Peat Decomposition Research Articles

Holocene vegetation and hydroclimate changes in the Kansk forest steppe, Yenisei River Basin, East Siberia

Our study focuses on the Holocene hydroclimate long‐term trends in southern East Siberia and places them in the context of the adjacent areas of the Siberian taiga in the north and the arid central Asia in the south. We present a new record from the eutrophic mire, in the forest‐steppe region, covering the last 9000 years. Our multi‐proxy approach includes physiochemical (ash content, grain size, micro‐charcoal, peat decomposition) and biological indicators (pollen, non‐pollen palynomorphs, plant macrofossils, testate amoebae, molluscs). The record indicates increased humidity during the Holocene Thermal Maximum at 8150–7400 cal. a BP, and drier conditions with evidence for fires at 7400–5100 cal. a BP. Next, wetter conditions occurred at the coring site at 5100–1400 cal. a BP based on evidence of fluvial influence, which is consistent with other records in the wider region. A short‐term dry episode occurred at 1400–1300 cal. a BP, followed by a wet Medieval Warm Period (1300–650 cal. a BP) and Little Ice Age (450–300 cal. a BP) and a moderately wet environment from 300 cal. a BP to the present day. These results are consistent with the previously published palaeoenvironmental reconstructions from the steppe and forest‐steppe regions in the south of East and West Siberia and taken together reveal a common trend towards wetter conditions with a maximum wetness between 4500 and 3000 cal. a BP. This differs from the taiga region further north and from the Altai‐Sayan Mountains and Kazakhstan Hills further south, which show the trend from dry to wet and then to drier conditions in the Holocene, and from the Trans‐Baikal region where the Holocene trend is to drier conditions. This study supports the predominant influence of the North Atlantic on the regional palaeoclimate changes in the forest‐steppe region of East Siberia during the Holocene.

Soil carbon loss from drained agricultural peatland after coverage with mineral soil

Drainage for agriculture has turned peatlands from a net sink to a net source of carbon (C). In order to reduce the environmental footprint of agricultural peatland drainage, and to counteract soil subsidence, mineral soil coverage is becoming an increasingly used practice in Switzerland. To explore the effect of mineral soil coverage on soil C loss and the source of CO2 from peatland drained for agriculture, we utilized the radiocarbon signature (F14C) of soil C and emitted CO2 in the field. The experiment, located in the Swiss Rhine Valley, was carried out on two adjacent drained organic soils, either without mineral soil cover (reference ‘Ref’), or covered with mineral soil (thickness ~ 40 cm) (coverage ‘Cov’) 13 years ago. Drainage already commenced 130 years ago and the site was managed as meadow since the 1970ies. Drainage induced 41–75 kg C m−2 loss, which is equivalent to annual C loss rates of 0.49–0.58 kg C m−2 yr−1 and 0.31–0.63 kg C m−2 yr−1 for Cov and Ref, respectively. Mineral soil coverage had no significant effect on the amount of heterotrophic respiration, however, at Cov, the radiocarbon signature of heterotrophic CO2 was significantly (p<0.01) younger than at Ref, indicating that mineral soil coverage moved the source of decomposition of soil organic carbon (SOC) from a higher share of old peat towards a higher share of relatively younger material. In summary, our study lends support to the hypothesis that mineral soil coverage might reduce the decomposition of old peat underneath, and may therefore be a promising peatland management technique for the future use of drained peatland for agriculture.

Constraints on potential enzyme activities in thermokarst bogs: Implications for the carbon balance of peatlands following thaw.

Northern peatlands store a globally significant amount of soil organic carbon, much of it found in rapidly thawing permafrost. Permafrost thaw in peatlands often leads to the development and expansion of thermokarst bogs, where microbial activity will determine the stability of the carbon storage and the release of greenhouse gases. In this study, we compared potential enzyme activities between young (thawed ~30years ago) and mature (~200years) thermokarst bogs, for both shallow and deep peat layers. We found very low potential enzyme activities in deep peat layers, with no differences between the young and mature bogs. Peat quality at depth was found to be highly humified (FTIR analysis) in both the young and mature bogs. This suggests that deep, old peat was largely stable following permafrost thaw, without a rapid pulse of decomposition during the young bog stage. For near-surface peat, we found significantly higher potential enzyme activities in the young bog than in the mature-associated with differences in peat quality derived from different Sphagnum species. A laboratory incubation of near-surface peat showed that differences in potential enzyme activity were primarily influenced by peat type rather than oxygen availability. This suggested that the young bog can have higher rates of near-surface decomposition despite being substantially wetter than the mature bog. Overall, our study shows that peat properties are the dominant constraint on potential enzyme activity and that peatland site development (successional pathways and permafrost history) through its influence on peat type and chemistry is likely to determine peat decomposition following permafrost thaw.

Optimizing fen peatland water‐table depth for romaine lettuce growth to reduce peat wastage under future climate warming

SummaryForty percentage of UK peatlands have been drained for agricultural use, which has caused serious peat wastage and associated greenhouse gas emissions (carbon dioxide (CO2) and methane (CH4)). In this study, we evaluated potential trade‐offs between water‐table management practices for minimizing peat wastage and greenhouse gas emissions, while seeking to sustain romaine lettuce production: one of the most economically relevant crop in the East Anglian Fenlands. In a controlled environment experiment, we measured lettuce yield, CO2, CH4 fluxes and dissolved organic carbon (DOC) released from an agricultural fen soil at two temperatures (ambient and +2°C) and three water‐table levels (−30 cm, −40 cm and −50 cm below the surface). We showed that increasing the water table from the currently used field level of −50 cm to −40 cm and −30 cm reduced CO2 emissions, did not affect CH4 fluxes, but significantly reduced yield and increased DOC leaching. Warming of 2°C increased both lettuce yield (fresh leaf biomass) and peat decomposition through the loss of carbon as CO2 and DOC. However, there was no difference in the dry leaf biomass between the intermediate (−40 cm) and the low (−50 cm) water table, suggesting that romaine lettuce grown at this higher water level should have similar energetic value as the crop cultivated at −50 cm, representing a possible compromise to decrease peat oxidation and maintain agricultural production.

Simulation modelling of greenhouse gas balance in continuous-cover forestry of Norway spruce stands on nutrient-rich drained peatlands

We used a simulation model to analyse the effect of continuous-cover forestry on the carbon dioxide (CO2) and methane (CH4) emissions from nutrient-rich drained peatland sites in southern Finland. The simulation scenarios were constructed by varying harvesting interval and post-harvest basal area in a typical mature Norway spruce (Picea abies (L.) H. Karst.) stand. A process-based model of soil organic matter dynamics supplied with some additional empirical routines was used for calculation of emission due to decomposition of fresh litter and peat. The amount and chemical properties of litter inputs, as well as the hydrothermal conditions and the water table depth in the peat layer were used as predictors. We estimated the net ecosystem production as a difference between carbon sequestration in stand biomass and carbon losses due to decomposition of dead organic matter, and the net biome production as the net primary production minus losses due to harvesting. Simulations showed that the peatland forest acted as a carbon sink with low and middle harvest intensity, while it turned into a carbon source with high harvesting intensities. This was mostly because intensive harvesting raised the water table level, thus decreasing tree production and increasing soil methane emission. Carbon dioxide emissions from peat and litter, in turn, correlated negatively with the intensity of harvesting. Correlation of site carbon balance with harvested roundwood indicated that there is a significant trade-off between maintaining carbon in drained peatland forests and providing harvest revenues. The simulations provide novel results and fill a gap of knowledge in ecosystem responses to alternative management regimes in continuous-cover forestry on drained peatlands.

Agricultural peatlands conservation: How does the addition of plant biomass and copper affect soil fertility?

AbstractSubsidence, erosion, and degradation in agricultural peatlands are leading to the disappearance of highly fertile farmland. This study investigated two strategies aimed at extending the lifespan of cultivated peat soils: the application of straw and wood chips to compensate for soil losses and the application of copper (Cu) to slow peat decomposition, based on previous recommendations. Peat soil samples (270 g) were amended with 11 t ha–1 of biomass materials (14.8 g kg–1) and 235.6 mg Cu kg–1 and incubated in glass jars at constant temperature and water content. Thirty chemical parameters were then monitored over a 56‐d period through repeated soil sampling. Discriminant analysis showed that the addition of biomass had the greatest affect on nitrogen (N) availability, immobilizing 7.8 to 12.1 kg of inorganic N per metric ton of incorporated biomass. Considering that peat soils may require from 4 to 40 t biomass ha–1 yr–1 to reach carbon equilibrium, the tested biomass materials could immobilize from 34 to 500 kg ha–1 of N if confirmed at the field scale. This may help capture excess N but may also limit crop growth. Alternatively, slowing decomposition could reduce both biomass requirements and N immobilization. However, the results show that Cu had little effect on parameters linked to organic matter decomposition. Indeed, dissolved organic carbon was decreased by 11% in Cu‐treated soils. A longer‐term study should be conducted to confirm these observations at the field scale, thus helping to develop conservation strategies suitable for agricultural production.

Conventional subsoil irrigation techniques do not lower carbon emissions from drained peat meadows

Abstract. The focus of current water management in drained peatlands is to facilitate optimal drainage, which has led to soil subsidence and a strong increase in greenhouse gas (GHG) emissions. The Dutch land and water authorities proposed the application of subsoil irrigation (SSI) system on a large scale to potentially reduce GHG emissions, while maintaining high biomass production. Based on model results, the expectation was that SSI would reduce peat decomposition in summer by preventing groundwater tables (GWTs) from dropping below −60 cm. In 2017–2018, we evaluated the effects of SSI on GHG emissions (CO2, CH4, N2O) for four dairy farms on drained peat meadows in the Netherlands. Each farm had a treatment site with SSI installation and a control site drained only by ditches (ditch water level −60 / −90 cm, 100 m distance between ditches). The SSI system consisted of perforated pipes −70 cm from surface level with spacing of 5–6 m to improve drainage during winter–spring and irrigation in summer. GHG emissions were measured using closed chambers every 2–4 weeks for CO2, CH4 and N2O. Measured ecosystem respiration (Reco) only showed a small difference between SSI and control sites when the GWT of SSI sites were substantially higher than the control site (&gt; 20 cm difference). Over all years and locations, however, there was no significant difference found, despite the 6–18 cm higher GWT in summer and 1–20 cm lower GWT in wet conditions at SSI sites. Differences in mean annual GWT remained low (&lt; 5 cm). Direct comparison of measured N2O and CH4 fluxes between SSI and control sites did not show any significant differences. CO2 fluxes varied according to temperature and management events, while differences between control and SSI sites remained small. Therefore, there was no difference between the annual gap-filled net ecosystem exchange (NEE) of the SSI and control sites. The net ecosystem carbon balance (NECB) was on average 40 and 30 t CO2 ha−1 yr−1 in 2017 and 2018 on the SSI sites and 38 and 34 t CO2 ha−1 yr−1 in 2017 and 2018 on the control sites. This lack of SSI effect is probably because the GWT increase remains limited to deeper soil layers (60–120 cm depth), which contribute little to peat oxidation. We conclude that SSI modulates water table dynamics but fails to lower annual carbon emission. SSI seems unsuitable as a climate mitigation strategy. Future research should focus on potential effects of GWT manipulation in the uppermost organic layers (−30 cm and higher) on GHG emissions from drained peatlands.

Paludiculture as paludifuture on Dutch peatlands: An environmental and economic analysis of Typha cultivation and insulation production

Paludiculture, the cultivation of crops on rewetted peatlands, is often proposed as a viable climate change mitigation option that reduces greenhouse gas emissions (GHGe), while simultaneously providing novel agricultural business options. In West Europe, experiments are ongoing in using the paludicrop cattail (Typha spp.) as feedstock for insulation panel material. Here, we use a Dutch case study to investigate the environmental potential and economic viability of shifting the use of peat soils from grassland (for dairy production) to Typha paludiculture (for cultivation and insulation panel production). Using a life cycle assessment and cost-benefit analysis, we compared the global warming potential (GWP), yearly revenues and calculated Net Present Value (NPV) of 1 ha Dutch peat soil used either for dairy production or for Typha paludiculture. We estimated that changing to Typha paludiculture leads to a GWP reduction of ~32% (16.4 t CO2-eq ha−1), mainly because of lower emissions from peat decomposition as a result of land-use management (−21.6 t CO2-eq ha−1). If biogenic carbon storage is excluded, the avoided impact of conventional insulation material is insufficient to compensate the impact of cultivating and processing Typha (9.7 t CO2-eq ha−1); however, this changes if biogenic carbon storage is included (following PAS2050 guidelines). Typha paludiculture is currently not competitive with dairy production, mainly due to high cultivation costs and low revenues, which are both uncertain, and will likely improve as the system develops. Its NPV is negative, mainly due to high investment costs. This can be improved by introducing carbon credits, with carbon prices for Typha paludiculture (30 years) comparable to EU-ETS prices.In conclusion, Dutch Typha paludiculture has a significant climate change mitigation potential by reducing emissions from deep drained peatlands. Nevertheless, attention is needed to increase its economic viability as this is a key aspect of the system change.

Soil carbon balance of afforested peatlands in the maritime temperate climatic zone

Drainage and conversion of natural peatlands into forestry increases soil CO2 emissions through decomposition of peat and modifies the quantity and quality of litter inputs and therefore the soil carbon balance. In organic soils, CO2 net emissions and removals, are reported using carbon emission factors (EF). The choice of specific default Tier 1 EF values from the IPCC 2013 Wetlands supplement depends on land use categories and climate zones. However, Tier 1 EF for afforested peatlands in the temperate maritime climate zone are based on data from eight sites, mainly located in the hemiboreal zone, and the uncertainty associated with these default values is a concern. In addition, moving from Tier 1 to higher-Tier carbon reporting values is highly desirable when large areas are affected by land use changes. In this study, we estimated site-specific soil carbon balance for the development of Tier 2 soil CO2 -C EFs for afforested peatlands. Soil heterotrophic respiration and aboveground litterfall were measured during two years at eight afforested peatland sites in Ireland. In addition, fine roots turnover rate and site-specific fine root biomass were used to quantify belowground litter inputs. Our findings found that draining of peatlands, and planting them with either Sitka spruce or lodgepole pine, resulted in soils being net carbon sources. The soil carbon balance at multi-year sites varied between 63 ± 92 and 309 ± 67 g C m-2 year-1 . Mean CO2 -C EF for afforested peatlands was 1.68 ± 0.33 tCO2 -Cha-1 year-1 . The improved CO2 -C EFs presented here for afforested peatlands are proposed as a basis to update national CO2 -C emissions from this land-use class in Ireland. Furthermore, new data from these sites will significantly contribute to the development of more reliable IPCC default Tier 1 CO2 -C EFs for afforested peatlands in the maritime temperate climate zone.

Impacts of vegetation and palaeohydrological changes on the n-alkane composition of a Holocene peat sequence from the Upper Vistula Valley (southern Poland)

PurposeThe analysis of n-alkanes in palaeoenvironmental studies of peatlands is mainly limited to ombrogenous peatlands which are a rare feature in the environment. Using n-alkane and plant macrofossil analysis, we have tracked changes in the environment in the valley of a large Central European river. We tested the possibilities for applying such studies to low-moor bogs which are the most commonly occurring type of bog in the world.Materials and methodsRepresentative peat samples were taken from two profiles in a peatland located in the Vistula Valley (southern Poland), and they were analysed for the occurrence and distribution of biomarkers. The distribution of n-alkanes was determined using gas chromatography-mass spectrometry (GC–MS). The botanical composition of the samples was determined by analysis of plant macrofossil remains, and the degree of peat decomposition was also determined.Results and discussionSamples of low-moor peat were characterised by a prevalence of medium- and long-chain n-alkane homologues, which is typical for higher plants. The variable values of the CPI, CPI (25–31), and the C23/C25 ratio have provided information on the stages of formation of the Zapadź bog. The source of n-alkane differentiation is vegetation change related to palaeohydrological dynamics and palaeoenvironmental conditions within the peatland.ConclusionsWe have shown that analysis of n-alkanes can be successfully used in low-moor bogs as a complement to palaeobotanical and palaeozoological methods. The bringing together of these types of research enables changes in the ecosystems of large river valleys to be tracked.

Assessing the carbon dioxide balance of a degraded tropical peat swamp forest following multiple fire events of different intensities

Tropical peat swamp forest is a unique ecosystem rich in carbon and water, accumulating a huge amount of carbon as peat. However, the huge carbon pool has been threatened by oxidative peat decomposition and fire loss mainly because of deforestation and drainage. Fire causes acute carbon dioxide (CO2) emissions through the combustion of biomass and peat. Also, fire should change the CO2 balance of postfire ecosystems. Although it is crucial to quantify CO2 balance even after a fire event to understand the total fire impact, information based on field measurement is lacking. Thus, we had measured eddy CO2 flux above a repeatedly burned degraded peat forest for about 13 years since 2004. The site was a stable CO2 source of 147−290 g C m−2 yr−1 for five years after a stand-replacing fire in 2002. Unexpectedly, a moderate-severity fire in 2009 changed the site to a CO2 sink of about −600 g C m−2 yr−1. The drastic change would have been caused by a large decrease in the decomposition of plant debris, which had accumulated since the 2002 fire but was burned by the 2009 fire. In contrast, gross primary production (GPP) remained about the same even though vegetation was damaged, mainly because year-round wet conditions caused by a La Niña event promoted the regrowth of hygrophilous herbaceous plants and were favorable to their GPP. The site also had a low-severity fire and was drained in 2014 but did not return to a CO2 source. However, the net ecosystem CO2 uptake after the 2009 fire was insufficient to recover a large amount of fire CO2 emission. If CO2 emissions from four fires in 1999, 2002, 2009 and 2014 are counted, the site is expected to owe an outstanding CO2 debt of 25 kg C m−2.

9000 years of changes in peat organic matter composition in Store Mosse (Sweden) traced using FTIR‐ATR

Store Mosse (the ‘Great Bog’ in Swedish) is one of the most extensive bog complexes in southern Sweden (~77 km2), where pioneering palaeoenvironmental research has been carried out since the early 20th century. This includes, for example, vegetation changes, carbon and nitrogen dynamics, peat decomposition, atmospheric metal pollution, mineral dust deposition, dendrochronology, and tephrochronology. Even though organic matter (OM) represents the bulk of the peat mass and its compositional change has the potential to provide crucial ecological information on bog responses to environmental factors, peat OM molecular composition has not been addressed in detail. Here, a 568‐cm‐deep peat sequence was studied at high resolution, by attenuated reflectance Fourier‐transform infrared spectroscopy (FTIR‐ATR) in the mid‐infrared region (4000–400 cm–1). Principal components analysis was performed on selected absorbances and change‐point modelling was applied to the records to determine the timing of changes. Four components accounted for peat composition: (i) depletion/accumulation of labile (i.e. carbohydrates) and recalcitrant (i.e. lignin and other aromatics, aliphatics, organic acids and some N compounds) compounds, due to peat decomposition; (ii) variations in N compounds and carbohydrates; (iii) residual variation of lignin and organic acids; and (iv) residual variation of aliphatic structures. Peat decomposition showed two main patterns: a long‐term trend highly correlated to peat age (r = 0.87), and a short‐term trend, which showed five main phases of increased decomposition (at ~8.4–8.1, ~7.0–5.6, ~3.5–3.1, ~2.7–2.1 and ~1.6–1.3 ka) – mostly corresponding to drier climate and its effect on bog hydrology. The high peat accumulation event (~5.6–3.9 ka), described in earlier studies, is characterized by the lowest degree of peat decomposition of the whole record. Given that FTIR‐ATR is a quick, non‐destructive, cost‐effective technique, our results indicate that it can be applied in a systematic way (including multicore studies) to peat research and provide relevant information on the evolution of peatlands.

Four peat humification-recorded Holocene hydroclimate changes in the southern Altai Mountains of China

In this study, Holocene humification records were derived from four ombrotrophic peatlands to investigate the millennial-scale and decadal-centennial-scale variability of peat decomposition and to explore the paleoclimatic and paleohydrological implications. After eliminating the species-specific and site-specific noise and removing the time-dependency effect for each of four peat sequences, the averaged residuals of four peat humification sequences exhibit two-order variations. The millennial-scale variation of averaged residuals of four peat humification is characterized by a bow-shaped curve and is basically moisture-dependent. In detail, the humification in the middle Holocene (~8200–~4000 cal. yr BP) was higher than in the early Holocene (before ~8200 cal. yr BP) and also than in the late Holocene (after ~4000 cal. yr BP). The decadal/centennial-scale variations are superimposed on the bow-shaped curve and have been primarily paced by the sea surface temperature in the North Atlantic whose signals were propagated to Central Asia via the prevailing westerlies, which implies that lower temperature and lower temperature-suppressed evaporation (i.e. elevated moisture level) were most likely responsible for limiting the decomposition activity in the uppermost peat layer. These results indicate the potential for humification records from ombrotrophic peatlands in Central Asia to elucidate paleoclimate variability.

Can nutrient uptake by Carex counteract eutrophication in fen peatlands?

Ground- and surface-water-fed peatlands (i.e., fens) of temperate Europe face high anthropogenic nutrient loads from atmospheric deposition, agricultural catchment areas, and from peat decomposition, if drained. As a result, nitrogen loads may exceed a fen's natural nutrient removal capacity, leading to increased eutrophication of adjacent water bodies. Therefore, it is important to address possible means to decrease a fen's nutrient load, including nutrient uptake by fen plants. To assess how much fen plants can contribute to nutrient removal by uptake, nutrient stocks of above- and below-ground biomass need to be quantified. Therefore, we investigated nitrogen, phosphorous, and potassium uptake capacities of sedges (Carex species), which are common dominants in fen plant communities. We grew specimens of five Carex species with varying preferences in nutrient availability under controlled, different nutrient levels. We show that Carex above-ground biomass harvest can remove up to one third of a system's total nitrogen even at high loads of about 40 g nitrogen m−2. Species-specific differences in biomass production, rather than preferences in nutrient availability under natural conditions, were drivers of standing nutrient stocks: Highly productive species, i.e., C. acutiformis and C. rostrata, had highest nutrient standing stocks across all nutrient levels. Amounts of nutrients stored in shoots increased almost linearly with increasing nutrient levels, whereas below-ground nutrient stocks species-specifically increased, saturated, or decreased, with increasing nutrient levels. As a rough estimate, depending on the species, 6–16 cycles of annual above-ground harvest would suffice to decrease nitrogen concentrations from the highest to the lowest level used in this study. Overall, our results indicate that Carex biomass harvest can be an efficient means to counteract anthropogenic nitrogen eutrophication in fens.

Peat depth as a control onSphagnummoisture stress during seasonal drought

AbstractPeatlands are globally important long‐term sinks of carbon, however there is concern that enhanced peat decomposition and moss moisture stress due to climate change mediated drought will reduce moss productivity making these ecosystems vulnerable to carbon loss and associated long‐term degradation. Peatlands are resilient to summer drought moss stress because of negative ecohydrological feedbacks that generally maintain a wet peat surface, but where feedbacks may be contingent on peat depth. We tested this ‘survival of the deepest’ hypothesis by examining water table (WT) position, near‐surface moisture content, and soil water tension in peatlands that differ in size, peat depth, and catchment area during a summer drought. All shallow sites (&lt;40 cm depth) lost their WT (i.e., the groundwater well was dry) for considerable time during the drought period. Near‐surface soil water tension increased dramatically at shallow sites following WT loss, increasing ~5–7.5× greater at shallow sites compared to deep sites (≥40 cm depth). During a mid‐summer drought intensive field survey, we found that 60–67% of plots at shallow sites exceeded a 100 mb tension threshold used to infer moss water stress. Unlike the shallow sites, tension typically did not exceed this 100 mb threshold at the deep sites. Using species dependent water content – chlorophyll fluorescence thresholds and relations between volumetric water content and WT depth, Monte Carlo simulations suggest that moss had nearly twice the likelihood of being stressed at shallow sites (0.38 ± 0.24) compared to deep sites (0.22 ± 0.18). This study provides evidence that mosses in shallow peatland may be particularly vulnerable to warmer and drier climates in the future, but where species composition may play an important role. We argue that a critical ‘threshold’ peat depth specific for different hydrogeological and hydroclimatic regions can be used to assess what peatlands are especially vulnerable to climate change mediated drought.

From Haymaking to Wood Production: Past Use of Mires in Northern Sweden Affect Current Ecosystem Services and Function

Mires form a large part of the boreal Swedish landscape and are important for biodiversity and natural ecosystem processes. Historically, mires also played a key role for the expansion of agricultural practices, and later to create new forest land, but knowledge is limited on how the land use has affected the current ecosystem services and functions of mires. In this case study from northern Sweden, we have combined historical maps with remote-sensing data to analyze the use of mires over time. Here, 22% of the mire area has been used for hay harvesting, an activity that peaked in the late 1800s. Later, about 3% was reclaimed for intensive agriculture. Drainage to enhance wood production followed in the 1940s, and about 40% of the original mire area is currently forested. The most productive mires have been relatively more affected by human measures. We suggest that this past land use has legacy effects on several ecosystem services. Haymaking likely had positive effects on biodiversity, but may have negatively influenced carbon sequestration. Reclamation led to habitat loss and likely less carbon sequestration. Drainage to promote forest growth generally lowered the ground water level, which in turn enhanced peat decomposition and subsequently released CO2. However, if tree growth outpaces peat decomposition, drainage could increase carbon sequestration. The overall carbon balance is hence influenced by past management regimes, which implies that past human use must be taken into account when considering the role of mires in providing ecosystem services.

Soil amelioration using steel slag in drained peatland under oil palm plantation increases CO2 emission

Increasing the productivity of tropical peatland can be achieved by soil ameliorations using steel slag and lateritic soil. However, the effect of such ameliorants on the peat decomposition is not well understood. This study was aimed to evaluate the influence of soil ameliorants of steel slag and lateritic soil to peat decomposition as reflected by CO2 emission. A year study was conducted in smallholder oil palm plantation in Jambi Province, Indonesia to monitor CO2 emission from treatments plots of control (T1), steel slag 600 kg ha−1 (T2), lateritic soil 600 kg ha−1 (T3) and a combination of T2 and T3 (T4), which each treatment had 5 replications. CO2 emission was measured every three months by a closed chamber method. Results showed that CO2 emission were followed the order of T4>T2>T1≥T3. CO2 emission from T4 (49 ± 20 t ha−1 year−1) was 20% higher than T1 (40 ± 23 t ha−1 year−1), while T2 (44 ± 17 t ha−1 year−1) was 9% higher than T1. CO2 emission from T3 (40 ± 14 t ha−1 year−1) was similar to T1. This study showed that steel slag accelerates peat organic matter decomposition which is indicated by higher CO2 emission of steel slag treatments compare to other treatments.

Dynamics of carbon of peat soils under several land uses in Kampar Peninsula, Riau Province, Indonesia

One of the main sources of greenhouse gases (GHGs) emissions is CO2 from peat decomposition. Land management, especially drainage, can trigger decomposition, causing carbon content depletion in peat soils. In this study, carbon dynamic was evaluated under various land uses of the peatland in Kampar Peninsula, Riau, Indonesia. Secondary data from 2016, supplemented by primary data until 2018 have been analysed to obtain multi-temporal data. The dynamic of land use types was analysed by interpreting multi-temporal imagery and ground check in the field. Results show that from 2016 to 2018, there was a soil carbon content decrease in the lands with intensive management, namely estate corps, Industrial Forest Plantation (IFP) and upland crops ranging from 0.12 to 1.39% per year. On the other hand, there was an increase of average carbon content on unmanaged land, covered by grass and shrub, between 0.24 to 0.75% per year. Below-ground carbon stock in the study area was between 1,926 to 6,644 Mg ha−1, the lowest was happened to be in abandoned bush land, and the highest was in the peat forest-bush area, and the variation was related to the peat depth.

Dynamic of groundwater table, peat subsidence and carbon emission impacted from deforestation in tropical peatland, Riau, Indonesia

Drainage canals have triggered peat subsidence and lowered groundwater table, enabling wildfires and peat degradation in Riau, Indonesia. This study examines the changes on groundwater table, peat subsidence rate, and carbon emission in response to deforestation and land cover changes. We established 31 study sites in some land cover types (i.e., oil palm plantation, acacia regrowth and shrub), with 124 monitoring shallow wells and 31 subsidence poles that were setup and have been monitored for 18 months. Groundwater table of all plots averaged -55 cm in Dosan Village, higher than that in Dayun Village (-66 cm). In accordance, peat had subsided in faster rate (8.4 cm year−1) in Dayun Village than that in Dosan (3.3 cm year−1). This average annual groundwater table has resulted in carbon emissions from peat decomposition up to 66 t CO2eq ha−1 year−1. On the other hand, canal discharge of these sites ranged from 2 to 73 dm3 s−1, averaging 26 dm3 s−1. These results evidence that land uses converted from peat forest, and the dimension of canal control the decrease in groundwater table, the pace of peat subsidence, and rate of carbon emissions in tropical peatlands.

The role of peat decomposition stage on iron solubility and distribution in tidal swamps

Most peat layers laying above sulfidic materials have important role in the geochemical cycle in tidal swampland. Depletion of the peat layer increase metal solubility and acidity from sulfidic materials which then potentially polluting and decreasing the quality of the surrounding environment. The purpose of this review was to describe the influence of peat layer thickness and its decomposition stage on iron solubility and distribution in the profile of peat soils and acid sulphate soils located around peatlands. This paper used observational data from a number of articles on peatlands with varies thickness and acid sulphate soils. Peat decomposition stage has important role on the distribution of Fe, the movement and ability of complex formation with Fe. Most of the Fe ions in peatlands were in organic complex form, and organic–Fe concentration in sapric peat layer was higher than hemic peat layer.