Conversion of peat swamp forests to oil palm plantations has significant implications for soil CO2 emissions, but the magnitude of this impact remains highly uncertain. To evaluate the effects of this conversion on soil CO₂ fluxes, monthly measurements of soil CO₂ flux, environmental conditions, and soil chemical properties were conducted in a peat swamp forest undergoing conversion to an oil palm plantation. The study covered three land use phases: peat swamp forest (January 2016-February 2017), land preparation (March 2017-April 2018), and oil palm plantation (May 2018-April 2023). Despite a reduction in groundwater level (GWL) and an increase in soil temperature during land preparation, soil CO₂ emissions (1768-2135 g C m-2 yr-1) did not differ significantly from those in peat swamp forest (1402-1430 g C m-2 yr-1). Soil CO₂ emissions increased during the first three years after oil palm plantation establishment (2606-3119 g C m-2 yr-1) and subsequently declined during the fourth and fifth years (1858-2348 g C m-2 yr-1). This decline was probably driven by multiple factors, including the accumulation of recalcitrant C, indicated by an increase in the pyrophosphate solubility index; an increase in GWL due to improved water management; and increased shading due to the development of the oil palm canopy. Continued monitoring beyond the first five years is needed to assess whether the declining trend persists as the plantation matures. Overall, these results highlight the need to protect remaining peat swamp forests to mitigate further carbon losses.

Tropical peat swamp forests are crucial global carbon (C) reserves. Prevailing waterlogged conditions in peat soils prevent the complete decomposition of dead plant material. As a result, more organic matter is produced than decomposed, leading to the gradual accumulation of peat. However, the destabilisation of tropical peatlands through climate warming, droughts, and changes in land use threaten this C sink capacity. Anaerobic conditions in peat soils lead to methane (CH4) production through decomposition and nitrous oxide (N2O) production under moderate levels of soil oxygen content. Earlier evidence suggests that tree stems in tropical peat swamp forests are significant sources of CH4; however, little information is available on their exchange of N2O.This study investigated CH4 and N2O exchange of soil and stems of Combretocarpus rotunditus and Shorea albida trees in a peat swamp forest in Sarawak, Malaysia, from September 2022 to September 2023. To describe the temporal dynamics of greenhouse gas (GHG) exchange, we measured gas fluxes from the soil and stems at different heights (10, 80 and 170 cm from the tree's base) using the manual static chamber method and spectroscopic gas analysis. The chemical composition of the soil was analysed and several environmental parameters, including groundwater level, soil moisture content, soil and air temperature, were simultaneously measured with the GHG fluxes to determine the relationships between the fluxes and environmental factors.Soil CH4 emissions varied between 52.3 and 807 μg C m−2 h−1, with higher values observed during the wet season in conjunction with higher groundwater levels. On the other hand, the soil N2O fluxes were relatively low and did not show a distinct seasonal pattern, ranging from -1.33 to 3.54 μg N m−2 h−1. Annual average soil CH4 and N2O emissions were 392 μg C m−2 h−1 and 0.65 μg N m−2 h−1, respectively. The highest average stem CH4 emissions (1.48 μg C m−2 h−1) were recorded at the lowest parts of trees, with a vertical decrease in emissions and an overall uptake observed at the highest measurement point. In contrast, stem N2O emissions were small, with no clear trend with measurement height. In summary, we observed moderate and variable soil CH4 emissions with limited generalisable relation to measured environmental parameters. Soil and stem N2O emissions were relatively small. These results indicate the need for further comprehensive soil and stem GHG analyses in tropical peat swamp systems to better understand the GHG dynamics of this critical ecosystem.

Tropical peatlands contain approximately 17% of the total global peat carbon and are under pressure for deforestation and the formation of oil palm plantations. The conversion of large peatland forests in Malaysia and Indonesia has resulted in these plantations becoming substantial sources of greenhouse gases. While previous research has focused on estimating the C loss from the soil, the impact of drainage ditches on the overall C budget remains largely unexplored. However, on average, drainage ditches with free surface water cover roughly one-third of the total drained land. Hence, these ditches could be significant CO2 and CH4 sources and while not considered for C budget calculation it could lead to significant underestimation of total C loss from these ecosystems. Here we represent the CO2 and CH4 emissions from drainage ditches in an oil palm plantation located in Sarawak, Malaysia. CO2 and CH4 samples (n=107) were collected from a recently created plantation (~5 y.o.) and from the plantation, which is under second rotation using a floating chamber and LI7810 analyzer (LICOR Biosciences). Additional parameters such as water pH, electrical conductivity, dissolved oxygen concentration, temperature, turbidity, salinity, water level, and dissolved gas concentration (dCO2 and dCH4; analyzed in the lab with GC-2014, Shimadzu) were measured from each sampling spot. After measurements, we collected sediment samples for soil TN, TOC, TIC, DOC, DIC, and DN analyses. The results revealed that the average net CH4 flux (combining both diffusive and ebullitive emissions) from drainage ditches in the first and second rotations was 0.31 ± 0.65 g m-2 d-1 and 0.29 ± 0.54 g CH4-C m-2 d-1, respectively. The average CO2 flux from the first and second rotations was 4.27 ± 2.1 g CO2-C m-2 d-1 and 4.4 ± 2.5 g CO2-C m-2 d-1, respectively. To estimate surface water coverage at the whole site, green vegetation, open water, and bare soil were mapped from the site drone imagery collected in Spring 2023 using object-based supervised classification and spectral indicators computed from red, green, and blue image bands. The total surface water coverage will give us an understanding of the total CO2 and CH4 flux in the entire region that originates from drainage ditches. Our results strongly underscore the significant role of drainage ditches in contributing to the overall carbon loss from oil palm plantations on organic soils. Proper consideration of these emissions is essential for accurate carbon budget calculations and for devising effective strategies to mitigate greenhouse gas emissions in these ecosystems.

Conservation of groundwater quality is of paramount importance for sustainable agricultural management. Hydrological factors such as rainfall patterns and water table (WT) management, including drainage practices, play a crucial role in groundwater recharge. This in turn has a significant impact on WT fluctuations, nutrient losses in the soil, and the leaching of fertilizers into groundwater which leads to groundwater pollution. Consequently, this study evaluates the long-term influence of seasonal rainfall and WT fluctuations on groundwater nutrient dynamics in tropical peatlands from an oil palm plantation (OPP). Linear regression analyses and Pearson correlation matrices were adopted to evaluate the relationships between seasonal rainfall, WT, and groundwater chemical parameters. The results showed that there was a significant increase in mean pH, NO3−, Na+, Ca2+, and PO43- values during the wet season compared to the dry season which could be attributed to the leaching of nutrients into groundwater due to rainfall, nutrient runoff from drainage systems and increased nitrification rate. A significant positive correlation (p < 0.01) was found between groundwater pH and NO3− during the wet season, suggesting that increased groundwater pH due to heavy rainfall directly affects the nitrification process. It was also observed that low WT promotes denitrification in shallow groundwater, with this effect being more significant (p < 0.05) during the dry season. This was reflected in the higher correlation values between the WT fluctuations and the NH4+ concentrations in the groundwater. This research represents the first study to explore the long-term impacts of rainfall and WT fluctuations on groundwater quality in tropical peatlands. The insights gained from this study offer valuable guidance for WT management strategies aimed at conserving groundwater quality in such environments, ultimately contributing to sustainable agricultural practices.

Oil palm is commonly replanted once reaching the end of its productive lifespan. This cyclical planting practice in oil palm plantations could have long-term implications for the humification and properties of tropical peat soil. This study aimed to investigate the changes observed across successive generations of oil palm plantations in Sarawak, Malaysia. Fourier Transform Infrared Spectroscopy (FTIR) was applied to examine the quality of the Soil Organic Matter (SOM), specifically the functional groups, humification index, Hydrophobicity Index (HI), and Degree of Degradation (DDI). Overall, the peat humification trend was in the order of 2nd Gen > Forest >1st Gen. The higher presence of recalcitrant compounds of lignin in the soil was attributed to the higher HI and lower DDI in the 2nd Gen. The relationship between the Pyrophosphate Solubility Index (PSI) and the humification index further revealed a significant increase in the relative abundance of humic substances with the maturity of degraded organic matter. These findings suggest a notable transition, implicating a shift towards a more stable form of SOM over the long-term utilization of tropical peatland for oil palm plantations. This is characterised by a significant increase in the relative abundance of aromatic, phenolic, and carboxylic functional groups. The study also highlights the need for further research on the linkage between these changes and greenhouse gas emissions to enhance our understanding of the long-term biogeochemical cycle of oil palm on tropical peatlands.

Information on temporal and spatial variations in soil greenhouse gas (GHG) fluxes from tropical peat forests is essential to predict the influence of climate change and estimate the effects of land use on global warming and the carbon (C) cycle. To obtain such basic information, soil carbon dioxide (CO2) and methane (CH4) fluxes, together with soil physicochemical properties and environmental variables, were measured at three major forest types in the Maludam National Park, Sarawak, Malaysia, for eight years, and their relationships were analyzed. Annual soil CO2 fluxes ranged from 860 to 1450 g C m⁻2 yr⁻1 without overall significant differences between the three forest sites, while soil CH4 fluxes, 1.2-10.8 g C m⁻2 yr⁻1, differed. Differences in GHG fluxes between dry and rainy seasons were not necessarily significant, corresponding to the extent of seasonal variation in groundwater level (GWL). The lack of significant differences in soil CO2 fluxes between the three sites could be attributed to set-off between the negative and positive effects of the decomposability of soil organic matter as estimated by pyrophosphate solubility index (PSI) and GWL. The impact of El-Niño on annual CO2 flux also varied between the sites. The variation in soil CH4 fluxes from the three sites was enhanced by variations in temperature, GWL, PSI, and soil iron (Fe) content. A positive correlation was observed between the annual CH4 flux and GWL at only one site, and the influence of soil properties was more pronounced at the site with the lowest GWL and the highest PSI. Variation in annual CH4 fluxes was controlled more strongly by temperature where GWL was the highest and GWL and plant growth fluctuations were the least. Inter-annual variations in soil CO2 and CH4 fluxes confirmed the importance of long-term monitoring of these at multiple sites supporting different forest types.

Soil respiration is a vital process in all terrestrial ecosystems, through which the soil releases carbon dioxide (CO2) into the atmosphere at an estimated annual rate of 68–101 Pg carbon, making it the second highest terrestrial contributor to carbon fluxes. Since soil respiration consists of autotrophic and heterotrophic constituents, methods for accurately determining the contribution of each constituent to the total soil respiration are critical for understanding their differential responses to environmental factors and aiding the reduction of CO2 emissions. Owing to its low cost and simplicity, the root exclusion (RE) technique, combined with manual chamber measurements, is frequently used in field studies of soil respiration partitioning. Nevertheless, RE treatments alter the soil environment, leading to potential bias in respiration measurements. This review aims to elucidate the current understanding of RE, i.e., trenching (Tr) and deep collar (DC) insertion techniques, by examining soil respiration partitioning studies performed in several ecosystems. Additionally, we discuss methodological considerations when using RE and the combinations of RE with stable isotopic and modeling approaches. Finally, future research directions for improving the Tr and DC insertion methods in RE are suggested.

Tropical peatlands serve as huge carbon (C) pools in the global C balance, and degradation due to agricultural use is a major concern. The objective of the present study was to examine the relationship between the C loss rate in agriculturally drained tropical peat soils in relation to groundwater level (GWL) and the chemical structure of the resulting soil organic matter (SOM). Soil mesocosms containing three peat soils collected from three forest types in Malaysia, Mixed peat swamp (MPS), Alan Batu (ABt), and Alan Bunga (ABg) forests, which are classified based on dominant plant species, species diversity, and forest structure, were buried in an oil palm plantation for a period of five years. Soil samples packed in the top layer (0-20 cm depth) and the bottom (60-80 cm depth) layer were then analyzed and the results were compared with the initial values for these soils. Weight loss, total C and N contents, ash content, and pyrophosphate solubility index (PSI; an index of the degree of humification) were measured. Changes in the chemical structure of the SOC were investigated using solid-state 13C nuclear magnetic resonance (NMR) spectroscopy with phase-adjusted spinning side bands and thermally assisted hydrolysis and methylation-gas chromatography/mass spectrometry (THM-GC/MS). The C loss in the MPS forest soil, 2-12%, was smaller than that in the ABt and ABg forest soils, 20-37%, especially in the bottom layer. The higher C loss in the ABt and ABg soils, without significant difference between the top and bottom layers, can be attributed to the greater accumulation of less decomposed plant components as evidenced by the larger yields of lignin-derived phenols and polysaccharide-related compounds in THM-GC/MS analysis. The C composition as estimated by 13C NMR did not vary during incubation of the ABt and ABg soils while the yields of lignin-derived and other phenols as well as polysaccharide-related compounds in THM-GC/MS were decreased, especially in the top layer. These findings suggest that plant components with a low degree of decomposition are susceptible to drainage regardless of their structure. The progression of the oxidative degradation of lignin in the top layer of all soils was also suggested by the increases in PSI and the vanillic acid/vanillin ratio. The % O-alkyl C and % alkyl C may control the rate of C loss positively and negatively, respectively. PSI also appears to be useful for roughly estimating the decomposability of tropical peat SOM in various GWLs.

To determine the variation in the rate of accumulation and chemical structure of soil organic matter (SOM) in a tropical coastal peatland, series of soil cores samples were collected in the Maludam National Park, Sarawak, Malaysia and analyzed. Duplicate soil core samples were collected from three phasic communities in the peat swamp forests, Mixed Peat Swamp (MPS; depth of 50-450 cm), Alan Batu (ABt; depth of 200-700 cm), and Alan Bunga (ABg; depth of 200-800 cm), which were located at outer, middle, and inner sites on the peat dome. The C-14 age of the SOM was determined at depths of every 50 or 100 cm and 4-6 samples from each profile were subjected to ramp cross polarization/magic angle spinning C-13 nuclear magnetic resonance (NMR) analysis. The C-14 age of SOM ranged from 1602 to 5162 years before the present (yBP), 1134-4043 yBP, and 928-3376 yBP in the cases of the MPS, ABt, and ABg forests, respectively. Those after calibration were in the ranges of 1482-5958 (MPS), 1322-4603 (ABt), and 837-3629 (ABg) yBP. The relationship between calibrated (14)C( )age and soil depth, when regressed to a linear function with the constraint that the age of surface sediment is 0 year, showed that the rate of peat accumulation was 0.60 +/- 0.01 (MPS), 1.5 +/- 0.0 (ABt), and 1.9 +/- 0.1 (ABg) mm y(-1). However, in the case of the MPS forest, this rate was not constant but decreased toward the present. The C-13 NMR results showed the decrease in the relative abundance of alkyl C and an increase in that of carbohydrate C with soil age/ depth in the MPS forest soil profiles, suggesting an acceleration in the decomposition of SOM as the cause of the decrease in the rate of accumulation of the peat. Variations in the C composition of the other two forest soils with soil age were small. The relative content of aromatic C remained relatively constant, indicating that aromatic C is consistently a major component of the C pool throughout the peat soil layers.

To understand the variations in the decomposability of tropical peat soil following deforestation for an oil palm plantation, a field incubation experiment was conducted in Sarawak, Malaysia. Peat soils collected from three types of primary forest, namely Mixed Peat Swamp (MPS; Gonystylus-Dactylocladus-Neoscrotechinia association), Alan Batu (ABt; Shorea albida-Gonstylus-Strenonurus association), and Alan Bunga (ABg; Shorea albida association), were packed in polyvinyl chloride pipes and installed in an oil palm plantation. Carbon dioxide (CO2) and methane (CH4) fluxes from soil were monthly measured for 3years. Environmental variables including soil temperature, soil moisture content, and groundwater table were also monitored. The pH, loss on ignition, and total carbon (C) content were similar among the three soils, while total N content was larger in the MPS than in the ABg soils. Based on 13C nuclear magnetic resonance (NMR) spectroscopy, C composition of the MPS and ABg soils was characterized by the largest proportion of C present as alkyl C and O-alkyl C, respectively. The C composition of the ABt soil was intermediate between the MPS and ABg soils. The CO2 fluxes from the three soils ranged from 78 to 625mgCm-2h-1 with a negative correlation to groundwater level. The CH4 fluxes ranged from -67 to 653μgCm-2h-1. Both total CO2 and CH4 fluxes were larger in the order ABg>ABt>MPS (P<0.05). Annual rate of peat decomposition as was estimated from cumulative C loss differed up to 2 times, and the rate constant in exponential decay model was 0.033y-1 for the MPS soil and 0.066y-1 for the ABg soil. The field incubation results of the three forest peat soils seem to reflect the difference in the labile organic matter content, represented by polysaccharides.

The ability to decorate silicate surface with different organoalkoxysilanes creates powerful new capabilities for catalyst, adsorbents and chemical separation. Mesopororus silica, MCM-41 was modified by grafting of amino and mercaptopropyl functional group. The structures of these materials were characterized by using Fourier Transform Infrared Spectroscopy (FT-IR), and X-Ray diffraction (XRD). The samples were found to exhibit structural properties similar to those reported earlier. Significant functional groups of the modified mesoporous silicates were found in the spectrum of FT-IR. Standard structure of mesoporous silicates were found to be preserved at planar [100] of XRD difractogram of mesoporous silicates. Adsorption of Cu (II) ions were done under different temperatures, initial concentrations and pH. Adsorption process also was determined from kinetic point of view and was found to be better fitted to pseudo second order of kinetic model.

MCM-41 functionalized with aminopropyl and vinyl group were studied as potential adsorbent for removal of Cu (II). Materials were characterized by using XRD, FT-IR and TGA. Standard structure of MCM-41 at [100] planar was retained after functionalization. Batch adsorption study was carried out to determine effect of variable parameters (i.e. initial concentration, pH and adsorbent dosage) towards adsorption of Cu (II) from aqueous solution. Cu (II) adsorption was found to be dependent on variable parameters. Adsorption of Cu (II) was also found to fit Langmuir isothermal compared to Freundlich isothermal model. Regeneration of adsorbent by using disodium EDTA and acid base treatment showed that percentage of metal recovery is higher when using disodium EDTA.

SBA-15 (Santa Barbara Amoprhous 15) was functionalized by using three different organosilane comprised of different functional group, namely 3-aminopropyltriethoxysilane (APTES), 3-mercaptopropyltriethoxysilane (MPTS) and triethoxyvinylsilane (TEVS). Materials were characterized by using X-ray Diffractor (XRD), Fourier Transform Infrared Specrometer (FT-IR) and Field Emission Scanning Electron Microscopy (FESEM). Batch adsorption study was done to determine the effect of variable parameters, like contact time, temperature, pH and agitation towards adsorption. Adsorption was found to be highly dependent on effects of variable parameters of heavy metal ions aqueous solution. Kinetic adsorption study was carried out by using three models, namely pseudo first order, pseudo second order and intraparticle diffusion. Adsorption rate was found to be fast and well presented by using pseudo second order.