With regard to the management of oil palm planta- tions on peatland, our measurements showed that all three Sabaju plantation sites had mean water table depths that were above the Roundtable on Sustainable Palm Oil’s (RSPO) tar- get range of 40 to 60 cm below the surface, whereas the Se- bungan site fell within this range. While the Sabaju plan- tation had lower DOC fluxes and all sites had lower rates of DOC loss than the highly degraded peatland sites stud- ies by Moore et al. (2013), the 14 C-depleted DOC measure- ments (relative to previous data from undrained peatswampforests) obtained from all study sites indicate release of older stored carbon. This suggests that even RSPO-compliant plan- tations may still be expected to experience elevated fluvial loss of previously stored peatcarbon, which is also indica- tive of drainage-induced C loss more generally (Evans et al., 2014). Managing oil palm plantations on peat to min- imise both gaseous and fluvialcarbonlosses thus remains a significant challenge, requiring coordination among gov- ernments, the plantation industry, and academia (Wijedasa et al., 2016). However, our results suggesting relationships be- tween drainage depth and DOC concentration and flux and
Previous attempts to quantify fluvialcarbonlossesfromtropical peatlands include Moore et al. (2013), Gandois et al. (2013), Wit et al. (2015), Rixen et al. (2016), and Yupi et al. (2016). Moore et al. (2013) reported that losses of DOC from disturbed tropical peatlands in Indonesia were around 50 % greater than those from an adjacent intact peatswamp forest. However, this research was based on a limited num- ber of field sites (three intact sites and five degraded sites, all of which had unregulated drainage). Additional data are needed to better understand the dynamics of DOC in more intensively managed peatland environments with controlled drainage systems. This includes tropical peatland oil palm plantations where fluvialcarbonlosses remain unquantified. In addition, existing data demonstrate that the radiocarbon content of exported DOC (DO 14 C) from intact tropicalpeatswampforests is consistently modern (Moore et al., 2013; Gandois et al., 2013; Müller et al., 2015). DO 14 C data for degraded tropical peatlands are more limited, particularly for peatland oil palm plantations. Moore et al. (2013) re- ported DO 14 C data from five channels in drained and de- forested peatlands in Indonesia, with mean ages of 92 to 2260 years BP, and two measurements from oil palm planta- tions in Peninsular Malaysia which had mean ages of around 3200 and 4200 years BP. These limited data clearly suggest that tropical peatland drainage releases DOC from long-term carbon stores but are insufficient to determine whether differ- ent forms of post drainage land use (e.g. oil palm cultivation versus abandonment) or hydrological management (e.g. reg- ulated versus unregulated drainage) lead to different rates or age of DOC export. There is a particular need to acquire ad- ditional data from oil palm plantations as the most extensive, but currently under-represented, post-clearance land use on tropicalpeat.
Susan Waldron 1 , Leena Vihermaa 1 , Stephanie evers 2,3 , Mark H. Garnett 4 ,
Jason newton 5 & Andrew C. G. Henderson 6
Southeast-Asian peatswampforests have been significantly logged and converted to plantation. Recently, to mitigate land degradation and C losses, some areas have been left to regenerate. Understanding how such complex land use change affects greenhouse gas emissions is essential for modelling climate feedbacks and supporting land management decisions. We carried out field research in a Malaysian swamp forest and an oil palm plantation to understand how clear-felling, drainage, and illegal and authorized conversion to oil palm impacted the C cycle, and how the C cycle may change if such logging and conversion stopped. We found that both the swamp forest and the plantation emit centuries-old co 2 from their drainage systems in the managed areas, releasing sequestered C to the atmosphere. Oil palm plantations are an iconic symbol of tropical peatland degradation, but CO 2 efflux from the recently-burnt, cleared swamp forest was as old as from the oil palm plantation. However, in the swamp forest site, where logging had ceased approximately 30 years ago, the age of the CO 2 efflux was modern, indicating recovery of the system can occur. 14 C dating of the C pool acted as a tracer of recovery as well as degradation and offers a new tool to assess efficacy of restoration management. Methane was present in many sites, and in higher concentrations in slow-flowing anoxic systems as degassing mechanisms are not strong. Methane loading in freshwaters is rarely considered, but this may be an important C pool in restored drainage channels and should be considered in C budgets and losses.
ABSTRACT. Southeast Asia’s tropicalpeat-swampforests (TPSF) are globally important for carbon storage and biodiversity conservation, but are at risk from multiple threats and urgently require improved management. Ants are often used as ecological indicators in monitoring programmes to guide adaptive management, but data on TPSF ants are scarce. We conducted a twelve-month study on ants in the Sabangau TPSF in Indonesian Borneo using baited traps, to compare community composition across three disturbance categories (forest gaps, forest edge and relatively undisturbed interior forest) and between dry and wet season. The three disturbance categories supported distinct ant communities across seasons. Differences in canopy cover likely underlie these changes in ant community composition. Surveying was more effective in the dry season, because ant capture rates were higher and more indicator taxa were identified than in the wet season, but overall ant community composition did not differ significantly between seasons. These findings suggest a potentially useful role of ants as ecological indicators in TPSF. Further surveys should be conducted in Sabangau and other TPSFs to test the transferability of our findings.
In summary, using an experimental approach, we show that lianas greatly reduce net carbon uptake and storage in this for- est by reducing tree growth and recruitment, increasing tree mortality, and shifting forest-level carbon allocation to leaves rather than woody tissue. In the presence of lianas, these forests act as carbon sinks, but, based on our results, they only reach ∼24% of their carbon sink potential when compared to liana- free forests. Longer-term data are needed to assess whether this initial difference in carbon sink potential persists over time. Notwithstanding, our results indicate that, due to their unique attributes, lianas have the potential to severely reduce both the carbon sink potential and long-term carbon storage capacity of tropicalforests. While the strength of the liana effect will vary with the density and biomass of lianas, the increase in liana density, biomass, and productivity reported in many neotropical forests (9, 10, 23) may be partially responsible for the long- term decline in the Amazonian carbon sink (24), which in turn contributes to increasing atmospheric carbon dioxide levels and accelerated climate change.
2.8. Enzyme Activities
Four soil enzymes, β-glucosidase and cellobiohydrolase (key enzymes in carbon cycling), chitinase (involved in both the N and C cycles), and acid phosphatases (involved in the phosphorous cycle) were selected for study based on their importance in nutrient cycling in soils (Girvan et al., 2003). Modified enzyme assay protocols of Tabatabai and Bremner’s original method (Tabatabai and Bremner, 1969) were used. This involved the use of p- nitrophenol (p-NP) linked substrates and the colorimetric determination of pNP released by each enzyme when soil was incubated with a buffered substrate solution. For each enzyme, soil (5 g) was mixed with 0.05 M acetate buffer (50 ml, pH 5.0 for all enzymes) and placed on a magnetic stirrer. Aliquots (2 ml) of slurry were pipetted and transferred to polypropylene tubes, which were kept chilled pending incubation. At the beginning of incubation, 2 ml of substrate (prepared at 2 mM concentration) were added to each sample. The tubes were then capped and placed on a rotary shaker for 2 h at 25 0 C. Following incubation, tubes were centrifuged at 3900 × g for 5 min and aliquots (150 µl) of supernatant were taken from each tube and transferred into microplates containing 1 M NaOH,(30 µl) to stop the reaction and cause a colour change. The assays were mixed and absorbance values measured with a BioRad iMark Microplate Reader at 410 nm. Substrate and sample controls were routinely included. The concentration of p-NP detected in samples after incubation was corrected by subtracting the combined absorption results for the sample and substrate controls from the analytical samples. Enzyme activity was expressed as µmol p-NP/g soil/hour.
Figure 3 shows the spatial changes in land covers detected by the DI model and its comparison of changes with high-resolution images from Google Earth™ in the same period (2006 and 2012). The model appears to detect and locate patterns of change in land covers, especially highlighting areas where vegetation has increased or re- mained unchanged. Increased vegetation is found mostly in plantation areas, but stable vegetation areas are lo- cated in agricultural regions and some parts of the native forest within the protected areas (Figure 4). The DI can indicate areas of vegetation decrease; however, some of these areas were not detected well, including native forest clearances. The interpretation of the Google Earth™ indicates that most forest clearance has occurred in relatively tiny areas, due to shifting cultivation practices and small-sized agriculture. Some of these small scat- tered areas of forest clearances went undetected by the model. This approach tends to capture large spatial changes in land covers, preferably >1 km 2 . For example, continuous extended areas showing an increase in ve- getation cover were well detected, such as rubber plantations.
lowland forest ecosystems, freshwater swamp forest provides a corridor for the migration of flora and fauna between these ecosystems as well as being floristi- cally unique . Swampforests contribute to the provision of ecosystem services across the Nigerian state and like other tropicalforests, are potential stores of carbon and important for climate regulation and biogeochemical cycling  . Swampforests support the majority of households across the region that has de- pended on it for subsistence and livelihood, over the last 400 years . However, this ecosystem has been steadily exploited, its extent has reduced, been degraded and is now confined to small pockets across the Niger Delta. As a result, its spe- cies like in most other old growth forests across the tropics  , are not only threatened and fragmented, but the ecosystem services they provide are reduced. These changes have impacted the forest landscape adversely and reduced the former extensive ecosystem into mosaics of forest islands.
In each plot, we deployed ﬁve 0.75 m x 0.75 m litterfall traps with 1 mm mesh 0.75 - 1 m above the ground. Litter traps were spaced at least 5 m apart and were arranged in a pattern that was consistent among plots. Litterfall was collected monthly starting in the second month after liana cutting, thus excluding the initial pulse of dead leaves from the liana cutting. Leaves were dried at ∼ 65 °C, sorted into different components in an air conditioned lab, and then weighed. The fractions included: leaves plus petioles, ﬂowers, fruits plus seeds, twigs (< 5 cm diameter) and unidentiﬁed ﬁne debris. In the control plots, we combined tree and liana litter to account for canopy- level productivity in a manner similar to the liana removal plots. To convert litter biomass into carbon estimates, we assumed a litterfall carbon fraction of 47.1% (41), which was based on ∼ 1000 leaf samples from across the Amazon. We did not attempt to correct the litterfall measurements for losses due to herbivory, branch falls, and biogenic organic compounds, nor did we account for palm litter. For both treatments, we assumed that the ﬂux of carbon into canopy productivity equalled the ﬂux of carbon out of it, i.e. the amount of above-ground net primary productivity allocated annually to the canopy should be equal to the litterfall. However, as a result of the liana cutting itself, litterfall in the liana removal plots was initially higher due to increased litter of dead liana twigs (SI Appendix 2), which violated the above-mentioned assumption for the ﬁrst 1.5 year of the experiment. Nonetheless, twig litterfall in the liana removal plots decreased to levels similar to that in the control plots approximately 1.5 year after liana cutting, and thus including twig litterfall in total canopy productivity estimates in year 3 did not change the patterns found (SI Appendix 2). To facilitate comparison between all years of the experiment, we therefore present estimates of canopy productivity excluding the twig component for both the liana removal and the control plots in the main text.
which may be due to our comprehensive experimental approach rather than an observational one, 11 and our focus on forest-level carbon
dynamics rather than on treefall gaps alone. 2
Lianas substantially augmented forest-level leaf productivity and changed the relative amounts of carbon stored in leaves and wood. Forests canopy productivity decreased by 14.0% (95% bootstrap CI, 5.8–22.8%) when lianas were removed (Fig. 2A), primarily due to the decrease in leaf productivity (SI Appendix 2). The difference in leaf productivity between the removal and control plots remained relatively constant over time (∼10–15% difference), indicating that the lower leaf productivity was not the result of tree canopies still recovering from previous liana infestation. Conversely, forest-level woody stem productivity increased by 64.5% (95% bootstrap CI, 18.4–120.6%) after liana removal (Fig. 2B), more than completely offsetting the lower canopy productivity (Fig. 2C). Thus, by increasing the contribution of leaf productivity to aboveground net primary
This study also represents the first global application of the CASA model’s  predictions of forest biomass using MODIS data inputs to infer carbon fluxes from land cover change. As recommended by Ramankutty et al. , our CASA modeling framework has been de- signed to estimate historical as well as current monthly patterns in plant carbon fixation, living biomass incre- ments, and long-term decay of slash pools before, during, and after land cover disturbance events . The unique aspects of our methodology are in the combination of MODIS satellite images to first quantify and map stand- ing vegetation biomass pools across the globe in manner consistent with stand age, tree production estimates, and soil properties, and second to simulate both the gross and net loss of carbon to the atmosphere in a mechanistic manner that maps and tracks all the pools of wood and herbaceous litter remaining for years following distur- bance. In tropical forested areas, we have used MODIS data to model the carbon cycle prior to deforestation, and then immediately reduce plant carbon uptake to observed levels in field-based studies of forest clearing. All model carbon pools (wood, leaf, and root) have been altered dynamically in the simulations of clearing and burning anywhere and everywhere that land cover change has been mapped out.
Peatlands can be found from almost all over the world, but in the tropical and subtropical region have a higher percentage. Around 88.6 Pg is stored in peat- lands worldwide, whereas 68.5 Pg soil carbon (C) (77%) presents in Southeast Asia. The reported evidence of carbon emissions is found in South Asia, USA, Canada, Australia, China, Siberia, Denmark, a Caribbean island, France, Brazil, mangrove forests, and tropical grasslands that have higher emissions rate -. However, most of the peat soils are mainly found in the USA, Western Europe, Eastern Asia, and Central America, Tibetan grassland   . Maitra et al. studied the distribution of peat soils in Bangladesh and possible economic uses as fuel . The distribution of peat soils in Bangladesh is hig- hlighting in Figure 1. There are lots of factors that control the carbon storage in the soil including temperature, slope, and elevation. Additionally, pasturing, land use change and vegetation pattern also have considerable influences on the presence of soil organic carbon in peat soils. Land modification on peatlands re- sults in enormous carbon instabilities by deforestation and sweltering  .
Microorganisms catalyze biogeochemical shifts through changes in enzyme production . In terms of enzyme activity, the activities in soils of peatswamp forest and those converted to agricultural land were found to vary considerably (0.13 - 4.96 µmol p-NP g −1 ·h −1 ) (Figure 1). Comparing the data from the current study with other reported soil enzyme activities in other environments, the values reported here were lower in terms of β-gluco- sidase, but higher for acid phosphatase . Generally, for mineral soil, enzyme activities in arable soil are higher than enzyme activities of forest soils; however, Kanokratana et al.  reported that metagenomicanaly- sis showed that for peatswamp forest soils, the number of genes encoding polysaccharide degrading enzymes was significantly higher than that found in sludge and farm soil. This study shows that apart from chitinase ac- tivities, conversion of peatland for agricultural use resulted in a reduction of β-glucosidase, cellobiohydrolase and acid phosphatase activities. The relatively high chitinase activity suggests a high metabolic demand for N released during chitin turnover . Although not significantly different, the slightly higher acid phosphatase activity in NF and RP soils may have be driven by microbial C demand, considering the relatively large P-availability . Currently there is comparatively limited information available on enzyme activities in peat- lands and the impact of conversion to agricultural use. Bowles, Acosta-Martínez  stated that variation in en- zyme activities could not be explained simply by soil type due to the narrow range of soil textures in peatland soil. The nutrient requirements of soil microbiota are dependent not only on the microbial community but also on the physical and chemical environment surrounding their habitats. Studies such as this are therefore impor- tant in generating baseline information on enzyme activities in converted tropical peatlands in addition to as- sessing the effects of peatland conversion.
resolution used in the present study. Earlier versions of the algorithm were criticized for underestimating burned area (van der Werf et al., 2017). In an effort to reduce this bias, the algorithms of Randerson et al., (2012) for detecting small fires using the MODIS 1-km thermal anomalies (active fires) product MOD14A1 were extended and incorporated into the GFED algorithm (van der Werf et al., 2017). The incorporation of small fires has significantly boosted the detection of burned area globally (van der Werf et al., 2017). Yet in the case of humid tropicalforests, which generally have dense closed canopies and experience relatively low- intensity understorey wildfires, burned area is evidently still substantially underestimated. GFAS uses empirical relationships between fire radiative power (FRP), as measured by the MODIS Aqua and Terra satellites, and dry matter combustion rates and gas species emissions rates without estimating burned area (Kaiser et al., 2012). This approach is much less demanding computationally and for this particular study region and period, has been more successful at capturing the CO 2 emissions from the understorey wildfires in central-eastern Amazonia.
considered an important factor of forest degradation. Selective logging consists in harvesting only a few trees and leaving the rest of the forest to natural regeneration until the next logging event. Selective logging practices result in long-lasting carbon emissions to the atmosphere . In the sole Brazilian Amazon, forestry-related carbon emissions are estimated to be equivalent to 60–123 % of deforestation emissions . Emissions come from (i) the extracted wood, (ii) logging damage, i.e. trees killed (purposely or incidentally) during logging operations and (iii) skid trails, logging roads and decks used for log yarding. Logging operations (e.g. tree felling, log yarding or skidding) induce incidental damage to surrounding trees, proportional to logging intensity in conventional  or reduced impact logging . Injured or smashed trees generally die soon after logging operation [8, 9], and, along with log residuals such as crowns or stumps, are left over in the forest. The quite slow decay of these woody debris and harvested logs is a long-term source of carbon to the atmosphere.
First, undisturbed forest areas of 3,393 ha, that had no or no visible impact, were identified. Second, logging trails were identified on the basis of high temporal and spatial resolution RapidEye data. Figure 7 depicts four different RapidEye scenes showing the example of a selective logged area. The narrow skid trail infrastructure, which is clearly visible, was fast evolving and the rapid regrowth of the vegetation after the logging activities stopped hindered the detection of the full extent of logging in the RapidEye images. All skid trails that could be detected with available RapidEye imagery are also shown in Figure 7 (“detected logging trails”). On the basis of repetitive field observations, the area within 30 m and 50 m of the detected logging trails was analyzed and amounted to 67 ha and 113 ha, respectively. Third, forested areas that burned once between both LiDAR acquisitions were evaluated. This is important because recurrent fires further reduce AGB. Altogether, 555 ha of initial peatswampforests within the study area burned.
Data set 1: hollow diameter at breast height
Large trees in Sarawak peatswampforests, such as S. albida have cylindrical hollow stems (Yamada 1997 ; Monda et al.
2015 ; Fig. 1 a, b). The diameter of the hollow region at breast height (D hollow , cm), in which breast height was defined as 1.3 m above the ground or 0.3 m above the buttress root, was used as an index of hollowness. Hollow trunks were determined by core sampling using an increment borer. Two core samples per tree were taken from at positioned at right angle or 180° to each other. This core sample corresponded to sound tissue thickness (including bark and wood). A hollow trunk was defined as one in which the sum of both core samples was less than the DBH. Shorea albida trees of diverse sizes were selected to cover the entire range of tree sizes likely to be encountered in each forest type of the Maludam National Park. We sampled 81 trees in Maludam National Park (26 trees in Type-1, 32 trees in Type-2, and 23 trees in Type-3). Destructive sampling was conducted in logged peatswamp forest for seven trees in Type-2 to collect data on hollow diameter per m height, and D hollow . Details