Upper Layer Research Articles

Microfluidic Device with an Oxygen Gradient Generator for Investigating Effects of Specific Hypoxia Conditions on Responses of Tumor Cells.

The oxygen level in the tumor microenvironment (TME) plays a critical role in regulating cell fates such as proliferation, migration, apoptosis, and so forth. To better elucidate how hypoxia affects tumor cell behaviors, a series of microfluidic strategies have been utilized to generate an oxygen gradient covering both hypoxia and normoxia conditions. However, in most studies, some chemicals are introduced into microfluidic chips, causing the potential of their poor biocompatibility. The common oxygen gradient with linear variation does not allow the effects of specific oxygen concentrations on tumor cells to be analyzed accurately. In this paper, based on the physical method of gas diffusion, a microfluidic device integrated with an oxygen gradient generator is proposed for investigating effects of different hypoxia levels on responses of tumor cells. This device consists of three layers, i.e., upper layer, thin film layer, and bottom layer. The upper layer is used for introducing the initial gas and generating an oxygen gradient in the form of gas. The bottom layer is used for introducing cells and culture medium. The thin film layer separates the former two layers, allowing the gas to diffuse from the top to the bottom through it. The oxygen gradient in the bottom layer is finally generated in the form of dissolved oxygen. The device is fabricated using microfabrication technology. The effects of structural and working parameters of the device on the oxygen gradient are evaluated by finite element simulation. The oxygen gradient in cell culture channels is characterized by using oxygen-sensitive fluorescence materials. The proliferation and morphology of HeLa cells under specific oxygen levels are compared after culturing for 48 h. The oxygen gradient with a ladder-like distribution demonstrates that this microfluidic device can provide a prospective experimental platform for in vitro cell studies and revelation of the mechanism of tumor metastasis associated with a specific hypoxic microenvironment.

Modeling of the Full-Scale Secondary Sedimentation Basin Using the GPS-X Model

The secondary sedimentation basin is being modeled in this study for the first time using the GPS-X model instead of the computational fluid dynamics (CFD) model. This study was conducted in the extended-aeration Al-Hur treatment plant that struggles with unstable sedimentation in its sedimentation tank. After collecting and entering the data into the GPS-X model, the model was calibrated and validated, and the results were statistically examined based on R and RMSE. To determine the efficiency of the sedimentation tank, the following scenarios were investigated: 1) testing the efficiency in removing pollutants; 2) conducting state point analysis (SPA); and 3) measuring the concentration of sludge in the layers of the sedimentation basin. Six factors were considered during the sensitivity analysis, namely sludge volume index (SIV), surface area, underflow rate (RAS), pumped flow (WAS), maximum settling velocity, and liquid temperature. The calibration and validation results were within the specified limits, and the secondary sedimentation basin demonstrated high efficiency in removing pollutants, with the analysis point (SPA) obtaining the highest MLSS concentration of 3000 mg/L. The sludge concentrations in the lower layers were 7000 mg/L, while those in the upper layer were 18 mg/L. These results suggest that a lower (100 ml/g) sludge volume index corresponds to a better sedimentation basin efficiency. Increasing the surface area of sedimentation basins can positively affect their efficiency, while increasing waste-activated sludge, maximum settling velocity, and liquid temperature may reduce pollutants and improve the sedimentation process. The GPS-X model is demonstrated as an excellent tool for understanding and predicting the work behavior of sedimentation basins, making this model particularly valuable for the management of sewage treatment plants. Doi: 10.28991/CEJ-2024-010-09-017 Full Text: PDF

Comment on: "Anomalous reflection from a two-layered marine sediment" [J. Acoust. Soc. Am. 155, 1285-1296 (2024)] (L).

Buckingham [(2024). J. Acoust. Soc. Am. 155, 1285-1296] analyzed the dependence of the reflection coefficient on the grazing angle in two-layer marine sediment model. The upper layer in his model consists of a fine-grained material (mud), while seawater and the basement below the mud layer are treated as homogeneous halfspaces. Buckingham's analyses revealed several narrow spikes in this dependence that appeared only in the presence of a sound velocity gradient in the mud layer, a phenomenon he called acoustic glint. His derivation was accomplished for certain specific dependencies of the sound velocity on the depth. Surprisingly, the authors appear to reach the conclusion that for a slightly different vertical sound speed profile in the mud layer the spikes are no longer present in the dependence of the reflection coefficient on the grazing angle. More precisely, the same problem is examined in this letter for the case of an n2-linear layer (often called Airy medium). Acoustic glint effect is therefore very sensitive to the exact parametrization of the mud layer.

Design of a multilayer absorber for ultra‐wideband radar cross section reduction

AbstractThis study proposes an ultra‐wideband multilayer absorber by combining frequency selective surface (FSS) and absorbing material. The structure is composed by three layers which are FSS loaded with resistors, absorbing material at the bottom and each layer is separated by air. The FSS in bottom has good absorption performance at high frequency while the upper layer is used to achieve low‐band absorption. To extend the absorption band to the low frequency, it further add a layer of absorbing material at the bottom. Equivalent circuit is employed to analyze the principle of the designed absorber. The simulation results show that an ultra‐wide absorption band from 0.61 to 12.33 GHz with a fractional bandwidth of 181% is realized for both TE and TM waves under the normal incidence. Furthermore, the thickness of the structure is only 0.07λL, where λL represents the wavelength of the minimum operating frequency. The designed absorber is fabricated and measured, and the measurement is in good agreement with the simulation.

Hierarchical Distributed Adaptive Fault-Tolerant Control of Nonlinear Fractional-Order Multiagent Systems With Faults and Periodic Disturbances Using Event-Triggered Communication.

This article presents a distributed fault-tolerant control (FTC) scheme for nonlinear fractional-order (FO) multiagent systems (MASs) with the order lying in (0, 1], such that the proposed control architecture can be directly applied to both FO and integer-order (IO) systems without any modifications. To handle the unexpected actuator faults encountered by the FO MASs, a hierarchical FTC mechanism is developed for each system by constructing an event-triggered distributed FO estimator at the upper layer to estimate the leader system's output via conditionally triggered neighboring information, and an FTC unit at the lower layer to counteract the loss-of-effectiveness faults via Nussbaum function with FO criteria. To further address the unknown nonlinear functions involving bias faults and periodic disturbances, the Fourier series expansion technique is used to construct the input variables of fuzzy neural networks (FNNs), such that the FNNs with dynamically adjusted weight matrices, centers, and widths can be developed for each FO system to act as the learning module. It is shown by FO Lyapunov stability analysis that all follower systems can track the leader system against faults and periodic disturbances. Simulation results on FO systems and hardware-in-the-loop experiment results on IO fixed-wing unmanned aerial vehicles show the extensive feasibility of the developed scheme.

Cooperative learning‐based practical formation‐containment control with prescribed performance for heterogeneous clusters of UAV/USV

SummaryIn this paper, a new approach for formation‐containment control with prescribed performances is introduced for heterogeneous autonomous vehicles involving a cluster of leader unmanned aerial vehicles (UAVs) and follower unmanned surface vessels (USVs). We introduce a two‐layer distributed control system: The upper layer focuses on guiding the UAVs to form a scalable lattice while synchronizing their movement along a predefined path, and the second layer guides the USVs to enter the convex hull formed by the UAVs, ensuring collision‐free operation with static/dynamic objects. To prevent collisions and ensure lattice formation, a set of well‐defined bump functions are utilized in the design of the backstepping control algorithm. Managing virtual controls, we incorporate a nonlinear dynamic surface control (NDSC), while a universal barrier function enhances the convergence of formation tracking errors. Furthermore, each USV employs a cooperative adaptive learning neural network to handle uncertainties in heterogeneous vehicle models. Utilizing the Lyapunov theorem, the stability of the formation‐containment of UAV/USV is achieved, and all signals in the formation‐containment systems are semiglobal uniform ultimate bounded (SGUUB). A simulation example showcases the effectiveness of our proposed approach, highlighting contributions in collision avoidance, synchronization speed, and adaptive learning. Our work advances the heterogeneous formation‐containment literature towards more realistic scenarios with safety‐critical considerations amidst multiple layers of uncertainties and unknown parameters.

Diameter-dependent classification of dermal vasculature using optical coherence tomography angiography.

Dermal blood vessels beneath the epidermis play critical roles in epidermal homeostasis and are functionally divided into several types, such as capillaries. Optical coherence tomography angiography (OCTA) is a powerful tool for the non-invasive assessment of dermal vasculature. However, the classification of vessel types has been limited. To address this issue, we proposed an algorithm for diameter-dependent classification that preserves three-dimensional (3D) information using OCTA. OCTA data were acquired by a prototype swept-source-type optical coherence tomography (OCT) system, which was processed through several imaging filters: an optical microangiography (OMAG) imaging filter, a vesselness imaging filter, and a diameter map filter. All vessels were visually classified into three types based on their diameters, as micro-vessels, intermediate vessels, and thick vessels. Aging-related alterations and their association with the epidermis were investigated for each vessel type. The measurements were conducted on the cheeks of 124 female subjects aged 20-79 years. The 3D vascular structure was visualized by applying our proposed post-processing filters. Based on visual assessment, the thresholds for the diameters of the micro, intermediate and thick vessels were set at 80 and 160 µm. It was found that micro-vessels were predominantly located in the upper layer of the dermis and thick vessels in the deeper layer. Analysis of vessel metrics revealed that the volume density of the micro-vessels decreased significantly with age (r=-0.36, P<0.001) and was positively correlated with epidermal thickness (r=0.50, P<0.001). In contrast, the volume density of thick vessels significantly increased with age (r=0.2, P<0.05) and was not significantly correlated with epidermal thickness (r=0.13, P≥0.05). In this study, we proposed a 3D quantification method using OCTA for dermal blood vessels and various vessel metrics, such as vessel volume density. This proposed classification will be beneficial for determining the function of the dermal vasculature and its diagnostic applications.

On the Significance of Ageostrophic Meridional Eddy-Induced Heat Flux in the Surface Ocean of the Antarctic Circumpolar Current

Abstract Eddy-induced heat flux (EHF) convergence plays an important role in balancing the cooling of mean flows in the heat budget of the Southern Ocean. This study investigates the EHF in the Southern Ocean and the surface ocean heat budget over the Antarctic Circumpolar Current (ACC) estimated through a high-resolution ocean assimilation product. In contrast to previous studies in which the estimation of the EHF in the Southern Ocean was based on the assumption that mesoscale eddies are quasigeostrophic turbulence, we find that more than one-third of the total meridional EHF in the surface layer is attributed to ageostrophic currents of eddies and that the ageostrophic component of the EHF convergence is as important as its geostrophic component for the surface ocean heat budget over the ACC. In particular, the ageostrophic meridional EHF convergence accounts for 22% of the warming needed to balance the cooling from the mean flows during winter, equivalent to warming the surface ocean of the ACC by 0.14°C. The ageostrophic meridional EHF is likely caused by the stirring effect of ageostrophic secondary circulations in mesoscale eddies, which are induced by the turbulent thermal wind balance to restore the vertical shear of the upper layer in mesoscale eddies destructed by intense winter winds.

ESPRESSO reveals blueshifted neutral iron emission lines on the dayside of WASP-76 b

Context. Ultra hot Jupiters (gas giants with Teq &gt; 2000 K) are intriguing exoplanets due to the extreme physics and chemistry present in their atmospheres. Their torrid daysides can be characterised using ground-based high-resolution emission spectroscopy. Aims. We search for signatures of neutral and singly ionised iron (Fe I and Fe II, respectively) in the dayside of the ultra hot Jupiter WASP-76 b, as these species were detected via transmission spectroscopy in this exoplanet. Furthermore, we aim to confirm the existence of a thermal inversion layer, which has been reported in previous studies, and attempt to constrain its properties. Methods. We observed WASP-76 b on four epochs with ESPRESSO at the VLT, at orbital phases shortly before and after the secondary transit, when the dayside is in view. We present the first analysis of high-resolution optical emission spectra for this exoplanet. We compare the data to synthetic templates created with petitRADTRANS, using cross-correlation function techniques. Results. We detect a blueshifted (−4.7 ± 0.3 km s−1) Fe I emission signature on the dayside of WASP-76 b at 6.0σ. The signal is detected independently both before and after the eclipse, and it is blueshifted in both cases. The presence of iron emission features confirms the existence of a thermal inversion layer. Fe II was not detected, possibly because this species is located in the upper layers of the atmosphere, which are more optically thin. Thus the Fe II signature on the dayside of WASP-76 b is too weak to be detected with emission spectroscopy. Conclusions. We propose that the blueshifted Fe I signature is created by material rising from the hot spot to the upper layers of the atmosphere, and discuss possible scenarios related to the position of the hotspot. This work unveils some of the dynamic processes ongoing on the dayside of the ultra hot Jupiter WASP-76 b through the analysis of the Fe I signature from its atmosphere, and complements previous knowledge obtained from transmission studies. It also highlights the ability of ESPRESSO to probe the dayside of this class of exoplanets.

Lrig1 regulates cell fate specification of glutamatergic neurons via FGF-driven Jak2/Stat3 signaling in cortical progenitors.

The cell-intrinsic mechanisms underlying the decision of a stem/progenitor cell to either proliferate or differentiate remain incompletely understood. Here, we identify the transmembrane protein Lrig1 as a physiological homeostatic regulator of FGF2-driven proliferation and self-renewal of neural progenitors at early-to-mid embryonic stages of cortical development. We show that Lrig1 is expressed in cortical progenitors (CPs), and its ablation caused expansion and increased proliferation of radial/apical progenitors and of neurogenic transit-amplifying Tbr2+ intermediate progenitors. Notably, our findings identify a previously unreported EGF-independent mechanism through which Lrig1 negatively regulates neural progenitor proliferation by modulating the FGF2-induced IL6/Jak2/Stat3 pathway, a molecular cascade that plays a pivotal role in the generation and maintenance of CPs. Consistently, Lrig1 knockout mice showed a significant increase in the density of pyramidal glutamatergic neurons placed in superficial layers 2 and 3 of the postnatal neocortex. Together, these results support a model in which Lrig1 regulates cortical neurogenesis by influencing the cycling activity of a set of progenitors that are temporally specified to produce upper layer glutamatergic neurons.

Bonding Properties of Package-on-Package Stack Interconnection Using by 150 ㎛ Height Copper Posts

In this study, we used copper (Cu) posts, plated to a height of 150 μm, as interconnections to form electrodes between different package layers. The upper layer consisted of a chip-scale package (CSP), while the lower layer was made up of a flip chip-chip scale package (FCCSP). We plated a Cu post on the side of FCCSP substrate, and produced the FCCSP package by thermo-compression (TC) bonding with copper pillar solder bumps on the center of substrate. The surface of the bottom electrode for the upper CSP received a surface finish of electroless nickel, electroless palladium, and immersion gold (ENEPIG). The bonding surface of the lower FCCSP was the bare Cu surface of the epoxy-molded Cu post. The PoP joining process used a vacuum reflow process with solder paste and solder balls. To understand the package joint's characteristics, we measured voids and shear strength, and analyzed the cross-sectional microstructure. The temperature profile used in the PoP joining process demonstrated optimal joint characteristics with a joint void content of 2.3% and a joint strength of approximately 44 MPa when formic acid was utilized and the activation preheating time was extended. Cross-sectional warpage analysis of the PoP package revealed a minimal difference of approximately 31 μm between the center and the ends. This study successfully developed a stacked package with a PoP structure using Cu Post, and the bonding process was optimized to minimize warpage in the PoP package.

Study on the relationships between particle shapes and motion responses in the geotechnical coarse-grained system subjected to vibration loads

The vibration-induced deformation of coarse-grained soil originates from the internal particle motions, which are reflected in translational and rotational behaviors controlled by particle shapes. However, the mechanism by which particle shapes affect particle motions in granular systems remains unclear, and diverse shape parameters make it difficult to accurately express the motion behaviors through a single shape parameter. Leveraging the advantages of the discrete element method (DEM) and machine learning methods, therefore, the relationships between shape features and motion behaviors were explored in complex-shaped granular systems. Firstly, a shape database containing hundreds of gravel particles was constructed, from which 10 representative shape parameters were selected to characterize the Form, Sphericity, and Roundness features through hierarchical clustering and principal component analysis. Then, three DEM models, established based on the shape database, were simulated to obtain particles’ translational and rotational indicators. Following, a regression relationship between representative shape parameters and motion indicators was established through the XGBoost model, and the SHAP values were utilized to explore the main shape parameters influencing particle motions. The results indicate that particle motions in the upper layer are primarily influenced by the Form parameter, and the equiaxial shape can promote the vertical displacement. The particle motions in the middle layer are mainly controlled by the Sphericity and Roundness parameters, and the flatness or angular shape has a suppressing effect on the vertical displacement.

Influence of spatial and temporal diversity and succession of microbial communities on physicochemical properties and flavor substances of soy sauce

In this study, the influence and relationship between the microbial structure composition at different spatial locations during soy sauce fermentation and the quality of soy sauce were investigated. Within 3–7 days of fermentation, the abundance of Chromohalobacter in the surface and upper layers of moromi was initially high but subsequently decreased. In contrast, Tetragenococcus exhibited low abundance on the surface of moromi at the beginning of fermentation but emerged as the absolute dominant bacteria by the end of the fermentation process. Throughout the fermentation period of 3–42 days, Staphylococcus and Bacillus were the predominant bacterial genera observed at the bottom of the moromi. In addition, Halanaerobium was the dominant bacterial genus in the crude soy sauce layer throughout the fermentation process. Tetragenococcus and Zygosaccharomyces were strongly positively correlated with total acid and ammonia nitrogen. Bacillus and Staphylococcus were significantly negatively correlated with the salt content.

Effect of chemical inhomogeneity on the structure and properties of the two-layer TiAl-based coating obtained by non-vacuum electron beam cladding: Experimental investigations and density functional theory simulations

Non-vacuum electron beam cladding is a highly effective technology for producing protective coatings on metal workpieces. In this study, the 3.8 mm thick TiAl-based coating with Cr and Nb additions was obtained on the Ti alloy substrate in two passes of the electron beam. To evaluate inhomogeneity of the two-layer coating, energy-dispersive synchrotron X-ray diffraction (EDSXRD) in combination with energy-dispersive X-ray spectroscopy (EDX) was applied. It was found that in the direction from the top of the coating to the substrate, the dilution of the cladding layers with Ti increased. It influenced the phase constitution of the coating and led to a variation in the chemical composition of different phases (α2-Ti3Al, β-phase, and TiN). The properties of the first (lower) and the second (upper) cladding layers were evaluated separately. The upper layer exhibited greater oxidation resistance than the lower one due to the presence of the γ-phase, which has superior high-temperature stability compared to the α2-Ti3Al phase, predominant in the coating. The influence of varying chemical composition on the oxidation resistance was also estimated using density functional theory (DFT) simulations. It was found that decrease in Al content in the α2 phase leads to an increase in oxygen absorption energy. This could potentially result in a decrease in oxidation resistance. Wear resistance of the first and the second cladding layers was at the same level mainly due to the low contribution of minor phases. Additionally, DFT simulations show that the variations in chemical composition of the major phase (Ti3Al) are not likely to impact the coating wear resistance.

Mechanical Response and Anti-Reflective Crack Design in New Asphalt Overlays on Existing Asphalt Overlaying Composite Portland Cement Pavement

A detection and evaluation system containing a two-level index of structural integrity and bearing capacity was constructed based on ground-penetrating radar (GPR) and a falling weight deflector (FWD). This system was constructed to solve problems with the detection, evaluation, and structural and material design of asphalt rehabilitation for the prevention and control of asphalt reflection cracks in asphalt overlaying composite Portland cement pavement. Based on the detected data from the GPR and FWD, the reasonable and recommended thickness range of the stress-absorbing layer was determined by the finite element method, and the optimization design of an anti-reflective crack structure is proposed. Furthermore, a material design and engineering application of the stress-absorbing layer was carried out. The results show that an additional 10 cm layer of repaved asphalt can reduce temperature stress by 64.1%, reduce fatigue stress by 29.3% at the cement slab bottom, and extend the service life by 23.1 years. The reasonable thickness of the stress-absorbing layer ranges from 1.6 cm to 2.0 cm, and the recommended structural combination design is a 4 cm SMA-13 upper layer, a 4 cm AC-16 lower layer, and a 2 cm stress-absorbing layer overlaying existing asphalt overlay. The impact toughness of the designed stress-absorbing layer is 1.05 times and 1.44 times that of the other stress-absorbing layer and the AC-16 asphalt mixture, respectively, which have been successfully used for more than 5 years. The recommended design rehabilitation has good engineering application. The uniformity of the stress-absorbing layer can reach 63%, and an anti-reflective crack effect is expected. The results of this study provide design methodology and experience for composite pavement repaving.

An improved hierarchical deep reinforcement learning algorithm for multi-intelligent vehicle lane change

Lane change is a pivotal technology in autonomous driving, playing a significant role in improving traffic conditions. The control task of lane change becomes exceptionally complex for coordination of multiple intelligent vehicles, especially in unpredictable situations. To address this issue, the paper proposes a novel multi-intelligent vehicle lane change method (MVLC) based on Deep Reinforcement Learning (DRL). The MVLC features a hierarchical framework that includes a lower-layer lane change controller and an upper-layer reinforcement learning decision-making method. In the lower layer, a lane change controller is designed to execute motion control for a single vehicle, consisting of a lateral controller utilizing dueling double deep Q-network to make lane change decision and a longitudinal controller that employs Intelligent Driver Model (IDM) to follow the preceding vehicle. In the upper layer, a model-free DRL method is used for simultaneous control of multiple intelligent vehicles. To learn the optimal policy, a comprehensive reward function is designed. Finally, experiments are conducted in mixed traffic to valid the effectiveness of the proposed method. Results show that MVLC achieves secure and timely lane changes for multiple vehicles. Therefore, the method is expected to have significant potential for improving overall traffic efficiency and mitigating traffic congestion.

Dependency of crossover point on absorption changes in bilayer diffusion reflection measurements.

A better understanding of diffusion reflection (DR) behavior may allow it to be used for more noninvasive applications, including the development of in vivo non-damaging techniques, especially for medical topical diagnosis and treatments. For a bilayer opaque substance where the attenuation of the upper layer is larger than the attenuation of the lower layer, the DR crossover point ( ) is location where the photons coming from the bottom layer start affecting the DR. We aim to study the dependency of the on absorption changes in different layers for constant scattering and top layer thickness. Monolayer and bilayer optical tissue-like phantoms were prepared and measured using a DR system. The results were compared with Monte Carlo simulations. There is an agreement between the experiments and the simulations. correlates with the square root of the absorption coefficient ratio of the lower layer to the top layer. The experimental findings support and validate the theoretical prediction describing the dependency of the on the square root of the ratio of the layers' absorption coefficients. In addition, a secondary breaking point is suggested to be observed experimentally at the entrance to the noise area.

Load motion on an ice cover in the presence of a liquid layer with velocity shear

The behavior of an ice cover on the surface of an ideal incompressible fluid of finite depth under the action of a pressure domain that moves rectilinearly at a constant velocity in the presence of a current with velocity shift in the upper layer is studied. It is assumed that the ice deflection is steady in the coordinate system moving with the load. The Fourier transform method is used within the framework of the linear wave theory. The critical velocities, the deflection of ice cover, and the wave forces are studied depending on the current velocity gradient, the shear layer thickness, the direction of motion, and the compression ratio.

Information Gap Decision-Making Theory-Based Medium- and Long-Term Optimal Dispatching of Hydropower-Dominated Power Grids in a Market Environment

In the high-proportion hydropower market, the fairness of the execution of traded electricity and clean energy consumption are two issues that need to be considered in medium- and long-term dispatching. Aiming at the fairness of medium- and long-term optimal dispatching of hydropower-dominated grids and the problem of water abandonment in the power market environment, this paper proposes a medium- and long-term optimal dispatching method for hydropower-dominated grids based on the information gap decision-making theory (IGDT). Firstly, IGDT is used to establish a two-layer model of medium- and long-term optimal dispatching that considers runoff uncertainty, in which the lower layer solves the maximum value of the maximum difference in the contract power completion rate of the power stations, and the upper layer solves the maximum fluctuation range of the interval inflow. Then, a mixed-integer linear programming (MILP)-based single-layer optimization model is obtained through a variety of linearization techniques, and the model is solved via the CPLEX solver (version 12.10.0). The medium- and long-term optimal dispatching of 10 thermal power stations and 22 hydropower stations in Yunnan Power Grid, China, is taken as an example to verify the proposed model. The results show that the maximum difference in the contracted electricity completion rate of each power station is 0.412, and the amount of abandoned hydropower is reduced by 81.33% compared to when the abandoned water penalty function is not considered. It is proved that the proposed model can effectively alleviate the problems of excessive power generation, insufficient power generation and large-scale hydropower abandonment, which are of great significance for realizing the fair dispatching of hydropower-dominated power grids and promoting clean energy consumption in the market environment.

Effects of fire on tree species composition and carbon stocks of a peat swamp forest in Central Kalimantan, Indonesia

ABSTRACT Peat swamp forests are important in the global carbon (C) budget because of the huge amount of C stored in these ecosystems, particularly in below-ground components. Indonesia has some of the greatest extent of peat swamp forests globally, yet many of them are being disturbed by fires that are becoming increasingly frequent. In Kalampangan, Central Kalimantan, the tree species (≥4.8 cm diameter) composition, aboveground biomass (AGB) and litter standing crop of peat swamp forests were sampled, and the overall ecosystem C stock estimated, within two 1-ha sampling plots, one of which was undisturbed (natural) and the other previously burned. The AGB and litter standing crop found in the natural forest totaled 341 and 6.77 Mg ha−1, respectively. The AGB declined more than six-fold to 53.2 Mg ha−1, and the litter standing crop declined by about half to 3.30 Mg ha−1 in the disturbed forest; the total number of tree species declined from 114 to 80 per hectare. The disturbed peat swamp lost just over 200 Mg C ha−1 to the atmosphere due to the combustion of tree biomass and the upper layer of the peat, but C stocks still remained very high overall (c. 1100 Mg ha−1) due to the thick layer of peat (>2 m) making peat swamp forest conservation imperative due to their huge carbon stocks.