Water table variations on different land use units in a drained tropical peatland island of Indonesia

Restoration and water table control on peatlands to limit fire risk are national priorities in Indonesia. The present study was initiated at Padang Island, Sumatra, to increase understanding on peatland hydrology in the tropic. At the pilot site, water table and precipitation were monitored at different stations. The results show variation in water table depths (WTDs) over time and space due to spatial and temporal variability in rain intensity and drainage networks. In part of the island, large-scale drainage for plantations led to deep WTD (−1.8 m) and high WTD recession rates (up to 3.5 cm/day). Around villages, farm-scale drainages had a smaller impact with a lower recession rate (up to 1.8 cm/day) and shallow WTD, typically below −0.4 m, the threshold for sustainable peatland management in Indonesia. The recession rates levelled off at 1.0 cm/day near the drained forest/plantation and at 0.5 cm/day near the farm. Deeper layers had much lower specific yield (Sy), 0.1 at −1.5 m depth, compared with top peat soils with Sy up to 0.3. Proximity to drainages extended discharge flow to deeper layers. The results highlighted the severity of peatland drainage impact on most coastal zones of Padang Island, which have intensive drainage networks.

Holocene wildfire regimes in forested peatlands in western Siberia: interaction between peatland moisture conditions and the composition of plant functional types

Wildfire is the most common disturbance type in boreal forests and can trigger significant changes in forest composition. Waterlogging in peatlands determines the degree of tree cover and the depth of the burning horizon associated with wildfires. However, interactions between peatland moisture, vegetation composition and flammability, and fire regime in forested peatland in Eurasia remain largely unexplored, despite their huge extent in boreal regions. To address this knowledge gap, we reconstructed the Holocene fire regime, vegetation composition, and peatland hydrology at two sites in Western Siberia near Tomsk Oblast, Russia. The palaeoecological records originate from forested peatland areas in predominantly light taiga (Pinus-Betula) with the increase in dark taiga communities (Pinus sibirica, Picea obovata, Abies sibirica) towards the east. We found that the past water level fluctuated between 8 and 30 cm below the peat surface. Wet peatland conditions promoted broadleaf trees (Betula), whereas dry peatland conditions favoured conifers and a greater forest density (dark-to-light-taiga ratio). The frequency and severity of fire increased with a declining water table that enhanced fuel dryness and flammability and at an intermediate forest density. We found that the probability of intensification in fire severity increased when the water level declined below 20 cm suggesting a tipping point in peatland hydrology at which wildfire regime intensifies. On a Holocene scale, we found two scenarios of moisture-vegetation-fire interactions. In the first, severe fires were recorded between 7.5 and 4.5 ka BP with lower water levels and an increased proportion of dark taiga and fire avoiders (Pinus sibirica at Rybanya and Abies sibirica at Ulukh Chayakh) mixed into the dominantly light taiga and fire-resister community of Pinus sylvestris. The second occurred over the last 1.5 ka and was associated with fluctuating water tables, a declining abundance of fire avoiders, and an expansion of fire invaders (Betula). These findings suggest that frequent high-severity fires can lead to compositional and structural changes in forests when trees fail to reach reproductive maturity between fire events or where extensive forest gaps limit seed dispersal. This study also shows prolonged periods of synchronous fire activity across the sites, particularly during the early to mid-Holocene, suggesting a regional imprint of centennial to millennial-scale Holocene climate variability on wildfire activity. Increasing human presence in the region of the Ulukh-Chayakh Mire near Teguldet over the last four centuries drastically enhanced ignitions compared to natural background levels. Frequent warm and dry spells predicted for the future in Siberia by climate change scenarios will enhance peatland drying and may convey a competitive advantage to conifer taxa. However, dry conditions, particularly a water table decline below the threshold of 20 cm, will probably exacerbate the frequency and severity of wildfire, disrupt conifers’ successional pathway and accelerate shifts towards more fire-adapted broadleaf tree cover. Furthermore, climate-disturbance-fire feedbacks will accelerate changes in the carbon balance of forested boreal peatlands and affect their overall future resilience to climate change.

Rewetting and Drainage of Nutrient-Poor Peatlands Indicated by Specific Bacterial Membrane Fatty Acids and a Repeated Sampling of Stable Isotopes (δ15N, δ13C)

Peatland degradation impairs soil functions such as carbon storage and the existence of biodiversity hotspots. Therefore, and in view of the ongoing climate change, an efficient method of evaluating peatland hydrology and the success of restoration efforts is needed. To understand the role of microbial groups in biogeochemical cycling, gaseous loss and isotopic fractionation that lead to specific isotopic depth patterns (δ13C, δ15N), we integrated previously published stable isotope data with a membrane fatty acid (mFA) analysis related to various microbial groups that are known to be common in peatlands. We performed two sampling campaigns to verify the observed stable isotope depth trends in nutrient-poor peatlands in Northern Europe. Cores were taken from adjacent drained (or rewetted) and undrained sites. Fungal-derived mFA abundance was highest in the uppermost part of the drained layer. We found increasing bacterial-derived mFA concentrations with depth peaking in the middle of the drained layers, which correlates with a δ15N peak of bulk material. The results support our hypothesis that changing peatland hydrology induce a shift in microbial community and metabolism processes and is therefore also imprinted in stable isotope values. Under waterlogged conditions overall levels of microbial-derived mFAs were generally low. Drained layers showed simultaneous changes in microbial abundance and composition and depth trends in stable isotope bulk values. Bacteria, particularly acidobacteria, can be expected to dominate increased denitrification with low oxygen saturation accompanied by increased δ15N bulk values in the remaining substrate. Interestingly, cores from recent rewetted peatlands show no depth trend of δ15N in the layers grown under rewetting conditions; this is congruent with relatively low concentrations of microbial-derived mFAs. Hence, we conclude that stable isotopes, especially δ15N values, reflect changing microbial metabolic processes, which differ between drained and undrained - and especially also for recent rewetted–peatlands. As today stable isotope measurements are routine measurements, these findings enable us to get cost- and time efficient reliable information of drainage and restoration success.

The impacts of peat slides on upland blanket peatland hydrology, ecology and soil structure. A paired catchment approach.

<p>Rainfall-induced landslides are difficult to forecast and often evolve into highly destructive flows, as such, they are one of the most dangerous natural hazards globally. While our understanding of peatland hydrology has improved greatly in the past two decades, there has been less focus on the response of peat hydrology following perturbations such as wildfires and landslides.  Here we report on a new paired catchment experiment in Ireland. Our focus is to quantify the hydrological changes following peat landslides and further, to establish the short-term and longer-term impacts on local peatland hydrology, ecology and recovery.</p><p>The two paired sites are located in Co. Leitrim, Ireland, in two adjacent, small upland blanket bog catchments. The first peat catchment (0.2km<sup>2</sup>) is an area of a recent (June 2020) slope failure. According to preliminary estimates ~178,000 – 188,000 tonnes of peat were transported downstream during the peat slide event, resulting in a large landslide scar section (~0.059 km<sup>2</sup>) in a special area of conservation [SAC]. Preliminary impacts are assessed to include: habitat loss, decreased slope stability, impacts on hydrology and water quality, as well as increased local erosion.</p><p>This catchment is paired with an adjacent upland blanket peat catchment (0.11 km<sup>2</sup>) which is deemed to have been under the same anthropogenic pressures (grazing, upslope forestry plantation).</p><p>A hydrometric suite, including weather station, piezometers, and water level recorders to evaluate the surface and subsurface hydrology has been installed at both sites. In addition, we are monitoring the response of landslide deposits (e.g. rafted peat, some with still-standing sika spruce), ecology, soil structure, permeability and shear strength in both catchments.</p><p>Here we will report on the initial results of our monitoring.</p>

Interaction between peatland moisture and plant functional types drives fire dynamics in forested peatlands in central-western Siberia

<p>Boreal forests are among the ecosystems most significantly impacted by wildfires as a consequence of climate warming. A large proportion of the global boreal forest area is located in Siberia, however, its vast extent and restricted access limit datasets recording changes in wildfire activity, especially from a longer-term perspective. Such long-term records of wildfire activity are vital to understanding how fire regimes vary with changes in climate, vegetation composition and human-vegetation interaction, as well as the impacts of wildfires on boreal forests.</p><p>Here, we explore how patterns in fire regime (biomass burned, fire frequency, fire type) have changed over the Holocene. We focus on the relationship between fire regime, forest density and the fire-related traits of the main tree species, and peatland hydrology. We used charcoal-morphologies based reconstructions of fire regimes, along with pollen-based assessments of vegetation composition and testate amoebae-based hydro-climate reconstructions in Pinus-Betula dominated peatlands from central-western Siberia, Tomsk Oblast, Russia.</p><p>The occurrence of more severe fires (i.e., higher biomass burning per fire episode and abundant woody morphotypes) were recorded between 7500 and 5000 cal yr BP. Higher temperatures during that time, likely enhanced peatland dryness and fuel flammability creating conditions conducive to peat and forest fires. Drier peatland conditions also affected forest composition and density by favouring the expansion of a mix of light taiga and fire resisters (e.g., Pinus sylvestris, P. sibirica, Larix) with denser taiga and fire avoiders (Picea obovata and Abies sibirica) on the peatland. A shift to the lowest biomass burning and fire types affecting mostly litter and understorey vegetation, was registered between 4000 and 1500 cal yr BP. Temporally, it coincides with an increase in peatland surface moisture and a change in forest composition characterised by a decline in fire resisters, while fire avoiders remained abundant. An almost synchronous intensification in fires frequency and severity from ca. 2000 cal yr BP to the present at all sites, was concurrent with the rise to dominance of fire-invader species (Betula), as well as a more abundant biomass in the understory layer (shrubs, herbs, ferns, moss), while fire resisters and avoiders declined substantially. We found that Picea obovata to be highly vulnerable tree taxa to frequent, severe fires.</p><p>This long-term perspective demonstratesthat peatland hydrology is connected to, and feedbacks on peatland and forest composition and fuel dryness and ultimately fire regime. It also shows that more frequent fires of higher severity can lead to compositional or structural changes of forests, if trees cannot reach reproductive ages prior to the next burning events. Future predicted increases in temperatures are likely to enhance peatland drying, with cascading effects on forest and peat plant composition, subsequently exacerbating wildfire activity. This study thus contributes to an understanding of disturbance regimes in boreal forests and considers their potential to adapt to new climate conditions and fire regimes.</p><p> </p>

Characterization of nested water supplies in a mid latitude/altitude peatland using long-term monitoring data before and after restoration. The case study of the Frasne peatland (Jura Mountains, France)

<p>Peatland hydrology forms, together with vegetation cover and carbon dynamics, a sensitive interconnected three-pillar system, which furnishes essential ecosystem services from the local (specific biodiversity, interaction with the watershed) to the global scale (carbon and fresh water storage). The present study focuses on the hydrological function of the Frasne peatland, and especially investigates how restoration of water supplies can be used to mitigate climate change effects on peatland hydrology and sustainability.</p><p>In this perspective, the Forbonnet bog, belonging to the Frasne peatland complex (300 ha; French Jura Mountains; 46.826 N, 6.1754 E; 850 m a.s.l) is monitored in the framework of the French observatory of peatland (SNO Tourbières) since 2008. The site, restored in 2015 (European program "Life Tourbières"), is located in a wide karstifed syncline overlain by moraine deposits. Between 2009 and 2019, mean annual precipitation and air temperature were respectively 1618 mm and 7 °C.</p><p>In order to identify and model water supply and transfers at the ecosystem scale, this study combines a range of hydrological, geochemical and reservoir modeling approaches. This enabled us to propose a conceptual scheme of the hydrological functioning that implies a nested organization of 3 water origins:</p><p>(1) The superficial reservoir (acrotelm) featuring a low mineralization, has a fast (daily) reactivity to precipitation, suggesting a strong dependence to direct atmospheric inputs. In addition, the outlet discharge shows a complex relation with the water level of this layer, highlighting a threshold effect where the saturation degree of the acrotelm seems to be involved.</p><p>(2) Five years of outlet discharge and electrical conductivity (EC) monitoring highlight a seasonal pattern. During low flow periods (June-Oct.) EC is positively correlated with rainfall recharge of the previous winter (Nov.-May). Furthermore, the bog water budget is loss-making when only considering the topographical watershed. Considering the geological context, these elements argue for groundwater inflows from the surrounding karst aquifer likely occurring at the base of the bog, throughout the permeable or discontinuous moraine layers. Vertical EC profiles show that these inflows supply the mineralized water deep reservoir of the bog.</p><p>(3) The monitoring of the restoration effects (by backfilling of drainage channels) through panpipe piezometers suggests that lateral seepage from the neighboring wooded, more elevated and mature peatlands supplies a transitional peat reservoir.</p><p>Moreover, spatial (horizontal and vertical) and temporal EC variability argue for advective water transfers through the bog.</p><p>This work supports the interest in monitoring over the long-term (several and contrasted hydrological years) for constraining hydrological processes. The three water supplies delineated could have contrasted responses to climate change and then impact both biological and carbon cycles. This work also highlights the importance to integrate hydrological processes beyond the ecosystem scale, to consider climate change and anthropogenic pressure effects on the regional hydrology that probably interact with peatlands in mountainous environments. In this perspective, the current hydrological monitoring is nowadays combined with isotopic (δ<sup>18</sup>O and δ<sup>2</sup>H) evaluation to refine this conceptual scheme and quantify the contribution of the 3 identified water flow paths.</p>

General considerations for modeling water table dynamics in peatlands

<p>A basic and universal characteristic of peatlands is that the water table frequently rises near the surface of the soil profile. Surface peat is naturally loose and open-structured, and often has microtopographic features; the water table frequently rises above the level of local depressions. Therefore, water table fluctuations in peatlands cause rapid changes in the permeability and effective porosity of the medium through which flow occurs. We use a simple model based on Boussinesq's equation to explore the challenges that arise from these basic and universal physical aspects of peatland hydrology. We show that simulation of water table fluctuations in peatlands requires precipitation data with a high temporal resolution, and careful attention to the time derivative for accuracy of the mean water tables and correct water balance for two reasons. First, large vertical gradients in specific yield can result in large mass balance errors analogous to errors from naive discretization of the Richards equation; a change of variables from water table elevation to water storage can eliminate these errors and also speed up calculations by allowing larger time steps. Second, large vertical gradients in permeability near the peat surface cause a strongly nonlinear response to precipitation, so that time-averaged precipitation data or neglect of diurnal cycles of evapotranspiration results in erroneously high water levels, and careful time stepping is required around rain storms.  Consideration of these features of peatland hydrology results in efficient hydrologic models that can be used to predict spatial and temporal patterns in greenhouse gas uptake and emissions in peatlands.</p>

RESTORASI LAHAN RAWA GAMBUT MELALUI METODE REWETTING DAN PALUDIKULTUR

Degradasi di lahan rawa gambut umumnya diakibatkan oleh alih fungsi lahan dan pemilihan komoditas yang tidak tepat. Alih fungsi lahan yang disertai dengan pembuatan drainase tanpa perencanaan yang matang menyebabkan lahan menjadi kering, mudah terbakar, subsiden, banjir, emisi CO2 dan permasalahan sosial-ekonomi.Penelitian ini dilakukan melalui studi literatur terkait persoalan dan solusi pemulihan lahan gambut terdegradasi melalui restorasi hidrologi dengan metode rewetting (sekat/canal blocking) dan penanaman jenis tanaman yang tidak membutuhkan drainase (paludikultur).Terdapat empat tipe sekat yang biasa digunakan, yaitu sekat papan, sekat isi, sekat plastik, dan sekat geser. Pemilihan tipe sekat sangat tergantung kepada kondisi bio-fisik, dimensi kanal, topografi gambut, ketersediaan material dan aksesibilitas ke lokasi penabatan. Dari penelitian ini diketahui adanya korelasi yang kuat antara keberadaan sekat terhadap penambahan ketinggian muka air tanah, dimana sekat bermanfaat untuk menaikkan muka air tanah dan melembabkan tanah.Selanjutnya, dalam penerapan paludikultur, diketahui bahwa komoditas tertentu lebih tahan terhadap genangan namun tetap memiliki nilai ekonomi seperti: Metroxylon spp, Nypa fruticans Wurmb, Alseodaphne spp. dan Nothaphoebe spp., dan Shorea spp. Agar dapat bertahan hidup jenis-jenis tanaman tersebut harus dipilih dan disesuaikan dengan ketinggian air yang terdapat di lahan gambut. Kata kunci: Gambut, paludikultur, sekat kanal, restorasi, muka air tanahIn general, degradation on peatlands is mainly caused by excessive conversion and selection of commodities that cannot grow in wet condition. Conversion of peatlands and extreme canalization have become major threats to peatlands which leads to peat fire, subsidence, flooding, green house emission, as well as economic and social problems.This study was obtained from literature study on current problems and solutions of degraded peatlands through peatland hydrology restoration by rewetting method (canal blocking) and cultivation of species that do not require drainage. There are four types of dams that are often used to control water flows, plank dam, composite dam, plastic dam, and sluice. The selection of dam is highly dependent on bio-physical condition, dimensions of canals, peat-topography, availability and accessibility of transportation to the dam site. This research shows that there is strong correlation between canal blocking and the increasing of ground water level, where canal blocking is useful for raising the water table and moisturizing the soil.In the implementation of paludiculture, the certain species / commodities can survive to wet condition, and also have economic value such as: Metroxylon spp, Nypa fruticans Wurmb, Alseodaphne spp. dan Nothaphoebe spp), dan Shorea spp. In order to survive the type of plants has to be selected and adjusted to the condition of peatlands water level. Keywords : Peatlands, paludikultur, canal blocking, restoration, ground water level

Challenges to peatland restoration in Indonesia

<p>Challenges to peatland restoration in Indonesia<br>By <br>Nyoman Suryadiputra*) </p><p><br>Tropical peat swamps in Indonesia are currently experiencing degradation at a very alarming rate. Degradation starts from the time of land clearing (generally burned / uses fire) for both private and community-owned plantations, then a very massive network of drainage canals is built (every 1 Ha of peat land cleared, about 120 m - 700 m long canals are needed). These drainage canals aim to reduce the surface water level of peat so that the land can be planted (especially for) oil palm or acacia. However, peat water release can go out of control, beyond the peatland water level threshold determined by government regulation No 71/2014 on Peatland Management, as a result peat becomes dry, flammable and emits large amount of GHGs. In the long run, if drainage and fires continue, peatlands will experience subsidence, form basins, peat even disappear, flooded during rain and eventually the land becomes unproductive (stranded) and difficult to restore. Such conditions will be more severe and difficult to overcome if in the landscape (peatland hydrology unit) there are various activities by various parties, each of whom has different interests and understandings of peatland use. Regarding the above, restoration of peatland that has been damaged has a very serious challenge. Damage that is getting heavier will have a high level of difficulty and a long recovery time. In addition, the success rate of restoration is determined by benchmarks or recovery criteria that have not been scientifically determined and adopted by the Indonesian government.</p><p><em>Keywords : peatland, degradation, landscape, restoration    </em></p><p><br>*)  Director of Wetlands International Indonesia</p>