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Greenhouse gas fluxes from tropical peatlands in South-East Asia
Abstract
The lowland peatlands of south-east Asia represent an immense reservoir of fossil carbon and are reportedly responsible for 30% of the global carbon dioxide (CO2) emissions from Land Use, Land Use Change and Forestry. This paper provides a review and meta-analysis of available literature on greenhouse gas fluxes from tropical peat soils in south-east Asia. As in other parts of the world, water level is the main control on greenhouse gas fluxes from south-east Asian peat soils. Based on subsidence data we calculate emissions of at least 900 g CO2 m−2 a−1 (∼250 g C m−2 a−1) for each 10 cm of additional drainage depth. This is a conservative estimate as the role of oxidation in subsidence and the increased bulk density of the uppermost drained peat layers are yet insufficiently quantified. The majority of published CO2 flux measurements from south-east Asian peat soils concerns undifferentiated respiration at floor level, providing inadequate insight on the peat carbon balance. In contrast to previous assumptions, regular peat oxidation after drainage might contribute more to the regional long-term annual CO2 emissions than peat fires. Methane fluxes are negligible at low water levels and amount to up to 3 mg CH4 m−2 h−1 at high water levels, which is low compared with emissions from boreal and temperate peatlands. The latter emissions may be exceeded by fluxes from rice paddies on tropical peat soil, however. N2O fluxes are erratic with extremely high values upon application of fertilizer to wet peat soils. Current data on CO2 and CH4 fluxes indicate that peatland rewetting in south-east Asia will lead to substantial reductions of net greenhouse gas emissions. There is, however, an urgent need for further quantitative research on carbon exchange to support the development of consistent policies for climate change mitigation.
... We then compared simulated (restored) NEE values to those ob- A summary analysis of cumulative annual NEE is presented in C losses were 21.2 Mg CO 2 ha −1 year −1 , a value 18% lower than C losses of 25.8 Mg CO 2 ha −1 predicted using the Couwenberg WTD model (Couwenberg et al., 2010). By raising the mean annual WTD from 60 to 30 cm (REST_30), annual C losses are decreased to only 2.0 Mg CO 2 ha −1 year −1 . ...
... The projected decrease in CO 2 losses at PD and PLNWR to the atmosphere due to a rise of the water table suggests that rewetted (rehydrated) pocosins can be a substantial C sink on the landscape. While it has been shown in other studies that rewetted peatlands can become CO 2 sinks, with large positive climatic effects coming from the avoidance of large CO 2 emissions from drained peatlands (Couwenberg et al., 2010;Joosten et al., 2016;Morse et al., 2012), problems often exist with elevated CH 4 and N 2 O releases (Bossio et al., 2020), which is not the case in pocosins. Additionally, it has recently been argued using a radiative forcing model and data from the Global Peatland Database that even for peatlands that release substantial amounts of CH 4, the radiative forcing does not undermine the climate change mitigation potential of peatland rewetting (Günther et al., 2020). ...
... diation R g explains most of the variation in NEE, with WTD explaining the remaining variation. Importantly, our model is more robust than models using only WTD(Couwenberg et al., 2010) as it captures variance of NEE due to both key driving variables: (i) seasonal patterns of solar radiation and temperature and (ii) changes in both short-and long-term WTD. The high solar radiation values in the F I G U R E 5 Daily eddy covariance (EC) carbon flux measured throughout 1 year in a pocosin shrub bog ecosystem at the private drained (PD) G11 site in Hyde County NC (Phase II). ...
Peatlands drained for agriculture or forestry are susceptible to the rapid release of greenhouse gases (GHGs) through enhanced microbial decomposition and increased frequency of deep peat fires. We present evidence that rewetting drained subtropical wooded peatlands (STWPs) along the southeastern USA coast, primarily pocosin bogs, could prevent significant carbon (C) losses. To quantify GHG emissions and storage from drained and rewetted pocosin we used eddy covariance techniques, the first such estimates that have been applied to this major bog type, on a private drained (PD) site supplemented by static chamber measurements at PD and Pocosin Lakes National Wildlife Refuge. Net ecosystem exchange measurements showed that the loss was 21.2 Mg CO2 ha-1 year-1 (1 Mg = 106 g) in the drained pocosin. Under a rewetted scenario, where the annual mean water table depth (WTD) decreased from 60 to 30 cm, the C loss was projected to fall to 2 Mg CO2 ha-1 year-1 , a 94% reduction. If the WTD was 20 cm, the peatlands became a net carbon sink (-3.3 Mg CO2 ha-1 year-1 ). Hence, net C reductions could reach 24.5 Mg CO2 ha-1 year-1 , and when scaled up to the 4000 ha PD site nearly 100,000 Mg CO2 year-1 of creditable C could be amassed. We conservatively estimate among the 0.75 million ha of southeastern STWPs, between 450 and 770 km2 could be rewet, reducing annual GHG emissions by 0.96-1.6 Tg (1 Tg = 1012 g) of CO2 , through suppressed microbial decomposition and 1.7-2.8 Tg via fire prevention, respectively. Despite covering <0.01% of US land area, rewetting drained pocosin can potentially provide 2.4% of the annual CO2 nationwide reduction target of 0.18 Pg (1 Pg = 1015 g). Suggesting pocosin restoration can contribute disproportionately to the US goal of achieving net-zero emission by 2050.
... However, over the past few decades, tropical peatlands in SE Asia have been heavily degraded by deforestation, drainage and often set on fire for land development (Sorensen, 1993). These disturbances together with climate change threaten their C sequestration potential and in turn can convert them from a C sink to a net C source to the atmosphere (Couwenberg et al., 2010;Hoyos-Santillan et al., 2019;Page et al., 2011;Turetsky et al., 2014). More importantly, as per recent estimates (in 2015), the extent of such degraded areas have increased to almost one-tenth of the total peatland cover in SE Asia (Miettinen et al., 2016). ...
... vegetation composition and hence labile C in the form of root exudates) factors . For intact tropical peatlands, studies have well reported the effects of pH (Dunfield et al., 1993), temperature (Hirano et al., 2009;Sjögersten et al., 2018), water table height (Couwenberg et al., 2010;Jauhiainen et al., 2005), oxidation-reduction conditions (Ueda et al., 2000), nutrients (Sjögersten et al., 2011), and vegetation influencing soil properties in form of labile carbon (Girkin et al., 2018a;Hoyos-Santillan et al., 2015;Wright et al., 2013) on the rate of greenhouse gases (GHGs; CO 2 and CH 4 ) emissions. However, for fire-degraded tropical peatland areas, these effects remain understudied. ...
... We found that the mean CO 2 production significantly (p < 0.05) differed among control treatment where rate of CO 2 production in mesic conditions (65.1 ± 8.59 μgCO 2 g − 1 hr − 1 ) were up to three times higher when compared to anoxic conditions (26.7 ± 2.4 μgCO 2 g − 1 hr − 1 ) (Fig. 4a). In line with findings from field studies, our results also confirm that the water level can strongly regulate CO 2 emissions from degraded tropical peatland (Couwenberg et al., 2010;Lupascu et al., 2020). We also observed a gradient in CO 2 production across treatments where it decreased from mesic to flooded oxic to anoxic, further reflecting the importance of water table regime in controlling aerobic decomposition of tropical peat, and hence CO 2 production and emissions (Couwenberg et al., 2010;Jauhiainen et al., 2005;Sjögersten et al., 2018). ...
Repeated fires can alter the microtopography, vegetation composition, peat surface temperature and can increase the risk of flooding in tropical peatlands. However, difficult site conditions limit our understanding of these critical factors regulating greenhouse gas (GHG, viz. CO2 and CH4) production and emissions from fire-degraded tropical peatlands. We aimed to relate the complex interactions between peat oxic and anoxic conditions due to changes in microtopography, labile C inputs in the form of plant root exudates (from ferns and sedges), and diurnal temperature change in affecting CO2 and CH4 production from fire-degraded tropical peat. We found that the mesic condition, which reflects the field moisture or water-saturated oxic conditions in hummocks, acted as a strong source of CO2 (230 ± 29 μgCO2 g⁻¹ hr⁻¹) and weak sink for CH4 (−5.6 ± 0.2 ngCH4 g⁻¹ hr⁻¹), while anoxic acted as a weak source of CO2 and strong source of CH4 (61.3 ± 6.2 μgCO2 g⁻¹ hr⁻¹; 592 ± 111 ngCH4 g⁻¹ hr⁻¹). Addition of labile C enhanced both the CO2 and CH4 production across treatments by five and two times for the two gases, respectively. Temperature sensitivity (Q10) for CO2 was higher for peat incubated under mesic conditions (1.21 ± 0.28) whereas for CH4 it was higher in peat under anoxic conditions (1.56 ± 0.35). Collectively, our result highlights how microscale changes in microtopography coupled with the quality and quantity of labile C and temperature variation can regulate GHGs production from fire-degraded tropical peatland areas, which are projected to increase with frequent fire episodes and future climate warming in the region. More importantly, changes in these critical factors may result in a net positive carbon emission with long-term elevated CH4 production and emissions rates from such fire-degraded tropical peatland areas.
... Several researchers found that water table level (GWL) dictated CO2 flux (Hirano et al., 2009;Sundari et al., 2012;Itoh et al., 2017), intensifying particularly during its rise near the peat surface (Ishikura et al., 2017). Otherwise, opposite (Couwenberg et al., 2010;Marwanto and Agus 2014;Ishikura et al., 2018) and obscured effect (Husnain et al., 2014) of GWL in governing CO2 flux were also observed. Notwithstanding that, Meiling et al. (2005) and Ishikura et al. (2018) reported that peat temperature was significantly related to CO2 flux, albeit its effects might be restricted under dense canopy cover of the mature oil palm tree (Jauhainen et al., 2014). ...
... Some reports conducted in tropical peatland found that higher WFPS owing to the rise of GWL could increase CO2 flux during the rewetting period (Ishikura et al., 2017). However, this finding was opposed by Couwenberg et al. (2010), Marwanto and Agus (2014), and Ishikura et al. (2018) studies, who suggested the CO2 flux increased along with the deepening of GWL. These contradictory results might arise from various states of discontinuing capillary pores in peat (Ishikura et al., 2017). ...
... Previous studies highlighted the critical role of GWL in governing CO2 flux, which enlarges at a closer depth to peat surface, especially during the rewetting period (T3 treatment) (Hirano et al., 2009;Ishikura et al., 2017). The correlation in Table 4 exhibited a significantly opposite direction, which was consistent with Couwenberg et al. (2010), Sundari et al. (2012), Marwanto and Agus (2014), Itoh et al. (2017), and Ishikura et al. (2018). The GWL distribution in Figure 8 can explain this condition. ...
The amount of CO2 gas emissions in drained peatland for oil palm cultivation has been widely reported. However, the research addressing the contribution of litter respiration to peat and total respiration and its relationship with several environmental factors is found rare. The aim of this study was to measure peat and heterogeneous litter respiration of drained tropical peat in one year at a distance of 2.25 m and 4.50 m from mature oil palm trees of 14 years using the chamber method (Licor Li-830). In addition to CO2 efflux, we measured other environmental parameters, including peat temperature (10 cm depth), air temperature, groundwater table (GWL), and rainfall. Results showed that the mean total peat respiration (Rt) was 12.06 g CO2 m-2day-1, which consisted of 68% (8.24 g CO2 m-2day-1) peat (Rp) and root (Rr) respiration and 32% (3.84 g CO2 m-2day-1) of litter respiration (Rl) at the distance of 2.25 m from the palm tree. Meanwhile, at a farther distance, the Rt was 12.49 g CO2m-2day-1, the contribution of Rp was 56% (6.78 g CO2 m-2day-1), and Rl was higher than the closest distance (46%; 5.71 g CO2 m-2day-1). Thus, one-year observation resulting the mean Rt and Rr was 0.07–0.08 Mg CO2 ha-1 day-1, while Rl was 0.04–0.06 Mg CO2 ha-1 day-1. The means of Rt, Rp, and Rl were significantly different in the dry season than those recorded in the rainy season. The climatic-related variable such as peat and air temperature were chiefly governing respiration in peat under mature oil palm plantation, whereas the importance of other variables present at particular conditions. This paper provides valuable information concerning respiration in peat, especially for litter contribution and its relationship with environmental factors in peatland, contributing to global CO2 emission.
... Carbon dioxide emissions have been linked to drained peatland, where substantial and rapid responses to changes in the WT level have been notable [5,14]. In this study, the CO2 emissions at the OP site where the WT level was −0.8 to −0.7m below the ground was caused mainly by the enhancement of peat decomposition, which was evidenced by the lower C/N ratio compared to the undisturbed NF site (Table 1) [82]. ...
... The observed high cumulative CO2 emissions in the drained OP site (Figure 5a) was considered to be due to the increased oxygen availability, which lead to aeration and greater aerobic respiration [83]. The effect of peat drainage indicates that CO2 emissions are positively correlated with lowering the WT level [5,14] where heterotrophic respiration dominates (up to 82%) the total respiration from drained peatlands [29,77]. Marwanto et al. [42], in their study, found that CO2 production in mature oil palm plantations is derived from 50 to 10 cm below the surface (subsoil), where the active decomposition layer of peat occurs, and is more pronounced by the moisture condition above the WT level. ...
... The annualized CO2 emissions at the NF were comparable to other reported emissions in the same region [14], but it were lower than the data recorded for Southeast Asian peat Swamp Forest [4,36,43] and higher than values for undrained natural bog (180 g m −2 yr −1 [95]). The CO2 emissions from the natural NF forest in this study were not directly correlated with the measured environmental factors, which is inconsistent with previous studies in tropical peatlands, where the WT level [5,31,96], decomposability and quantity of the organic material available for decomposition (litter, peat and root exudates) and peat nutrient status [84,92] have all been shown to be correlated with CO2 emissions. The unexpectedly low organic matter decay rates (high C/N ratio, Table 1), but no significant difference in either CO2 fluxes or cumulative CO2 emission at the NF compared to the RF and OP (Figure 5a), suggests that root respiration contributed to CO2 emissions more than aerobic decomposition. ...
For agricultural purposes, the drainage and deforestation of Southeast Asian peatland resulted in high greenhouse gases’ (GHGs, e.g., CO2, N2O and CH4) emission. A peatland regenerating initiative, by rewetting and vegetation restoration, reflects evidence of subsequent forest recovery. In this study, we compared GHG emissions from three Malaysian tropical peatland systems under the following different land-use conditions: (i) drained oil palm plantation (OP), (ii) rewetting-restored forest (RF) and (iii) undrained natural forest (NF). Biweekly temporal measurements of CO2, CH4 and N2O fluxes were conducted using a closed-chamber method from July 2017 to December 2018, along with the continuous measurement of environmental variables and a one-time measurement of the soil physicochemical properties. The biweekly emission data were integrated to provide cumulative fluxes using the trapezoidal rule. Our results indicated that the changes in environmental conditions resulting from draining (OP) or rewetting historically drained peatland (RF) affected CH4 and N2O emissions more than CO2 emissions. The cumulative CH4 emission was significantly higher in the forested sites (RF and NF), which was linked to their significantly higher water table (WT) level (p < 0.05). Similarly, the high cumulative CO2 emission trends at the RF and OP sites indicated that the RF rewetting-restored peatland system continued to have high decomposition rates despite having a significantly higher WT than the OP (p < 0.05). The highest cumulative N2O emission at the drained-fertilized OP and rewetting-restored RF sites was linked to the available substrates for high decomposition (low C/N ratio) together with soil organic matter mineralization that provided inorganic nitrogen (N), enabling ideal conditions for microbial mediated N2O emissions. Overall, the measured peat properties did not vary significantly among the different land uses. However, the lower C/N ratio at the OP and the RF sites indicated higher decomposition rates in the drained and historically drained peat than the undrained natural peat (NF), which was associated with high cumulative CO2 and N2O emissions in our study.
... Aktivitas tersebut menyebabkan perubahan sifat fisik, kimia dan biologi seperti perubahan suhu dan ketersediaan oksigen yang akan meningkatkan aktivitas mikroorganisme dalam mendekomposisikan gambut. Beberapa penelitian mengungkapkan bahwa terdapat korelasi positif antara kedalaman muka air tanah dengan emisi CO 2 (Hirano et al. 2009;Couwenberg et al. 2010). Hasil ini menunjukkan perlunya kandungan air tanah yang tinggi untuk menghindari mineralisasi gambut dan degradasi tanah. ...
... -1 . Beberapa penelitian sebelumnya juga telah mengungkapkan bahwa terdapat korelasi positif antara tinggi muka air tanah dengan emisi CO 2 (Hirano et al. 2009;Couwenberg et al. 2010). ...
Capillary water in the peat has a very important role in supplying water to the root zone of plants. The purpose of this study is to see the relationship with the ground water level of CO 2 emissions from peat soils. This research was conducted in the greenhouse on Indonesian Swamp Land Agricultural Research Institute (ISARI) Banjarbaru, South Kalimantan. The design used in this study was a randomized block design of 2 factors with 3 replications. The first factor was bulk density of (BD), namely: 1) BD-1 (actual 0.1 g cm-3), 2) BD-2 (compressed to 0.2 g cm-3). The second factor is the water level (TMA) which simulated from the height of peat soil in the mica pipeline, namely: 1) TMA-1 (-100 cm), 2) TMA-2 (-70 cm), (3) TMA-3 (-40 cm). The results showed the highest CO 2 emissions was seen in the treatment TMA-1 with BD-2 amounted to 21.87 ton.ha-1 .month-1 and the lowest CO 2 emission was seen in the treatment of TMA-3 with BD-1 amounted to 3.69 ton.ha-1 .month-1. CO 2 emissions had pattern on TMA-2 and TMA-3 which the amount rise in the 1 st period and then decreased in the 2 nd period. The highest rise in capillary water reached up to 50 cm showed with the water content of 136.6% on a BD-1 and 126.9% on a BD-2.
... Total C content, BD, ash content, PSI, and CEC, which were greater in the MPS forest soil, than in the ABt and ABg forest soils (Table 4), were negatively correlated with soil CH 4 flux over the three forests (Table 5). These observations suggest that the amount and degree of decomposition/humification of SOM are among the important factors that determine soil CH 4 flux (Ler Mer and Roger, 2001;Couwenberg et al., 2010). The total Fe and SO 4 2contents in soil were also higher at the MPS than at the ABt and ABg forest sites (Table 4) and were negatively correlated (n = 288; P < 0.05) with CH 4 fluxes ( Table 5). ...
... DISCUSSION4.1 Characteristics of the environment in three forest types as potential factors that control soil CO 2 and CH 4 fluxesEnvironmental variables that were shown to significantly affect soil CO 2 and CH 4 fluxes included GWL, air or soil temperature, and RH. GWL had a negative correlation with soil CO 2 flux and a positive correlation with soil CH 4 flux(Table 5) as has been shown in previous studies(Jauhiainen et al., 2005;Couwenberg et al., 2010;Ishikura et al., 2019; Hoyos-Santillan et al., 2019). The enhanced aeration of soil under low GWL may have promoted the decomposition of soil organic matter (SOM) to CO 2 , while CH 4 production and CH 4 oxidation may have been inhibited and promoted, respectively. ...
Information on temporal and spatial variations in soil greenhouse gas (GHG) fluxes from tropical peat forests is essential to predict the influence of climate change and estimate the effects of land use on global warming and the carbon (C) cycle. To obtain such basic information, soil carbon dioxide (CO2) and methane (CH4) fluxes, together with soil physicochemical properties and environmental variables, were measured at three major forest types in the Maludam National Park, Sarawak, Malaysia, for eight years, and their relationships were analyzed. Annual soil CO2 fluxes ranged from 860 to 1450 g C m⁻2 yr⁻1 without overall significant differences between the three forest sites, while soil CH4 fluxes, 1.2–10.8 g C m⁻2 yr⁻1, differed. Differences in GHG fluxes between dry and rainy seasons were not necessarily significant, corresponding to the extent of seasonal variation in groundwater level (GWL). The lack of significant differences in soil CO2 fluxes between the three sites could be attributed to set-off between the negative and positive effects of the decomposability of soil organic matter as estimated by pyrophosphate solubility index (PSI) and GWL. The impact of El-Niño on annual CO2 flux also varied between the sites. The variation in soil CH4 fluxes from the three sites was enhanced by variations in temperature, GWL, PSI, and soil iron (Fe) content. A positive correlation was observed between the annual CH4 flux and GWL at only one site, and the influence of soil properties was more pronounced at the site with the lowest GWL and the highest PSI. Variation in annual CH4 fluxes was controlled more strongly by temperature where GWL was the highest and GWL and plant growth fluctuations were the least. Inter-annual variations in soil CO2 and CH4 fluxes confirmed the importance of long-term monitoring of these at multiple sites supporting different forest types.
... However, a range of other factors such as vegetation cover and prior fire disturbance also affect subsidence, although their effects are difficult to quantify. Couwenberg et al., (2009) in their survey of the literature found a linear relationship between subsidence rate and water depth for Southeast Asian tropical peat soils, with subsidence increasing by 0.9 cm a-1 for each 10 cm of additional drainage depth. This is substantially more than in other parts of the world (Hooijer et al., 2006;Couwenberg et al., 2009). ...
... Couwenberg et al., (2009) in their survey of the literature found a linear relationship between subsidence rate and water depth for Southeast Asian tropical peat soils, with subsidence increasing by 0.9 cm a-1 for each 10 cm of additional drainage depth. This is substantially more than in other parts of the world (Hooijer et al., 2006;Couwenberg et al., 2009). ...
Penelitian sebelumnya telah mengkonfirmasi bahwa upaya pengendalian kebakaran hutan dan lahan di Indonesia belum optimal sehingga kebakaran masih terjadi dengan tingkat eskalasi yang tinggi. Hal ini terjadi karena sangat sedikitnya hasil penelitian yang digunakan untuk memecahkan masalah kebakaran hutan dan lahan, sehingga informasi yang bermanfaat menjadi tidak berguna. Kegiatan penelitian terus berlanjut, yang tidak hanya mencakup masalah teknis pengendalian kebakaran hutan dan lahan tetapi juga implikasi negatif yang ditimbulkannya, yaitu produksi emisi GRK khususnya di lahan gambut karena merupakan salah satu sumber utama emisi GRK yang signifikan. Yang juga tidak kalah pentingnya adalah prosedur penghitungan emisi GRK, yang berdasarkan penelitian ini justru menghasilkan estimasi emisi yang terlalu tinggi dari yang seharusnya dihasilkan. Tentu hal ini perlu diluruskan agar Indonesia tidak dirugikan hanya karena mengikuti perhitungan yang tidak tepat.Kata kunci: Gas rumah kaca, kebakaran hutan dan lahan, penelitian, gambut, pengendalian kebakaran
... In addition to its direct effect on microbial processes and activities, a lower water table exerts cascading (and potentially long-lasting) effects that lead to substantial CO 2 losses, as observed in our analysis. Long-term tropical peat subsidence is estimated to result in losses of CO 2 ranging from 2.5-11 megagrams of C per hectare per year (Mg C ha -1 yr -1 ) (Couwenberg et al. 2010). The substantial C loss resulting from conversion of tropical peatland highlights the urgency of developing mitigation strategies to minimize further loss. ...
... To avoid the rapid loss of C through the breakdown of organics and encroachment by fire, the natural hydrology should be restored (Ojanen and Minkkinen 2020). This is evidenced by the reduction in soil CO 2 emissions observed in our study under raised water tables (Figure 4), as was also noted by Couwenberg et al. (2010). Raising the water table reverts aerobic conditions back to anaerobic conditions, a process that avoids the negative consequences of drainage on CO 2 loss via rapid decomposition, drying, and burning of peat. ...
Conversion of tropical peat swamp forests to meet the demand for industrial plantations and agricultural production systems has triggered rapid and substantial carbon loss in the Asia‐Pacific region. Various management practices have been designed to reduce carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions from tropical peat soils after changes in land use. We conducted a meta‐analysis using 506 paired observations on greenhouse‐gas (GHG) emissions from peat soils under different land uses and the effects of management practices on emissions. As compared to peat swamp forest, other land uses had higher emissions of CO2 (heterotrophic respiration) and N2O from soils, whereas soil‐based CH4 emissions were also increased but not significantly so. Raising the water table decreased CO2 emissions but increased N2O emissions; reducing nitrogen fertilizer inputs led to decreased CO2 and N2O emissions in oil‐palm (Elaeis spp) plantations and cropping systems; and shading and growing cover crops decreased CO2 emissions. Practices such as these are needed for careful management of tropical peatlands, and additional measurements at appropriate spatial and temporal scales are required to guide future GHG mitigation strategies in tropical peatlands.
... It is well known from previous studies that the GWL is a significant factor in controlling carbon emissions from peat soil [72,73]. A deeper GWL from the peat surface creates a larger aerobic zone, increasing the aerobic microbial activities and soil respiration. ...
... In February 2019, the chambers at the rewetted and undrained sites were mainly inundated, with an average GWL of around 10 cm above the peat surface. This condition, a GWL of around 10 cm, has been demonstrated to create hotspots of CH 4 emissions, which can be nearly 10 times greater compared with the dry season [32,72,73]. In the flooded condition, the number of aerobic microbes is decreased, but the number of anaerobic microbes is increased. ...
Degraded and drained peat swamp forests (PSFs) are major sources of carbon emissions in the forestry sector. Rewetting interventions aim to reduce carbon loss and to enhance the carbon stock. However, studies of rewetting interventions in tropical PSFs are still limited. This study examined the effect of rewetting interventions on carbon dynamics at a rewetted site and an undrained site. We measured aboveground carbon (AGC), belowground carbon (BGC), litterfall, heterotrophic components of soil respiration (Rh), methane emissions (CH4), and dissolved organic carbon (DOC) concentration at both sites. We found that the total carbon stock at the rewetted site was slightly lower than at the undrained site (1886.73 ± 87.69 and 2106.23 ± 214.33 Mg C ha−1, respectively). The soil organic carbon (SOC) was 1685 ± 61 Mg C ha−1 and 1912 ± 190 Mg C ha−1 at the rewetted and undrained sites, respectively, and the carbon from litterfall was 4.68 ± 0.30 and 3.92 ± 0.34 Mg C ha−1 year−1, respectively. The annual average Rh was 4.06 ± 0.02 Mg C ha−1 year−1 at the rewetted site and was 3.96 ± 0.16 Mg C ha−1 year−1 at the undrained site. In contrast, the annual average CH4 emissions were −0.0015 ± 0.00 Mg C ha−1 year−1 at the rewetted site and 0.056 ± 0.000 Mg C ha−1 year−1 at the undrained site. In the rewetted condition, carbon from litter may become stable over a longer period. Consequently, carbon loss and gain mainly depend on the magnitude of peat decomposition (Rh) and CH4 emissions.
... pH, availability of terminal electron acceptors and nutrient levels), and vegetation type. Peat surface CO 2 emissions generally increase with increasingly aerobic conditions associated with low water tables, whilst CH 4 emissions increase with increasingly anaerobic conditions under high water tables (Couwenberg et al., 2010). N 2 O on the other hand shows a nonlinear relationship with soil moisture content (Couwenberg et al., 2010). ...
... Peat surface CO 2 emissions generally increase with increasingly aerobic conditions associated with low water tables, whilst CH 4 emissions increase with increasingly anaerobic conditions under high water tables (Couwenberg et al., 2010). N 2 O on the other hand shows a nonlinear relationship with soil moisture content (Couwenberg et al., 2010). Increases in soil temperature, occurring in response to climate warming and increased exposure to solar radiation through deforestation and degradation of tropical peatlands, can drive feedbacks that drastically increase CO 2 and CH 4 emissions, although we hypothesise the tropical peat swamp forest is likely to remain a net carbon sink in the absence of other dis- Table I. ...
The Cuvette Centrale is the largest tropical peatland complex in the world, covering approximately 145,000 km2 across the Republic of Congo and the Democratic Republic of Congo. It stores ca. 30.6 Pg C, the equivalent of three years of global carbon dioxide emis- sions and is now the first trans-natio- nal Ramsar site. Despite its size and importance as a global carbon store, relatively little is known about key aspects of its ecology and history, including its formation, the scale of greenhouse gas flows, its biodiversity and its history of human activity. Here, we synthesise available knowledge on the Cuvette Centrale, identifying key areas for further research. Finally, we review the potential of mathematical models to assess future trajectories for the peatlands in terms of the potential impacts of resource extraction or climate change.
... These fragile and unique ecosystems have vital roles for human life with various ecological, economic, and socio-cultural benefits. On the global scale, tropical peat swamp forests are highly concerned because of their high carbon stock inside (Ahirwal et al., 2021;Kimmel & Mander, 2010;Osaki & Tsuji, 2015), which means that they are associated with global carbon emissions, forest fires, and air pollution (Couwenberg, 2010;Hooijer et al., 2012;Murdiyarso et al., 2019). These ecosystems also have high biodiversity values , such as various species that are endemic, rare, and endangered (Posa et al., 2011;Symes et al., 2018;Yule, 2010), as well as a source of livelihood for local people (Chokkalingam et al., 2005;Silvius & Diemont, 2007;Taufik et al., 2019) Central Kalimantan, Indonesia, is where most tropical peat swamp forests can be found S. E. Page et al., 2007). ...
... However, these unique and priceless ecosystems have been experiencing deforestation and degradation for various reasons until now. One of the causes of degradation and deforestation in peat forests is fire (Couwenberg, 2010;Dohong, 2016;Lestari et al., 2021;Pindilli et al., 2018). These forest fires are always accompanied by other impacts, such as converting peatlands into plantation and agricultural areas and the drought (Cole et al., 2021;Hooijer et al., 2010;Jauhiainen et al., 2014;Uda et al., 2020) Degradation and deforestation of peat swamp forest due to fires caused a lot of neglected peat swamp forest. ...
The massive forest fire disasters have left an enormous area of degraded peatland. This study aims to analyze the performance of two species, namely C. arborescens and C. rotundatus, as the natural regeneration post forest fires. This research was conducted in 5 different locations that experienced severe fires in 2006. We made a total of 25 plots for each location to measure biodiversity at four growth levels. We analyzed the data with vegetation analysis formulas from Magurran. The results show that at the tree growth level, C. rotundatus can withstand the fires in 2006 and is currently still growing in more significant numbers than C. arborescens. At the pole, sapling, and seedling growth levels, these species perform well as natural regeneration species with many individuals, but C. arborescens is a bit more dominant. Both species are suitable for natural regeneration after fires in degraded peat swamp forests based on survived and existing individuals. On the other hand, both species could not improve the vegetation diversity in the whole ecosystem. These two species can be the option for natural regeneration if there a limited budget and the degraded areas are in a very remote location.
... Peatlands have been drained mainly for large-scale monoculture of palm oil and pulp plantations . Peatland drainage has led to major carbon emissions (Hirano et al. 2012;Hooijer et al. 2012;Jauhiainen et al. 2012;Wakhid et al. 2017;Marwanto et al. 2019), with an estimated increase of 900 g CO 2 m À2 a À1 for every 10 cm of drainage depth (Couwenberg et al. 2010), and thus exacerbating global climate change (Warren et al. 2017). Peatland drainage also poses a high risk of wildfire (Wösten et al. 2008;Cattau et al. 2016;Taufik et al. 2018). ...
... In natural conditions, the water table in peatlands lies close to the surface but may drop to À0.3 m from the surface in the dry season (Hooijer 2005;Cobb & Harvey 2019) or even deeper during extreme conditions such as El Niño (Wösten et al. 2008). Lowering the water table results in carbon emissions (Couwenberg et al. 2010;Hooijer et al. 2012;Wakhid et al. 2017), with strong empirical evidence of a relationship between water table and carbon emissions (Hirano et al. 2012;Mezbahuddin et al. 2014;Carlson et al. 2015). Restoration of degraded peatlands aims to raise the water table to a level closer to that prevailing in natural conditions (Jauhiainen et al. 2008;Jaenicke 2010;Ritzema et al. 2014;Dohong et al. 2018;Urzainki et al. 2020). ...
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. HIGHLIGHTS
High spatial and temporal variability of water table was observed in Padang Island.;
The variability was partially driven by variation in land use and farm drainages.;
Recession rate near pulp plantations remained high (0.01 m/day) at −1.5 m depth.;
... Methane generated in tropical peatlands can escape through several pathways: (a) Diffusion of methane from the peat surface has been widely described in the literature (e.g., Deshmukh et al., 2020;Hirano et al., 2009;Melling et al., 2005). This flux is typically small relative to temperate and northern peatlands and is often negative, indicating a slight uptake of methane by the surface peat (Couwenberg et al., 2010). (b) Ebullition can carry methane to the peat surface producing large and sporadic surface fluxes, if dissolved gas concentrations are sufficiently high (Teh et al., 2017). ...
Most peat domes in Southeast Asia are crisscrossed by networks of drainage canals. These canals are a potentially important source of methane to the atmosphere because the groundwater that discharges into them carries high concentrations of dissolved methane that is produced within peat. In this study, we present an isotope‐enabled numerical model that simulates transport, degassing, and oxidation of methane and dissolved inorganic carbon (DIC) along a drainage canal. We then estimate methane fluxes through a 5‐km canal that crosses a disturbed, forested, but undeveloped, peat dome in Brunei Darussalam by applying this model to field data: concentrations and stable carbon isotopic ratios of both methane and dissolved inorganic carbon from both peat porewater and canal water. We estimate that approximately 70% of the methane entering the canal is oxidized within the canal, 26% is degassed to the atmosphere, and 4% is transported toward the ocean, under low to moderate flow conditions. The flux of methane to the atmosphere is lowest at the maximum elevation of the canal, where flow is stagnant and methane concentrations are highest. Downstream, as flow velocity increases, methane emissions plateau even as methane concentrations decrease. The resulting methane emissions from the canal are large compared to emissions from the peat surface and vegetation on a per‐area basis. However, since the canal covers only a small portion of the catchment area, the canal may be a substantial but not dominant source of methane from the peatland.
... A recent meta-analytical study has shown that the lowering of the groundwater table associated with the creation of drainage channels promotes increased N 2 O emission from soil surface (Prananto et al., 2020). At present, however, there are still limited number of studies on N 2 O emissions in oil palm plantations in southeast Asia (e.g., Couwenberg et al., 2010;Melling and Henson, 2011;van Lent et al., 2015;Oktarita et al., 2017;Cooper et al., 2020), with fewer on indirect N 2 O emissions. Observations of N 2 O dynamics related to peat drainage ditches, not only in the tropics, are lacking compared to studies of CO 2 and CH 4 (Hyvönen et al., 2013;Evans et al., 2016). ...
Oil palm plantations in Southeast Asia are the largest supplier of palm oil products and have been rapidly expanding in the last three decades even in peat-swamp areas. Oil palm plantations on peat ecosystems have a unique water management system that lowers the water table and, thus, may yield indirect N2O emissions from the peat drainage system. We conducted two seasons of spatial monitoring for the dissolved N2O concentrations in the drainage and adjacent rivers of palm oil plantations on peat swamps in Sarawak, Malaysia, to evaluate the magnitude of indirect N2O emissions from this ecosystem. In both the dry and wet seasons, the mean and median dissolved N2O concentrations exhibited over-saturation in the drainage water, i.e., the oil palm plantation drainage may be a source of N2O to the atmosphere. In the wet season, the spatial distribution of dissolved N2O showed bimodal peaks in both the unsaturated and over-saturated concentrations. The bulk δ15N of dissolved N2O was higher than the source of inorganic N in the oil palm plantation (i.e., N fertilizer and soil organic nitrogen) during both seasons. An isotopocule analysis of the dissolved N2O suggested that denitrification was a major source of N2O, followed by N2O reduction processes that occurred in the drainage water. The δ15N and site preference mapping analysis in dissolved N2O revealed that a significant proportion of the N2O produced in peat and drainage is reduced to N2 before being released into the atmosphere.
... tons ha −1 year −1 . The annual average value of CO 2 emissions in this study of 33.82 ± 6.98 tons ha −1 year −1 . It could be influenced by the groundwater depth which significantly increases emissions of CO 2(Fig. 4A). A similar result has been reported byIshikura et al., (2017) that the decrease in groundwater depth increases the value of CO 2 .Couwenberg et al., (2010);Ishikura et al., (2018) added that the groundwater depth is the main controlling factor of CH 4 emissions, an increase in CH 4 emissions significantly at the groundwater depth above 20 cm. Furthermore,Handayani et al., ...
... In some cases, the relationship between water table depth and CO 2 emissions is not linear (e.g. Tiemeyer et al., 2020;Couwenberg et al., 2010). In dry summers, the mineralization of peat in the upper layer may be limited by soil moisture (Glatzel et al., 2006;Hahn-Schöfl et al., 2011;Tiemeyer et al., 2016). ...
Organic soils of intact peatlands store 1/4 of the global soil organic carbon (SOC). Despite being an important source of methane (CH4), they are climate coolers because they continuously accumulate new organic carbon. However, when these organic soils are drained for agriculture, the resulting aerobic conditions lead to fast decomposition of the peat and the release of carbon dioxide (CO2) and nitrous oxide (N2O), turning them into net greenhouse gas (GHG) sources. Reducing the environmental footprint of managing these soils requires a good understanding of the processes during drainage of formerly anoxic soil horizons and eventual subsequent rewetting. We describe changes in soil properties and carbon dynamics following drainage of peatlands and discuss management strategies to reduce carbon loss from drained peatlands by raising the water table to either restore the peatland ecosystem, or to cultivate water-tolerant crops. In addition to rewetting, engineering approaches with continuous management at deeper water tables are evaluated in terms of SOC loss.
... Although wetlands cover a small percentage of the land surface, they have a great influence on the dynamics and cycles of CO 2 and N 2 O in nature [5,6]. Therefore, strengthening Studies that have been conducted on CO 2 and N 2 O fluxes from natural wetlands worldwide [5,7,8], including estuarine tidal marshes with varying salinity [6], temperate and tropical wetlands [9], and boreal and subarctic wetlands [10], indicate that CO 2 flux was higher during the warm growing season because of high temperatures and high aboveground biomass. The spatio-temporal CO 2 and N 2 O fluxes varied obviously within one wetland and among different wetlands [11,12]. ...
Plants regulate greenhouse gas (GHG) fluxes in wetland ecosystems, but the mechanisms of plant removal and plant species that contribute to GHG emissions remain unclear. In this study, the fluxes of carbon dioxide (CO2) and nitrous oxide (N2O) were measured using the static chamber method from an island forest dominated by two different species, namely Betula platyphylla (BP) and Larix gmelinii (LG), in a marsh wetland in the Great Xing’an Mountains. Four sub-plots were established in this study: (1) bare soil after removing vegetation under BP (SBP); (2) bare soil after removing vegetation under LG (SLG); (3) soil with vegetation under BP (VSBP); and (4) soil with vegetation under LG (VSLG). Additionally, the contributions of the dark respiration from plant aerial parts under BP (VBP) and LG (VLG) to GHG fluxes were calculated. We found that the substantial spatial variability of CO2 fluxes ranged from −25.32 ± 15.45 to 187.20 ± 74.76 mg m−2 h−1 during the study period. The CO2 fluxes decreased in the order of SBP > VSLG > VSBP > SLG > VLG > VBP, indicating that vegetation species had a great impact on CO2 emissions. Particularly, the absence of vegetation promoted CO2 emission in both BP and LG. Additionally, CO2 fluxes showed dramatically seasonal variations, with high CO2 fluxes in late spring (May) and summer (June, July, and August), but low fluxes in late summer (August) and early autumn (September). Soil temperatures at 0–20 cm depth were better predictors of CO2 fluxes than deeper soil temperatures. N2O fluxes were varied in different treatments with the highest N2O fluxes in SLG and the lowest N2O fluxes in VBP. Meanwhile, no significant correlation was found between N2O fluxes and air or soil temperatures. Temporally, negative N2O fluxes were observed from June to October, indicating that soil N2O fluxes were reduced and emitted as N2, which was the terminal step of the microbial
denitrification process. Most of the study sites were CO2 sources during the warm season and CO2 sinks in the cold season. Thus, soil temperature plays an important role in CO2 fluxes. We also found
that the CO2 flux was positively related to pH in a 10 cm soil layer and positively related to moisture content (MC) in a 50 cm soil layer in VSBP and VSLG. However, the CO2 flux was negatively related
to pH in a 30 cm soil layer in SBP and SLG. Our findings highlight the effects of vegetation removal on GHG fluxes, and aid in the scientific management of wetland plants.
... Estimation of carbon emissions based on subsidence according to Wösten et al. (1997), assuming no fires occur, contributes to 60% of subsidence value while compaction is 40%. In contrast, Couwenberg et al. (2010) reported that the peat decomposition Various factors affect the rate of peat decomposition, which affects the rate of emission too. Emission rates can be different depending on peat maturity classified based on the stage of decomposition, fertilization, and the influence of plant root respiration. ...
Peatlands are one of the important parameters to determine environmental quality because peatlands can store carbon stocks in their biomass. Based on the official page pantaugambut.id, Kalimantan Island is the second largest area that has peatlands. Land subsidence (subsidence) on peatland is one of the physical environmental impacts due to the shrinking volume of peat due to the drought process at a certain level in peatland processing, but also due to the decomposition process, erosion, and peat fires. This subsidence phenomenon will be measured using the InSAR technique, which is one of the existing methods in active remote sensing technology to measure changes in the earth's surface which is calculated based on changes in the phase difference between two SAR image acquisitions. Our research used the time series InSAR technique with the incorporation of Persistent Scatterer (PS) and small baseline approach to accurately calculate the value of soil subsidence rate to the cm-mm level. Furthermore, the estimation of CO 2 emission was calculated from the carbon parameters observed by the in-situ measurement, the affected peatland area, and its subsidence obtained by satellite remote sensing. We found that the highest CO 2 emission was located in the southern part of the study area. Since years ago, the region has been affected by deforestation and land expansion due to the need for fiscal revenues from palm oil and urbanization.
... The emissions described in this study are slightly lower than those reported in degraded mangrove forests and salt marshes. Degraded mangrove forests emissions average around 1-2 μmol CO 2 m −2 s −1 , showing punctual peaks up to 20 μmol CO 2 m −2 s −1 right after disturbance events that returned to base levels after 2 days (Burford & Longmore, 2001;Couwenberg et al., 2009;Lovelock et al., 2011). Average emissions from salt marshes are even larger, between 2 and 2.6 μmol CO 2 m −2 s −1 , also experiencing prominent summer peaks linked to temperature rises Dausse et al., 2012;Ford et al., 2012). ...
Posidonia oceanica beds are recognized to be an essential carbon sink in the Mediterranean Sea. However, when seagrass cover disappears, seagrass sediments may become net carbon sources contributing to the CO2 atmospheric increase. Determining CO2 efflux from degraded seagrass beds is required to understand potential emissions from this Mediterranean ecosystem. This study presents one of the very first experimental CO2 efflux estimates from P. oceanica degraded seagrass sediments under future warming and hydrodynamic scenarios. Sediments were sampled from a P. oceanica seagrass meadow in Pollença, a sheltered bay on Mallorca Island. Sediment samples were kept in mesocosms for 98 days at five different temperatures (26, 27.5, 29, 30.5, and 32) and two treatments (agitation/repose). CO2 effluxes were higher in the agitated treatments (0.75 μM m⁻² s⁻¹) than in repose (0.51 μM m⁻² s⁻¹). CO2 efflux clearly increased with temperature in repose treatments, while treatments under agitation presented larger variation. Our results indicate that exposure to hydrodynamics plays a key role in the remineralization of organic carbon (Corg) under climate change conditions and that denuded seagrass meadows have the potential to emit in a single summer season (3 months) the amount of carbon (C) that a healthy meadow sequestrates during an entire year. This study provides brand new information required to quantify the dynamics of Corg stock loss and CO2 emissions in degraded seagrass meadows.
... Tropical peatlands occur in South and Southeast Asia, Central and South America, and Central Africa (Pfadenhauer, 1990;Lappalainen, 1996). Apart from their essential role in the global biodiversity, they are significant carbon sinks, hence playing a critical role in balancing the budget of atmospheric CO 2 and other greenhouse gasses via their respiration and/ or degassing (Chimner, 2004;Couwenberg et al., 2010;Leng et al., 2019;Treat et al., 2019;Waldron et al., 2019; and references therein). Inaccessibility, due to dense jungles, meant that the tropical peatlands were discovered and explored much later than the boreal ones (Shier, 1985). ...
Peatlands are important carbon sinks, therefore their degradation mainly due to lowering of the water table, has an adverse effect to the carbon cycle and largely burden the atmosphere. Annually, extensive areas of these peatlands are affected by wildfires, therefore large peatland areas have been degraded, directly or indirectly related to anthropogenic activities, largely contributing to greenhouse gas emissions. Some of the most pristine tropical peatlands worldwide occur primarily at the coastal lowlands of Southeast Asia. In terms of their geological features and evolution, these sites are generally understudied despite covering more than half of the global area of tropical peatlands. This review compiles geological data from 52 peatlands from insular and continental Southeast Asia, providing a comprehensive geological dataset for future research. The Southeast Asian peatlands are mostly ombrogenous and hence poorly supplied by nutrients. During the Last Glacial Period (ca. 115,000–11,000 years ago), extensive areas were exposed because of the lowering of the seawater level, which caused a consequent lowering of the groundwater table landwards; the forests were under severe threat, mainly due to dry conditions, thus resulting in the retreat of the forest boundaries inland. This was an unfavourable environment for peatland formation and hence, most of the Southeast Asian peatlands were formed right after that period. Almost 40% of the reviewed sites are located on Borneo Island, highlighting the importance of Bornean peatlands, where many peatlands are already deforested and drained and converted to plantations. Overall, the available geological data from the Southeast Asian peatlands is incomplete and non-comparable to each other because each study has a different focus. Details, such as the type of peat-forming plants, age of peat, peat thickness, substrate type and the pH value are not reported systematically in approximately 30% of the reviewed sites, while other important geological data, such as the ash yield and the carbon content of peat are only reported in 30% and 10% of the reviewed sites, respectively. Characterisation of peatlands using data imputation and principal component analysis (PCA) is based on three physical parameters (maximum ash yield, maximum thickness and oldest age), and includes the study of their relation in terms of climatic periods, peatland type, region and substrate. It is observed that peatlands which were developed in warming periods share similar physical parameters (such as accumulation rates, ash yield, peatland type, and environment of the substrates). With better data reporting on these parameters, the PCA analysis can provide a more accurate reflection of peatland characteristics and their relationships. The study aims to raise awareness on the importance and vulnerability of the Southeast Asian peatlands and to highlight their role in the global climate fluctuations.
... The most important requirement for the preservation of peat is permanent saturation by water (Page et al. 2009, Evers et al. 2017, and to curb peat loss in peatlands affected by drainage it is essential that peat is rewetted and peat hydrology is restored to near-natural conditions. The relationship between groundwater levels and emissions is relatively well understood, and as mentioned earlier Couwenberg et al. (2010) found a relationship for converted peatland of 2.45 tC/ha. yr12 per 10 cm of drainage. ...
Kebakaran hutan dan lahan, tidak hanya di Indonesia tetapi juga di belahan dunia lain, sebenarnya telah menimbulkan dampak negatif yang luar biasa. Menimbulkan dampak negatif terhadap lingkungan (asap, kabut), sosial, pendidikan, kesehatan, flora dan fauna, kehidupan bernegara, dan sebagainya yang bersumber dari sebagian besar aktivitas manusia, yang berdampak pada perubahan iklim global. Dampak negatif kebakaran hutan dan lahan harus dikendalikan melalui pengendalian kebakaran hutan dan lahan yang serius dan sistematis serta didukung oleh kemauan politik pemerintah. Perlu dipahami bahwa kegiatan pengendalian kebakaran hutan dan lahan harus didasarkan pada fakta lapangan yang diperoleh dari hasil penelitian dan bukan berdasarkan hasil fiktif atau perkiraan sementara. Upaya penelitian juga dapat diharapkan melalui kerjasama regional dan internasional. Kata kunci: Hutan, kebakaran, penelitian, perubahan iklim, kolaborasi
... Peatland drainage contributes 1.3 to 3.1% of current global CO2 emissions from the burning of fossil fuels, according to study by Hooijer et al. (2010) and Couwenberg et al. (2010) in Southeast Asia, and peatland rewetting might significantly reduce net GHG emissions (AR5). ...
Based on the available evidence and studies, freshwater resources can be intensely affected by climate change, with extensive consequences for human communities and ecosystems. Climate change has immediate and long-term effects on water resources such as floods, droughts, rising sea levels in estuaries, drying up of rivers, poor water quality in surface and groundwater systems, distortions of water vapor and precipitation patterns, improper distribution Ice is snow and earth and the amount of access and demand for water resources.
... Peatland drainage contributes 1.3 to 3.1% of current global CO 2 emissions from the burning of fossil fuels, according to study by Hooijer et al. (2010) and Couwenberg et al. (2010) in Southeast Asia, and peatland rewetting might significantly reduce net GHG emissions (AR5). ...
Hydrological modelling can be characterized as the process of abstracting real hydrological features through small-scale physical models, mathematical analogs, or computer simulations. Hydrologic models can be separated into several classes according to model structures and spatial processes. In this chapter, after a discussion about the history of these models, a concise glance at the impacts of clime change is examined. Finally, in the last part, the structure of some recognized hydrological models is explained.
... A plethora of studies is available that have examined the role of the agricultural sector as a determinant of environmental quality in various economies. Couwenberg et al. (2010) analyzed the influence of peat soil, rice paddy, and fertilizers on the ecological quality of the countries of Southeast Asia by employing meta-analysis. Their findings confirmed that peatland rewetting upsurged methane and carbon discharges. ...
The study investigates the symmetric and asymmetric impact of agriculturalization on CO2 emissions in a sample of selected Asian economies for time period 1985 to 2019. For empirical analysis, the study adopted panel linear and nonlinear autoregressive distributed lag (ARDL) approaches. The long-run findings of panel ARDL reveal that agriculturalization contributes to environmental quality by mitigating CO2 emissions. The panel nonlinear results clearly indicate that the effects of agriculturalization on CO2 emissions are asymmetric. The findings demonstrate that agriculturalization improves environmental quality and de-agriculturalization mitigates environmental quality. Our empirical results are also robust to alternative model specifications. Based on these findings, the study recommends that the relevant authorities should formulate reforms in the agriculture sector that controls and reduces carbon emissions in Asian economies.
... 110 ). There is a robust correlation between long-term water-table depth and Rh emissions [110][111][112][113][114] , as well as time since conversion 104 . For an annual average water-table depth of -0.70 m (representative of drainage depths in many agricultural peatlands), an Rh value of 17 ± 3 t CO 2 -C ha -1 yr -1 , based on a modelled relationship between water table and C loss, has been proposed 110 . ...
Tropical peatlands store around one-sixth of the global peatland carbon pool (105 gigatonnes), equivalent to 30% of the carbon held in rainforest vegetation. Deforestation, drainage, fire and conversion to agricultural land threaten these ecosystems and their role in carbon sequestration. In this Review, we discuss the biogeochemistry of tropical peatlands and the impacts of ongoing anthropogenic modifications. Extensive peatlands are found in Southeast Asia, the Congo Basin and Amazonia, but their total global area remains unknown owing to inadequate data. Anthropogenic transformations result in high carbon loss and reduced carbon storage, increased greenhouse gas emissions, loss of hydrological integrity and peat subsidence accompanied by an enhanced risk of flooding. Moreover, the resulting nutrient storage and cycling changes necessitate fertilizer inputs to sustain crop production, further disturbing the ecosystem and increasing greenhouse gas emissions. Under a warming climate, these impacts are likely to intensify, with both disturbed and intact peat swamps at risk of losing 20% of current carbon stocks by 2100. Improved measurement and observation of carbon pools and fluxes, along with process-based biogeochemical knowledge, is needed to support management strategies, protect tropical peatland carbon stocks and mitigate greenhouse gas emissions. Tropical peatlands hold around 105 gigatonnes of carbon but are increasingly affected by anthropogenic activities. This Review describes the biogeochemistry of these systems and how deforestation, fire, drainage and agriculture are disturbing them. Tropical peatlands are important in terms of the global carbon cycle and in efforts to combat climate change, with a growing recognition of their potential role in natural climate solutions.Tropical peatlands occupy approximately 440,000 km2 across Southeast Asia, Central Africa and South and Central America, and are mostly forested. They are among the world’s most carbon-dense ecosystems with a belowground carbon stock of about 105 gigatonnes (Gt).Although tropical peatlands in Africa and in South and Central America remain largely intact, those in Southeast Asia have undergone widespread transformations owing to deforestation, drainage and agricultural conversion.Land-use changes result in rapid peat carbon loss, high greenhouse gas emissions, land subsidence, changes in hydrology and nutrient cycling, and an increased risk of fire.Management priorities include protection of the carbon sink function of intact forested peatlands; restoration of degraded, forested peatlands; and improved management of agricultural peatlands by raising water levels to mitigate carbon losses and greenhouse gas emissions.The response of tropical peatlands and their carbon stocks to anthropogenic warming and associated changes in hydroclimate remain an area of uncertainty. Tropical peatlands are important in terms of the global carbon cycle and in efforts to combat climate change, with a growing recognition of their potential role in natural climate solutions. Tropical peatlands occupy approximately 440,000 km2 across Southeast Asia, Central Africa and South and Central America, and are mostly forested. They are among the world’s most carbon-dense ecosystems with a belowground carbon stock of about 105 gigatonnes (Gt). Although tropical peatlands in Africa and in South and Central America remain largely intact, those in Southeast Asia have undergone widespread transformations owing to deforestation, drainage and agricultural conversion. Land-use changes result in rapid peat carbon loss, high greenhouse gas emissions, land subsidence, changes in hydrology and nutrient cycling, and an increased risk of fire. Management priorities include protection of the carbon sink function of intact forested peatlands; restoration of degraded, forested peatlands; and improved management of agricultural peatlands by raising water levels to mitigate carbon losses and greenhouse gas emissions. The response of tropical peatlands and their carbon stocks to anthropogenic warming and associated changes in hydroclimate remain an area of uncertainty.
... As a result of peat drainage, the water table declines exposing the peat to the atmosphere. This drainage introduces the peat to an aerobic environment by increasing oxygen levels, triggering peat decomposition (Couwenberg et al. 2010, Hooijer et al. 2012, Page & Hooijer 2016, Miettinen et al. 2017. Decomposition causes carbon to be released into the atmosphere as carbon dioxide , Carlson et al. 2015. ...
Tropical peatlands in Southeast Asia are a significant carbon sink, but are under major threat of fire resulting in significant carbon emissions. This study focused on the residual ash method, which has not been applied before for a tropical peatland, to determine the amount of carbon lost due to fire along two transects. To evaluate the method in a tropical peatland, we sampled peat cores to a depth of 150 cm along two transects in a drainage-affected peatland in Brunei Darussalam and analysed Landsat images to determine burn count at individual sampling locations between 1988 and 2020. The ash residue method indicated that the carbon release from the two transects was 3.61 ± 1.08 kg m-2 and 3.77 ± 0.80 kg m-2 respectively due to peat decomposition and fire. However, our results show that although some locations burned up to five times, the expected ash content (of at least 4 %) was not found in the surface peat. Therefore, the majority of the resulting ash from these fires must have been transported out of the peatland, possibly in smoke or washed away via ground and surface water transport. We conclude that the residual ash method to determine carbon loss is not a reliable method to determine carbon loss in degraded tropical peatlands.
... In RA, CH4 release increased from −0.10 ± 6.46 to 8.02 ± 3.28 mg m −2 h −1 (p > 0.05); in OP, it increased from 0.34 ± 3.06 to 5.36 ± 8.67 mg m −2 h −1 (p > 0.05); and in RP, it increased from −0.19 ± 3.82 to 3.47 ± 7.93 mg m −2 h −1 (p > 0.05). These relatively low emissions were confirmed by a large body of literature from the tropics, which conclude an average CH4 release rate around 3 mg m −2 h −1 [33]. Table 2. CH4 and N2O fluxes in reforested area (RA), oil palm (OP), and rubber plantation (RP) before and after rewetting (mean ± SE; n = 4). ...
Draining deforested tropical peat swamp forests (PSFs) converts greenhouse gas (GHG) sinks to sources and increases the likelihood of fire hazards. Rewetting deforested and drained PSFs before revegetation is expected to reverse this outcome. This study aims to quantify the GHG emissions of deforested PSFs that have been (a) reforested, (b) converted into oil palm, or (c) replanted with rubber. Before rewetting, heterotrophic soil respiration in reforested, oil palm, and rubber plantation areas were 48.91 ± 4.75 Mg CO2 ha −1 yr −1 , 54.98 ± 1.53 Mg CO2 ha −1 yr −1 , and 67.67 ± 2.13 Mg CO2 ha −1 yr −1 , respectively. After rewetting, this decreased substantially by 21%, 36%, and 39%. Conversely, rewetting drained landscapes that used to be methane (CH4) sinks converted them into CH4 sources; almost twice as much methane was emitted after rewetting. Nitrous oxide (N2O) emissions tended to decrease; in nitrogen-rich rubber plantations, N2O emissions halved; in nitrogen-poor reforested areas, emissions reduced by up to a quarter after rewetting. Overall, rewetting reduced the net emissions up to 15.41 Mg CO2-eq ha −1 yr −1 (25%) in reforested, 18.36 Mg CO2-eq ha −1 yr −1 (18%) in oil palm, and 28.87 Mg CO2-eq ha −1 yr −1 (17%) in rubber plantation areas.
... In particular for the SE Asian peatlands, it is constrained by the regional hydrological balance (Dommain et al., 2011(Dommain et al., , 2014. Peatlands are also vulnerable to climatic change for they are generally sensitive to changes in precipitation and temperature (Couwenberg et al., 2010;Page et al., 2011) and quantitative research has been developed and widely used to predict the future responses of peatland toward global change (e.g., Cobb et al., 2017;Hoyt et al., 2020;Whittle & Gallego-Sala, 2016). ...
Southeast Asian peatlands, along with their various important ecosystem services, are mainly distributed in the coastal areas of Sumatra and Borneo. These ecosystems are threatened by coastal development, global warming and sea level rise (SLR). Despite receiving growing attention for their biodiversity and as massive carbon stores, there is still a lack of knowledge on how they initiated and evolved over time, and how they responded to past environmental change, that is, precipitation, sea level and early anthropogenic activities. To improve our understanding thereof, we conducted multi‐proxy paleoecological studies in the Kampar Peninsula and Katingan peatlands in the coastal area of Riau and Central Kalimantan, Indonesia. The results indicate that the initiation timing and environment of both peatlands are very distinct, suggesting that peat could form under various vegetation as soon as there is sufficient moisture to limit organic matter decomposition. The past dynamics of both peatlands were mainly attributable to natural drivers, while anthropogenic activities were hardly relevant. Changes in precipitation and sea level led to shifts in peat swamp forest vegetation, peat accumulation rates and fire regimes at both sites. We infer that the simultaneous occurrence of El Niño‐Southern Oscillation (ENSO) events and SLR resulted in synergistic effects which led to the occurrence of severe fires in a pristine coastal peatland ecosystem; however, it did not interrupt peat accretion. In the future, SLR, combined with the projected increase in frequency and intensity of ENSO, can potentially amplify the negative effects of anthropogenic peatland fires. This prospectively stimulates massive carbon release, thus could, in turn, contribute to worsening the global climate crisis especially once an as yet unknown threshold is crossed and peat accretion is halted, that is, peatlands lose their carbon sink function. Given the current rapid SLR, coastal peatland managements should start develop fire risk reduction or mitigation strategies. Our interdisciplinary research shows how the changes in precipitation and sea level influenced the dynamics of coastal peatlands in Indonesia. It was inferred that the simultaneous occurrence of El Niño‐Southern Oscillation (ENSO) events and sea level rise (SLR) synergized in the past which led to the occurrences of severe forest fires, although it did not interrupt peat accretion. In the future, intensified ENSO and SLR can potentially magnify human‐induced peat fires in the coastal area, worsening global climate crisis. Coastal peatland managements should anticipate such hidden risk of current rapid SLR.
... These modules facilitate the integration of tropical peatland hydrology into Earth system models, possibly resulting in better understanding and projecting current and future global C fluxes (Loisel et al., 2021;Müller & Joos, 2021). Peatland hydrology and C dynamics are intrinsically linked, including in tropical peatlands where water level dynamics are the main force driving long-term peat C sequestration (Cobb et al., 2017;Couwenberg et al., 2010;Dargie et al., 2017). A survey of 44 peat experts conducted by Loisel et al. (2021) found that the increasing uncertainty in the peat C dynamics for the future is partly due to the lack of models that estimate the effect of (changing) critical drivers, such as the water level. ...
Tropical peatlands are among the most carbon-dense ecosystems on Earth, and their water storage dynamics strongly control these carbon stocks. The hydrological functioning of tropical peatlands differs from that of northern peatlands, which has not yet been accounted for in global land surface models (LSMs). Here, we integrated tropical peat-specific hydrology modules into a global LSM for the first time, by utilizing the peatland-specific model structure adaptation (PEATCLSM) of the NASA Catchment Land Surface Model (CLSM). We developed literature-based parameter sets for natural (PEATCLSM Trop,Nat) and drained (PEATCLSM Trop,Drain) tropical peatlands. Simulations with PEATCLSM Trop,Nat were compared against those with the default CLSM version and the northern version of PEATCLSM (PEATCLSM North,Nat) with tropical vegetation input. All simulations were forced with global meteorological reanalysis input data for the major tropical peatland regions in Central and South America, the Congo Basin, and Southeast Asia. The evaluation against a unique and extensive data set of in situ water level and eddy covariance-derived evapotranspiration showed an overall improvement in bias and correlation compared to the default CLSM version. Over Southeast Asia, an additional simulation with PEATCLSM Trop,Drain was run to address the large fraction of drained tropical peatlands in this region. PEATCLSM Trop,Drain outperformed CLSM, PEATCLSM North,Nat and PEATCLSM Trop,Nat over drained sites. Despite the overall improvements of PEATCLSM Trop,Nat over CLSM, there are strong differences in performance between the three study regions. We attribute these performance differences to regional differences in accuracy of meteorological forcing data, and differences in peatland hydrologic response that are not yet captured by our model.
... The protection and restoration of wetlands and peatlands is expected to reduce net carbon loss to the atmosphere between 0.15 and 0.81 GtCO2e year −1 up to 2050 (Couwenberg et al., 2009;Griscom et al., 2017;IPCC, 2019) and provide continued or restored natural CO 2 removal (IPCC, 2019). There has been significant knowledge gained over the last decade on wetland drainage and rewetting practices (IPCC, 2013), while the carbon storage and flux rates, in particular the balance between CH 4 sources and CO 2 sinks are still hard to quantify (IPCC, 2019;Spencer et al., 2016). ...
The two most urgent and interlinked environmental challenges humanity faces are climate change and biodiversity loss. We are entering a pivotal decade for both the international biodiversity and climate change agendas with the sharpening of ambitious strategies and targets by the Convention on Biological Diversity and the United Nations Framework Convention on Climate Change. Within their respective Conventions, the biodiversity and climate interlinked challenges have largely been addressed separately. There is evidence that conservation actions that halt, slow or reverse biodiversity loss can simultaneously slow anthropogenic mediated climate change significantly. This review highlights conservation actions which have the largest potential for mitigation of climate change. We note that conservation actions have mainly synergistic benefits and few antagonistic trade‐offs with climate change mitigation. Specifically, we identify direct co‐benefits in 14 out of the 21 action targets of the draft post‐2020 global biodiversity framework of the Convention on Biological Diversity, notwithstanding the many indirect links that can also support both biodiversity conservation and climate change mitigation. These relationships are context and scale‐dependent; therefore, we showcase examples of local biodiversity conservation actions that can be incentivized, guided and prioritized by global objectives and targets. The close interlinkages between biodiversity, climate change mitigation, other nature’s contributions to people and good quality of life are seldom as integrated as they should be in management and policy. This review aims to re‐emphasize the vital relationships between biodiversity conservation actions and climate change mitigation in a timely manner, in support to major Conferences of Parties that are about to negotiate strategic frameworks and international goals for the decades to come.
... Natural drainage of these systems are then important pathways for terrestrial carbon export in the forms of DOC, particulate organic carbon (POC), and dissolved inorganic carbon (DIC) (Kiew et al., 2018;Waldron et al., 2019). In some regions such as Southeast Asia, however, increasing human disturbances of tropical peatlands by fire and artificial drainage for agriculture have resulted in emissions of stored carbon at very fast rates (Page et al., 2002;Couwenberg et al., 2010;Itoh et al., 2017;Cooper et al., 2019). Therefore, an assessment of the stability of these tropical carbon stocks across different ecosystems is necessary to estimate the potential effects of increasing anthropogenic disturbances (Drake et al., 2019;Ribeiro et al., 2021). ...
Tropical peatlands are distributed mainly in coastal lowlands; however high elevation regions exhibit a large prevalence of small and fragmented peatlands that are mostly understudied. Artificial drainage of peatlands to expand the area of cattle farming, horticulture, and urbanization is increasing carbon losses to the atmosphere and streams worldwide. Here, we present an exploratory characterization of dissolved carbon optical properties in ombrotrophic peat bogs of the Talamanca range of Costa Rica, across an altitudinal gradient (2,400-3,100 m a.s.l.) during the rainy season. Dissolved organic matter (DOM) sources and decomposition processes were evaluated in the light of dissolved organic and inorganic carbon (DOC and DIC), optical properties, and major water chemistry. DOC concentrations ranged from 0.2 up to 47.0 mg/L. DIC concentrations were below 2 mg/L and δ 13 C DIC values indicated a mixture between soil organic matter, CO2 in soil water, and to a lesser degree DIC derived from bacterial CO2. Absolute fluorescence intensity of humic-like peaks was 6-7 times greater than fresh-like peaks across all sites. Fluorescence peak ratios coupled with the biological and humification indexes point to a greater relative contribution of recalcitrant soil-derived DOM. Excitation/Emission matrices denoted a high prevalence of humic and fulvic acids in the peat bogs, with moderate intensities in soluble microbial by-products-like and aromatic protein regions at three sites. Our data provides a baseline to underpin tropical carbon dynamics across high elevation peatlands.
... Source and sink function of N 2 O and N addition. In contrast to the third hypothesis, N addition did not increase N 2 O emissions but enhanced absorption, which was rarely observed in previous studies (Couwenberg et al. 2010, Oktarita et al. 2017). Similar to our study, Leeson et al. (2017) found that 13 years of N input in the level of 64 kg/ha/a which was lower than the level in our study could reduce N 2 O emissions, and they inferred that vegetation composition might be related to the N 2 O flux. ...
Peatlands, as important global nitrogen (N) pools, are potential sources of nitrous oxide (N<sub>2</sub>O) emissions. We measured N<sub>2</sub>O flux dynamics in Hani peatland in a growing season with simulating warming and N addition for 12 years in the Changbai Mountains, Northeastern China, by using static chamber-gas chromatography. We hypothesised that warming and N addition would accelerate N<sub>2</sub>O emissions from the peatland. In a growing season, the peatland under natural conditions showed near-zero N<sub>2</sub>O fluxes and warming increased N<sub>2</sub>O emissions but N addition greatly increased N<sub>2</sub>O absorption compared with control. There was no interaction between warming and N addition on N<sub>2</sub>O fluxes. Pearson correlation analysis showed that water table depth was one of the main environmental factors affecting N<sub>2</sub>O fluxes and a positive relationship between them was observed. Our study suggests that the N<sub>2</sub>O source function in natural temperate peatlands maybe not be so significant as we expected before; warming can increase N<sub>2</sub>O emissions, but a high dose of N input may turn temperate peatlands to be strong sinks of N<sub>2</sub>O, and global change including warming and nitrogen deposition can alter N<sub>2</sub>O fluxes via its indirect effect on hydrology and vegetation in peatlands.
... Drainage causes rapid decay (oxidative loss) and an increase in the bulk density of peat, both leading to subsidence (Carlson et al., 2015;Hooijer et al., 2012;Sinclair et al., 2020). Couwenberg et al. (2010) suggested that each additional water-table lowering of 10 cm will trigger an approximate 0.25 Â 10 À6 Pg of C loss per year per km 2 of tropical peatland, and 0.9 cm of annual peat subsidence. ...
Many tropical peatlands are subjected to artificial drainage that leads to degradation. Hence, hydrological restoration has recently been prioritized. Nevertheless, as field monitoring data are limited, little is known about how restoration measures, such as ditch dams and bunds, can regulate tropical peatland water tables. We used a hydrodynamic model – DigiBog_Hydro – to simulate the effectiveness of ditch dams and bunds across three El Niño – Southern Oscillation (ENSO) scenarios, which are El Niño, La Niña and Neutral, in three typical sites. The sites were moderately degraded (Mod-Dgr) and severely degraded (Sev-Dgr) peatland plots (each 0.2 km²), representing typical peatland conditions in Sebangau National Park, Kalimantan, Indonesia. Our fine-scale (1 m × 1 m spatial resolution) modelling revealed that in the dry season of any ENSO scenario, the significant effects of ditch-dams alone on peatland water-level were limited to lateral distances of 26 m (in Mod-Dgr) and 12 m (in Sev-Dgr) from the ditch. In the dry season of an El Niño year, the combination of ditch dams and bunds helped maintain water levels up to 72 cm (in Mod-Dgr) and 69 cm (in Sev-Dgr) higher than in the no-restoration condition. During the extreme-dry period of an El Niño year, the bunds reduced the number of days when the water table was deeper than 40 cm in Mod-Dgr and in Sev-Dgr by 50% and 73% respectively. We suggest that bunds used in combination with ditch dams are a practical restoration measure for tropical peatlands, providing critical extra water storage and helping maintain water tables near the peatland surface in dry periods. We also demonstrate how fine-scale hydrodynamic modelling is beneficial for planning and assessment of restoration measures in tropical peatlands.
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... In Malaysia, tropical peatlands are mainly located within lowland areas and coastal areas with high GWL (Wan Mohtar et al. 2019). In comparison with temperate and boreal peatland, one-fifth of CH 4 emissions come from tropical peatlands (Couwenberg et al. 2010). This comparatively low CH 4 emission level is due to the woody characteristics of tropical peat, which comprises lignin, which is a barely decomposable component. ...
Tropical peatlands have high potential function as a major source of atmospheric methane (CH4) and can contribute to global warming due to their large soil carbon stock, high groundwater level (GWL), high humidity and high temperature. In this study, a process-based denitrification–decomposition (DNDC) model was used to simulate CH4 fluxes in a pristine tropical peatland in Sarawak. To test the accuracy of the model, eddy covariance tower datasets were compared. The model was validated for the year 2014, which showed the good performance of the model for simulating CH4 emissions. The monthly predictive ability of the model was better than the daily predictive ability, with a determination coefficient (R²) of 0.67, model error (ME) of 2.47, root mean square error (RMSE) of 3.33, mean absolute error (MAE) of 2.92 and mean square error (MSE) of 11.08. The simulated years of 2015 and 2016 showed the good performance of the DNDC model, although under- and overestimations were found during the drier and rainy months. Similarly, the monthly simulations for the year were better than the daily simulations for the year, showing good correlations at R² at 0.84 (2015) and 0.87 (2016). Better statistical performance in terms of monthly ME, RMSE, MAE and MSE at − 0.11, 3.38, 3.05 and 11.45 for 2015 and − 1.14, 5.28, 4.93 and 27.83 for 2016, respectively, was also observed. Although the statistical performance of the model simulation for daily average CH4 fluxes was lower than that of the monthly average, we found that the results for total fluxes agreed well between the observed and the simulated values (E = 6.79% and difference = 3.3%). Principal component analysis (PCA) showed that CH4, GWL and rainfall were correlated with each other and explained 41.7% of the total variation. GWL was found to be relatively important in determining the CH4 fluxes in the naturally inundated pristine tropical peatland. These results suggest that GWL is an essential input variable for the DNDC model for predicting CH4 fluxes from the pristine tropical peatland in Sarawak on a monthly basis.
... Several studies directly correlate the CO2 flux with the groundwater level. A decrease in groundwater level causes increments in CO2 flux (Furukawa et al., 2005;Couwenberg et al., 2010;Hooijer et al., 2010;Hirano et al., 2014;Wakhid et al., 2017;Ishikura et al., 2018). However, in this study, the decrease in the groundwater level was not followed by an increase in CO2 flux (Figure 7). ...
The CO2 flux from peat soil planted with oil palm is temporally and spatially dynamic related to various environmental factors. This flux can be partitioned into fluxes from oil palm root respiration, litter decomposition, and peat material decomposition. This study aimed to determine the temporal and spatial dynamics of CO2 fluxes, the contribution of oil palm roots respiration, the contribution of litter decomposition, and the relation between flux and environmental factors in oil palm plantations on peatland. The measurements of CO2 flux using an infrared gas analyzer (IRGA) were carried out in harvesting path and inter-row of oil palm plantation and nearby shrubs. Flux measurements were replicated three to four days for almost five months. The results showed the dynamics of the CO2 fluxes temporally and spatially. Temporally, the CO2 flux in oil palm plantation and shrubs ranged from 10.5-40.0 to 2.0-23.3 Mg C-CO2 ha/year, respectively. Spatially, the flux in oil palm plantation and shrubs ranged from 17.0-32.0 to 9.9-12.4 Mg C-CO2 ha/year, respectively. The contribution of oil palm roots respiration and litter decomposition were 47.6 and 6.1%, respectively. The CO2 flux in oil palm plantations was significantly and negatively correlated with soil moisture content in the range of 145-450% (w/w), but not significantly correlated with groundwater level, air humidity, air temperature, soil temperature, and solar radiation.
... Wetlands are one of the largest global sources of atmospheric methane, estimated to contribute up to approximately 35% of global methane emissions (e.g. [8,53]), with the latitudinal gradient in atmospheric methane mole fractions observed in the NOAA network indicating the bulk of these emissions are situated in tropical rather than high latitude regions. Therefore, atmospheric δ 13 C CH 4 values predicted by global atmospheric models are sensitive to the δ 13 C CH 4 isotopic signature applied to tropical wetland emissions. ...
We report methane isotopologue data from aircraft and ground measurements in Africa and South America. Aircraft campaigns sampled strong methane fluxes over tropical papyrus wetlands in the Nile, Congo and Zambezi basins, herbaceous wetlands in Bolivian southern Amazonia, and over fires in African woodland, cropland and savannah grassland. Measured methane δ ¹³ C CH 4 isotopic signatures were in the range −55 to −49‰ for emissions from equatorial Nile wetlands and agricultural areas, but widely −60 ± 1‰ from Upper Congo and Zambezi wetlands. Very similar δ ¹³ C CH 4 signatures were measured over the Amazonian wetlands of NE Bolivia (around −59‰) and the overall δ ¹³ C CH 4 signature from outer tropical wetlands in the southern Upper Congo and Upper Amazon drainage plotted together was −59 ± 2‰. These results were more negative than expected. For African cattle, δ ¹³ C CH 4 values were around −60 to −50‰. Isotopic ratios in methane emitted by tropical fires depended on the C3 : C4 ratio of the biomass fuel. In smoke from tropical C3 dry forest fires in Senegal, δ ¹³ C CH 4 values were around −28‰. By contrast, African C4 tropical grass fire δ ¹³ C CH 4 values were −16 to −12‰. Methane from urban landfills in Zambia and Zimbabwe, which have frequent waste fires, had δ ¹³ C CH 4 around −37 to −36‰. These new isotopic values help improve isotopic constraints on global methane budget models because atmospheric δ ¹³ C CH 4 values predicted by global atmospheric models are highly sensitive to the δ ¹³ C CH 4 isotopic signatures applied to tropical wetland emissions. Field and aircraft campaigns also observed widespread regional smoke pollution over Africa, in both the wet and dry seasons, and large urban pollution plumes. The work highlights the need to understand tropical greenhouse gas emissions in order to meet the goals of the UNFCCC Paris Agreement, and to help reduce air pollution over wide regions of Africa.
This article is part of a discussion meeting issue 'Rising methane: is warming feeding warming? (part 2)'.
In Finland, the widespread drainage of boreal peatlands has led to increased forest productivity. The cost is a dramatic increase in soil greenhouse gas emissions. Empirical research of drained peatlands has found a correlation between greenhouse gas emissions and the ground water table. This suggests an opportunity to mitigate greenhouse gas emissions through forest management. We explore this opportunity at the landscape level through a simulation and optimization framework. We explore how forest management actions can impact the ground water table and the related greenhouse gas emissions. There are various economic and societal constraints for a set of forested peatland landscapes in Finland. Firstly, we link forest simulations with hydrological and statistical models to predict CO2, CH4, and N2O emissions from the drained peatlands. We present the range of landscape level solutions that prioritize between minimizing the net ecosystem greenhouse gas emissions, the economic timber value and the even flow of timber income over time. Our results highlight the impact integrating peatland soil greenhouse gas emissions will have on the planning process. This promotes the use of management options that benefit both biomass growth and reduced peatland soil greenhouse gas emissions.
Numerous studies claim that rewetting interventions reduce CO2 and increase CH4 fluxes. To verify the claim, we conducted a systematic review and meta-analysis of the effects of rewetting on CO2 and CH4 fluxes and dissolved organic carbon (DOC). We identified 28 primary articles eligible for meta-analysis, from which we calculated 48 effect sizes for CO2 emissions, 67 effect sizes for CH4 emissions, and 5 effect sizes for DOC. We found that rewetting significantly decreased CO2 fluxes, with temperate zones showing the highest Hedges’ g effect size (−0.798 ± 0.229), followed by tropical (−0.338 ± 0.269) and boreal (−0.209 ± 0.372) zones. Meanwhile, rewetting increased CH4 fluxes, with the highest Hedges’ g effect size shown in temperate zones (1.108 ± 0.144), followed by boreal (0.805 ± 0.183) and tropical (0.096 ± 0.284) zones. In addition, based on yearly monitoring after rewetting, the CH4 emissions effect size increased significantly over the first 4 years (r² = 0.853). Overall, the rewetting intervention reduced CO2 emissions by −1.43 ± 0.35 Mg CO2–C ha⁻¹ year⁻¹, increased CH4 emissions by 0.033 ± 0.003 Mg CH4–C ha⁻¹ year⁻¹, and had no significant impact on DOC. To improve the precision and reduce the bias of rewetting effect size quantification, it is recommended to conduct more experimental studies with extended monitoring periods using larger sample sizes and apply the before-after control-impact study design, especially in boreal and tropical climate zones.
Methane is a potent greenhouse gas. Wetlands are considered as significant sources of methane emission, prompting the need to understand determinants of methane flux in these critical ecosystems. The importance of the water table in methane emission has been noted in terrestrial wetlands; however, the role of the water table in methane emission remains to be clarified in order for the development of strategies to mitigate methane emission from wetland ecosystems. This review examines the current literature on factors influencing methane emission in terrestrial wetlands. The water table was illustrated as an overriding factor that controls both methane generation and consumption. The contribution of other main factors, including substrate characteristics, wetland plants and temperature, to methane emission was also discussed. Building upon the growing understanding of processes underlying methane emission, strategies centered around the control of water table was proposed to minimize methane emission in wetland management and restoration efforts to maximize the ecological value of wetlands.
Tropical peatlands are a globally important carbon store. They host significant biodiversity and provide a range of other important ecosystem services, including food and medicines for local communities. Tropical peatlands are increasingly modified by humans in the rapid and transformative way typical of the “Anthropocene,” with the most significant human—driven changes to date occurring in Southeast Asia. This review synthesizes the dominant changes observed in human interactions with tropical peatlands in the last 200 years, focusing on the tropical lowland peatlands of Southeast Asia. We identify the beginning of transformative anthropogenic processes in these carbon-rich ecosystems, chart the intensification of these processes in the 20th and early 21st centuries, and assess their impacts on key ecosystem services in the present. Where data exist, we compare the tropical peatlands of Central Africa and Amazonia, which have experienced very different scales of disturbance in the recent past. We explore their global importance and how environmental pressures may affect them in the future. Finally, looking to the future, we identify ongoing efforts in peatland conservation, management, restoration, and socio-economic development, as well as areas of fruitful research toward sustainability of tropical peatlands.
Natural wetlands are widely considered important for mitigation of climate change, but they have been impacted by land use and land cover change (LULCC), often resulting in ecosystem degradation and significant changes in soil carbon (C) and nitrogen (N) dynamics. However, the impact of various LULCC types on wetland soil C and N dynamics remains unclear. Global. 1982–2021. Wetland. We present a global meta‐analysis using a database of 487 sites compiled from the literature, demonstrating the response of soil C and N concentrations and stocks in coastal wetlands, riparian wetlands and peatlands to various types of LULCCs, including agricultural lands, drained wetlands, aquaculture ponds, pastures and constructed wetlands. The conversion of coastal wetlands, riparian wetlands and peatlands to most LULCC types decreased the mean soil C and N concentrations and stocks by 17.8 ± 10.3, 25.3 ± 13.4 and 23.2 ± 6.3%, respectively. The loss of wetland soil C owing to LULCC is estimated to cause a potential CO2 emission of 1.8–22.8 Mg CO2 equivalent emission/ha/year, except for conversion to constructed wetlands. The soil C and N contents were more sensitive to LULCCs, relative to the stocks. We also found that the patterns of soil C and N variations were closely related to the conversion time since completion of LULCC. After LULCC, the response of soil C and N variables was sensitive to changes in plant biomass, soil water conditions, bulk density, pH and NH4+‐N concentration, with the major controlling factors varying with the conversion age. Our results highlight the important role of LULCC in triggering soil C and N loss in natural wetlands, which enhances the greenhouse effect. As such, our study calls for sustainable land management strategies aiming at wetland conservation as a powerful tool to mitigate climate warming.
Copernicus Atmosphere Monitoring Service (CAMS) melaporkan bahwa peningkatan emisi GRK hutan dan lahan Indonesia pada tahun 2019 terutama disebabkan oleh pembakaran lahan gambut yang kaya karbon. Sekitar 1,65 juta ha terbakar dan setengah juta ha gambut terbakar dalam peristiwa kebakaran hebat pada tahun 2019, namun emisi GRK (gas rumah kaca) yang dihasilkan hampir mendekati dibandingkan dengan kebakaran tahun 2015 di mana 2,6 juta ha area terbakar. Ribuan hektar lahan yang secara ekologis penting dibakar, mengakibatkan kabut asap beracun yang mengancam kesehatan manusia serta mengganggu hutan alam dan habitat satwa liar. Lahan gambut terdiri dari bahan organik yang terdekomposisi, dan degradasi gambut akan menghasilkan emisi GRK dalam jumlah yang signifikan, terutama jika areal tersebut terbakar. Penurunan muka air tanah (GWL) di lahan gambut akan meningkatkan kepekaan terhadap kebakaran karena kondisi permukaan gambut yang lebih kering. Upaya restorasi yang dilakukan di ekosistem gambut yang terdegradasi (yaitu: pembasahan dan revegetasi) tampaknya merupakan solusi terbaik, jika dan jika kegiatan manajemen pencegahan kebakaran benar-benar dilaksanakan dengan baik. Pemadaman kebakaran memiliki potensi tinggi untuk mengurangi emisi GRK akibat kebakaran gambut ke atmosfer. Keberhasilan pemadaman kebakaran lahan gambut akan sangat bergantung pada keterampilan petugas pemadam kebakaran, strategi, dan ketersediaan peralatan, baik langsung maupun tidak langsung di lapangan. Kurangnya pengetahuan dan pengalaman untuk memerangi kebakaran gambut akan menyebabkan lebih banyak kebakaran dan berpotensi menimbulkan kebakaran yang tidak terkendali. Terakhir, kondisi ini akan menghasilkan emisi GRK yang signifikan karena gambut kering yang terbakar sulit dikendalikan. Kata kunci: CAMS, GRK, kebakaran gambut, pemadaman, restorasi
Greenhouse gas (GHG) emissions from peatlands are influenced by many factors and most of them are difficult to control. Soil temperature and moisture regulate biological reactions in the soil leading to gas production. It is a complex mechanism, considering the difficulty in controlling soil moisture and temperature. The study aimed to assess the consequence of soil moisture and temperature alteration on Carbon Dioxide (CO 2 ) emission through water level management. Soil samples were collected using a 21 cm (diameter) and 100 cm (length) of polyvinyl chloride (PVC); each was dipped into big bucket to control water level. Water levels were controlled in daily basis. Three different water levels were arranged, i.e., at 15 cm, 35 cm and 55 cm beneath earth surface and were replicated 3 times. The results showed that water levels affected soil and water temperature. Non-linear relationship between temperature and CO 2 emission ( P < 0.01) was discovered in this research. The lowest soil moisture was recorded at -55 cm water level below surface, then by experiments at -35 cm and -15 cm water levels. Lower water level increased aeration of peat soil and created optimal conditions for microorganisms to oxidize organic matters that produced and emitted CO 2 into the atmosphere.
The study investigates the symmetric and asymmetric impact of agriculturalization on environmental quality in sample of selected Asian economies for time period 1991 to 2019. For empirical analysis, the study adopted ARDL-PMG and NARDL-PMG approaches. The long-run findings of ARDL-PMG reveal that agriculturalization tends to significantly improve the quality of environment. The empirical outcomes of NARDL-PMG infer that positive shock in agriculturalization results in enhancing environmental quality, however, the negative shock in agriculturalization (i.e., de-agriculturalization) leads to deterioration of environmental quality in the long-run. The findings demonstrate that agriculturalization improves environmental quality and de-agriculturalization mitigates environmental quality. Based on these findings, the study recommends that the relevant authorities should formulate such reforms in the agriculture sector that controls and reduces carbon emissions in Asian economies.
Most recent estimates of carbon emissions from Indonesia's peatland fires are based on extrapolation from a narrow base of empirical evidence, raising concerns about the reliability of fire emissions estimates. Measurements of peat fires during ENSO periods are not representative of fires in other years, yet they underlie many estimates of peat fire emissions in ‘normal’ years. Errors may enter into estimates of area burned, quantity of peat combusted and fire emission factors. Problems arise in extrapolating from a few empirical measurements without accounting for conditions that influence combustibility of peat and the heavy fuels through which surface fires transition to become peat fires. These conditions are influenced by drainage and fire history. Our analysis is based on a critical look at a sample of peat fire and emissions studies, including the two most widely cited ones, as well as at the uses made of those studies. Undue extrapolation from unrepresentative empirical studies contributes significantly to the uncertainty of emissions estimates in studies that rely on models rather than empirical observation. We do not offer our own estimates; rather, we argue that the base of evidence must be broadened. We point to examples of empirically based research that more reliably show the contribution of peat fires to overall peatland carbon emissions.
Peatlands are especially important but fragile tropical landscapes. The importance of peatlands is owing to their ability to 1) sequester a considerable amount of terrestrial carbon, 2) store freshwater, and 3) regulate floods during the rainy season. Nowadays, extensive peatland degradation occurs because of peatland utilization for agriculture purposes, causing severe environmental consequences such as carbon emission, loss of biodiversity, risk of flooding, and peat fire. Meanwhile, local planners and decision makers tend to overlook the long-term strategic function of peatlands for carbon storage and hydrological regulation, preferring peatland utilization for short-term economic benefits. The objective of our study is to quantify the total ecosystem services (except biodiversity) of a tropical peatland landscape in various peat-utilization scenarios to help build awareness among local planners and decision makers on the strategic tradeoff between peatland utilization and restoration. Studies on the total ecosystem services in a tropical peatland landscape involving hydrological regulation are still rare. Based on the net present value calculation, provisioning services, carbon regulation, and hydrological regulation in our study area account for 19, 70, and 11% of the total ecosystem services, respectively. Based on uncertainty analysis, at any combination of the social cost of carbon emission (within a range of USD 52.7–USD 107.4) and discount rate (within a range of 5–10%), the enrichment of peatlands with paludiculture crops (e.g., jelutong) shows superior ecosystem services compared to other peatland-utilization scenarios. Conversely, planting peatlands with monoculture crops, which are associated with peatland drainage, shows a rapid decrease in the total ecosystem services. The fluvial carbon export in our study, which is often neglected in a peatland carbon budget, increases the estimate of the total carbon budget by 8%. Restoring undrained peatlands with paludiculture crops such as jelutong contributes positively to carbon sequestration and potentially reduces carbon emissions by 11%. These quantitative findings can help local planners and decision makers in understanding the tradeoff between the long-term benefits of peatland restoration and the short-term economic benefits of peatland utilization for monoculture crops.
Peat swamp forests in Southeast Asia are under heavy pressure. Deforestation, forest degradation, wildfires, and drainage have damaged or destroyed substantial areas of the once extensive peat swamp forest formations. Several efforts are underway to rehabilitate degraded peat forests areas in order to restore some of the valuable ecosystem services these forested areas once provided. However, these efforts often result in (mixed)-plantations that only partly resemble the original peat forests. Information about these peat swamp forests’ complex origin and ecology is needed to improve restoration outcomes further. Our paper analyses historical data from coastal peat swamp forests in Sarawak and Brunei and discusses the potential to use this as the reference value for intact peat forests. We describe the observed stand structure and species composition for pristine peat swamp forest, and we analyze the population structure of three dominant peat swamp forest species: Gonystylus bancanus ( ramin ), Dactylocladus stenostachys ( jongkong ) and Shorea albida ( alan batu ). We compare the historical data with data from recently measured, degraded peat swamp forests. We discuss our results in relation to processes of peat dome formation, nutrient availability and hydrology, and give recommendations for peat swamp forest management and restoration.
The Second State of the Carbon Cycle Report (SOCCR2) culminated in 19 chapters that spanned all North American sectors – from Energy Systems to Agriculture and Land Use – known to be important for understanding carbon (C) cycling and accounting. Wetlands, both inland and coastal, were found to be significant components of C fluxes along the terrestrial to aquatic hydrologic continuum. In this chapter, we synthesize the role of wetlands in the overall C footprint of North America (from Canada to Mexico) as one metric of the societal values placed on these terrestrial‐aquatic interfaces. We also summarize the effects of management activities and climate change on the wetland C cycle and give some perspectives on the current and future importance of wetlands to society.
The recognition that wetlands play an important role in regulating global climate has led to management actions intended to maintain and enhance the globally significant amounts of carbon preserved in wetland soils while minimizing greenhouse gas emissions. Our goal in this chapter is to review the biogeochemical processes that are relevant to wetland climate regulation, which we do by discussing: (1) the concepts of radiative balance and radiative forcing; (2) the mechanisms for wetland carbon preservation; (3) factors influencing greenhouse gas emissions and other carbon losses; and (4) opportunities for wetland management actions to influence carbon preservation and flux. Wetland carbon preservation, which reflects the accumulation of undecomposed organic material, is a function of the redox environment, organic matter characteristics, and physicochemical factors that inhibit decomposition. However, the conditions that favor carbon preservation often result in increased emissions of methane and nitrous oxide such that there is a biogeochemical tradeoff between carbon preservation and greenhouse gas emissions. The losses of carbon via gaseous and dissolved pathways are sensitive to environmental disturbances and raise challenges about fully accounting for the climatic impacts of wetlands. Wetland management and disturbance intentionally or unintentionally affect biogeochemical processes, such that wise environmental management offers opportunities to enhance wetland carbon preservation, prevent the destabilization of accumulated soil carbon, and reduce greenhouse gas emissions, thus maintaining the role of wetlands as regulators of global climate.
We studied the distribution of dissolved O2, CO2, CH4, and N2O in a coastal swamp system in Thailand with the goal to characterize the dynamics of these gases within the system. The gas concentrations varied spatially and seasonally in both surface and ground waters. The entire system was a strong sourcefor CO2 and CH4, and a possible sink for atmospheric N2O. Seasonal variation in precipitation primarily regulated the redox conditions in the system. However, distributions of CO2, CH4, and N2O in the river that received swamp waters were not always in agreement with redox conditions indicated by dissolvedO2 concentrations. Sulfate production through pyriteoxidation occurred in the swamp with thin peat layerunder aerobic conditions and was reflected by elevatedSO
42−/Cl− in the river water. When SO
42−/Cl− was high, CO2 and CH4 concentrations decreased, whereas the N2O concentration increased. The excess SO
42− in the river water was thus identified as a potential indicator for gas dynamics in this coastal swamp system.
The inorganic geochemistry of three domed ombrogenous peat deposits in Riau and West Kalimantan provinces, Indonesia, was investigated as a possible modern analogue for certain types of low-ash, low-sulfur coal. Mineral matter entering the deposits is apparently limited to small amounts from the allogenic sources of dryfall, rainfall, and diffusion from substrate pore water. In the low-ash peat in the interior of the deposits, a large portion of the mineral matter is authigenic and has been mobilized and stabilized by hydrological, chemical, and biological processes and conditions. Ash yield and sulfur content are low through most of the peat deposits and average 1.1% and 0.14%, respectively, on a moisture-free basis. Ash and sulfur contents only exceed 5% and 0.3%, respectively, near the base of the deposits, with maximum concentrations of 19.9% ash and 0.56% sulfur. Peat water in all three deposits has a low pH, about 4 units, and low dissolved cation concentration, averaging 14 ppm. Near the base, in the geographic interior of each peat deposit, pH is about two units higher and dissolved cation concentration averages 110 ppm. Relative concentrations of the inorganic constituents vary, resulting in chemical facies in the peat. In general, Si, Al, and Fe are the abundant inorganic constituents, although Mg, Ca, and Na dominate in the middle horizon in the geographic interior of coastal peat deposits. The composition of the three deposits reported in this paper indicates that domed ombrogenous peat deposits will result in low ash and sulfur coal, probably less than 10% ash and 1% sulfur, even if marine rocks are laterally and vertically adjacent to the coal.
Tropical peat swamp forest (PSF), being a unique dual ecosystem, i.e. tropical rainforest and tropical peatland, is highly influenced by the characteristics and nature of the latter. For tropical peatland, vegetation is both a biotic and parent material in the peat-forming factors. Elemental composition of peat soil differs from that of geological materials in its striking enrichment of carbon and nitrogen compounds relative to most rocks. The organic compounds of the plants are the ultimate sources of the large amount of C and N sequestered in the natural peatland. Thus different forest types that live on the tropical peatland influence the peat properties and are themselvesinfluencedbythepeatproperties.Tropicalpeatlandhasbeenvariouslyclaimedtobebothacarbonsink and source to the atmosphere and may contribute to global warming. These bipolar roles of tropical peatland are probably the result of site-specific composition of vegetation, the chemical properties of the peat and environmental factors, above and below ground. However, the quantification of the effects of these factors on carbon fluxes and the dominant conditions that cause it to switch from a carbon sink to a source are still uncertain.
The original objective of the Mega Rice Project (MRP) in Central Kalimantan, Indonesia – to convert one mil-lion hectares of tropical swamp forest to paddy fields – instead produced large areas of abandoned farmland with bare peat subject to frequent fires. To understand how peat fire occurrence is related to drought, we an-alyzed 1997 to 2007 United States Department Com-merce National Oceanic and Atmospheric Adminis-tration (NOAA) hotspot data, sea surface temperature (SST) anomalies, and weather data. We found that peat fire activity was proportional to drought severity as determined by SST anomalies, and that peat fires – the number of hotspots – correlated strongly with SST anomalies, implying that MRP area peat fires are re-lated to peat dryness. Surface fires start when ground water levels (GWL) are about 20 cm below the ground surface, and hundreds of such fires can occur with deeper GWL. A detailed and precise hotspot distribu-tion map showed that large MRP areas (Blocks A and C) located on deep peat layers have high fire density due to ongoing human disturbance, classifying MRP area peat fires as a man-made disaster.
The biogeochemistry of the Dumai River estuary in eastern Sumatra, Indonesia, was studied in order to obtain information on the sources, transformation, and fate of organic matter. Between October and December 2003, water, total suspended matter (TSM), and sediments were sampled along a salinity gradient during four campaigns, and plants and soils were collected from the catchment. Water samples were analyzed for dissolved inorganic nutrients and dissolved organic carbon (DOC). The concentrations of organic carbon (C<sub>org</sub>) and total nitrogen (N) and the stable carbon (δ<sup>13</sup>C<sub>org</sub>) and nitrogen (δ<sup>15</sup>N) isotope distributions were determined in TSM, sediments, plants, and soils. The pH as well as the concentrations of dissolved inorganic nutrients and TSM were very low in the river and increased toward the sea. A maximum DOC concentration of $5,050 \mu mol L^{-1}$ was measured in the river, and concentrations decreased toward the sea. Low-gradient relief and a dense vegetation cover, and hence little weathering and erosion, appear to be responsible for low river loads of dissolved nutrients and TSM in this black-water river. Leaching from extensive peat soils in its catchment may account for the high DOC content of the Dumai River. Peat swamps drained by numerous small rivers are estimated to cover $3.3 times 10^{4} km^2$ in eastern Sumatra, suggesting that leaching of DOC may be a significant source of carbon to the adjacent coastal seas. A comparison with "normal" rivers shows that black-water rivers can export similar amounts of DOC from catchments that are orders of magnitude smaller. Thus, export from small black-water rivers may be quantitatively more significant for the global DOC input into the ocean than previously thought.
[1] Peatlands deform elastically during precipitation cycles by small (±3 cm) oscillations in surface elevation. In contrast, we used a Global Positioning System network to measure larger oscillations that exceeded 20 cm over periods of 4–12 hours during two seasonal droughts at a bog and fen site in northern Minnesota. The second summer drought also triggered 19 depressuring cycles in an overpressured stratum under the bog site. The synchronicity between the largest surface deformations and the depressuring cycles indicates that both phenomena are produced by the episodic release of large volumes of gas from deep semi-elastic compartments confined by dense wood layers. We calculate that the three largest surface deformations were associated with the release of 136 g CH4 m−2, which exceeds by an order of magnitude the annual average chamber fluxes measured at this site. Ebullition of gas from the deep peat may therefore be a large and previously unrecognized source of radiocarbon depleted methane emissions from northern peatlands.
Carbon dioxide is by far the dominant greenhouse gas released from biomass burning activities for agricultural purposes, which can lead to a global warming potential if emissions to the atmosphere were left uncontrolled. The emissions of greenhouse gases from Sumatera, Indonesia during a major haze episode that occurred in August 2005 were investigated. The highest rate of burning occurred mainly in the province of Riau during the first two weeks of August. Total greenhouse gases emitted were estimated from the active fire counts derived from the \{NOAA\} satellite. During the haze episode that hit the western coast of Peninsular Malaysia, much green house gases such as carbon dioxide, carbon monoxide, nitrous oxide and methane were emitted to the atmosphere. The dispersion patterns of one the greenhouse gases during the height of the haze episode showed the path of transportation of the gas and the locations affected within the vicinity of the sources. The emission and transportation of the greenhouse gases, mainly carbon monoxide, from the biomass burnt in Sumatera also increased the local concentration in Peninsular Malaysia.
CO2 efflux from tropical peat swamp substrates was measured under three different land uses (selectively logged forest, recently
burned and cleared forest, and agriculture) in Jambi Province, eastern Sumatra over a six-month period that incorporated parts
of both the major wet and dry seasons. Clearance of peat swamp forest and cultivation led to increased emissions: mean CO2 effluxes ranged from 2.59 ± 0.22 μmolCO2 m−2 sec-1 for peat beneath selectively logged forest to 4.44 ± 1.16 μmolCO2 m−2 sec-1 beneath recently burned and cleared forest to 5.58 ± 1.34 μmolCO2 m−2 sec-1 beneath settled agriculture. Mean CO2 effluxes were significantly correlated with soil temperature at 20 cm depth (Q10 = 2.5) and water-table position. We combined SPOT satellite and CO2 efflux data to establish that the conversion of selectively logged forest to agricultural land has led to a substantial increase
in annual emissions of CO2-C in the study area.
An intercomparison is made of the Net Ecosystem Exchange of CO<sub>2</sub>, NEE , for eight Dutch grassland sites; four natural grasslands, two production grasslands and two meteorological stations within a rotational grassland region. At all sites the NEE was determined during at least 10 months per site, using the eddy-covariance (EC) technique, but in different years. The photosynthesis-light response analysis technique is used along with the respiration-temperature response technique to partition NEE among Gross Primary Production ( GPP ) and Ecosystem Respiration ( R<sub>e</sub> ) and to obtain the eco-physiological characteristics of the sites at the field scale. Annual sums of NEE , GPP and R<sub>e</sub> are then estimated using the fitted response curves with observed radiation and air temperature from a meteorological site in the centre of The Netherlands as drivers. These calculations are carried out for four years (2002?2005). The estimated annual R<sub>e</sub> for all individual sites is more or less constant per site and the average for all sites amounts to 1390±30 gC m<sup>?2</sup> a<sup>?1</sup>. The narrow uncertainty band (±2%) reflects the small differences in the mean annual air temperature. The mean annual GPP was estimated to be 1325 g C m<sup>?2</sup> a<sup>?1</sup>, and displays a much higher standard deviation, of ±100 gC m<sup>?2</sup> a<sup>?1</sup> (8%), which reflects the relatively large variation in annual solar radiation. The mean annual NEE amounts to ?65±85 gC m<sup>?2</sup> a<sup>?1</sup>, which implies that on average the grasslands act as a source, with a relatively large standard deviation. From two sites, four-year records of CO<sub>2</sub> flux were available and analyzed (2002?2005). Using the weather record of 2005 with optimizations from the other years, standard deviation of annual GPP was estimated to be 171?206 gC m<sup>?2</sup> a<sup>?1</sup> (8?14%), of annual R<sub>e</sub> 227?247 gC m<sup>?2</sup> a<sup>?1</sup> (14?16%) and of annual NEE 176?276 gC m<sup>?2</sup> a<sup>?1</sup>. The inter-site standard deviation was higher for GPP and R<sub>e</sub> , 534 gC m<sup>?2</sup> a<sup>?1</sup> (37.3%) and 486 gC m<sup>?2</sup> a<sup>?1</sup> (34.8%), respectively. However, the inter-site standard deviation of NEE was similar to the interannual one, amounting to 207 gC m<sup>?2</sup> a<sup>?1</sup>. Large differences occur due to soil type. The grasslands on organic (peat) soils show a mean net release of CO<sub>2</sub> of 220±90 g C m<sup>?2</sup> a<sup>?1</sup> while the grasslands on mineral (clay and sand) soils show a mean net uptake of CO<sub>2</sub> of 90±90 g C m<sup>?2</sup> a<sup>?1</sup>. If a weighing with the fraction of grassland on organic (20%) and mineral soils (80%) is applied, an average NEE of 28±90 g C m<sup>?2</sup> a<sup>?1</sup> is found, which means that on average the Dutch grasslands behave like a small sink for CO<sub>2</sub>. The results from the analysis illustrate the need for regionally specific and spatially explicit CO<sub>2</sub> emission estimates from grassland.
Seasonal discharge measurements and water samplings were carried out at the upper reaches of the Sebangau River in Central Kalimantan, Indonesia. The samples were analyzed for chemical contents and total suspended solids, in order to clarify the relationship between river discharge (flux) and water chemistry. The river runs through tropical peat forest in Palangka Raya, Central Kalimantan. The Sebangau River flux was classified into dry season flux and rainy season flux by flow quantity. But water quality did not differ greatly between the two seasons. The great rainfall-retentiveness of tropical peat bogs may contribute to stability of the runoff load factor.
We tested a set of surface common mid-point (CMP) ground penetrating radar (GPR) surveys combined with elevation rods (to monitor surface deformation) and gas flux measurements to investigate in-situ biogenic gas dynamics and ebullition events in a northern peatland (raised bog). The main findings are: (1) changes in the two-way travel time from the surface to prominent reflectors allow estimation of average gas contents and evolution of free-phase gas (FPG); (2) peat surface deformation and gas flux measurements are strongly consistent with GPR estimated changes in FPG content over time; (3) rapid decreases in atmospheric pressure are associated with increased gas flux; and (4) single ebullition events can induce releases of methane much larger (up to 192 g/m2) than fluxes reported by others. These results indicate that GPR is a useful tool for assessing the spatial distribution, temporal variation, and volume of biogenic gas deposits in peatlands.
This article was submitted without an abstract, please refer to the full-text PDF file.
Please do not request full text of this old conference abstract. Only preliminary results are presented in it.
The full study is available in the following peer reviewed papers;
Jauhiainen, J., Takahashi, H., Heikkinen, J.E.P., Martikainen, P.J. & Vasander, H. (2005). Carbon fluxes from a tropical peat swamp forest floor. Global Change Biology 11(10): 1788-1797.
DOI: 10.1111/j.1365-2486.2005.001031.x
Hirano,T., Jauhiainen, J., Inoue, T. & Takahashi, H. (2009). Controls on the carbon balance of tropical peatlands. Ecosystems 12: 873-887. DOI: 10.1007/s10021-008-9209-1
The marshland was reclaimed by pumped canal drainage, lowering the water table by as much as 3 m, and the addition of landfill to compensate for initial subsidence. This causes three types of land subsidence: 1) primary consolidation of the drained peat and underlying clay strata, 2) secondary compression of the peat and underlying clay from the loading of land fill and drained peat, and 3) oxidation of the drained peat. Differential subsidence of up to one meter between buildings on piles and their surroundings has been measured. -Author
CO2-C fluxes were measured by using static chamber technique devices in hummocks, hollows and dy-hollows of an ombrotrophic peatland during a 1 1/2 year period. Additionaly, factors controlling the CO2-C fluxes were examined. Peat temperature in 5 cm depth was strongly positively correlated with CO2-C emissions rates. The relationship between groundwater table and CO2-C emissions is more complex. A lowering of water table down to 0-40 cm is positively correlated with an increase of CO2-C fluxes, whereas a lowering of the water table in more than 40 cm depth decreases the CO2-C fluxes. The influence of abiotic parameters depends on microsite conditions. Applied multiple regression analysis explained between 66 and 77% of the seasonal variability in CO2-C flux. Cumulated CO2-C fluxes ranged from 233 ± 29 g/m2*a (dy hollows) to 452 ± 78 g/m2*a (hollows) with an area mediated CO2-C flux of 362 ± 70 g/m2. Based on regression models, a rewetting of the peatland by an increase of the water table by 5 cm results in a decrease of 22 g CO2-C/m2*a.
C and N-fluxes in fen sites were studied in field experiments after removing the upper soil layer to a depth of 20 cm (A20) and 60 cm (A60), respectively. The different cutting of peat led to a different ground-water table below surface. The study concentrates on the estimate of the N2O, CH4, and CO2 trace gas fluxes. The results show that the fluxes of these trace gases were markedly influenced by the different water regime. The N2O-N emission amounted to 1.68 (A20) and 5.97 kg ha-1 yr-1 (A60). The higher emission from site A60 could be attributed to an increase in N2O production after a period of complete flooding, and to higher nitrate concentrations due to a low biomass production. Because of the different oxygen availability site A20 was a sink for methane (591 g CH4-C ha-1 yr-1) and site A60 was a source of methane (36 g CH4-C ha-1 yr-1). The seasonal variation of the CO2 release rates could be explained by changes in groundwater table below surface and soil temperature (r2 = 93%). On the basis of this relationship we calculated a peat mineralization of 2910 kg C ha-1 yr-1.
Malaysian tropical peat soils were examined for their microbial decomposability by incubation under aerobic conditions at 35°C. Incubation data fitted well into the one compartment exponential decay model. Decomposition rate constants ranged from 0.0000241 to 0.000388 day-1, equivalent to a half-life time of 78.6 and 4.89 years. No promotive effect of pre-air-drying on the decomposition rate was detected. The decomposition rate tended to increase with the increase of the soil pH and/or ash content of soil. The promotive effect of pH amendment of strong soil acidity by liming on the decomposition rate was confirmed, while no effect of NPK fertilizer application on the decomposition rate was observed. The inhibitory effect of sulfate salts of Cu, Zn and a highly polymerized hydroxyaluminium chloride solution on the microbial decomposition was observed.
In situ decomposition of Malaysian peat soil organic matter in the field was estimated by the measurement of the CO2 flux from the soil surface. The CO2 flux ranged from 5.8 to 30.3 mmol h-1m-2, equivalent to 0.7 to 3.6 kg carbon per hour per ha. The CO2 flux was correlated with the soil acidity and ash content: the higher the soil pH and/or ash content, the greater the CO2 flux. Annual surface subsidence of arable peatland caused by the microbial decomposition of peat soil was estimated by the CO2 flux measurement to be 50-70% of the whole annual surface subsidence. Annual amount of CO2 emission from arable peatland in Peninsular Malaysia was estimated to be 2.23 × 106 t of carbon.
Histosols may grade spatially and temporally into mineral soils. Spatial gradation can occur at the margins of basins containing Histosols. A Medihemist, for example, may thin and/or contain increasing quantities of disseminated or layered mineral material as the basin margin is approached. At some point, the soil no longer meets one or more of the requirements for inclusion in the order Histosols; and although it may still contain a considerable quantity of organic material, it will be classified in one of the mineral soil orders, most commonly in the order Inceptisols. Within this order, the soil will probably be included with the Aquepts (the wet Inceptisols) at the subgroup level—it may be a Histic Cryaquept in the northern latitudes and a Haplaquept or a Humaquept in the midlatitudes. Once drained, by whatever mechanism, a Histosol quickly oxidizes. In a relatively short time (a few decades to perhaps a century or more), the thickness of the organic materials or the amount of organic material in the organic layer becomes insufficient for the soil to meet the requirements for the order Histosols.