronous in the watershed, suggesting an influence of both latitude and topography (altitude) on the length of the growing season (GGD0). Results show that peat initiation within the three peatlands (respectively ca. 9070, 8400, and 6270 cal BP) was delayed after the deglaciation and that LORCA (respectively 35.5, 15.4, and 9.0 g C m−2 yr−1) decreased from South to North. Peatland development and fen to bog transitions were found to be almost synchronous for the two southernmost sites. The fen to bog transition in the northernmost subarctic site was delayed until the 20th century, owing to the less favorable climatic conditions. This suggests that recent warming has extended the length of the growing season and increased Sphagnum growth enough to potentially influence an ecosystem state-shift as observed in other Subarctic regions of eastern Canada.

ISSUANCE OF GREEN BOND FOR SUSTAINABLE DEVELOPMENT OF PEATLANDS

Peatlands, with their important role, are in need of great attention, both from the government and also environmentalists. The role of corporations is really needed and is expected to be able to accelerate the improvement of the quality of peatlands, so that the benefits are maintained. Issuance of Green Bond is expected to be able to encourage the achievement of this goal. It is hoped that companies operating in and around the Peatland area will be able to create sustainable Peatland development efforts. The synergy between companies and green investors is expected to be an aspect of improving the economy, both for companies, investors and the public. Companies as publishers have an increasingly large role in maintaining the balance of peatlands. Benefits in the form of incentives from the Financial Services Authority (OJK) will also be obtained by companies that issue green bonds. Investors, especially green investors who are interested in environmental issues will have new investment alternatives. The emergence of a development program initiated by the company, of course, will also have an impact on society, in the form of the withdrawal of a number of workers, as well as the increase in other economic activities as a result of the increase in the standard of living of the community. Keywords: Green Bond, Peatland

Mire Development and Disappearance due to River Capture as Hydrogeological and Geomorphological Consequences of LGM Ice-Marginal Valley Evolution at the Vistula-Neman Watershed

The advances and retreats of ice sheets during Pleistocene significantly changed high- and mid-latitude landscapes and hydrological systems, albeit differently, in North America and Europe. On the southern margin of the Last Glacial Maximum (LGM) in the Baltic Sea basin, a specific type of valley has developed between glacial margins and upland or mountain slopes. We studied new geological data (boreholes, electrical resistivity imaging (ERI) from this geomorphic setting in Northeast Poland to understand: (1) how the landscape and river network evolved to eventually produce peat mires during the Holocene, and (2) the nature of groundwater recharge to fens in the upper Biebrza Valley. We present the results on a geological cross-section with hydrogeological interpretation. We also discuss regional geomorphology. In addition, we present the LGM extent derived from a spatial distribution of Vistulian (Weichselian) terminal moraines. These end moraines are also interpreted as Saalian kames. Thus, we additionally present another method of LGM extent delineation from a physicogeographical division. We link the steep slopes of the studied valley walls (kame terrace fronts) with thermokarst erosion in the periglacial zone. We then document the hydrogeological window (DISCONTINUITY in the till layer over the confined aquifer), which enables the outflow of groundwater into the peat bog. Although minerotrophic fen mire development in the study area is likely to be sustained in the near future through sufficient groundwater supply, the projected capture of the Biebrza River by the Neman River will not allow for sustaining peatland development.