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Tropical peat swamp forests can sequester significant amount of carbon (C). However, there is dearth of understanding on the tropical soils’ C stocks and emissions because of the changes in peatland use, land use policies, and micro-climate. The objective of this study was to determine the C stocks and fluxes of two peat swamp forests and a peatland under mixed cropping in Selangor, Malaysia. Standard procedures were used to determine aboveground biomass, belowground biomass, selected peat soil physical, chemical, and biological properties, and environmental variables that are related to peat soil respirations. The mean C stocks for the peat swamp forest and mixed cropping sites were 1788.79 Mg C ha-1 and 1023.57 Mg C ha-1, respectively. The carbon dioxide emission rates of peat swamp forest and mixed cropping sites ranged from 7.20 to 73.13 tCO2 ha-1 year-1 and 26.50 to 43.43 tCO2 ha-1 year-1, respectively. These emissions are related to seasonal changes because the relative humidity, soil temperature, and ground water of the experimental sites had significant effects on soil respiration. Unlike the mixed cropping sites, the fluxes of the peat swamp forest were significantly higher in the dry season compared with the wet season. These findings suggest that peat soil respiration is controlled by relative humidity, temperature, and the changes in ground water table. Continued monitoring and conservation efforts to preserve stored C in peatlands are essential.

Tropical peat swamp forest is a global store of carbon in a water-saturated, anoxic and acidic environment. This ecosystem holds diverse prokaryotic communities that play a major role in nutrient cycling. A study was conducted in which a total of 24 peat soil samples were collected in three forest types in a tropical peat dome in Sarawak, Malaysia namely, Mixed Peat Swamp (MPS), Alan Batu (ABt), and Alan Bunga (ABg) forests to profile the soil prokaryotic communities through meta 16S amplicon analysis using Illumina Miseq. Results showed these ecosystems were dominated by anaerobes and fermenters such as Acidobacteria, Proteobacteria, Actinobacteria and Firmicutes that cover 80–90% of the total prokaryotic abundance. Overall, the microbial community composition was different amongst forest types and depths. Additionally, this study highlighted the prokaryotic communities’ composition in MPS was driven by higher humification level and lower pH whereas in ABt and ABg, the less acidic condition and higher organic matter content were the main factors. It was also observed that prokaryotic diversity and abundance were higher in the more oligotrophic ABt and ABg forest despite the constantly waterlogged condition. In MPS, the methanotroph Methylovirgula ligni was found to be the major species in this forest type that utilize methane (CH4), which could potentially be the contributing factor to the low CH4 gas emissions. Aquitalea magnusonii and Paraburkholderia oxyphila, which can degrade aromatic compounds, were the major species in ABt and ABg forests respectively. This information can be advantageous for future study in understanding the underlying mechanisms of environmental-driven alterations in soil microbial communities and its potential implications on biogeochemical processes in relation to peatland management.

Tropical peatlands are complex and globally-important ecosystems that are increasingly threatened by anthropogenic disturbances, primarily via agricultural development. Microbes in peatlands play important roles in governing overall ecosystem functions and sustenance, with specific population dynamics governing carbon sink or source dynamics. We determined phenotypic microbial community structures under forest, drained, burned and oil palm plantation peatlands, using phospholipid fatty acid (PLFA) profiling. Communities were distinct under each land-use type, varied consistently with depth down to two metres, but with a distinct characteristic shift at circa one metre depth. There was bacterial dominance across all land-use types and depths. The burnt peatland showed the greatest contrast relative to forest, possibly due to the difference in water table level. Gram-positive bacteria was the most dominant group in surface layers under all land-use types except burnt, and their relative abundance decreased with depth, replaced by Gram-negative groups in deeper layers. Fungal relative abundance remained low across both land-use types and depth ranges. Our results shed light on a hitherto virtually unknown tropical peat microbial phenotypic community structure and indicate that anthropogenic disturbance in tropical peatlands severely alter microbial communities.

Tropical peatlands are vital ecosystems that play an important role in global carbon storage and cycles. Current estimates of greenhouse gases from these peatlands are uncertain as emissions vary with environmental conditions. This study provides the first comprehensive analysis of managed and natural tropical peatland GHG fluxes: heterotrophic (i.e. soil respiration without roots), total CO2 respiration rates, CH4 and N2 O fluxes. The study documents studies that measure GHG fluxes from the soil (n = 372) from various land uses, groundwater levels and environmental conditions. We found that total soil respiration was larger in managed peat ecosystems (median = 52.3 Mg CO2 ha-1 year-1 ) than in natural forest (median = 35.9 Mg CO2 ha-1 year-1 ). Groundwater level had a stronger effect on soil CO2 emission than land use. Every 100 mm drop of groundwater level caused an increase of 5.1 and 3.7 Mg CO2 ha-1 year-1 for plantation and cropping land use, respectively. Where groundwater is deep (≥0.5 m), heterotrophic respiration constituted 84% of the total emissions. N2 O emissions were significantly larger at deeper groundwater levels, where every drop in 100 mm of groundwater level resulted in an exponential emission increase (exp(0.7) kg N ha-1 year-1 ). Deeper groundwater levels induced high N2 O emissions, which constitute about 15% of total GHG emissions. CH4 emissions were large where groundwater is shallow; however, they were substantially smaller than other GHG emissions. When compared to temperate and boreal peatland soils, tropical peatlands had, on average, double the CO2 emissions. Surprisingly, the CO2 emission rates in tropical peatlands were in the same magnitude as tropical mineral soils. This comprehensive analysis provides a great understanding of the GHG dynamics within tropical peat soils that can be used as a guide for policymakers to create suitable programmes to manage the sustainability of peatlands effectively.

Tropical peatlands are a known source of methane (CH4) to the atmosphere, but their contribution to atmospheric CH4 is poorly constrained. Since the 1980s, extensive areas of the peatlands in Southeast Asia have experienced land‐cover change to smallholder agriculture and forest plantations. This land‐cover change generally involves lowering of groundwater level (GWL), as well as modification of vegetation type, both of which potentially influence CH4 emissions. We measured CH4 exchanges at the landscape scale using eddy covariance towers over two land‐cover types in tropical peatland in Sumatra, Indonesia: (a) a natural forest and (b) an Acacia crassicarpa plantation. Annual CH4 exchanges over the natural forest (9.1 ± 0.9 g CH4 m−2 year−1) were around twice as high as those of the Acacia plantation (4.7 ± 1.5 g CH4 m−2 year−1). Results highlight that tropical peatlands are significant CH4 sources, and probably have a greater impact on global atmospheric CH4 concentrations than previously thought. Observations showed a clear diurnal variation in CH4 exchange over the natural forest where the GWL was higher than 40 cm below the ground surface. The diurnal variation in CH4 exchanges was strongly correlated with associated changes in the canopy conductance to water vapor, photosynthetic photon flux density, vapor pressure deficit, and air temperature. The absence of a comparable diurnal pattern in CH4 exchange over the Acacia plantation may be the result of the GWL being consistently below the root zone. Our results, which are among the first eddy covariance CH4 exchange data reported for any tropical peatland, should help to reduce the uncertainty in the estimation of CH4 emissions from a globally important ecosystem, provide a more complete estimate of the impact of land‐cover change on tropical peat, and develop science‐based peatland management practices that help to minimize greenhouse gas emissions., We measured methane exchanges at the landscape scale using eddy covariance towers over a natural forest and an Acacia crassicarpa plantation in tropical peatland in Sumatra, Indonesia. Groundwater level (GWL) controls diurnal and seasonal variability in methane emissions. Annual methane emissions over the natural forest were around twice as high as those of the Acacia plantation. Lower methane emissions over the Acacia plantation may be attributed to lower GWL. Results highlight that tropical peatlands are significant methane sources, and probably have a greater impact on global atmospheric methane concentrations than previously thought.

Despite their importance for global biogeochemical cycles and carbon sequestration, the microbiome of tropical peatlands remains under-determined. Microbial interactions within peatlands can regulate greenhouse gas production, organic matter turnover, and nutrient cycling. Here we analyze bacterial and fungal communities along a steep P gradient in a tropical peat dome and investigate community level traits and network analyses to better understand the composition and potential interactions of microorganisms in these understudied systems and their relationship to peatland biogeochemistry. We found that both bacterial and fungal community compositions were significantly different along the P gradient, and that the low-P bog plain was characterized by distinct fungal and bacterial families. At low P, the dominant fungal families were cosmopolitan parasites and endophytes, including Clavicipitaceae (19%) in shallow soils (0–4 cm), Hypocreaceae (50%) in intermediate-depth soils (4–8 cm), and Chaetothyriaceae (45%) in deep soils (24–30 cm). In contrast, high- and intermediate-P sites were dominated by saprotrophic families at all depths. Bacterial communities were consistently dominated by the acidophilic Koribacteraceae family, with the exception of the low-P bog site, which was dominated by Acetobacteraceae (19%) and Syntrophaceae (11%). These two families, as well as Rhodospirillaceae, Syntrophobacteraceae, Syntrophorhabdaceae, Spirochaetaceae, and Methylococcaceae appeared within low-P bacterial networks, suggesting the presence of a syntrophic-methanogenic consortium in these soils. Further investigation into the active microbial communities at these sites, when paired with CH4 and CO2 gas exchange, and the quantification of metabolic intermediates will validate these potential interactions and provide insight into microbially driven biogeochemical cycling within these globally important tropical peatlands.

This study investigates the factors controlling the soil CO2 and CH4 fluxes and quantifies annual cumulative soil respiration (RS), heterotrophic respiration (RH), and soil CH4 emission in an undrained forest on tropical peat by continuous measurement using an automated chamber system for 2 years. Daily mean soil CO2 flux was increased by lowering groundwater level (GWL), which indicates oxidative peat decomposition is promoted by the enhancement of aeration. On the other hand, soil CH4 flux showed a bell-shaped relationship with GWL, which suggested that the development of anaerobic conditions promoted CH4 production by the rise in GWL, whereas hydrostatic pressure suppressed CH4 diffusion when the GWL was above the peat surface. Mean annual gap-filled CO2 emissions were 926 ± 610 and 891 ± 476 g C m−2 y−1 (mean ± 1 SD) for RS (n = 10) and RH (n = 6), respectively, and were not significantly different from each other. The annual RH in this study was similar to that of previous studies despite the higher annual mean GWL in this study, possibly due to the inclusion of litter decomposition in contrast to most of the previous studies in tropical peatland. Mean annual gap-filled CH4 emission was 4.32 ± 3.95 g C m−2 y−1 (n = 9), which was the high end of the previous studies in tropical peatland due to higher annual mean GWL in this study. In conclusion, RS was lower and CH4 emission was higher in the undrained peat swamp forest than those previously reported for drained and disturbed forests on tropical peat.

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. Ministry of Education (MOE) Nanyang Technological University National Research Foundation (NRF) Published version Patrick Martin acknowledges funding through a Nanyang Technological University Start-Up Grant, an Academic Research Fund Tier 1 grant from the Singapore Ministry of Education (RG 175/16), and a grant from the National Research Foundation under the Marine Science Research & Development Programme (MSRDP-P32).

We evaluate the influences of elevation and climate on the spatio-temporal distribution of wetland and dryland biomes during the Pennsylvanian and early Permian in tropical Pangea. The longstanding “upland model” places drought-tolerant vegetation in elevated habitats, where slope and drainage created moisture-limited substrates under a humid climate that simultaneously promoted peat accumulation in contemporaneous lowlands. Upland plants were periodically transported to, and buried in, lowlands. Rare preservation of dryland vegetation thus reflects its general absence in basins, and taphonomic vagaries of long-distance transport. The alternative “climate model” proposes that drought-tolerant plants dominated tropical habitats when climate was seasonally dry, with wetland vegetation reduced to scattered refugia. Environmental changes attending glacial-interglacial cycles caused alternating wetter-drier conditions, and the relative abundance of wetland versus dryland biomes in basinal lowlands thus varied with climatic oscillations. The paucity of drought-tolerant plants reflects a preservational megabias against habitats with seasonal moisture deficits. The environmental signal of “mixed” plant-fossil assemblages, comprising taxa characteristic of both wetland and dryland biomes, may help resolve these debates. We review key Pennsylvanian and lower Permian mixed assemblages from tropical Euramerican Pangea, and interpret their original habitats and climatic contexts based on multidisciplinary lines of evidence, including sedimentology, taphonomy, physiology, and paleoecology. Evaluations also consider patterns of vegetational distribution and taphonomy in modern tropical environments. We suggest that even a cursory view of current tropical plant distribution exposes flaws in the upland model. Where tropical climate is sufficiently humid to support peat swamps, slopes and elevated habitats do not host drought-tolerant vegetation, but are occupied by plants similar to those in lowland settings. This occurs because equable, high precipitation strongly dampens water-table variation across entire landscapes. Furthermore, taphonomic studies indicate that most plant-fossil assemblages record vegetation living near the burial site. Fossil floras thus reflect environmental conditions near their growth site, excluding an upland origin for most occurrences of drought-tolerant taxa. Conversely, the climate model is consistent with modern tropical vegetational distribution and soundly explains late Paleozoic floristic patterns. When Pangean tropical lowlands experienced seasonally dry conditions, plants tolerant of moisture deficits dominated most habitats, whereas wetland vegetation was restricted to wetter sites with greater preservation potential. This occurred because topographic variations are magnified under seasonal precipitation regimes, creating a complex habitat mosaic with wetland patches in a landscape subject to seasonal drought. Accordingly, we propose that a macrofloral assemblage with even rare drought-tolerant taxa indicates seasonality in the broader landscape. At larger spatio-temporal scales, disagreement also persists about whether tectonic uplift or long-term climatic drying was the primary driver of changes in late Paleozoic floristic patterns and areal extent of tropical peat swamps. We argue that tectonic activity alone cannot explain the drastic reduction in peat swamps or coincident changes in dominance-diversity of wetland vegetation. Rates of plant dispersal and evolution far outpace that of mountain building, and peat-forming wetlands persisted in elevated habitats well into the Late Pennsylvanian. Therefore, progressive late Paleozoic aridification was the most probable driver of changing floral patterns and the distribution of wetland and dryland biomes in tropical Pangea.

Funding: The research was carried out as part of a project funded by the Malaysian Palm Oil Board (MPOB). L. K. K and E. R. are both employees of MPOB. The research was carried out with the support of Sarawak Oil Palm Berhard (SOPB) on whose land the research project was based. Need for regional economic development and global demand for agro‐industrial commodities has resulted in large‐scale conversion of forested landscapes to industrial agriculture across South East Asia. However, net emissions of CO2 from tropical peatland conversions may be significant and remain poorly quantified, resulting in controversy around the magnitude of carbon release following conversion. Here we present long term, whole ecosystem monitoring of carbon exchange from two oil palm plantations on converted tropical peat swamp forest. Our sites compare a newly converted oil palm plantation (OPnew) to a mature oil palm plantation (OPmature) and combine them in the context of existing emission factors. Mean annual net emission (NEE) of CO2 measured at OPnew during the conversion period (137.8 Mg CO2 ha‐1 yr ‐1) were an order of magnitude lower during the measurement period at OPmature (17.5 Mg CO2 ha‐1 yr‐1). However, mean water table depth (WTD) was shallower (0.26 m) than a typical drainage target of 0.6 m suggesting our emissions may be a conservative estimate for mature plantations, mean WTD at OPnew was more typical at 0.54 m. Reductions in net emissions were primarily driven by increasing biomass accumulation into highly productive palms. Further analysis suggested annual peat carbon losses of 24.9 Mg CO2‐C ha‐1 yr‐1 over the first 6 years, lower than previous estimates for this early period from subsidence studies, losses reduced to 12.8 Mg CO2‐C ha‐1 yr‐1 in the later, mature phase. Despite reductions in NEE and carbon loss over time, the system remained a large net source of carbon to the atmosphere after 12 years with the remaining 8 years of a typical plantation’s rotation unlikely to recoup losses. These results emphasise the need for effective protection of tropical peatlands globally and strengthening of legislative enforcement where moratoria on peatland conversion already exist. Publisher PDF

Deforestation of tropical peat swamp forests is rapidly taking place across Southeast Asia to make way for agricultural expansion. Within forest ecosystems, macrofungi play a vital role, including wood decomposition and nutrient cycles. To reveal the effects of deforestation and land cover conversion on macrofungi in Southeast Asian tropical forests we assessed the relationship between environmental variables such as air temperature, relative air humidity, soil pH, soil moisture, canopy cover, canopy closure, habitat type (i.e., peat swamp forest, large-scale plantation, monoculture smallholding, and polyculture smallholding) and available substrata with macrofungal species richness and abundance. We sample macrofungi across four habitats on Peninsula Malaysia including peat swamp forest, large-scale plantations, monoculture smallholding and polyculture smallholding. We found that substrate richness had a positive effect on macrofungal morphospecies richness, while soil pH and air temperature had a negative effect. For macrofungal abundance, canopy closure and soil moisture had negative effects, whereas substrate richness and relative air humidity had positive effects. Our data showed considerable variation in functional group responses to environmental variables. The abundance of wood-inhabiting fungi was driven primarily by substrate richness, while relative air humidity, soil moisture, and habitat type play minor roles. The abundance of terricolous saprotrophic fungi was determined principally by habitat type, substrate richness, and relative air humidity. Macrofungal community structure was mainly influenced by substrate richness, followed by microclimates and soil characteristics. Our results can provides critical ecological data to support conservation stakeholders conserve macrofungi in natural and agricultural peatlands. Our study suggests that the expansion of oil palm monocultures, to the detriment of peat swamp forests, is likely to have negative effects on macrofungal biodiversity and further agricultural expansion should be prevented.

Tropical peat swamp forests (PSFs) are globally important carbon stores under threat. In Southeast Asia, 35% of peatlands had been drained and converted to plantations by 2010, and much of the remaining forest had been logged, contributing significantly to global carbon emissions. Yet, tropical forests have the capacity to regain biomass quickly and forests on drained peatlands may grow faster in response to soil aeration, so the net effect of humans on forest biomass remains poorly understood. In this study, two lidar surveys (made in 2011 and 2014) are compared to map forest biomass dynamics across 96 km2 of PSF in Kalimantan, Indonesia. The peatland is now legally protected for conservation, but large expanses were logged under concessions until 1998 and illegal logging continues in accessible portions. It was hypothesized that historically logged areas would be recovering biomass while recently logged areas would be losing biomass. We found that historically logged forests were recovering biomass near old canals and railways used by the concessions. Lidar detected substantial illegal logging activity-579 km of logging canals were located beneath the canopy. Some patches close to these canals have been logged in the 2011-2104 period (i.e. substantial biomass loss) but, on aggregate, these illegally logged regions were also recovering. Unexpectedly, rapid growth was also observed in intact forest that had not been logged and was over a kilometre from the nearest known canal, perhaps in response to greater aeration of surface peat. Comparing these results with flux measurements taken at other nearby sites, we find that carbon sequestration in above-ground biomass may have offset roughly half the carbon efflux from peat oxidation. This study demonstrates the power of repeat lidar survey to map fine-scale forest dynamics in remote areas, revealing previously unrecognized impacts of anthropogenic global change.

Antimicrobial resistance is a significant threat to the healthcare sector. For the past century, there has been a decline in the discovery of new antibiotics. This has urged researchers to bio-prospect for new bioactive agents from microbes originating from untapped environments, as well as to explore the potential of other microbial genera apart from the wellknown Streptomyces. Tropical peat swamp forests are an example of such an environment. Two novel antimicrobial-producing bacteria from the genera Burkholderia and Paenibacillus have been identified to produce potent antimicrobials. These two genera of bacteria have recently gained tremendous interest due to their genome complexity. They are known as multifaceted organisms not only because of their genetic content, but also due to their positive interactions with the environment along with a plethora of organisms including plants and animals. The interactions observed are attributed to their genomes and to their production of secondary metabolites including antimicrobials. Hence, this review provides an overview of the nature of tropical peat swamp forests, taxonomy and production of secondary metabolites of both Burkholderia and Paenibacillus, as well as discussing the future perspective of isolating antimicrobial-producing microbes from tropical peat swamp forests.

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.

The status of tropical peatlands, one of Earth’s most efficient natural carbon stores, is of increasing international concern as they experience rising threat from deforestation and drainage. Peatlands form over thousands of years, where waterlogged conditions result in accumulation of organic matter. Vast areas of Southeast Asian peatlands have been impacted by land use change and fires, whilst lowland tropical peatlands of Central Africa and South America remain largely hydrologically intact. To predict accurately how these peatlands may respond to potential future disturbances, an understanding of their long-term history is necessary. This paper reviews the palaeoecological literature on tropical peatlands of Southeast Asia, Central Africa and South America. It addresses the following questions: (i) what were the past ecological dynamics of peatlands before human activity?; (ii) how did they respond to anthropogenic and natural disturbances through the palaeoanthropocene, the period from whence evidence for human presence first appeared?; and, (iii) given their past ecological resilience and current exposure to accelerating human impacts, how might the peatlands respond to drivers of change prevalent in the anthropocene? Throughy synthesising palaeoecological records, this review demonstrates how tropical peatland ecosystems have responded dynamically, persisting through fire (both natural and anthropogenic), climatic and human-induced disturbances in the palaeoanthropocene. Ecosystem resilience does, however, appear to be compromised in the past c. 200 years in Southeast Asian peatlands, faced with transformative anthropogenic impacts. In combination, this review’s findings present a pantropical perspective on peatland ecosystem dynamics, providing useful insights for informing conservation and more responsible management. Natural Environment Research Council (NERC): NE/R016860/1 and NE/R000751/1.

Tropical peat swamp forest (PSF) is one of the most endangered ecosystems in the world. However, the impacts of anthropogenic activities in PSF and its conversion area towards fish biodiversity are less understood. This study investigates the influences of water physico-chemical parameters on fish occurrences in peat swamp, paddy field and oil palm plantation in the North Selangor peat swamp forest (NSPSF), Selangor, Malaysia. Fish and water samples were collected from four sites located in the peat swamps, while two sites were located in the paddy field and oil palm plantation areas. Multivariate analyses were used to determine the associations between water qualities and fish occurrences in the three habitats. A total of 1,382 individual fish, belonging to 10 families, 15 genera and 20 species were collected. The family Cyprinidae had the highest representatives, followed by Bagridae and Osphronemidae. The most abundant species was Barbonymus schwanefeldii (Bleeker 1854), while the least abundant was Wallago leerii Bleeker, 1851. The paddy field and oil palm plantation area recorded significantly higher fish diversity and richness relative to peat swamp (p 0.05), but was significantly different from the peat swamp (p

Data on ecosystem-scale methane (CH4 ) fluxes in tropical peatlands are currently lacking in the global CH4 budget. Although the waterlogged Indonesian peatlands contain the largest share of peat carbon in South-East Asia, ecosystem-scale CH4 budgets have not yet been reported, although these peatlands have the potential to emit CH4 . We observed 1-year variations in the ecosystem-scale CH4 flux in an undrained secondary peat swamp forest in central Kalimantan, Indonesia, using the eddy covariance method. We found that the peat swamp forest switched from being a CH4 sink during the dry season (as low as -8.9 mg C m-2 day-1 ) to a source of CH4 during the wet season (up to 10.7 mg C m-2 day-1 ), and this was dependent on changes in the groundwater level (GWL). The high GWL during the wet season enhanced the anaerobic CH4 production in the surface layer that had more labile organic matter. However, the CH4 emission also increased when the GWL dropped during dry spells in the wet season. The annual CH4 budget in the studied tropical peat swamp forest (0.09-0.17 g C m-2 year-1 ) was much lower than that in northern, temperate, and subtropical wetlands. We found that CH4 fluxes had almost no effect on the global warming gas budget of the peat swamp forest, and values were only a few percent less than the CO2 fluxes at the same site. In addition, we conducted anaerobic soil incubation experiments to examine the effect of land-use change on CH4 production. The results indicated much higher CH4 production potential in undrained forest soil than in drained or drained and burned ex-forest soils. However, although CH4 production decreased in drained soils relative to undrained soils, conserving pristine peat swamp forests with high GWLs is important to suppress global warming because CO2 emissions increase in drained peatlands.

Carbon dioxide (CO2) emissions from Southeast Asia peatlands are contributing substantially to global anthropogenic emissions to the atmosphere. Peatland emissions associated with land-use change, and fires are closely related to changes in the water table level. Remote sensing is a powerful tool that is potentially useful for estimating peat CO2 emissions over large spatial and temporal scales. We related ground measurements of total soil respiration and water table depth collected over 19 months in an Indonesian peatland to remotely sensed gravity recovery and climate experiment (GRACE) terrestrial water storage anomoly (TWSA) data. GRACE TWSA can be used to predict changes in water storage on land. We combined ground observations from undrained forest and drained smallholder oil palm plantations on peat in Central Kalimantan to produce a representation of the peatland landscape in one 0.5° × 0.5° GRACE grid cell. In both ecosystem types, total soil respiration increased with increasing water table depth. Across the landscape grid, monthly changes in water table depth were significantly related to fluctuations in GRACE TWSA. GRACE TWSA explained 76% of variation in water table depth and 75% of variation in total soil respiration measured on the ground. By facilitating regular sampling across broad spatial scales that captures essential variation in a major driver of soil respiration and peat fires, our approach could improve information available to decision makers to monitor changes in water table depth and peat CO2 emissions. This would enable measures better targeted in space and time to more effectively mitigate CO2 emissions from tropical peat drainage and fires. Testing over larger regions is needed to operationalize this exploratory approach.

Shorea albida trees, which grow in oligotrophic tropical peat swamp forests, invest less in defense than growth, and therefore develop tall hollow stems that regrow after breakage. The tropical peat swamp forests of Sarawak, Malaysia are low-nutrient soils, but nonetheless have tall Shorea albida trees. Most of these large trees have hollow stems and broken crowns. We examined tree morphology to determine how this species develops and maintains tall above-ground parts in oligotrophic peat soils. We measured hollow diameter at breast height (Dhollow), tree diameter at breast height (DBH), tree height, and height of breakage of 81 trees. Destructive sampling was also conducted for seven trees, and these data were used to determine wood density and both hollow diameter and stem diameter per meter height. All sampled trees developed hollow trunks before they reach the canopy layer. Linear regression of Dhollow on DBH indicated that the radial expansion rate of the hollow was slightly less than the thickening growth. Stem breakage and crown breakage reduced tree height, but most broken trees regrew from pre-existing upper branches or by epicormic branching. These results suggest that S. albida trees devote more resources to growth than defense, and therefore become large with hollow stems.

Tropical peat swamp forests are carbon-rich ecosystems that have been threatened by high rates of land use change (LUC). Despite the ecosystem’s shifts from sequestering carbon (C) to emitting carbon, few studies have quantified the changes in ecosystem productivity associated with LUC in tropical peatlands. This study quantified net primary production (NPP) in intact peat swamp forests (PSF), logged forests (LPSF), early seral sites (ES), and smallholder oil palm plantations (OP) in a peat dome of West Kalimantan, Indonesia. All sites were dominated by peat forest prior to deforestation. The NPP of intact forests was 13.2 Mg C ha−1 year−1 making it among the world’s most productive terrestrial ecosystems, exceeding that of many tropical rainforests and similar to the most productive mangrove ecosystems (12.9 Mg C ha−1 year−1). Land cover change resulted in large shifts in NPP. Logged forest and early seral sites were

Tropical wetlands such as peat swamp forests (PSFs) have been known globally as one of the carbon (C)-rich ecosystems. However, there is still a lack of understanding on the C cycle in PSFs, especially in association with land use and cover changes (e.g., ecosystem degradation and restoration). This study presents the C stocks, removals, and emissions dataset, as well as the determining factors from an early restoration stage of secondary tropical PSFs in Central Kalimantan. We assessed various biophysical parameters such as forest structure, above- and belowground C-stocks, aboveground primary productivity, total and heterotrophic soil respirations, and groundwater level (GWL). We found that tree density varied from 1200 to 1825 trees per hectare (ha) across the plots, whereas the mean of stand basal area was 32.86 ± 4.72 m2 ha−1. Mean ecosystem C stocks in the study site was 1752 ± 401 Mg-C ha−1, of which 93% was stored in belowground organic peat soils. A mean aboveground litterfall production of 4.6 ± 0.5 Mg-C ha−1 year−1 and biomass C sequestration through tree diameter increment with 2.7 ± 0.5 Mg-C ha−1 year−1 was obtained. We observed slightly larger portion of annual mean total soil respiration with 14.2 ± 1.1 Mg-C ha−1 year−1 than heterotrophic respiration 11.1 ± 0.9 Mg-C ha−1 year−1, emphasizing the lower contribution of autotrophic respiration from the belowground rooting system. Findings imply that further conservation management efforts through ecosystem restoration may preserve C stored and enhance C input in PSFs substantially, and could be potentially included in national climate change mitigation strategies.

Soil carbon dioxide (CO₂) efflux was measured continuously for two years using an automated chamber system in an oil palm plantation on tropical peat. This study investigated the factors controlling the CO₂ efflux and quantified the annual cumulative CO₂ emissions through soil respiration and heterotrophic respiration, which is equivalent to oxidative peat decomposition. Soil respiration was measured in close-to-tree (< 2.5 m, CT) and far from-tree (> 3 m, FT) plots, and heterotrophic respiration was measured in root-cut (RC) plots by a trenching method. The daily mean CO2 efflux values (mean ±1 standard deviation) were 2.80±2.18, 1.59±1.18, and 1.94±1.581 μmol m⁻² s⁻¹ in the CT, FT, and RC plots, respectively. Daily mean CO₂ efflux increased exponentially as the groundwater level or water-filled pore space decreased, indicating that oxidative peat decomposition and gas diffusion in the soil increased due to enhanced aeration resulting from lower groundwater levels. Mean annual gap-filled CO₂ emissions were 1.03 ± 0.53, 0.59 ± 0.26, and 0.69 ± 0.21 kg C m⁻² yr⁻¹ in the CT, FT, and RC plots, respectively. Soil CO₂ emissions were significantly higher in the CT plots (P < 0.05), but did not differ significantly between the FT and RC plots. This implies that root respiration was negligible in the FT plots. Heterotrophic respiration accounted for 66% of soil respiration. Annual CO₂ emissions through both soil and heterotrophic respiration were smaller than those of other oil palm plantations on tropical peat, possibly due to the higher groundwater levels, land compaction, and continuous measurement of soil CO₂ efflux in this study. Mean annual total subsidence was 1.55 to 1.62 cm yr⁻¹, of which oxidative peat decomposition accounted for 72 to 74%. In conclusion, water management to raise groundwater levels would mitigate soil CO₂ emissions from oil palm plantations on tropical peatland.

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.

Restoration of deforested and drained tropical peat swamp forests is globally relevant in the context of reducing emissions from deforestation and forest degradation. The seasonal flux of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) in a restoration concession in Central Kalimantan, Indonesia, was measured in the two contrasting land covers: shrubs and secondary forests growing on peatlands. We found that land covers had high, but insignificantly different, soil carbon stocks of 949 + 56 and 1126 + 147 Mg ha−1, respectively. The mean annual CO2 flux from the soil of shrub areas was 52.4 ± 4.1 Mg ha−1 year−1, and from secondary peat swamp forests was 42.9 ± 3.6 Mg ha−1 year−1. The significant difference in mean soil temperature in the shrubs (31.2 °C) and secondary peat swamp forests (26.3 °C) was responsible for the difference in total CO2 fluxes of these sites. We also found the mean annual total soil respiration was almost equally partitioned between heterotrophic respiration (20.8 + 1.3 Mg ha−1 year−1) and autotrophic respiration (22.6 + 1.5 Mg ha−1 year−1). Lowered ground water level up to − 40 cm in both land covers caused the increase of CO2 fluxes to 40–75%. These numbers contribute to the provision of emission factors for rewetted organic soils required in the national reporting using the 2013 Supplement of the 2006 Intergovernmental Panel on Climate Change (IPCC) Guidelines for wetlands as part of the obligation under the United Nations Framework Convention on Climate Change (UNFCCC).

Tropical tree species distributions are determined by a wide range of biotic and abiotic factors, including topography and hydrology. Tropical peat swamp forests (TPSFs) are characterized in part by small‐scale variations in topography (‘hummocks’ and ‘hollows’) that create distinct microhabitats and thus may contribute to niche diversification among TPSF tree species. Using tree elevations calibrated to daily peat water levels collected using a data logger and a permutation test, we evaluated topographical microhabitat preferences for 21 tree species in a relatively undisturbed TPSF in Central Kalimantan, Indonesia, to determine whether these species show preferential association with hummocks or hollows and to quantify the prevalence of microhabitat specialization among them. Only one species, Tetractomia tetrandrum, emerged as a hollow specialist, with no hummock specialists among the species tested. The remaining 20 species, including Psydrax dicoccos, which had the lowest mean observed elevation, and Maasia hypoleuca, which had the highest mean observed elevation, showed no clear microtopographic preference. This suggests that many TPSF species may be resilient to the natural hydrologic variations that occur in relatively intact peat swamp forests. Such studies of microtopographic preferences of tree species in TPSF and other wetland forest ecosystems can inform selection of tree species for reforestation projects, and potentially also provide information on how future climate change may impact these habitats and their resident tree species.

Tropical peatlands are important for the global carbon cycle as they store 18% of the total global peat carbon. As they are vulnerable to changes in temperature and precipitation, a rapidly changing environment endangers peatlands and their carbon storage potential. Understanding the mechanisms of peatland carbon accumulation from studying past developments may, therefore, help to assess the future role of tropical peatlands. Using a multi-proxy palaeoecological approach, a peat core taken from the Sungai Buluh peatland in Central Sumatra has been analyzed for its pollen and spore, macro charcoal and biogeochemical composition. The result suggests that peat and C accumulation rates were driven mainly by sea level change, river water level, climatic variability and anthropogenic activities. It is also suggested that peat C accumulation in Sungai Buluh is correlated to the abundance of Freycinetia , Myrtaceae, Calophyllum , Stemonuraceae, Ficus and Euphorbiaceae. Sungai Buluh has reasonable potential for being a future global tropical peat C sinks. However, considering the impact of rapid global climate change in addition to land-use change following rapid economic growth in Indonesia, such potential may be lost. Taking advantage of available palaeoecological records and advances made in Quaternary studies, some considerations for management practice such as identification of priority taxa and conservation sites are suggested.

The biodiversity inhabiting tropical peat swamp forests in Southeast Asia is currently threatened by commercial logging and agricultural expansion. The occurrence of mammals in such forests is often poorly known and the factors influencing their occurrence in these ecosystems have rarely been quantified. We aim to determine the key habitat and landscape drivers of mammal species richness in fragmented peat swamp reserves. We conducted camera trap surveys in the North Selangor Peat Swamp Forest (NSPSF), the last remaining area of peat swamp forest on the west coast of Peninsular Malaysia. We also measured vegetation structure and landscape metrics to investigate the relationship between these factors and mammal richness. We recorded a total of 16 mammal species from 45 sampling sites using camera traps located in peat swamp forest reserves. Mammal species richness increased with the abundance of large trees and distance away from roads. Species richness decreased significantly with canopy cover and height, the abundance of fallen trees, the abundance of forest palms and saplings, distance away from rivers, and a measure of landscape compositional heterogeneity. Our findings underscore the high conservation value of logged peat swamp forests and the urgent need to halt further deforestation. We recommend: (1) protecting riparian habitat; (2) avoiding further forest conversion particularly areas supporting large trees into oil palm plantations; and (3) limiting road development within and around the NSPSF.

The recent expansion of oil palm (OP, Elaeis guineensis) plantations into tropical forest peatlands has resulted in ecosystem carbon emissions. However, estimates of net carbon flux from biomass changes require accurate estimates of the above ground biomass (AGB) accumulation rate of OP on peat. We quantify the AGB stocks of an OP plantation on drained peat in Malaysia from 3 to 12 years after planting using destructive harvests supported by non-destructive surveys of a further 902 palms. Peat specific allometric equations for palm (R2 = 0.92) and frond biomass are developed and contrasted to existing allometries for OP on mineral soils. Allometries are used to upscale AGB estimates to the plantation block-level. Aboveground biomass stocks on peat accumulated at ~6.39 ± 1.12 Mg ha−1 per year in the first 12 years after planting, increasing to ~7.99 ± 0.95 Mg ha−1 yr−1 when a ‘perfect’ plantation was modelled. High inter-palm and inter-block AGB variability was observed in mature classes as a result of variations in palm leaning and mortality. Validation of the allometries defined and expansion of non-destructive inventories across alternative plantations and age classes on peat would further strengthen our understanding of peat OP AGB accumulation rates.

Since the 1970s Southeast Asian peat swamp forests have been increasingly threatened by anthropogenic disturbance. Peat swamps act as refuge for many endangered species, and they may turn into a net producer of CO2 and greatly contribute to climate change if cleared and drained. As one of the main invertebrate decomposers in the tropics, termites are likely to play a major role in peat forests. In this paper, we used a grid-based sampling plot protocol to sample termites in Brunei. We sampled termite communities in pristine and selectively logged peat swamp forests, that we compared with termite communities sampled in heath and dipterocarp forests. More precisely, we determined: (i) termite species diversity in peat swamp forests, and (ii) how termites respond to peat swamp logging. We found that species richness was the highest in the mixed dipterocarp forest. Selective logging had limited impact on species richness in peat swamp forest, suggesting that termite communities are resilient to limited amount of perturbations. Further data are needed to better understand the impact peat swamp clearance has on termite populations and their contribution to climate change.

Tropical peat forests are a globally important reservoir of carbon, but little is known about CO2 exchange on an annual basis. We measured CO2 exchange between the atmosphere and tropical peat swamp forest in Sarawak, Malaysia using the eddy covariance technique over 4 years from 2011 to 2014. The CO2 fluxes varied between seasons and years. A small carbon uptake took place during the rainy season at the beginning of 2011, while a substantial net efflux of >600 g C/m2 occurred over a 2 month period in the middle of the dry season. Conversely, the peat ecosystem was a source of carbon during both the dry and rainy seasons in subsequent years and more carbon was lost during the rainy season relative to the dry season. Our results demonstrate that the forest was a net source of CO2 to the atmosphere during every year of measurement with annual efflux ranging from 183 to 632 g C m-2 year-1 , noting that annual flux values were sensitive to gap filling methodology. This is in contrast to the typical view of tropical peat forests which must have acted as net C sinks over time scales of centuries to millennia to create the peat deposits. Path analyses revealed that the gross primary productivity (GPP) and ecosystem respiration (RE) were primarily affected by vapour pressure deficit (VPD). Results suggest that future increases in VPD could further reduce the C sink strength and result in additional net CO2 losses from this tropical peat swamp forest in the absence of plant acclimation to such changes in atmospheric dryness.

This research was fully supported by a NERC Ph.D. Grant, from 2008 to 2012. The open access publication fees will be paid for by the University of St Andrews. Tropical peat swamp forests are invaluable for their role in storing atmospheric carbon, notably in their unique below-ground reservoirs. Differing from terra firme forests, the peat-forming function of tropical swamps relies on the integrity of discrete hydrological units, in turn intricately linked to the above-ground woody and herbaceous vegetation. Contemporary changes at a local, e.g. fire, to global level, e.g. climatic change, are impacting in the integrity and functioning of these ecosystems. In order to determine to what extent and predict their likely future response, it is essential to understand past ecosystem disturbance and resilience. Here, we explore the impact of burning on tropical peat swamp forests. Fires within degraded tropical peatlands are now commonplace; whilst fires within intact peat swamp forests are thought to be rare events. Yet little is known about their long-term natural fire regime. Using fossil pollen and charcoal data from three peat cores collected from Sarawak, Malaysian Borneo, we looked at the incidence and impact of local and regional fire on coastal peat swamp forests over the last 7000 years. Palaeoecological results demonstrate that burning has occurred in these wetland ecosystems throughout their history, with peaks corresponding to periods of strengthened ENSO. However, prior to the Colonial era c. 1839 when human presence in the coastal swamp forests was relatively minimal, neither local nor regional burning significantly impacted on the forest vegetation. After the mid-19th Century, at the onset of intensified land-use change, fire incidence elevated significantly within the peatlands. Although fire does not correlate with past vegetation changes, the long-term data reveal that open vegetation, a proxy for human forest clearance, does follow a similar pattern. Our results suggest that human activity may be strongly influencing and acting synergistically with fire in the recent past, leading to the enhanced degradation of these peatland ecosystems. However, intact tropical peat swamp forests can and did recover from local fire events. These findings support present-day concerns about the increase in fire incidence and combined impacts of fire, human disturbance and El Niño on peat swamp forests, with serious implications for biodiversity, human health and global climate change. Publisher PDF

Peatlands are environmental matrices that store large amounts of organic carbon (TOC) and work as records of environmental changes. Recent record of organic carbon accumulated were assessed in two Forest National Parks, Itatiaia and Serra dos Orgaos in the Southeastern of Brazil. Based on organic and inorganic characterization, the cores from peatlands presented a predominance of organic material in an advanced stage of decomposition and those soils were classified as typical Haplosaprists Histosols. The combination of favorable topographic and climatic conditions led to rapid C accumulation across coastal mountain in the tropical peatlands studied, presenting an average accumulation rate of C, in the last century, of 194 g C m− 2 yr− 1 about 7 higher times than the rate found in boreal and subarctic peatlands, those higher values may be related to changes in the hydrological cycle occurred since 1950s.

Tropical peat swamp forests (TPSFs) are found mainly in Southeast Asia and especially Indonesia. A total of 61% were lost between 1990 and 2015 and 6% remained in a pristine condition by 2015. Tropical peat swamps store vast amounts of carbon in their peat, but peat degradation, through drainage and fire, leads to high greenhouse gas emissions. This is gaining much international attention and, with it, policy initiatives and funding for restoration from local to landscape scales are being promoted. Unfortunately, although there is a now strong desire and need for TPSF restoration, methods are lacking. Ecological understanding is still at an early stage, and, even more so, in its applied use. There is an imbalance between the activities of TPSF restoration and sound ecological application. Furthermore, while many activities are underway and knowledge is being gained, these techniques are yet to be published. This article has been written to provide a common-sense, practical guide to tropical peatland forest restoration which summarizes what we know to date, while acknowledging the gaps in our understanding. Topics covered include species selection, land assessment, land selection, and appropriate nursery, transplanting, and monitoring methods. The authors make no apologies that in places this reads like a manual as, given the importance of tropical peatland recovery and the recent attention and funding opportunities available, it is essential we now provide techniques to restoration practitioners working on the ground, and a basic common-sense approach must be the starting point.

Fossil charcoal is reported for the first time from a Cisuralian coal bed of the Shanxi Formation in the Qiaotou Section, Baode, Shanxi, North China. Based on anatomical characteristics, these charcoal fragments consist of coniferous or cordaitalean xylem, unidentified primary xylem and cordaitalean and possible fern leaves. These charcoal fragments represent the evidence of palaeowildfire taking place in tropical peat swamps during the Cisuralian in Cathaysia. The palaeowildfire is most likely to be a surface fire and burning litter and shrubby vegetation. Fire frequency for this early Permian peat swamp might have been on the order of 176–(294–588)–1429 years, close to modern values. Compared with modern analogues, the North China Block during the Cisuralian was probably wet in general but could be occasionally seasonally dry for short time intervals. Previous charcoal and inertinite records moreover indicate that palaeowildfires were globally common during the Cisuralian. Overall, more wildfire evidence was found in the Artinskian–Kungurian than the Asselian-Sakmarian (except in the Euramerican Realm), probably due to more suitable regional climate, vegetation to fuel fires and taphonomic circumstances.

Tropical peat swamp forests in Southeast Asia account for approximately 72% of global peatland. However, extensive forest exploitation following peat drainage for agricultural expansion has been leading to catastrophic peat fires. In this study, we compared the termite assemblage in burnt and unburnt peats in Sumatra, Indonesia. We also identified which taxonomic group is particularly resistant to fire disturbance and the traits that correlate with its persistence in fire-impacted peatlands. Overall, the termite species richness in fire-impacted peats was up to 40% lower than that of the total species found in peat swamp forests. Although the estimated species richness values in fire-impacted peats and peat swamp forests were not significantly different, fire changed termite community structure significantly. Only termites of the family Rhinotermitidae survived in the fire event, whereas members of the Termitidae that were reportedly resilient to fire and open habitats elsewhere disappeared during the fire events. The rhinotermitids found in the burnt sites were exclusively wood nesters. This suggests that the desiccation tolerance of termites in open habitat is not the simple underlying survival strategy, but tree branches and barks might have provided a refuge from heat during fire. The result also suggests that the high similarity in species composition in recently burnt peats and long burnt peats implies low species turnover. Thus, regardless of how much time had passed since the fire-impacted peats were abandoned or cultivated, the increase in habitat complexity did not favor colonization by the forest-dependent group.

Increased demand for oil palms has led to a massive expansion of logging and conversion of peat swamp forests in Southeast Asia. Although palm oil is a primary driver of economic growth, the unsustainable expansion of the oil palm industry has led to the widespread degradation of peat swamp forests. Birds have been studied to determine their responses to landscape changes in the North Selangor Peat Swamp Forest (NSPSF). We captured 1045 birds from 72 species of the NSPSF and 168 individual birds from 13 species in oil palm plantations using mist-netting. Our results show that peat swamp forest supports more bird species than the oil palm areas. Non-metric Multidimensional Scaling revealed that both vegetation types had an influence on bird species composition. SIMPER analysis also showed that the percentage of the assemblage similarity within the oil palm areas was 51.30 %, while it was 31.32 % in the peat swamp. We found that the populations of frugivores, insectivores, and omnivores were significantly higher in the peat swamp forest, whereas there was no significant difference in the granivores between the two sites. To conserve peat swamp forests, stakeholders should implement habitat restoration, maintain landscape connectivity, and retain a forest area network.

Fire disturbance in many tropical forests, including peat swamps, has become more frequent and extensive in recent decades. These fires compromise a variety of ecosystem services, among which mitigating global climate change through carbon storage is particularly important for peat swamps. Indonesia holds the largest amount of tropical peat carbon globally, and mean annual CO 2 emissions from decomposition of deforested and drained peatlands and associated fires in Southeast Asia have been estimated at ∼2000 Mt y-1. A key component to understanding and therefore managing fire in the region is identifying the land use/land cover classes associated with fire ignitions. We assess the oft-asserted claim that escaped fires from oil palm concessions and smallholder farms near settlements are the primary sources of fire in a peat-swamp forest area in Central Kalimantan, Indonesia, equivalent to around a third of Kalimantan's total peat area. We use the MODIS Active Fire product from 2000 to 2010 to evaluate the fire origin and spread on the land use/land cover classes of legal, industrial oil palm concessions (the only type of legal concession in the study area), non-forest, and forest, as well as in relation to settlement proximity. We find that most fires (68–71%) originate in non-forest, compared to oil palm concessions (17%–19%), and relatively few (6–9%) are within 5 km of settlements. Moreover, most fires started within oil palm concessions and in close proximity to settlements stay within those boundaries (90% and 88%, respectively), and fires that do escape constitute only a small proportion of all fires on the landscape (2% and 1%, respectively). Similarly, a small proportion of fire detections in forest originate from oil palm concessions (2%) and within close proximity to settlements (2%). However, fire ignition density in oil palm (0.055 ignitions km −2 ) is comparable to that in non-forest (0.060 km-2 ignitions km- 2 ), which is approximately ten times that in forest (0.006 ignitions km −2 ). Ignition density within 5 km of settlements is the highest at 0.125 ignitions km −2 . Furthermore, increased anthropogenic activity in close proximity to oil palm concessions and settlements produces a detectable pattern of fire activity. The number of ignitions decreases exponentially with distance from concessions; the number of ignitions initially increases with distance from settlements, and, around from 7.2 km, then decreases with distance from settlements. These results refute the claim that most fires originate in oil palm concessions, and that fires escaping from oil palm concessions and settlements constitute a major proportion of fires in this study region. However, there is a potential for these land use types to contribute substantially to the fire landscape if their area expands. Effective fire management in this area should therefore target not just oil palm concessions, but also non-forested, degraded areas where ignitions and fires escaping into forest are most likely to occur.

Reliable information on total tree height (H) is fundamental in forest resource management and forest ecological studies, including in forest biomass assessment. Adding an H variable can improve the performance of the biomass allometric equations by reducing the average deviation significantly. However, measuring H is relatively complex, less accurate, time consuming, and expensive. Thus, H is only measured for sampled trees within the plots, whilst diameter at breast height (DBH) is commonly measured for each tree during the forest inventory. The missing H information is usually estimated based on a stand-specific allometric relationship between H and DBH (H-D model) constructed from sampled trees. Despite extensive studies on H-D model for boreal forests and for single-species/plantation forests, few studies have focused on tropical forests. Furthermore, relationships for peat swamp forest tree species, and especially those in Indonesia, have not been widely published. Thus, the objective of this study was to develop site-specific H-D models for tropical peat swamp forests using linearized and non-linear regression functions. The results indicated that the non-linear models outperformed the linearized models based on the statistical parameters and the biological criteria. The modified logistic function (Model 7) is recommended for estimating H in the study area as it has comparable model performances to the exponential function (Model 6) and passed the point diameter-height of (0, 1.3). However, all five non-linear models performed equally well and the differences between them were trivial. Further improvements are needed to improve the accuracy, the predictive ability and the geographical applicability of the models by grouping the species, adding stand variables and (or) using advanced techniques of mixed-effect modelling. In addition, model validation should be carried out prior to their application by collecting a new dataset from the forest being studied.

Intensive land use plays a major role in tropical peat swamp deforestation in Southeast Asia. In Peninsular Malaysia, the North Selangor Peat Swamp Forest (NSPSF) is the second largest remaining peatland ecosystem. Although the NSPSF is recognized as a biodiversity hotspot area in the region, this peat swamp forest is rapidly shrinking because of the expansion of commercial oil palm agriculture. More than 87% of the NSPSF has been designated as reserves, but in reality, this is not comparable to protected area status. The NSPSF is under constant threats from forest conversions, forest fires, and road constructions. Faunal biodiversity loss is likely to occur in the NSPSF unless immediate action is taken by stakeholders. To determine the habitat occupancy and activity rate of native mammals, we conducted camera-trap survey at 45 sites located within the NSPSF. From a total survey effort of 2565 trap nights in an area of 778 km2, 16 mammal species were recorded. Our data provide vital information on the occupancy of high conservation value species in the NSPSF. However, we did not record Sumatran rhinoceros (Dicerorhinus sumatrensis) and Malayan tiger (Panthera tigris), nor did we find any indirect evidence such as footprints, indicating that these species are extirpated from this region. We found that mammal activity rate responded differently to in situ habitat quality and landscape factors according to feeding guild. Government stakeholders should focus on prohibiting further forest conversion and prioritize the upgrading NSPSF’s conservation status from reserve to protected area.

The increased frequency and spread of tropical peat fires over the last two decades have attracted global attention because they cause significant environmental and health impacts at local to global scales. To understand the relative importance of key factors controlling tropical peatland burning events, we developed PeatFire, an agent-based model simulating the interaction between human-induced ignitions, fire and peat characteristics. The model describes (1) above- and belowground fires, which spread independently but interact with each other; (2) above- and belowground biomass; and (3) the watertable determining peat dryness and susceptibility to fire. We applied PeatFire to a region in South Sumatra that has experienced profound natural rainforest loss due to peat fires. Sensitivity analysis of the model suggests that fire sizes depend mostly on watertable depth, peat-dry-index and number of dry days before ignition. Using pattern-oriented modelling, these factors were parameterised so that the model output matches spatiotemporal fire patterns observed in the study region in 2015. Our results emphasise the risk of a sudden shift from moderate fire occurrence to complete burning and highlight the importance of local context to peatland regulation, which should consider both biophysical and socioeconomic factors and strategies for peatland fire management.

Tropical peat swamp forests (PSF) are characterized by high quantities of carbon (C) stored as organic soil deposits due to waterlogged conditions which slows down decomposition. Globally, Peru has one of the largest expanse of tropical peatlands, located primarily within the Pastaza-Marañón river basin in the Northwestern Peru. Peatland forests in Peru are dominated by a palm species—Mauritia flexuosa, and M. flexuosa-dominated forests cover ~ 80% of total peatland area and store ~ 2.3 Pg C. However, hydrologic alterations, land cover change, and anthropogenic disturbances could lead to PSF’s degradation and loss of valuable ecosystem services. Therefore, evaluation of degradation impacts on PSF’s structure, biomass, and overall C stocks could provide an estimate of potential C losses into the atmosphere as greenhouse gases (GHG) emissions. This study was carried out in three regions within Pastaza-Marañón river basin to quantify PSF’s floristic composition and degradation status and total ecosystem C stocks. There was a tremendous range in C stocks (Mg C ha −1 ) in various ecosystem pools—vegetation (45.6–122.5), down woody debris (2.1–23.1), litter (2.3–7.8), and soil (top 1 m; 109–594). Mean ecosystem C stocks accounting for the top 1 m soil were 400, 570, and 330 Mg C ha −1 in Itaya, Tigre, and Samiria river basins, respectively. Considering the entire soil depth, mean ecosystem C stocks were 670, 1160, and 330 Mg C ha −1 in Itaya, Tigre, and Samiria river basins, respectively. Floristic composition and calcium to Magnesium (Ca/Mg) ratio of soil profile offered evidence of a site undergoing vegetational succession and transitioning from minerotrophic to ombrotrophic system. Degradation ranged from low to high levels of disturbance with no significant difference between regions. Increased degradation tended to decrease vegetation and forest floor C stocks and was significantly correlated to reduced M. flexuosa biomass C stocks. Long-term studies are needed to understand the linkages between M. flexuosa harvest and palm swamp forest C stocks; however, river dynamics are important natural drivers influencing forest succession and transition in this landscape.

Dryobalanops rappa Becc. and Shorea albida Sym. are Bornean endemics of high conservation value and increasingly threatened by anthropogenic disturbances. In-situ study of seedling abundance and growth performance of these Dipterocarp species was conducted in two selected peat swamp forests of Brunei Darussalam, following a mast fruiting event in March–May 2014. Within six 6 x 6 m plots at each forest site, D. rappa seedlings at the Anduki peat swamp forest and S. albida seedlings at the Badas peat swamp forest were measured for abundance at the initial census in September 2014, as well as survival and relative growth rates (RGR) after a period of 5 months, with the final census in February 2015. We found significantly higher seedling abundance for D. rappa (1885 ± 208) than S. albida (160 ± 71). Significantly higher percentage survival was recorded for D. rappa seedlings (90.8 ± 2.2%) in comparison to S. albida seedlings (81.7 ± 2.2%). S. albida seedlings (0.24 ± 0.02 mm mm -1 month -1 ) showed significantly greater RGR in stem diameter than D. rappa seedlings (0.18 ± 0.02 mm mm -1 month -1 ) , however, there were no significant differences in the RGRs based on seedling height, leaf number and biomass between D. rappa and S. albida seedlings. In terms of seedling abundance and percentage survival, D. rappa seedlings appeared to be more successful in regeneration and may potentially be used for rehabilitation of degraded tropical peat swamps and other forest types. Our results suggested that greater conservation efforts of peat swamps must be made to protect the Bornean endemic plant species, in particular S. albida .

The tropical peat swamp forests of South-East Asia are being rapidly converted to agricultural plantations of oil palm and Acacia creating a significant global "hot-spot" for CO2 emissions. However, the effect of this major perturbation has yet to be quantified in terms of global warming potential (GWP) and the Earth's radiative budget. We used a GWP analysis and an impulse-response model of radiative forcing to quantify the climate forcing of this shift from a long-term carbon sink to a net source of greenhouse gases (CO2 and CH4 ). In the GWP analysis, five tropical peatlands were sinks in terms of their CO2 equivalent fluxes while they remained undisturbed. However, their drainage and conversion to oil palm and Acacia plantations produced a dramatic shift to very strong net CO2 -equivalent sources. The induced losses of peat carbon are ~20× greater than the natural CO2 sequestration rates. In contrast, a radiative forcing model indicates that the magnitude of this shift from a net cooling to warming effect is ultimately related to the size of an individual peatland's carbon pool. The continuous accumulation of carbon in pristine tropical peatlands produced a progressively negative radiative forcing (i.e., cooling) that ranged from -2.1 to -6.7 nW/m2 per hectare peatland by 2010 CE, referenced to zero at the time of peat initiation. Peatland conversion to plantations leads to an immediate shift from negative to positive trend in radiative forcing (i.e., warming). If drainage persists, peak warming ranges from +3.3 to +8.7 nW/m2 per hectare of drained peatland. More importantly, this net warming impact on the Earth's radiation budget will persist for centuries to millennia after all the peat has been oxidized to CO2 . This previously unreported and undesirable impact on the Earth's radiative balance provides a scientific rationale for conserving tropical peatlands in their pristine state.

Forest fire in Malaysia’s peat swamp forest is a major concern since it is contributing to the country’s haze episode. Forest fire in peat areas is difficult to be extinguished and may occur for days. Understanding fuel characteristics is the key to develop effective fuel management in peat swamp forest. The objectives of this study were to evaluate the common species coverage and calorific value of the common plants species in the burnt peat swamp forest. The study was conducted in the rehabilitated areas of Raja Musa Forest Reserved, Selangor, Malaysia. 9 plots were established along canal 6 in Compartment 100 of the Raja Musa Forest Reserved. Plants were surveyed in the 9 plots and based on the survey, 8 species (Imperata cylindrica, Macaranga pruinosa, Nephrolepis biserrata, Melastoma malabathricum, Lygodium flexuosum, Uncaria tomentosa, Scleria sumatrensis and Melicope latifolia) most higest coverage found in that area. Scleria sumatrensis had the highest coverage of 40% followed by Melastoma malabathricum of coverage of 21%. The data suggested that the 8 species covered most of the study area and have the potential to be forest fuel. Uncaria Tomentosa had the highest calorific value with 4832.8 cal/g while Nephrolepis biserrata had the lowest value of 3825.2 cal/g. The findings concluded that the Sceleria sumatrensis had the highest coverage and calorific values of the selected plants vary with species. These information provide insight on the species common in burnt tropical peat swamp forest and are helpful in formulating forest fire control programme.

In South East Asia, increased population and agricultural demands, especially for oil palm cultivation, have led to peatland conversion, resulting in environmental degradation. To conserve peatland’s function as a biodiversity and carbon reservoir, restoration of an oil palm plantation after burning in tropical peat swamp area was carried out by revegetation using native peat swamp forest plants, together with land rewetting. To monitor the success of the restoration process, soil sampling was carried from that restoration area as well as surrounding natural forest and burned oil palm plantation as comparisons. Analyses of physico-chemical and biological revealed substantial differences after 3.5 years of restoration between the restored soil and both burned oil palm plantation and the natural forest soils. These differences were seen in both physical and chemical characteristics (including water holding capacity (WHC), bulk density (ρb), organic matter, and concentration of ammonium, nitrate and phosphate) as well as the activity and diversity of soil microbial community. Increased viable microbial biomass (118% compared with burned oil palm plantation soil) and substrate utilising capacity (31% increase compared with the natural forest soil) as determined by Community Level Physiological Profiling (CLPP) indicated that the restoration of the soil has resulted in significant changes in soil microbial activity. Analysis of all the parameters measured using Principal Component Analysis (PCA) allowed examination of the relationship between the physical-chemical and biological properties of each of the three soils and revealed that, as like other ecosystems, pH and soil phosphatase activity may be useful management parameters in terms of monitoring the restoration progress of tropical peatlands.

Tropical peat forest ecosystems have multiple benefits as regulating hydrological system, carbon storage, timber and non-timber products, and protecting the biodiversity. Lack of understanding of these functions, short-term economic benefits is more preferable despite reducing its ecological benefits. This study proposed a system dynamics model of tropical peat forest ecosystem in determining its optimum management for extractive utilizations (timber and non-timber forest products), environmental services, and biodiversity. A dynamics model was used to describe changes in peatland and forest cover, biomass accumulation and carbon storage, and total economic value of tropical peat forest ecosystem in Trumon and Singkil, Southern Aceh. The projection showed that peat forest ecosystem benefits would decline in the long term if degradations continue at the same rate over last decade. Efforts to change the primary peat forest to plantation would reduce the total economic value of ecosystem and biodiversity values at level -19.63% and -26.28% from current conditions. Carbon emissions were increased at 117.32 tons CO2 eq ha-1 year-1, higher than average of carbon losses from peatland oxidation. Preserving 50% of forest vegetation on moderate depth and protection very deep peatlands would reduce emission -6.96% to -35.06% and increase forest carbon storage at significant rate +15.06% to +63.32%, respectively. These mitigation schemes would improve the biodiversity and hydrological function. Forest rehabilitation with agroforestry practices will enhance carbon uptake, especially on degraded lands.

Forest canopy structure is strongly influenced by environmental factors and disturbance, and in turn influences key ecosystem processes including productivity, evapotranspiration and habitat availability. In tropical forests increasingly modified by human activities, the interplay between environmental factors and disturbance legacies on forest canopy structure across landscapes is practically unexplored. We used airborne laser scanning (ALS) data to measure the canopy of old-growth and selectively logged peat swamp forest across a peat dome in Central Kalimantan, Indonesia, and quantified how canopy structure metrics varied with peat depth and under logging. Several million canopy gaps in different height cross-sections of the canopy were measured in 100 plots of 1 km2 spanning the peat dome, allowing us to describe canopy structure with seven metrics. Old-growth forest became shorter and had simpler vertical canopy profiles on deeper peat, consistent with previous work linking deep peat to stunted tree growth. Gap size frequency distributions (GSFDs) indicated fewer and smaller canopy gaps on the deeper peat (i.e. the scaling exponent of Pareto functions increased from 1.76 to 3.76 with peat depth). Areas subjected to concessionary logging until 2000, and illegal logging since then, had the same canopy top height as old-growth forest, indicating the persistence of some large trees, but mean canopy height was significantly reduced. With logging, the total area of canopy gaps increased and the GSFD scaling exponent was reduced. Logging effects were most evident on the deepest peat, where nutrient depletion and waterlogged conditions restrain tree growth and recovery. A tight relationship exists between canopy structure and peat depth gradient within the old-growth tropical peat swamp forest. This relationship breaks down after selective logging, with canopy structural recovery, as observed by ALS, modulated by environmental conditions. These findings improve our understanding of tropical peat swamp ecology and provide important insights for managers aiming to restore degraded forests.

In Southeast Asia, peatland is widely distributed and has accumulated a massive amount of soil carbon, coexisting with peat swamp forest (PSF). The peatland, however, has been rapidly degraded by deforestation, fires and drainage for the last two decades. Such disturbances change hydrological conditions, typically groundwater level (GWL), and accelerate oxidative peat decomposition. Evapotranspiration (ET) is a major determinant of GWL, whereas information on the ET of PSF is limited. Therefore, we measured ET using the eddy covariance technique for four to six years between 2002 and 2009, including El Niño and La Niña events, at three sites in Central Kalimantan, Indonesia. The sites were different in disturbance degree: a PSF with little drainage (UF), a heavily drained PSF (DF) and a drained burnt ex-PSF (DB); GWL was significantly lowered at DF, especially in the dry season. The ET showed a clear seasonal variation with a peak in the mid-dry season and a large decrease in the late dry season, mainly following seasonal variation in net radiation (Rn). The Rn drastically decreased with dense smoke from peat fires in the late dry season. Annual ET forced to close energy balance for four years was 1636 ± 53, 1553 ± 117 and 1374 ± 75 mm yr-1 (mean ± 1 standard deviation), respectively, at UF, DF and DB. The undrained PSF (UF) had high and rather stable annual ET, independently of El Niño and La Niña events, in comparison with other tropical rainforests. The minimum monthly-mean GWL explained 80% of interannual variation in ET for the forest sites (UF and DF); the positive relationship between ET and GWL indicates that drainage by a canal decreased ET at DF through lowering GWL. In addition, ET was decreased by 16% at DB in comparison with UF chiefly because of vegetation loss through fires.