METHOD FOR PRESENTING THE RESULTS OF OEDOMETER TESTS UNDER A SURVEY OF A PEAT DEPOSIT

The use of the average values of physical and deformation characteristics for the entire extremely heterogeneous peat layer leads to mistakes in estimation a settlement of the embankments set up over it. The results of numerous oedometer tests of peat and empirical equations for calculating the void ratio of peat as a function of its initial value and the load are presented. A new approach to carrying out the geotechnical surveys in a wetland is proposed.

Loss and Recovery of Carbon in Repeatedly Burned Degraded Peatlands of Kalimantan, Indonesia

Although accurate estimates of biomass loss during peat fires, and recovery over time, are critical in understanding net peat ecosystem carbon balance, empirical data to inform carbon models are scarce. During the 2019 dry season, fires burned through 133,631 ha of degraded peatlands of Central Kalimantan. This study reports carbon loss from surface fuels and the top peat layer of 18.5 Mg C ha−1 (3.5 from surface fuels and 15.0 from root/peat layer), releasing an average of 2.5 Gg (range 1.8–3.1 Gg) carbon in these fires. Peat surface change measurements over one month, as the fires continued to smolder, indicated that about 20 cm of the surface was lost to combustion of peat and fern rhizomes, roots and recently incorporated organic residues that we sampled as the top peat layer. Time series analysis of live green vegetation (NDVI trend), combined with field observations of vegetation recovery two years after the fires, indicated that vegetation recovery equivalent to fire-released carbon is likely to occur around 3 years after fires.

Submarine Groundwater Discharge From Non-Tidal Coastal Peatlands Along the Baltic Sea

Submarine groundwater discharge (SGD) is an important pathway for water and materials within the land-ocean transition zone that can impact coastal environments and marine life. Although research from sandy shorelines has rapidly advanced in recent years, there is very little understanding of coastal areas characterized by a low hydraulic conductivity, such as carbon-rich coastal peatlands. The objective of this study was to determine the magnitude and location of terrestrial SGD to be expected from a non-tidal low-lying coastal peatland located along the Baltic Sea and to understand the controlling factors using numerical modeling. We employed the HYDRUS-2D modeling package to simulate water movement under steady-state conditions in a transect that extends from the dune dike-separated rewetted fen to the shallow sea. Soil physical properties, hydraulic gradients, geological stratifications, and topography were varied to depict the range of properties encountered in coastal peatlands. Our results show that terrestrial SGD occurs at the study site at a flux of 0.080 m2 d−1, with seepage rates of 1.05 cm d−1 (upper discharge region) and 0.16 cm d−1 (lower discharge region above submerged peat layer). These calculated seepage rates compare to observations from other wetland environments and SGD sites in the Baltic Sea. The groundwater originates mainly from the dune dike—recharged by precipitation and infiltration from ponded peatland surface water—and to a lesser extent from the sand aquifer. The scenario simulations yielded a range of potential SGD fluxes of 0.008–0.293 m2 d−1. They revealed that the location of terrestrial SGD is determined by the barrier function of the peat layer extending under the sea. However, it has little impact on volume flux as most SGD occurs near the shoreline. Magnitude of SGD is mainly driven by hydraulic gradient and the hydraulic conductivity of peat and beach/dune sands. Anisotropy in the horizontal direction, aquifer and peat thickness, and peatland elevation have little impacts on SGD. We conclude that SGD is most probable from coastal peatlands with high water levels, large Ks and/or a dune dike or belt, which could be an essential source for carbon and other materials via the SGD pathway.

Quantification of Blue Carbon in Salt Marshes of the Pacific Coast of Canada

Tidal salt marshes are known to accumulate “blue carbon” at high rates relative to their surface area, which render these systems among the Earth’s most efficient carbon (C) sinks. However, the potential for tidal salt marshes to mitigate global warming remains poorly constrained because of the lack of representative sampling of tidal marshes from around the globe, inadequate areal extent estimations, and inappropriate dating methods for accurately estimating C accumulation rates. Here we provide the first estimates of organic C storage and accumulation rates in salt marshes along the Pacific Coast of Canada, within the Clayoquot Sound UNESCO Biosphere Reserve and Pacific Rim National Park Reserve, a region currently underrepresented in global compilations. Within the context of other sites from the Pacific Coast of North America, these young Clayoquot Sound marshes have relatively low C stocks but are accumulating C at rates that are higher than the global average, with pronounced differences between high and low marsh habitats. The average C stock calculated during the past 30 years is 54 ± 5 Mg C ha−1 (mean ± standard error), which accounts for 81 % of the C accumulated to the base of the marsh peat layer (67 ± 9 Mg C ha−1). The total C stock is just under one-third of previous global estimates of salt marsh C stocks, likely due to the shallow depth and young age of the marsh. In contrast, the average C accumulation rate (CAR) (184 ± 50 g C m−2 yr−1 to the base of the peat layer) is higher than both CARs from salt marshes along the Pacific coast (112 ± 12 g C m−2 yr−1) and global estimates (91 ± 7 g C m−2 yr−1). This difference was even more pronounced when we considered individual marsh zones: CARs were significantly greater in high marsh (303 ± 45 g C m−2 yr−1) compared to the low marsh sediments (63 ± 6 g C m−2 yr−1), an observation unique to Clayoquot Sound among NE Pacific Coast marsh studies. We attribute low CARs in the low marsh zones to shallow-rooting vegetation, reduced terrestrial sediment inputs, negative relative sea level rise in the region, and enhanced erosional processes. Per-hectare, CARs in Clayoquot Sound marsh soils are approximately 2–7 times greater than C uptake rates based on net ecosystem productivity in Canadian boreal forests, which highlights their potential importance as C reservoirs and the need to consider their C accumulation capacity as a climate mitigation co-benefit when conserving for other salt marsh ecosystem services.

Effects of different biomass materials as a salt-isolation layer on water and salt migration in coastal saline soil

The aim of this study was to find a material suited for the prevention of evaporative water loss and salt accumulation in coastal saline soils. One-dimensional vertical water infiltration and phreatic evaporation experiments were conducted using a silty loam saline soil. A 3-cm-thick layer of corn straw, biochar, and peat was buried at the soil depth of 20 cm, and a 6-cm-thick layer of peat was also buried at the same soil depth for comparison. The presence of the biochar layer increased the upper soil water content, but its ability to inhibit salt accumulation was poor, leading to a high salt concentration in the surface soil. The 3-cm-thick straw and 6-cm-thick peat layers were most effective to inhibit salt accumulation, which reduced the upper soil salt concentration by 96% and 93%, respectively. However, the straw layer strongly inhibited phreatic evaporation and resulted in low water content in the upper soil layer. Compared with the straw layer, the peat layer increased the upper soil water content. Thus, burying a 6-cm-thick peat layer in the coastal saline soil is the optimal strategy to retain water in the upper soil layer and intercept salt in the deeper soil layer.

PERKUATAN TANAH DENGAN METODE SAND COMPACTION PILE PADA TANAH GAMBUT DAN ALUVIAL

Construction on the peat soil and alluvial soil will increase rapidly in the future, if we don’t know the characteristics of the soil, construction problems and failures will occur. Peat soil and alluvial soil has a very low bearing capacity, so they have a very large settlement. Alluvial soil and any other sandy soils has a very low bearing capacity, just like peat soil, and sandy soil has a highly potential of liquefaction. This research is to find out whether Sand Compaction Pile method can improve the bearing capacity of the peat and alluvial soil, and prevent liquefaction in sandy soil. In this case study, we only focus to one bore hole that has a peat layer above the alluvial layer and then improve it with Sand Compaction Pile method. Comparing the bearing capacity results, before and after the improving, with Sand Compaction Pile method, we can find out whether the Sand Compaction Pile can be used for the soil improving method on the peat and alluvial soil. Pembangunan di atas tanah gambut dan tanah aluvial akan meningkat secara drastis kedepannya, apabila kita tidak mengetahui karakteristik dari tanah tersebut maka akan banyak masalah da/atau kegagalan konstruksi. Tanah gambut dan tanah aluvial memiliki daya dukung yang rendah sehingga akan mengakibatkan terjadinya penurunan yang besar. Tanah aluvial atau tanah berpasir lainnya juga memiliki daya dukung yang rendah dan kemungkinan potensi terjadinya likuefaksi sangat tinggi. Penelitian ini bertujuan untuk mengetahui apakah dengan metode Sand Compaction Pile (SCP) dapat memperbaiki parameter tanah, meningkatkan daya dukung dari tanah gambut dan tanah aluvial, dan mencegah potensi terjadinya likuefaksi pada tanah berpasir. Studi kasus ini lebih difokuskan terhadap salah satu bor log yang memiliki lapisan gambut yang tebal dan kemudian di perbaiki dengam metode Sand Compaction Pile. Dengan membandingkan hasil dari daya dukung tanah sebelum di perbaiki dan setelah di perbaiki dengan metode Sand Compaction Pile, kita dapat mengetahui apakah Sand Compaction Pile dapat di gunakan sebagai metode perbaikan tanah di tanah gambut dan tanah aluvial.

Extreme-flood-related peat blocks: An Anthropocene analogue to ancient coal-forming environments

Coal clasts associated with extreme floods are prone to survive and maintain their large size, contrary to the general belief that distance from the parent peat layer reduces the size of transported clasts. Contrary to apparent logic, moreover, a second flood event favors the preservation potential of such soft organic clasts, this being the minimal fragmentation. An Anthropocene example from an urban park in Spain demonstrates that peat clasts up to 1 m long can survive due to flotation for a distance of almost a hundred meters and are well preserved and stabilized thanks to a second flood. These peat blocks were generated by catastrophic flooding of urban peatlands along the Ebro River (city of Zaragoza) during exceptional rainfalls in Iberia. The water flow from the Ebro River flooded the peatland at the surface of the meander, ripping up peat clasts from a shear or detachment level formed by an indurated level characterized by rounded quartzite pebbles, which acted as a hydrological discontinuity surface. Extensive evidence of the paleoflow direction is provided by oriented crushed reeds and the widespread occurrence of imbricated and thrusted peat blocks on the eroded and exposed peatland and in the main urban accumulation areas. To be specific, peat blocks and minor clasts accumulated in four areas associated with different modes of transport and topographic steps. From proximal to distal these are as follows: i) a proximal rim including thrusted peat blocks on the eroded peatland, ii) two intermediate accumulation zones associated with topographic steps in the park, characterized by peat-clast imbrication, iii) gravity-fall peat clasts deposited in an artificial channel in the park, and iv) peat rafts of more than 1 m in diameter scattered over the surface of the park (at a distance of 90 m from the eroded peatland).

Insights into the carbon dynamics of a wasted peatland under long term drainage and intensive agriculture.

<p>Lowland fen peatlands in East Anglia, United Kingdom (UK), have had a long history of drainage and agricultural use, with some having been drained for several centuries. This has led to the loss of up to 4.0 m of the original peat layer through initial consolidation and subsequent decomposition.</p><p>Today, the primary land use of these peatlands is intensive arable and horticultural agriculture, resulting in continued loss and degradation of the remaining peat layer. This has led to the classification of a large part of these peatlands as ‘wasted’ - i.e. the peat-forming vegetation has been lost along with a significant depth of peat and the underlying mineral layer increasingly determining soil properties.</p><p>Despite a significant fraction of the UK lowland peatlands being classified as wasted (1922 km<sup>2</sup> or 13.5%), there have been no previous studies of the carbon (C) emissions from these peatlands. Studies on non-wasted ‘deep’ agricultural peatlands (peat depths > 1m) suggest emission factors of 5.2 to 8.3 t CO<sub>2</sub>-C ha<sup>-1</sup> yr<sup>-1</sup> indicating the potential for wasted peatlands, despite having a lower soil organic C content, to still generate large emissions representing a significant component of the UK’s national greenhouse gas inventory.</p><p>Using Eddy Covariance, the CO<sub>2</sub> emissions of two co-located fen peatlands within East Anglia under similar intensive agriculture were quantified throughout 2018-2020.  The first site, EN-SP3, is a wasted fen peatland where the surface organic layer has been depleted to <40cm. The second site, EF-DA, is a deep peat with an organic soil layer >1m deep. We present initial analysis of C emissions data from EN-SP3, which represent the first emission estimates from a wasted agricultural fen peatland in the UK, in comparison with data collected from EF-DA, the co-located deep peat agricultural fen peatland, over the last ~6 years.</p><p>Preliminary analysis of the first full year of emissions data from the wasted peat site (EN-SP3) indicates an approximate net C balance of  5.4 t C ha<sup>-1 </sup>yr<sup>-1 </sup>(17<sup>th</sup> May 19 – 17<sup>th</sup> May 20, Celery crop following a Phacelia & Buckwheat cover crop), whilst there was a higher estimated rate of emission during the previous year under a maize crop (222 days; 4<sup>th</sup> May 18 – 11<sup>th</sup> Dec 18) indicating a net C balance of 4.7 t C ha<sup>-1</sup> over the 222 day period. These data compare with 7.8 - 11.2 t C ha<sup>-1 </sup>yr<sup>-1 </sup>from between 2012-2019 from the deep peat site (EF-DA). We highlight key differences between sites, enabling us to draw early insights into how C dynamics may differ between shallow and deep lowland agricultural peat soils.</p>

InSAR time series over rewetted bogs highlight spatially heterogeneous surface deformation

<p>Peatlands represent the largest natural terrestrial carbon store and provide a multitude of ecosystem services. Many peatlands across the world have been intensively used for centuries either for peat extraction, agricultural usage or forestry. Drainage and removal of the peat layer have led to a disruption of respective ecosystem functioning caused by falling water levels, altered microbial activity and the shrinkage or depletion of the peat layer. Lately, some areas have been restored and brought back to a semi-natural state by prohibiting their use and closing drainage ditches to raise the water table. All these activities have resulted in very heterogeneous peatlands composed by severely degraded, less disturbed or successfully rehabilitated patches. The respective state of peatlands affects not only the hydrology and the typical shrinkage and swelling of peat known as mire breathing, it also determines the role of peatlands as carbon sink or source and is thus of high relevance for climate change mitigation. </p><p>Through the application of interferometric Synthetic Aperture Radar (InSAR) time series to several rewetted semi-natural pre-alpine bogs south of the city of Munich, Germany, it was possible to monitor the surface deformation of the peat layer caused by mire breathing for the period 2016-2020. An experimental InSAR data set was used where both the Persistent Scatterer Interferometry (Ferretti et al. 2001) as well as the distributed scatterers technique (Ansari et al. 2018) were applied to satellite images from the Sentinel-1A and B platforms. The use of distributed scatterers allows to obtain a good coverage over semi-natural peatlands.</p><p>The seasonal height fluctuations peatlands are naturally subject to are clearly visible from the time series. The overall trend for the observation period shows a subsidence for the largest part of the test sites of up to 2 cm. Throughout the year 2018, a stronger negative trend, expectedly related to the extremely dry conditions in 2018 in this part of Europe, was observed, which caused the peat layer to dry out and to shrink. Furthermore, the combination of persistent and distributed scatterers captures spatial differences in the sign and intensity of the surface movement. Such deviations might be related to former uses, the degree of degradation and the implementation of restoration measures which have affected the hydrology, soil chemistry and vegetation cover of the bogs.</p><p>The findings show that peatlands respond to dry periods in a spatially heterogeneous manner. In the light of climate change, such InSAR time series can be used to monitor surface changes over long time frames to assess the long-term vulnerability of semi-natural peatlands and to indicate whether and which restoration measures prove successful.</p><p>The work presented here is part of the KliMoBay project, funded by the Bavarian State Ministry for the Environment and Consumer Protection through the European Regional Development Fund (ERDF).</p><p> </p><p><em>Ansari, H.; De Zan, F.; Bamler, R. (2018): Efficient Phase Estimation for Interferogram Stacks. In: IEEE Trans. Geosci. Remote Sensing 56 (7). 4109-4125.</em></p><p><em>Ferretti, A.; Prati, C.; Rocca, F. (2001): Permanent scatterers in SAR interferometry. In: IEEE Trans. Geosci. Remote Sensing 39 (1). 8-20.<br><br></em></p>

Degradation of reclaimed peat soils

The article presents the results of studies of the water-physical properties of reclaimed peat soils of four objects of Ryazan region, included in Ryazan Meschera. Drainage systems are destroyed due to lack of maintenance, which leads to an increase in the level of groundwater in the drained areas. The peat soils of the objects have similar changes, expressed in the utilization of peat over 65 years of drainage by 28-38 %, soil compaction by 0.08-0.12 g/cm3, a decrease in the ash content of peat by 2-2.9 % and a decrease in the thickness of the peat layer by 18-31 cm.