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Tropical peatlands are carbon-dense ecosystems that are significant sources of atmospheric methane (CH4). Recent work has demonstrated the importance of trees as an emission pathway for CH4 from the peat to the atmosphere. However, there remain questions over the processes of CH4 production in these systems and how they relate to substrate supply. Principally, these questions relate to the relative contribution of recent photosynthetically fixed carbon, released as root exudates, versus carbon substrate supply from the slowly decomposing peat matrix to CH4 emissions within these ecosystems. Here, we examined the role of root inputs in regulating CH4 production inferred from soil emissions using a combination of in situ tree girdling, in situ13C natural abundance labelling via stem injections, and a 13CO2 labelling of transplanted plants of two contrasting plant functional types, a broadleaved evergreen tree, and a canopy palm. Girdling of broadleaved evergreen trees reduced CH4 fluxes by up to 67%. Stem injections of trees and palms with a natural abundance label resulted in significant isotopic enrichment of CH4 fluxes, reinforcing the link between root carbon inputs and peat CH4 fluxes. Ex situ13CO2 labelling of plants resulted in significant 13C enrichment of peat CH4 fluxes. Taken together, our results demonstrate for the first time that plant root exudates make a substantial contribution to CH4 production in tropical peatlands. [ABSTRACT FROM AUTHOR]

Conservation of groundwater quality is of paramount importance for sustainable agricultural management. Hydrological factors such as rainfall patterns and water table (WT) management, including drainage practices, play a crucial role in groundwater recharge. This in turn has a significant impact on WT fluctuations, nutrient losses in the soil, and the leaching of fertilizers into groundwater which leads to groundwater pollution. Consequently, this study evaluates the long-term influence of seasonal rainfall and WT fluctuations on groundwater nutrient dynamics in tropical peatlands from an oil palm plantation (OPP). Linear regression analyses and Pearson correlation matrices were adopted to evaluate the relationships between seasonal rainfall, WT, and groundwater chemical parameters. The results showed that there was a significant increase in mean pH, NO3−, Na+, Ca2+, and PO43- values during the wet season compared to the dry season which could be attributed to the leaching of nutrients into groundwater due to rainfall, nutrient runoff from drainage systems and increased nitrification rate. A significant positive correlation (p

Highly organic soil and peat are problematic soils due to their low bearing capacity and high compressibility. In tropical regions, the presence of woody material in these soils often affects the stress-compression and time-compression curves in load-increment consolidation tests, leading to unusual shapes. Consequently, conventional inorganic soil theory and the Cα/Cc concept are inadequate for analyzing their compression behavior. As an alternative, the Gibson and Lo model can be used to obtain compression parameters from single-load consolidation tests. However, this method introduces considerable discrepancies when predicting the primary settlement. To address this issue, this paper proposes a formula for predicting the primary settlement in highly organic soil and peat in the field, especially in tropical regions. Samples were collected from several locations in Indonesia. The formula was constructed from the stress-strain relationship during the primary compression stage, obtained from numerous single-load consolidation tests. Long-term field settlement is predicted by combining this empirical equation for primary settlement with the Gibson and Lo model for secondary settlement. The proposed formula was verified using field soil monitoring data, demonstrating reasonable accuracy in predicting the primary settlement of highly organic soil and peat. [ABSTRACT FROM AUTHOR]

The function of tropical peatland as a carbon sink is a balance between peat accumulation and peat loss; however, various interacting factors are involved affecting this process. In this study, we collected and intensively radiocarbon dated peat cores from two peat domes, visualized their cross-sectional profiles of geochemical properties, and developed three macrocharcoal records from each peat dome. We find that the young (4500 y calBP) and shallow (6 m) coastal peat has a simple and linear age–depth relationship, showing stable accumulation of carbon during the late Holocene. In contrast, the older (ca. 40,000 y cal BP) and deeper (15 m) inland peat shows a more complex history, where we observed age reversals and hiatuses, likely caused by climate variability from the Last Glacial Maximum (LGM) to the Holocene. The charcoal record reveals a continuous presence of low-severity fire as indicated by charcoal morphotypes, though fire frequency increased after agriculture was established. An age reversal during the LGM was likely caused by a flood. Two periods of hiatuses occurred, each several millennia in length, at the end of the LGM and during the early Holocene. One cause of the hiatuses may have been a climatically halted peat formation from low precipitation and cooler climate during the LGM. Another cause may have been that severe fires consumed thousands of years of accumulated peat. If the hiatuses were entirely due to fire, the carbon released from these paleo-fire events (600 t C ha−1) suggests several times the impact of the most intense modern peat fires. [ABSTRACT FROM AUTHOR]

Tropical sapric peat originates from highly decomposed woods. It consists of organic particles with colloidal microstructure and jelly-like texture. The complex fabric influences the permeability and the rate of pore water dissipation. The objective of this paper is to measure the permeability of tropical sapric peat using the flexible wall permeameter procedure. A special preparation method is presented, where each specimen was isotropically compressed under different effective stresses using a modified triaxial apparatus and monitored for 2 days-long permeability tests. The results showed that the permeability decreases with time following a negative power function, indicating gradual progress from the transient to semi-steady states. A graphical method is proposed to separate the transient state and the semi-steady state flow phases and to determine a representative coefficient of permeability. The time taken to achieve the semi-steady state was correlated with the level of compression. There is a good statistical correlation between the coefficient of permeability and the log of effective stress. The tropical sapric peat reported in this study has a lower permeability-to-effective stress ratio when compared to the amorphous sapric peat data from the literature. The findings of this paper offer excellent measurements for academic and engineers to better understand the permeability behavior of tropical sapric peat. [ABSTRACT FROM AUTHOR]

Peatlands of the central Congo Basin have accumulated carbon over millennia. They currently store some 29 billion tonnes of carbon in peat. However, our understanding of the controls on peat carbon accumulation and loss and the vulnerability of this stored carbon to climate change is in its infancy. Here we present a new model of tropical peatland development, DigiBog_Congo, that we use to simulate peat carbon accumulation and loss in a rain‐fed interfluvial peatland that began forming ~20,000 calendar years Before Present (cal. yr BP, where 'present' is 1950 CE). Overall, the simulated age‐depth curve is in good agreement with palaeoenvironmental reconstructions derived from a peat core at the same location as our model simulation. We find two key controls on long‐term peat accumulation: water at the peat surface (surface wetness) and the very slow anoxic decay of recalcitrant material. Our main simulation shows that between the Late Glacial and early Holocene there were several multidecadal periods where net peat and carbon gain alternated with net loss. Later, a climatic dry phase beginning ~5200 cal. yr BP caused the peatland to become a long‐term carbon source from ~3975 to 900 cal. yr BP. Peat as old as ~7000 cal. yr BP was decomposed before the peatland's surface became wetter again, suggesting that changes in rainfall alone were sufficient to cause a catastrophic loss of peat carbon lasting thousands of years. During this time, 6.4 m of the column of peat was lost, resulting in 57% of the simulated carbon stock being released. Our study provides an approach to understanding the future impact of climate change and potential land‐use change on this vulnerable store of carbon. [ABSTRACT FROM AUTHOR]

Tropical peatland condition across southeast Asia is deteriorating as a result of conversion to agriculture and urban zones. Conversion begins by lowering the water table, which leads to peat decomposition, subsidence and increased risk of large-scale forest fires. Associated changes in mechanical peat properties impact the magnitude and timing of changes in peatland surface motion, making them a potential proxy for peatland condition. However, such a relationship is yet to be observed in a tropical peatland setting. This study aimed to establish whether patterns of tropical peatland surface motion were a function of peat condition at North Selangor Peat Swamp Forest in Selangor, Malaysia. Results showed that subsidence was greatest at fire-affected scrubland sites, whilst the lowest mean water table levels were found at smallholder oil palm sites. Peat condition and magnitude of tropical peat surface oscillation were significantly different between peat condition classes, whilst peat condition differed with depth. More degraded tropical peats with high bulk density throughout the peat profile due to high surface loading and low mean water table levels showed greater surface oscillation magnitudes. The dominant peat surface oscillation mechanisms present at all sites were compression and shrinkage from changes in water table level. Mean water table level and subsidence rate were related to surface oscillation magnitude. However further work towards measuring surface and within-water table range bulk densities and surface loading is required to better understand the controls on surface oscillation magnitudes.

The drainage and cultivation of peatlands will lead to subsidence and mineralisation of organic matter, increasing carbon (C) loss as more CO2 is emitted. There is little information about carbon emissions from bare peat soil. A study was undertaken to measure the CO2 emissions from a logged-over peat swamp area that was purposely vegetation-free. We aimed to report CO2 emissions from a bare, drained peatland developed for an oil palm plantation. For 12 months, we used eddy covariance (EC), closed chambers, and soil subsidence measurements to derive CO2 emissions from a logged-over peat swamp area. Significant variations in the estimated soil CO2 efflux were observed in the three tested measurement techniques. The average CO2 flux rate measured by the EC technique was 4.94 ± 0.12 µmol CO2 m−2 s−1 (or 68.55 tonnes CO2 ha−1 year−1). Meanwhile, the soil CO2 efflux rate measured by the closed chamber technique was 4.19 ± 0.22 µmol CO2 m−2 s−1 (or 58.14 tonnes CO2 ha−1 year−1). Subsidence amounted to 1.9 cm year−1, corresponding to 36.12 tonnes CO2 ha−1 year−1. The estimation of the C loss was found to be highest by the EC technique, lower by the soil chamber technique, and lowest by the peat subsidence rate technique. The higher CO2 emission rate observed in the EC technique could be attributed to soil microbial respiration and decomposing woody residues in the nearby stacking rows due to the large EC footprint. It could also be affected by CO2 advection from oil palms adjacent to the study site. Despite the large differences in the CO2 emission rates by the different techniques, this study provides valuable information on the soil heterotrophic respiration of deep peat in Sarawak. Carbon emissions from a bare peat area cover only a fraction of the soil CO2 respiration component, i.e., the soil heterotrophic respiration. Further investigations are needed to determine the CO2 emissions by soil microbial activities and plant roots from other peat areas in Sarawak. [ABSTRACT FROM AUTHOR]

The expansion of oil palm plantations is one of the greatest threats to carbon-rich tropical peatlands in Southeast Asia. More than half of the oil palm plantations on tropical peatlands of Peninsular Malaysia are smallholder-based, which typically follow varied cropping systems, such as intercropping. In this case study, we compare the immediate biogeochemical impacts of conversion of an oil palm and pineapple intercropping to an oil palm monocropping system. We also assess how these changes affect the subsequent temperature sensitivity of greenhouse gas (GHG) production. We found that peat bulk density is unchanged, while organic matter content, pH and temperature is slightly yet significantly altered after conversion from oil palm intercropping to monocropping. Both in-situ and ex-situ CO2 emissions and temperature sensitivity of CO2 and CH4 production did not significantly vary between conversion stages; however, in-situ CO2 emissions in monocropping system exhibited a unique positive correlation with moisture. The findings show that some of the defining peat properties, such as bulk density and organic matter content, were mostly conserved immediately after conversion from intercropping to oil palm monocropping. However, there were signs of deterioration in other functional relationships, such as significantly greater CO2 emissions observed in the wet season to that of the dry season, showing moisture limitation to CO2 emissions in monocropping, post-conversion. Nevertheless, there is a need for further research to identify the long-term impacts, and also the sustainability of intercropping practices in mature oil palm plantations for the benefit of these peat properties.

The carbon pool of Amazonian peatlands is immense and mediates critical ecological functions. As peatlands are dynamic, similar to other wetland systems, modeling of the relationship between organic matter and dry bulk density allows the estimation of the accumulation and/or decomposition of peats. We tested several models: the generalized linear mixed logarithmic, to test depth, and the non-linear logarithmic and power-law models. There is a negative power-law relationship between organic percentage and dry bulk density using peat samples collected in Amazonian peatlands (n = 80). This model is supported by the coefficient of determination (R2) estimates garnered from model fitting, while Akaike Information Criterion (AIC) values further support parsimonious models. We also ran trials of the ideal mixing model with two parameters: k1 representing organic density and k2 representing mineral. The mixture of organic and inorganic components generally falls in accordance with the theory that decreasing k1 trends with increasing k2, although k2 values for these peat samples are negative. The organic k1 coefficient allows us to identify two sites out of the nine investigated, which can be prioritized for their carbon dynamics. The presence of high-density samples, which were not related to depth, indicates clay intrusion in these peatlands. We hope the modeling can explain processes significant to these globally important carbon-rich ecosystems. [ABSTRACT FROM AUTHOR]

Our study measured heterotrophic carbon dioxide (CO2) emissions in a drained peatland under potato cultivation in south-western Uganda. Soil carbon losses have not previously been reported for this land use, and our study set out to capture the range and temporal variation in emissions, as well as investigate relationships with key environmental variables. Soil chamber-based emission measurements were taken over five days at four points in time over the year to capture daily and monthly variability, including day and night sampling to capture any diurnal variations in temperatures and soil flux. Differences in soil microtopography from mounding of soils for potato beds and drainage trenches had a significant effect on the rate of soil flux. Diurnal sampling showed no significant difference in emissions or soil temperatures in the raised potato beds between day and night. More significant effects on soil flux from environmental drivers, such as water table depth, were observed between months, rather than hours and days. There were significant differences in the relationships between environmental variables and soil flux, depending on if soils had been recently disturbed or not. Area-weighted emissions based on microtopography gave a mean annual emissions factor of 98.79 ± 1.7 t CO2 ha-1 y-1 (± standard error) from this peatland use. [ABSTRACT FROM AUTHOR]

Our study measured heterotrophic carbon dioxide (CO2) emissions in a drained peatland under potato cultivation in south-western Uganda. Soil carbon losses have not previously been reported for this land use, and our study set out to capture the range and temporal variation in emissions, as well as investigate relationships with key environmental variables. Soil chamber-based emission measurements were taken over five days at four points in time over the year to capture daily and monthly variability, including day and night sampling to capture any diurnal variations in temperatures and soil flux. Differences in soil microtopography from mounding of soils for potato beds and drainage trenches had a significant effect on the rate of soil flux. Diurnal sampling showed no significant difference in emissions or soil temperatures in the raised potato beds between day and night. More significant effects on soil flux from environmental drivers, such as water table depth, were observed between months, rather than hours and days. There were significant differences in the relationships between environmental variables and soil flux, depending on if soils had been recently disturbed or not. Area-weighted emissions based on microtopography gave a mean annual emissions factor of 98.79 ± 1.7 t CO2 ha-1 y-1 (± standard error) from this peatland use.

Peat deposits (>50 ka) in the montane Nilgiris (Western Ghats, India), have been central to the reconstruction of late Quaternary paleoclimate using paleovegetation changes in the forest-grassland vegetation mosaic that coexist here. However, it is well-known that short-term disturbances can also cause vegetation switches when multiple stable vegetation states exist. We studied paleovegetation changes within the alternative stable states framework using stable carbon isotopes (relative abundance of C3-C4 vegetation) on the cellulose fraction from two high-resolution radiocarbon-dated peat cores ~170 m apart in the Sandynallah valley: Core 1 closer to the hillslope (32,000 years old) and Core 2 from the centre of the valley (45,000 years old). Core 1 is located in an ecotone showing shola -sedgeland dynamics with vegetation switching at c.22 ka from shola (possibly due to fire) to a prolonged unstable state until 13 ka sustained by low waterlogging. Following a hiatus c.13 ka, sedgeland dominates, with a shift into shola at 3.75 ka driven by increasing aridity. Core 2 shows a stable sedgeland mixed C3-C4 composition responding to temperature, enriched in C3-vegetation in the last glacial with C4-dominance beginning c.18.5 ka, indicative of deglacial warming. The distinctive vegetation states at corresponding times in Cores 1 and 2 within the same valley, responding independently to disturbances and climate, respectively, is the first paleo-record from an alternative stable states landscape in the montane tropics. Thus, short-term disturbances and site attributes need to be accounted for before ascribing vegetation change to changing climate in such vegetation mosaics. [ABSTRACT FROM AUTHOR]

The drainage and cultivation of peatlands will lead to subsidence and mineralisation of organic matter, increasing carbon (C) loss as more CO2 is emitted. There is little information about carbon emissions from bare peat soil. A study was undertaken to measure the CO2 emissions from a logged-over peat swamp area that was purposely vegetation-free. We aimed to report CO2 emissions from a bare, drained peatland developed for an oil palm plantation. For 12 months, we used eddy covariance (EC), closed chambers, and soil subsidence measurements to derive CO2 emissions from a logged-over peat swamp area. Significant variations in the estimated soil CO2 efflux were observed in the three tested measurement techniques. The average CO2 flux rate measured by the EC technique was 4.94 ± 0.12 µmol CO2 m−2 s−1 (or 68.55 tonnes CO2 ha−1 year−1). Meanwhile, the soil CO2 efflux rate measured by the closed chamber technique was 4.19 ± 0.22 µmol CO2 m−2 s−1 (or 58.14 tonnes CO2 ha−1 year−1). Subsidence amounted to 1.9 cm year−1, corresponding to 36.12 tonnes CO2 ha−1 year−1. The estimation of the C loss was found to be highest by the EC technique, lower by the soil chamber technique, and lowest by the peat subsidence rate technique. The higher CO2 emission rate observed in the EC technique could be attributed to soil microbial respiration and decomposing woody residues in the nearby stacking rows due to the large EC footprint. It could also be affected by CO2 advection from oil palms adjacent to the study site. Despite the large differences in the CO2 emission rates by the different techniques, this study provides valuable information on the soil heterotrophic respiration of deep peat in Sarawak. Carbon emissions from a bare peat area cover only a fraction of the soil CO2 respiration component, i.e., the soil heterotrophic respiration. Further investigations are needed to determine the CO2 emissions by soil microbial activities and plant roots from other peat areas in Sarawak.

The expansion of oil palm plantations is one of the greatest threats to carbon-rich tropical peatlands in Southeast Asia. More than half of the oil palm plantations on tropical peatlands of Peninsular Malaysia are smallholder-based, which typically follow varied cropping systems, such as intercropping. In this case study, we compare the immediate biogeochemical impacts of conversion of an oil palm and pineapple intercropping to an oil palm monocropping system. We also assess how these changes affect the subsequent temperature sensitivity of greenhouse gas (GHG) production. We found that peat bulk density is unchanged, while organic matter content, pH and temperature is slightly yet significantly altered after conversion from oil palm intercropping to monocropping. Both in-situ and ex-situ CO2 emissions and temperature sensitivity of CO2 and CH4 production did not significantly vary between conversion stages; however, in-situ CO2 emissions in monocropping system exhibited a unique positive correlation with moisture. The findings show that some of the defining peat properties, such as bulk density and organic matter content, were mostly conserved immediately after conversion from intercropping to oil palm monocropping. However, there were signs of deterioration in other functional relationships, such as significantly greater CO2 emissions observed in the wet season to that of the dry season, showing moisture limitation to CO2 emissions in monocropping, postconversion. Nevertheless, there is a need for further research to identify the long-term impacts, and also the sustainability of intercropping practices in mature oil palm plantations for the benefit of these peat properties. [ABSTRACT FROM AUTHOR]

Conversion of tropical peat swamp forests to increase and agricultural production has generated substantial peat carbon loss in the Asia-Pacific region. Different land-uses and management practices oxidize the tropical peat at diverse rates due mainly to different water table levels. In recent years, several studies have measured soil carbon dioxide emissions in-situ; however, only few studies have evaluated the effect of moisture on carbon dioxide fluxes in incubation experiments. Here, we present the dataset of an incubation performed with 360 intact peat cores from three different land-uses (i.e. 120 from intact peat swamp forest; 120 from drained logged peat forest; and 120 from oil palm plantation) collected on the peat dome of Jambi Sumatra Indonesia. Different moisture levels in the intact cores were set by either drying the intact peat cores for short period of time or by adding extra water before the incubation. Dynamic dark aerobic incubation in airtight containers coupled with carbon dioxide measurement with an infrared gas analyser and the gas fluxes was used to measure to gas fluxes. The average carbon dioxide fluxes were 5.38 ± 0.91, 4.15 ± 0.35 and 1.55 ± 0.13 µg CO2-C g−1 h−1 for the intact peat swamp forest, drained logged peat forest and oil palm plantation, respectively.

Peat deposits of the Muara Siran, East Kalimantan area, were investigated for their vertical and lateral succession, to examine the characteristic variability, particularly its macro- and microtextures. The deposits are situated in the Kutai Basin, in the vicinity of several Cenozoic coal deposits. Peat samples were taken from twenty-seven coring sites in the area, using a MacCaulay peat corer. The Muara Siran peatlands lie between the Kedang Kepala and Belayan Rivers. Siran Lake lies between these rivers and within the peat system. The peat thickness varied from 0.5 m to 12 m. Decomposed sapric peat formed the basal and margins of the deposit, overlain by moderatelydecomposed hemic peat in the central part of the peatlands, though both sapric and hemic peat types are interbedded at the margins of the mire. The fibric peat types were found mostly at the top of the mire and only distal from any active streams. Twenty-four samples of peat were freeze-dried for petrographic analyses of both plant part and maceral analyses using a reflected microscope. On the average, the dominant plant parts were stems and wood (i.e. secondary xylem). Maceral composition was mostly from the huminite group (on the average 89%), particularly the macerals humodetrinite and textinite. Macroscopic peat type and microscopic composition are linked. Fibric peat was found to be rich in wood and textinite. Hemic was mostly composed of stems and wood with textinite and humodetrinite as the most abundant macerals. Sapric peat has near equal proportions of stems, wood, and macerated tissue. Humodetrinite is the most abundant maceral in sapric. The average ash and sulfur content were low, 1.29 wt.% and 0.11 wt.%, respectively. Understanding the physical characteristics of inland peat as in Muara Siran peatland is essential to build knowledge of how inland peat is formed and what makes it different from coastal peat. Muara Siran is a unique, relatively small peatland in the central eastern Kalimantan which is still considerably pristine, hence may serve the aim of this study well. [ABSTRACT FROM AUTHOR]

Southeast Asia's extensive tropical peatlands account for a significant proportion of the global riverine dissolved organic carbon (DOC) flux to the ocean. Peat‐derived DOC is rich in polyphenolic compounds, the microbial degradation of which is thought to rely on extracellular phenol oxidases. Despite substantial interest in the biogeochemical fate of terrigenous DOC (tDOC), few studies have quantified phenol oxidase activity in aquatic environments, and microbial remineralization rates of tDOC have never been measured in Southeast Asia. Here, we assess the potential for using phenol oxidase assays as a proxy for tDOC biodegradation across peat‐draining rivers and the coastal waters of Sarawak, Borneo, and report experimental measurements of microbial tDOC remineralization rates from this region. We first show that phenol oxidase assays in aquatic samples are problematic because of the rapid, pH‐dependent autoxidation of the assay substrate. Our field measurements of phenol oxidase activity detected only substrate autoxidation, suggesting that real phenol oxidase activity was low or absent. Second, we report that peatland tDOC, collected from one of the few remaining intact peatlands on Borneo, showed at most very limited biodegradation (0%–6% loss of DOC, and 0%–12% loss of colored dissolved organic matter) during several 56‐day incubation experiments at an in situ temperature of ∼30°C, even when diluted with seawater or amended with nutrients. Our results suggest that direct microbial respiration is perhaps not a major pathway for peatland tDOC remineralization in Southeast Asia and that photo‐oxidation is more likely to control the fate of this carbon. Plain Language Summary: Southeast Asia's extensive tropical peatlands deliver around 10% of the global flux of riverine terrestrial dissolved organic carbon (tDOC) to the ocean, but we still have a limited understanding of what happens to this tDOC. In the ocean, microbes are often responsible for decomposing tDOC to CO2. To decompose peat‐derived tDOC, microbes are thought to require enzymes called phenol oxidases. Our study consists of two parts: first, we assess the potential for using phenol oxidase assays as a measure of microbial tDOC decomposition activity in northwestern Borneo. Second, we experimentally measured the rate of microbial tDOC decomposition in this region. We first show that phenol oxidase assays in aquatic samples are problematic because of the high pH‐dependent background oxidation rate of the assay substrate molecule. Second, we show that tDOC from one of the few intact peatlands in Borneo is resistant to microbial degradation, even after diluting it with seawater or adding nutrients. Our results suggest that direct microbial respiration is perhaps less important for peatland tDOC decomposition in Southeast Asia than photooxidation. Key Points: Low biodegradability of peatland dissolved organic carbon during 56‐day incubations, including when diluted with seawater or amended with nutrientsNo measurable phenol oxidase activity in the peat‐draining rivers and coastal waters of SarawakAutoxidation of the phenol oxidase assay substrate L‐3,4‐dihydroxyphenylalanine occurs at pH ≥ 7; we recommend ultrafiltration to generate enzyme‐free controls [ABSTRACT FROM AUTHOR]

Changes in land use of tropical peat will lead to the release of carbon (C) on the condition that initially stabilized, and resulting in land subsidence. Peatland clearance which is preceded by the construction of the canals will cause the ground water table in peatlands fell. Along with that, the subsidence occurs, which at the beginning of peatland reclamation rate of decline very fast and gradually slow down over time with reduction of organic materials that decompose or burn. Therefore, knowledge of the rate of subsidence is very important to plan drainage and optimal use of peat land in order to preserve the peat. The method or scientific approach used is the assessment directly, include: measurement of the location of groundwater levels, land subsidence at various existing condition of land in different locations, peat soil sampling and calculation with the empirical formula. The calculation of land subsidence using average data groundwater levels during the dry season, in addition to the types of land cover took into account as well. This paper presented the results of the analysis of land subsidence and the projected decline in the next 50 years peatlands in Sei Ahaz, Kapuas, Central Kalimantan and Sungai Buluh, Tanjung Jabung, Jambi and comparative results between the two locations. The implications of this study indicate that the regulation of groundwater levels will control land subsidence.

• We link livelihoods and biocultural approaches to conservation. • This is done to counter the ecosystem service approach and nature-culture dichotomy. • Fish-river-spirit-human relationships require consideration in peatland conservation. • Fish are cultural keystone species for tropical peatlands. • We propose a new definition of biocultural diversity which incorporates livelihoods. Conservation projects are likely to fail if plans to preserve important wildlife habitats and species are not co-developed between conservation organisations and local communities to reflect the needs and diverse values of the latter. Tropical peatland conservation represents a case in point: local community livelihoods have only recently come into focus, particularly within academic literature. Instead, many previous studies emphasise the need to conserve intact peat swamp forests for their carbon storage, as a habitat for flagship species such as the orangutan, and to provide fire-free landscapes. Here, we explore the socio-environmental issues being faced in the peatland landscapes of Central Kalimantan, Indonesia. This includes the loss of peat-swamp forest, decreases in peatland fish populations and related socio-cultural challenges such as potential loss of fishing livelihoods along with historic and continued experiences of marginalisation of indigenous communities. To find solutions to these complex and interrelated problems, an interdisciplinary approach which focuses on interdependencies and includes multiple worldviews is required. We propose an approach which deploys both Ethan Miller's use of livelihoods (incl. Miller, 2019) and biocultural approaches to conservation to analyse human-nonhuman relationships, with a focus on fish and fishing livelihoods. We draw on data from in-depth social and ecological research in two village communities in Central Kalimantan, and in so doing illustrate how fish conservation has the potential to support important biocultural and livelihood relationships between human and nonhuman communities in peatland areas. Our findings lend support to previous calls for biocultural approaches to conservation in other socio-ecological contexts, and lead us to conclude that tropical peatland conservation initiatives that integrate such approaches will result in improved outcomes for peatlands, forests, biodiversity and people. These findings will be relevant to other tropical peatland areas with high dependence on fishing as a source of livelihood, such as the peatlands of the Amazon and Congo basins. [ABSTRACT FROM AUTHOR]

Tropical peatlands are an important carbon store and source of greenhouse gases, but the microbial component, particularly community structure, remains poorly understood. While microbial communities vary between tropical peatland land uses, and with biogeochemical gradients, it is unclear if their structure varies at smaller spatial scales as has been established for a variety of peat properties. We assessed the abundances of PLFAs and GDGTs, two membrane spanning lipid biomarkers in bacteria and fungi, and bacteria and archaea, respectively, to characterise peat microbial communities under two dominant and contrasting plant species, Campnosperma panamensis (a broadleaved evergreen tree), and Raphia taedigera (a canopy palm), in a Panamanian tropical peatland. The plant communities supported similar microbial communities dominated by Gram negative bacteria (38.9–39.8%), with smaller but significant fungal and archaeal communities. The abundance of specific microbial groups, as well as the ratio of caldarchaeol:crenarchaeol, isoGDGT: brGDGTs and fungi:bacteria were linearly related to gravimetric moisture content, redox potential, pH and organic matter content indicating their role in regulating microbial community structure. These results suggest that tropical peatlands can exhibit significant variability in microbial community abundance even at small spatial scales, driven by both peat botanical origin and localised differences in specific peat properties. [ABSTRACT FROM AUTHOR]

Introduction: The characteristics of coastal wetlands are the result of hydrogeomorphological interactions between the continent and the ocean, which cause an environmental gradient, hat results in different vegetation types such as mangroves, freshwater marshes, swamp forests and palm swamps. Objective: To characterize the hydroperiod and physicochemical variables of water and soil and their effect on the distribution of vegetation in the Sistema de Humedales El Castaño. Methods: A total of 11 permanent sampling units (UM) were established by defined strata: five in the mangrove, two in swamp forest, two in freshwater marshes and two in the flooded pasture. From May 2016 to October 2017 the vegetation was characterized and the water levels and physicochemical parameters (superficial, interstitial and groundwater) were sampled monthly for: salinity, and pH; and the soil for: bulk density, humidity percentage, and redox potential. Results: Mangroves are the closest to the sea, have the lowest diversity (H: 1.66) and species richness (14), they are dominated by Laguncularia racemosa and Rhizophora mangle, have the highest values of interstitial and groundwater salinity, (> 10.8 ups), remain flooded for 4 to 12 months per year, and have a redox potential of 14.57 mV. Immediately, inland, there are remnants of the swamp forests (H: 2.18 and 18 species), dominated by Pachira aquatica, with 5 ups interstitial and groundwater salinity, flooded from 0 to 6 months per year, with a redox potential of 119.07 mV. These forests are followed inland by freshwater marshes (H: 1.92 and 16 species), dominated by Typha domingensis with 6.1 ups interstitial and groundwater salinity, flooded for 5 to 8 months per year and a redox potential of 125.9 mV. Finally, furthest inland is the flooded pasture, a modified herbaceous wetland for cattle grazing (H: 3.44 and 50 species) dominated by Paspalum conjugatum, where interstitial and groundwater salinity is less than 0.5 ups, it stays flooded for 5 to 9 months and the redox potential is 151.23 mV. Conclusions: In each type of vegetation, the structure, composition, and diversity are different, with a high turnover of species that indicates a gradient defined by salinity. The vegetation in the SHC follows the patterns of typical organization of the tropical coastal wetlands, mangroves, swamp forests and herbaceous wetlands, in this case the freshwater marshes and flooded pastures. The factor that define the distribution of the vegetation is the salinity and the gradient that is observed are a function of the hydrological dynamics that depends on the mixing of marine and freshwater. [ABSTRACT FROM AUTHOR]

• Manual flux chambers are often utilized to measure emissions in converted tropical peatlands. • The temporal frequency of manual measurements is restricted by the time and effort required. • Diurnal trends in soil carbon emissions were observed on a tropical peat oil palm plantation. • Hourly measurements with automatic chambers can help to address biases in manual observations. • Chamber studies in tropical peat oil palm plantations should consider the impact of measurement sample timing. Large-scale conversion of tropical peat swamp forests to agricultural plantations has resulted in substantial carbon dioxide (CO 2) emissions. Despite consensus on the importance of these emissions, the cause of the large range in the magnitudes of reported values remains uncertain. Differences in reported fluxes might result from site specific factors and/or potential limitations of the manual flux chambers commonly used. It is important that any biases at the site level are explored as they ultimately affect regional and global emission estimates. Therefore, the aim of this study is to determine if measurement timing of commonly used infrequent manual chamber measurements leads to biased emission estimates. In this study we make use of six months of automated chamber data to provide a semi-continuous timeseries. This timeseries is used to explore the potential for time-of-day sampling biases in infrequent, monthly manual chambers measurements in a peatland oil palm plantation in Malaysian Borneo. Fluxes from Palm Base, Harvest Path, Frond Pile, Drain and Inter row microforms were recorded hourly using automatic chambers. From these hourly data, mean diurnal patterns of fluxes were produced. These diurnal patterns were used to characterize the biases in a larger, monthly flux manual chamber dataset. This monthly manual dataset was collected over six years at the same site and microforms, with individual measurements made in the daytime. Bias range was widest for Harvest Path (-18 to 24 %), followed by Palm Base (-13 to 11 %), Drain (-10 to 9 %) and Frond Pile (-5 to 3 %). Estimates of annual plantation scale emission over six years, corrected for sampling bias ranged from 36 – 53 Mg CO 2 ha−1 yr−1. We recommend careful consideration of artefacts sample timing might introduce in any sampling design, and where possible fluxes should be corrected with measured diurnals for each microform considered. [Display omitted] [ABSTRACT FROM AUTHOR]

Tropical peatlands are a significant carbon store and contribute to global carbon dioxide (CO2) and methane (CH4) emissions. Tropical peatlands are threatened by both land use and climate change, including the alteration of regional precipitation patterns, and the 3–4 °C predicted warming by 2100. Plant communities in tropical peatlands can regulate greenhouse gas (GHG) fluxes through labile carbon inputs, but the extent to which these inputs regulate the temperature response of CO2 and CH4 production in tropical peat remains unclear. We conducted an anoxic incubation experiment using three peat types of contrasting botanical origin to assess how carbon addition affects the temperature response (Q10) of CO2 and CH4 production. Peats from forested peatlands in Panama and Malaysia, and a converted oil palm and pineapple intercropping system in Malaysia, differed significantly in redox potential, total carbon and carbon: nitrogen ratio. The production of CO2 and CH4 varied significantly among peat types and increased with increasing temperature, with Q10s for both gases of 1.4. Carbon addition further increased gas fluxes, but did not influence the Q10 for CO2 or CH4 production or significantly affect the Q10 of either gas. These findings demonstrate that the production of CO2 and CH4 in tropical peat is sensitive to warming and varies among peat types, but that the effect of root inputs in altering Q10 appears to be limited. [ABSTRACT FROM AUTHOR]

Abstract Many peatlands in Europe and North America have been developed for agriculture for over a century, whilst in Southeast Asia development has largely occurred since 1990. Cultivation of drained peatlands now supports the livelihoods of large numbers of people, and the ongoing economic development of countries such as Indonesia and Malaysia. However, peat subsidence linked to plantation drainage represents both an environmental and a socio-economic challenge, associated with elevated CO 2 emissions, impacts on adjacent forest habitat, and long-term changes in plantation drainability. Whilst the fundamental challenges presented by peat subsidence are broadly recognised, the long-term rates and the potential for mitigation or avoidance of subsidence remain uncertain. We analysed over 2000 site-years of subsidence measurements from 312 sites in Sumatra, Indonesia, collected under Acacia pulpwood plantation and adjacent native forest, representing the largest peat subsidence dataset published to date. Subsidence averaged 4.3 cm yr−1 in the Acacia plantations, and extended at least 300 m into adjacent forest. Mean water table depth (WTD) was the best predictor of subsidence rate in both plantation and forest areas. We did not find conclusive evidence that subsidence was intrinsically faster under Acacia plantation than under native forest or (by comparison with previous studies) oil palm plantations for the same level of drainage. Our results suggest that raising average WTDs to the Indonesian Government's 40 cm target could – if practically and economically viable means of achieving this can be developed – reduce current plantation subsidence rates by 25–30%. Whilst some degree of peat subsidence under any form of plantation management may be unavoidable, these reductions would – if achieved at scale – both increase the economic lifetime of the plantations, and simultaneously deliver reductions in CO 2 emissions of national and global significance. Highlights • We analysed the largest current dataset of cultivated peatlands subsidence rates • Peatlands drained for Acacia in Indonesia are subsiding at over 4 cm yr−1. • Plantation drainage also leads to subsidence in adjacent natural forest • Drainage depth influences subsidence rate in both plantations and forests • Raising water tables to 40 cm could reduce subsidence and CO 2 emissions [ABSTRACT FROM AUTHOR]

Fluvial fluxes of dissolved organic carbon (DOC) may represent an important loss for terrestrial carbon stores in the tropics. However, there is currently limited guidance on the preservation of tropical water samples for DOC analysis. Commonly employed preservation techniques such as freezing or acidification can limit degradation but may also alter sample properties, complicating DOC analysis. We examined the effects of cold storage at 4 °C on DOC concentration and quality in water samples collected from a tropical peat catchment. Samples were stored in the dark at 4 °C for periods of 6–12 weeks. Freeze/thaw experiments were also made. Mean DOC concentrations in samples stored for six weeks at 4 °C were 6.1 % greater than in samples stored at ambient room temperature (33 °C) over the same period. Changes in DOC concentrations, in two sample sets, during cold storage were 2.25 ± 2.9 mg L-1 (8 %) to 2.69 ± 1.4 mg L-1 (11 %) over a 12-week period. Freeze/thaw resulted in alterations in the optical properties of samples, and this in turn altered the calculated DOC concentrations by an average of 10.9 %. We conclude that cold storage at 4 °C is an acceptable preservation method for tropical DOC water samples, for moderate time periods, and is preferable to freezing or storage at ambient temperatures.

ABSTRAK Ekosistem hutan gambut tropika merupakan penyimpan karbon potensial, tetapi konversi lahan dan penebangan tidak lestari menyebabkan ekosistem ini juga menjadi sumber emisi karbon ke atmosfer. Pengaruh perubahan penutupan lahan dan pembangunan drainase terhadap dinamika muka air, penurunan tanah dan kehilangan karbon masih belum banyak diketahui pada tipologi gambut pesisir dengan bentang lahan yang sempit. Penelitian dilaksanakan pada berbagai tipe penutupan lahan gambut di Trumon dan Singkil, Provinsi Aceh mulai Mei 2013 hingga Oktober 2014. Penyimpanan dan kehilangan karbon dihitung berdasarkan bobot isi, kadar abu, karbon organik tanah, dan kedalaman tanah. Hasil penelitian menunjukkan perubahan penutupan lahan dan pembangunan drainase mempengaruhi tata air, penurunan tanah, dan kehilangan karbon sebesar 38,54 – 58,52%. Penurunan permukaan tanah tertinggi sebesar 5,6 cm/tahun terjadi pada lahan dengan bobot isi rendah dan intensitas drainase yang tinggi. Kehilangan karbon dari degradasi lahan gambut melepaskan sekitar1,352 ton CO2 eq/ha/tahun. ABSTRACT Tropical peat forest is one of significant atmospheric carbon sequester, but land conversion and illegal logging affects carbon stocks and transform these ecosystem into source of carbon emissions. The influence of land use change and drainage on water table fluctuation, soil subsidence and carbon loss are insufficiently known especially on typhology of narrow marine peatland. A study was conducted in Trumon and Singkil, Aceh Province from May 2012 until October 2014 in various peat land use types. Carbon stocks and carbon loss were calculated from data of bulk density, ash and carbon content, and peat depth. Results showed that land use types and distance from drainage influences the level of water table depth, subsidence rate, and carbon loss 38.54 – 58.52%. The highest subsidence rate occurred on peatlands which low bulk density and highly drainage intensity. Carbon loss from peat degradation released flux 1.352 ton CO2 eq/ha/year, highly correlated with measured rates of subsidence, depth of water table and bulk density.

Indonesia is a country with the largest tropical peatlands in the world. utilization of peatlands has been widely associated with fires and environmental issues like carbon dioxide emissions because of the highest land-use. The reduction or loss of the peat forest ecosystem for the development of dry land plants on a massive scale has reduced the quality of the environment, so that the function and benefits of the peat ecosystem as a hydrological buffer for the surrounding area are disturbed. This paper aims to synthesize all research results qualitatively to explore the potential for developing agroforestry systems on peatlands in an effort to increase food security and protect the environment. This review paper uses the Qualitative Review Systematics method with stages: 1) formulation of questions, 2) literature search, 3) screening and selecting appropriate research articles, 4) analyzing and synthesizing qualitative findings, 5) presenting finding. Agroforestry has the potential to have a real impact on food security, climate change including mitigation and adaptation, and preserving the environment. Some research results show that the agroforestry systems can be an effective buffer in peatlands in fire control because the peat stabilization process requires control materials to maintain the elemental composition, carboxyl (COOH) and OH-phenol functional groups, so that the peat conditions become stable.

The use of Sentinel-1 (S1) radar for wide-area, near-real-time (NRT) tropical-forest-change monitoring is discussed, with particular attention to forest degradation and deforestation. Since forest change can relate to processes ranging from high-impact, large-scale conversion to low-impact, selective logging, and can occur in sites having variable topographic and environmental properties such as mountain slopes and wetlands, a single approach is insufficient. The system introduced here combines time-series analysis of small objects identified in S1 data, i.e., segments containing linear features and apparent small-scale disturbances. A physical model is introduced for quantifying the size of small (upper-) canopy gaps. Deforestation detection was evaluated for several forest landscapes in the Amazon and Borneo. Using the default system settings, the false alarm rate (FAR) is very low (less than 1%), and the missed detection rate (MDR) varies between 1.9% ± 1.1% and 18.6% ± 1.0% (90% confidence level). For peatland landscapes, short radar detection delays up to several weeks due to high levels of soil moisture may occur, while, in comparison, for optical systems, detection delays up to 10 months were found due to cloud cover. In peat swamp forests, narrow linear canopy gaps (road and canal systems) could be detected with an overall accuracy of 85.5%, including many gaps barely visible on hi-res SPOT-6/7 images, which were used for validation. Compared to optical data, subtle degradation signals are easier to detect and are not quickly lost over time due to fast re-vegetation. Although it is possible to estimate an effective forest-cover loss, for example, due to selective logging, and results are spatiotemporally consistent with Sentinel-2 and TerraSAR-X reference data, quantitative validation without extensive field data and/or large hi-res radar datasets, such as TerraSAR-X, remains a challenge.

Tropical peatland ecosystems are a significant component of the global carbon cycle and feature a range of distinct vegetation types, but the extent of links between contrasting plant species, peat biogeochemistry and greenhouse gas fluxes remains unclear. Here we assessed how vegetation affects small scale variation of tropical peatland carbon dynamics by quantifying in situ greenhouse gas emissions over 1 month using the closed chamber technique, and peat organic matter properties using Rock-Eval 6 pyrolysis within the rooting zones of canopy palms and broadleaved evergreen trees. Mean methane fluxes ranged from 0.56 to 1.2 mg m−2 h−1 and were significantly greater closer to plant stems. In addition, pH, ranging from 3.95 to 4.16, was significantly greater closer to stems. A three pool model of organic matter thermal stability (labile, intermediate and passive pools) indicated a large labile pool in surface peat (35-42%), with equivalent carbon stocks of 2236-3065 g m−2. Methane fluxes were driven by overall substrate availability rather than any specific carbon pool. No peat properties correlated with carbon dioxide fluxes, suggesting a significant role for root respiration, aerobic decomposition and/or methane oxidation. These results demonstrate how vegetation type and inputs, and peat organic matter properties are important determinants of small scale spatial variation of methane fluxes in tropical peatlands that are affected by climate and land use change. [ABSTRACT FROM AUTHOR]

Abstract Tropical peatlands are a significant carbon store and source of carbon dioxide (CO 2) and methane (CH 4) to the atmosphere. Plants can contribute to these gas emissions through the release of root exudates, including sugars and organic acids amongst other biomolecules, but the roles of concentration and composition of exudates in regulating emissions remains poorly understood. We conducted a laboratory incubation to assess how the type and concentration of root exudate analogues regulate CO 2 and CH 4 production from tropical peats under anoxic conditions. For CO 2 production, substrate concentration was the more important driver, with increased CO 2 fluxes following higher addition rates of four out of the six exudate analogues. In contrast, exudate type was the more important driver of CH 4 production, with acetate addition associated with the greatest production, and inverse correlations between exudate concentration and CH 4 emission for the remaining five treatments. Root exudate analogues also altered pH and redox potential, dependent on the type of addition (organic acid or sugar) and the concentration. Overall, these findings demonstrate the contrasting roles of composition and concentration of root exudate inputs in regulating greenhouse gas emissions from tropical peatlands. In turn this highlights how changes in plant communities will influence emissions through species specific inputs, and the possible impacts of increased root exudation driven by rising atmospheric CO 2 and warming. Graphical abstract Image Highlights • CO 2 production increased at higher C input rates. • CH 4 production was generally inhibited at higher C input rates. • Acetate additions were associated with highest CH 4 production. • Redox potential and pH showed concentration and composition dependent responses. [ABSTRACT FROM AUTHOR]

Abstract Rapid population growth in South-East Asia has placed immense pressure upon lowland regions both to supply food and employment and space for residential, commercial and infrastructure development. This pressure has led to sites on tropical peatland previously considered unsuitable for development to be revisited. One such site, the KLIA2 terminal and runway, Kuala Lumpur International Airport which opened in May 2014 at a cost of 3.6 billion MYR has been beset by well documented subsidence problems. Coverage of the tropics by the Sentinel-1 satellite constellation presents an opportunity to monitor the ongoing subsidence at KLIA 2, identify potential knowledge gaps and help inform more sustainable infrastructure development in tropical peatland regions. Our results show that the ISBAS InSAR method produces reproducible ground deformation maps which can clearly identify the patterns of deformation across both urban infrastructure and adjacent rural plantations and tropical peat swamp. This is particularly well defined around the terminal building at KLIA-2 where different ground preparation and foundation design have resulted in stable terminal buildings and subsidence of surrounding pavement. Deformation is greatest in the runway area where alternate bands of uplift and subsidence presumably accompany the greatest loads associated with landing aircraft. In contrast, areas where peat replacement was the primary form of ground preparation, ground motion is stable, however this comes at high economic and environmental cost. Highlights • ISBAS InSAR algorithm allows deformation of tropical peat to be detected. • Peat related subsidence has caused problems at Kuala Lumpur International Airport. • Subsidence extends outside the airport into adjacent rural plantations and peatland. • Some peat mitigation strategies are shown to be inappropriate in a tropical setting. • Complexity of tropical peatland means new peat mitigation strategies are required for future developments. [ABSTRACT FROM AUTHOR]

Tropical peatlands release significant quantities of greenhouse gases to the atmosphere, yet the relative contributions of heterotrophic and autotrophic respiration to net CO2 fluxes remains sparsely quantified. We used a combination of in situ trenching and vegetation removal in ex situ pots to quantify root-derived CO2 under two plant functional types within a mixed species forest. Trenching significantly reduced surface CO2 flux, indicating that approximately two-thirds of the released CO2 was derived from roots. In contrast, ex situ vegetation removal in pots indicated that root-derived CO2 accounted for 27% of the total CO2 flux for Campnosperma panamensis, a broadleaved evergreen tree, and 49% for Raphia taedigera, a canopy palm. The results show that root-derived CO2 is a major contribution to net CO2 emissions in tropical peatlands, and that the magnitude of the emissions is affected by plant species composition. This is important in the context of land use change driving alterations in vegetation cover. [ABSTRACT FROM AUTHOR]

Swamp forests on deep tropical peatlands have undergone extensive deforestation and draining for agriculture and plantations, consequently becoming globally significant carbon (C) sources. To study the effects of land-use change on peat as a biological environment, which directly affects decomposition dynamics and greenhouse gas emissions, we sampled peat from four common land-use types representing different management intensities in Central Kalimantan, Indonesia. The near-pristine swamp forest was used to describe unmanaged conditions, and the three other sites in order of increasing management intensity were reforested ; degraded ; and agricultural . We examined peat substrate quality (total C & nitrogen (N), dissolved organic C (DOC) and N (DON)), organic matter quality characterized by infrared spectroscopy, and microbial biomass and extracellular enzyme activity, to describe both biotic and abiotic conditions in peat. We found that the peat at altered sites was poorer in quality, i.e. decomposability, as demonstrated by the higher intensity of aromatic and aliphatic compounds, and lower intensity of polysaccharides, and concentration of total N, DOC, and DON compared to the peat in the swamp forest. The observed differences in peat properties can be linked to changes in litter input and decomposition conditions altered after deforestation and draining, as well as increased leaching and fires. The quality of the peat substrate was directly related to its biotic properties, with altered sites generally having lower microbial biomass and enzyme activity. However, irrespective of management intensity or substrate quality, enzyme activity was limited primarily to the first 0–3 cm of the peat profile. Some differences between wet and dry seasons were observed in enzyme activity especially in swamp forest, where the most measured enzyme activities were higher in dry season. Reforestation 6 years before our measurements had not yet restored enzyme activity in the peat to the level of the swamp forest, although the topmost peat characteristics in the reforested site already resembled those in the swamp forest. This is likely contributed by the limited capacity of the young tree stand to produce litter to support peat formation and restore the quality and structure of the peat, and the chemical weed control performed at the site. Therefore, we conclude that intensive land management, including deforestation and draining, leads to the surface peat becoming poorer biological environment, and it may take long time to restore the peat properties. [ABSTRACT FROM AUTHOR]

Abstract: Litter decomposition is an important control on carbon accumulation in tropical peatlands. Stoichiometric theory suggests that decomposition is regulated by elemental ratios in litter while the home field advantage (HFA) hypothesis predicts that decomposer communities are adapted to local conditions. To date, the relative importance of these contrasting theories for litter decomposition and therefore the carbon balance of tropical peatlands remain poorly understood. We conducted two in situ litter decomposition experiments in a lowland tropical peatland. The first experiment tested the importance of the stoichiometric theory using a factorial nutrient addition experiment at two sites with contrasting vegetation (Raphia taedigera and Campnosperma panamensis) to assess how nutrient addition affected microbial enzyme activity and litter mass loss at the peat surface and at 50 cm depth. The second experiment tested the importance of HFA by reciprocal translocation of leaf litter from R. taedigera and C. panamensis forests, which differed in both litter chemistry and soil nutrient availability, to separate the influence of litter chemistry and soil/site properties on litter mass loss. The activities of hydrolytic enzymes involved in the decomposition of large plant polymers were stimulated by nitrogen addition only where nitrogen availability was low relative to phosphorus, and were stimulated by phosphorus addition where phosphorus availability was low. The addition of nitrogen, but not phosphorus, increased leaf litter decomposition under waterlogged conditions at 50 cm depth, but not at the peat surface. Decomposition was greatest for autochthonous litter irrespective of site nutrient status, indicating that adaptation of the microbial community to low nutrients can partly overcome nutrient limitation, and suggesting that HFA can influence litter decomposition rates. Synthesis. Our study shows that leaf litter decomposition and the activity of microbial enzymes in tropical peatlands are constrained in part by nutrient availability. However, such nutrient limitation of litter decomposition can be overcome by adaptation of the microbial community. [ABSTRACT FROM AUTHOR]

The objective of this work was to evaluate the adsorption of macronutrients calcium, potassium, magnesium, nitrogen, and phosphorus in two Brazilian tropical peat samples, investigating the effect of pH and determining the kinetics of the adsorption process. Two different Brazilian tropical peat samples were characterized using FTIR, TG, and SEM techniques. Different pH conditions were tested, as well as different mass concentrations of the peats. Differences in the chemical structures of the peat samples directly influenced the adsorptive capacities for the macronutrients. The adsorptive capacity for nitrogen was highest at pH 3, while the best adsorption of calcium and potassium was obtained at pH 6. The best fit to the data was provided by the pseudo-second-order model, which confirmed the rapid adsorption of calcium by both peats. [ABSTRACT FROM AUTHOR]

Conversion of logged-over peatlands in Malaysia to oil palm plantations have led to changes in the microbial community in peat soil, mainly fungi. Therefore, this study was conducted to identify and compare the fungal species in four sites with different gradient of disturbances, namely a primary forest (Maludam NP), a logged-over forest (Cermat Ceria LOF), a 7.5-year-old oil palm plantation (Durafarm OPP), and an 11.5-year-old oil palm plantation (Naman OPP) by using a culture-dependent method. Fungi were isolated and identified based on morphological and molecular characterizations. The 18S rRNA gene was amplified, sequenced, and compared for the closest match in GenBank. Quantification of total fungal viable count, soil nutrients, and environmental aspects was also carried out. The total fungal viable count was not significantly different in all sites. Phylum Ascomycota was the dominant taxon isolated from all sites, which was about 90%. Basidiomycota and Zygomycota were also identified but found in low percentages. The most prevalent species for the different sites were Aspergillus fumigatus (20.6%) in Maludam NP, Penicillium chrysogenum in Cermat Ceria LOF (24.3%), Hypocrea muroiana in Durafarm OPP (27.4%), and Hypocrea atroviridis in Naman OPP (20%). Most of the species isolated were saprophytic fungi involved in decomposition of peat. In conclusion, fungal species composition in Sarawak peatlands with different gradient of disturbances was different in each site. [ABSTRACT FROM AUTHOR]

Tropical peatlands are a globally important source of methane, a potent greenhouse gas. Vegetation is critical in regulating fluxes, providing a conduit for emissions and regular carbon inputs. However, plant roots also release oxygen, which might mitigate methane efflux through oxidation prior to emission from the peat surface. Here we show, using in situ mesocosms, that root exclusion can reduce methane fluxes by a maximum of 92% depending on species, likely driven by the significant decrease in root inputs of oxygen and changes in the balance of methane transport pathways. Methanotroph abundance decreased with reduced oxygen input, demonstrating a likely mechanism for the observed response. These first methane oxidation estimates for a tropical peatland demonstrate that although plants provide an important pathway for methane loss, this can be balanced by the influence of root oxygen inputs that mitigate peat surface methane emissions.