Forest structure and carbon dynamics of an intact lowland mixed dipterocarp forest in Brunei Darussalam

Tropical forests play a critical role in mitigating climate change because they account for large amount o terrestrial carbon storage and productivity.However,there are many uncertainties associated with the estimation o carbon dynamics.We estimated forest structure and carbon dynamics along a slope（17.3°–42.8°）and to assess the relations between forest structures,carbon dynamics,and slopes in an intact lowland mixed dipterocarp forest,in Kuala Belalong,Brunei Darussalam.Living biomass,basa area,stand density,crown properties,and tree family composition were measured for forest structure.Growth rate,litter production,and litter decomposition rates were also measured for carbon dynamics.The crown form index and the crown position index were used to assess crown properties,which we categorized into five stages,from very poor to perfect.The living biomass,basal area and stand density were 261.5–940.7 Mg ha-1,43.6–63.6 m2ha-1and 6,675–8400 tree ha-1,respectively.The average crown form and position index were 4,which means that the crown are mostly symmetrical and sufficiently exposed for photosynthesis.The mean biomass growth rate,litter production,litter decomposition rate were estimated as11.9,11.6 Mg ha-1a-1,and 7.2 g a-1,respectively.Biomass growth rate was significantly correlated with living biomass,basal area,and crown form.Crown form appeared to strongly influence living biomass,basal area and biomass growth rate in terms of light acquisition.However,basal area,stand density,crown properties,and biomass growth rate did not vary by slope or tree family composition.The results indicate that carbon accumulation by tree growth in an intact lowland mixed dipterocarp forest depends on crown properties.Absence of any effect of tree family composition on carbon accumulation suggests that the main driver of biomass accumulation in old-growth forests of Borneo is not species-specific characteristics of tree species.

Assessing spatiotemporal variations of forest carbon density using bi-temporal discrete aerial laser scanning data in Chinese boreal forests

Assessing the changes in forest carbon stocks over time is critical for monitoring carbon dynamics,estimating the balance between carbon uptake and release from forests,and providing key insights into climate change mitigation.In this study,we quantitatively characterized spatiotemporal variations in aboveground carbon density(ACD)in boreal natural forests in the Greater Khingan Mountains(GKM)region using bi-temporal discrete aerial laser scanning(ALS)data acquired in 2012 and 2016.Moreover,we evaluated the transferability of the proposed design model using forest field plot data and produced a wall-to-wall map of ACD changes for the entire study area from 2012 to 2016 at a grid size of 30 m.In addition,we investigated the relationships between carbon dynamics and the dominant tree species,age groups,and topography of undisturbed forested areas to better understand ACD variations by employing heterogeneous forest canopy structural characteristics.The results showed that the performance of the temporally transferable model(R^(2)=0.87,rRMSE=18.25%),which included stable variables,was statistically equivalent to that obtained from the model fitted directly by the 2016 field plots(R^(2)=0.87,rRMSE=17.47%).The average rate of change in carbon sequestration across the entire study region was 1.35 Mg⋅ha^(-1)⋅year^(-1) based on the changes in ALS-based ACD values over the course of four years.The relative change rates of ACD decreased as the elevation increased,with the highest and lowest ACD growth rates occurring in the middle-aged and mature forest stands,respectively.The Gini coefficient,which represents forest canopy surface structure heterogeneity,is sensitive to carbon dynamics and is a reliable predictor of the relative change rate of ACD.This study demonstrated the applicability of bi-temporal ALS for predicting forest carbon dynamics and fine-scale spatial change patterns.Our research contributed to a better understanding of the in-fluence of remote sensing-derived environmental variables on forest carbon dynamic patterns and the development of context-specific management approaches to increase forest carbon stocks.

Carbon and nitrogen dynamics in early stages of forest litter decomposition as affected by nitrogen addition

The effects of nitrogen(N) availability and tree species on the dynamics of carbon and nitrogen at early stage of decomposition of forest litter were studied in a 13-week laboratory incubation experiment.Fresh litter samples including needle litter(Pinus koraiensis) and two types of broadleaf litters(Quercus mongolica and Tilia amurensis) were collected from a broadleaf-korean pine mixed forest in the northern slope of Changbai Mountain(China).Different doses of N(equal to 0, 30 and 50 kg·ha-1yr-1, respectively, as NH4NO3) were added to litter during the experiment period.The litter decomposition rate expressed as mass loss and respiration rate increased significantly with increasing N availability.The mass loss and cumulative CO2-C emission were higher in leaf litter compared to that in needle litter.The dissolved organic Carbon(DOC) concentrations in litter leachate varied widely between the species, but were not greatly affected by N treatments.Regardless of the N addition rate, both N treatments and species had no significant effect on dissolved organic N(DON) concentrations in litter leachate.About 52?78% of added N was retained in the litter.The percentage of N retention was positively correlated(R2=0.91, p<0.05) with the litter mass loss.This suggested that a forest floor with easily decomposed litter might have higher potential N sink strength than that with more slowly decomposed litter.

Carbon storage in a wolfberry plantation chronosequence established on a secondary saline land in an arid irrigated area of Gansu Province,China

Carbon（C） storage has received significant attention for its relevance to agricultural security and climate change. Afforestation can increase C storage in terrestrial ecosystems, and has been recognized as an important measure to offset CO_2 emissions. In order to analyze the C benefits of planting wolfberry（Lycium barbarum L.） on the secondary saline lands in arid areas, we conducted a case study on the dynamics of biomass carbon（BC） storage and soil organic carbon（SOC） storage in different-aged wolfberry plantations（4-, 7-and 11-year-old） established on a secondary saline land as well as on the influence of wolfberry plantations on C storage in the plant-soil system in an arid irrigated area（Jingtai County） of Gansu Province, China. The C sequestration and its potential in the wolfberry plantations of Gansu Province were also evaluated. An intact secondary saline land was selected as control. Results show that wolfberry planting could decrease soil salinity, and increase BC, SOC and litter C storage of the secondary saline land significantly, especially in the first 4 years after planting. The aboveground and belowground BC storage values in the intact secondary saline land（control） accounted for only 1.0% and 1.2% of those in the wolfberry plantations, respectively. Compared to the intact secondary saline land, the SOC storage values in the 4-, 7-and 11-year-old wolfberry plantations increased by 36.4%, 37.3% and 43.3%, respectively, and the SOC storage in the wolfberry plantations occupied more than 92% of the ecosystem C storage. The average BC and SOC sequestration rates of the wolfberry plantations for the age group of 0–11 years were 0.73 and 3.30 Mg C/（hm^2·a）, respectively. There were no significant difference in BC and SOC storage between the 7-year-old and 11-year-old wolfberry plantations, which may be due in part to the large amounts of C offtakes in new branches and fruits. In Gansu Province, the C storage in the wolfberry plantations has reached up to 3.574 Tg in 2013, and the C sequestration potential of the existing wolfberry plantations was 0.134 Tg C/a. These results indicate that wolfberry planting is an ideal agricultural model to restore the degraded saline lands and increase the C sequestration capacity of agricultural lands in arid areas.

Dynamics of dead wood decay in Swiss forests

Background: Forests are an important component of the global carbon(C) cycle and can be net sources or sinks of CO2, thus mitigating or exacerbating the effects of anthropogenic greenhouse gas emissions. While forest productivity is often inferred from national-scale yield tables or from satellite products, forest C emissions resulting from dead organic matter decay are usually simulated, therefore it is important to ensure the accuracy and reliability of a model used to simulate organic matter decay at an appropriate scale. National Forest Inventories(NFIs) provide a record of carbon pools in ecosystem components, and these measurements are essential for evaluating rates and controls of C dynamics in forest ecosystems. In this study we combine the observations from the Swiss NFIs and machine learning techniques to quantify the decay rates of the standing snags and downed logs and identify the main controls of dead wood decay.Results: We found that wood decay rate was affected by tree species, temperature, and precipitation. Dead wood originating from Fagus sylvatica decayed the fastest, with the residence times ranging from 27 to 54 years at the warmest and coldest Swiss sites, respectively. Hardwoods at wetter sites tended to decompose faster compared to hardwoods at drier sites, with residence times 45–92 and 62–95 years for the wetter and drier sites, respectively.Dead wood originating from softwood species had the longest residence times ranging from 58 to 191 years at wetter sites and from 78 to 286 years at drier sites.Conclusions: This study illustrates how long-term dead wood observations collected and remeasured during several NFI campaigns can be used to estimate dead wood decay parameters, as well as gain understanding about controls of dead wood dynamics. The wood decay parameters quantified in this study can be used in carbon budget models to simulate the decay dynamics of dead wood, however more measurements(e.g. of soil C dynamics at the same plots) are needed to estimate what fraction of dead wood is converted to CO2, and what fraction is incorporated into soil.

Early Snowmelt Enhances the Carbon Sequestration of Hummock-Forming Sphagnum Mosses on Boreal Wetlands

Sphagnum mosses are globally important owing to their considerable peat-forming ability and their potential impact on global climatic cycles acting as a long-term net carbon sink. However, changes in climatic conditions due to global warming may affect the relations between Sphagnum mosses and vascular plants but also the competition among Sphagnum, and thus alter the accumulation of carbon on boreal wetlands. Sphagnum mosses are a plant genus with a favorable ability to grow in low solar irradiance and temperature conditions compared to vascular plants. This may be increasingly beneficial in increased wintertime temperatures and predated snowmelt conditions. To understand particularly the importance of early spring photosynthetic activity and thus the role of the length of growing season on carbon balance, we analyzed the CO2 exchange of Sphagnum mosses with closed chamber technique in two categories of microtopographical habitats, hummocks and lawns, during four seasons 2010-2013 on a raised bog in Central Finland. During CO2 exchange measurements, instantaneous net ecosystem exchange (NEE) and ecosystem respiration (RE) were measured. Our results show that the mean measured seasonal NEE, i.e. the instantaneous net carbon sequestration, of hummocks was generally only slightly higher than the NEE of lawns, but the mean measured seasonal RE of hummocks was clearly and significantly higher than the RE of lawns in every study year. A reason for the observed still higher seasonal carbon sequestration of hummocks than that of lawns besides the slightly higher rate of carbon accumulation was the longer duration of physiologically active growing season. Therefore, hummock-forming Sphagnum mosses exposed firstly from snow cover showed to get the extra time for photosynthesis and thus extra benefit compared to other mire plants. This may be further enhanced by the expansion of hummock-forming Sphagnum moss dominated raised bogs towards northern aapa-mire region due to the global warming.

Emission Inventories of Carbon-containing Greenhouse Gases in China and Technological Measures for Their Abatement

The report summarizes surveys on carbon inventories and initiatives on sustainable carbon cycling taken by the Research Center for Eco-Environmental Sciences, where the authors work/worked. The first part of the report, which appeared in the preceding issue of this journal, deals with the concept of sustainable carbon cycling, the historic evolution of carbon cycling processes in China, carbon pool enhancement, value addition, carbon sequestration and carbon balance. This very paper, as the second part of the report, covers the results of carbon dynamics modeling, emission inventories of various carbon-containing greenhouse gases and their potential abatement measures.

The decomposition rate of the organic carbon content of suspended particulate matter in the tropical seagrass meadows

In terms of downward transport,suspended particulate matter(SPM)from marine or terrigenous sources is an essential contributor to the carbon cycle.Within mesoscale environments such as seagrass ecosystems,SPM flux is an essential part of the total carbon budget that is transported within the ecosystem.By assessing the total SPM transport from water column to sediment,potential carbon burial can be estimated.However,SPM may decompose or reforming aggregate during transport,so estimating the vertical flux without knowing the decomposition rate will lead to over-or underestimation of the total carbon budget.Here this paper presents the potential decomposition rate of the SPM in seagrass ecosystems in an attempt to elucidate the carbon dynamics of SPM.SPM was collected from the seagrass ecosystems located at Sikka and Sorong in Indonesia.In situ experiments using SPM traps were conducted to assess the vertical downward flux and decomposition rate of SPM.The isotopic profile of SPM was measured together with organic carbon and total nitrogen content.The results show that SPM was transported to the bottom of the seagrass ecosystem at a rate of up to(129.45±53.79)mg/(m^(2)·h)(according to carbon).Considering the whole period of inundation of seagrass meadows,SPM downward flux reached a maximum of 3096 mg/(m^(2)·d)(according to carbon).The decomposition rate was estimated at from 5.9μg/(mg·d)(according to carbon)to 26.6μg/(mg·d)(according to carbon).Considering the total downward flux of SPM in the study site,the maximum decomposed SPM was estimated 39.9 mg/(m^(2)·d)(according to carbon)and 82.6 mg/(m^(2)·d)(according to carbon)for study site at Sorong and Sikka,respectively.The decomposed SPM can be 0.6%–2.7%of the total SPM flux,indicating that it is a small proportion of the total flux.The seagrass ecosystems of Sorong and Sikka SPM show an autochthonous tendency with the primary composition of marine-end materials.

Climate warming suppresses abundant soil fungal taxa and reduces soil carbon efflux in a semi-arid grassland

Soil microorganisms critically affect the ecosystem carbon(C)balance and C-climate feedback by directly controlling organic C decomposition and indirectly regulating nutrient availability for plant C fixation.However,the effects of climate change drivers such as warming,precipitation change on soil microbial communities,and C dynamics remain poorly understood.Using a long-term field warming and precipitation manipulation in a semi-arid grassland on the Loess Plateau and a complementary incubation experiment,here we show that warming and rainfall reduction differentially affect the abundance and composition of bacteria and fungi,and soil C efflux.Warming significantly reduced the abundance of fungi but not bacteria,increasing the relative dominance of bacteria in the soil microbial community.In particular,warming shifted the community composition of abundant fungi in favor of oligotrophic Capnodiales and Hypocreales over potential saprotroph Archaeorhizomycetales.Also,precipitation reduction increased soil total microbial biomass but did not significantly affect the abundance or diversity of bacteria.Furthermore,the community composition of abundant,but not rare,soil fungi was significantly correlated with soil CO_(2) efflux.Our findings suggest that alterations in the fungal community composition,in response to changes in soil C and moisture,dominate the microbial responses to climate change and thus control soil C dynamics in semi-arid grasslands.

Multi-scale processes influencing global carbon storage and land-carbon-climate nexus:A critical review

Carbon(C)is a key constitutive element in living organisms(plants,microbes,animals,and humans).Carbon is also a basic component of agriculture because it plays a dynamic role in crop growth,development,nutrient cycling,soil fertility,and other agricultural features.The presence of C enhances soil physical,chemical,and biological properties.The C cycle supports all life on the Earth by transferring C between living organisms and the environment.The global climate is changing,and this change is attributable to the release of carbon dioxide and other greenhouse gases from human activities.Owing to the global climate change,agriculture is expected to be majorly affected.Agricultural production is directly linked to the climate.The five main global C pools are the oceanic,geologic,pedologic,atmospheric,and biotic pools,with specific reservoirs and inter-pool fluxes.The soil organic matter has various organic C pools(active,slow,and passive pools),containing various C-based fractions and specific liability pools.Climate,geology,land use,and management techniques are some of the variables that affect organic C and its reservoirs.The dynamics of each of these variables must be understood for a thorough knowledge of how they impact the soil C pools and storage capacity under the changing climate conditions.This review provides a comprehensive overview of the various factors that affect soil C pools/fractions and their C sequestration capacity.

Kinetics of native and added carbon mineralization on incubating at different soil and moisture conditions in Typic Ustochrepts and Typic Halustalf

The carbon dynamics in soils is of great importance due to its links to the global carbon cycle.The prediction of the behavior of native soil organic carbon(SOC)and organic amendments via incubation studies and mathematical modeling may bridge the knowledge gap in understanding complex soil ecosystems.Three alkaline Typic Ustochrepts and one Typic Halustalf with sandy,loamy sand,and clay loam texture,varying in percent SOC of 0.2;S_(1),0.42;S_(2),0.67;S_(3) and 0.82;S_(4) soils,were amended with wheat straw(WS),WS+P,sesbania green manure(GM),and poultry manure(PM)on 0.5%C rate at field capacity(FC)and ponding(P)moisture levels and incubated at 35℃for 1,15,30 and 45 d.Carbon mineralization was determined via the alkali titration method after 1,5,714,21,and 28 d.The SOC and inorganic carbon contents were determined from dried up(50℃)soil samples after 1,15,30,and 45 d of incubation.Carbon from residue mineralization was determined by subtracting the amount ofCO_(2)-C evolved from control soils.The kinetic models;monocomponent first order,two-component first or-der,and modified Gompertz equations were fitted to the carbon mineralization data from native and added carbon.The SOC decomposition was dependent upon soil properties,and moisture,however,added C was relatively independent.The carbon from PM was immobilized in S4.All the models fitted to the data predicted carbon mineralization in a similar range with few exceptions.The residues lead to the OC build-up in fine-textured soils having relatively high OC and cation exchange capacities.Whereas,fast degradation of applied OC in coarse-textured soils leads to faster mineralization and lower build-up from residues.The decline in CaCO_(3) after incubation was higher at FC than in the P moisture regime.

Unravelling charge carrier dynamics in protonated g-C3N4 interfaced with carbon nanodots as co-catalysts toward enhanced photocatalytic CO2 reduction： A combined experimental and first-principles DFT study

In this work, we demonstrated the successful construction of metal-free zero- dimensional/two-dimensional carbon nanodot （CND）-hybridized protonatedg=C3N4 （pCN） （CND/pCN） heterojunction photocatalysts b; means of electrostatic attraction. We experimentally found that CNDs with an average diameter of 4.4 nm were uniformly distributed on the surface of pCN using electron microscopy analysis. The CND/pCN-3 sample with a CND content of 3 wt.% showed thehighest catalytic activity in the CO2 photoreduction process under visible and simulated solar light. This process results in the evolution of CH4 and CO. Thetotal amounts of CH4 and CO generated by the CND/pCN-3 photocatalyst after 10 h of visible-light activity were found to be 29.23 and 58.82 molgcatalyst-1, respectively. These values were 3.6 and 2.28 times higher, respectively, than thearn＊ounts generated when using pCN alone. The corresponding apparent quantum efficiency （AQE） was calculated to be 0.076%. Furthermore, the CND/pCN-3 sample demonstrated high stability and durability after four consecutive photoreaction cycles, with no significant decrease in the catalytic activity.

Nano watermill driven by revolving charge

A novel nanoscale watermill for the unidirectional transport of water molecules through a curved single-walled carbon nanotube（SWNT） is proposed and explored by molecular dynamics simulations. In this nanoscale system, a revolving charge is introduced to drive a water chain confined inside the SWNT, the charge and the tube together serving as a nano waterwheel and nano engine. A resonance-like phenomenon is found, and the revolving frequency of the charge plays a key role in pumping the water chain. The water flux across the SWNT increases with respect to the revolving frequency of the external charge and it reaches its maximum when the frequency is 4 THz. Correspondingly, the number of hydrogen bonds in the water chain inside the SWNT decreases dramatically as the frequency increases from 4 THz to 25 THz. The mechanism behind the resonance phenomenon has been investigated systematically. Our findings are helpful for the design of nanoscale fluidic devices and energy converters.

Breakthrough CO_2 adsorption in bio-based activated carbons

In this work, the effects of different methods of activation on CO2 adsorption performance of activated carbon were studied. Activated carbons were prepared from biochar, obtained from fast pyrolysis of white wood, using three different activation methods of steam activation, CO2 activation and Potassium hydroxide（KOH） activation. CO2 adsorption behavior of the produced activated carbons was studied in a fixed-bed reactor set-up at atmospheric pressure, temperature range of 25–65°C and inlet CO2 concentration range of10–30 mol% in He to determine the effects of the surface area, porosity and surface chemistry on adsorption capacity of the samples. Characterization of the micropore and mesopore texture was carried out using N2 and CO2 adsorption at 77 and 273 K, respectively.Central composite design was used to evaluate the combined effects of temperature and concentration of CO2 on the adsorption behavior of the adsorbents. The KOH activated carbon with a total micropore volume of 0.62 cm3/g and surface area of 1400 m2/g had the highest CO2 adsorption capacity of 1.8 mol/kg due to its microporous structure and high surface area under the optimized experimental conditions of 30 mol% CO2 and 25°C. The performance of the adsorbents in multi-cyclic adsorption process was also assessed and the adsorption capacity of KOH and CO2 activated carbons remained remarkably stable after50 cycles with low temperature（160°C） regeneration.

Characterizations of Dynamic Strain-induced Transformation in Low Carbon Steel

Dynamic strain-induced transformation of the low carbon steel Q（235） at 770℃ and 850℃ leads to fine ferrite grains. The microstructure characterization and mechanism of the fine ferrite grain were studied by scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and electron backscattered diffraction （EBSD） technique. The results show that strain-induced microstructure is the mixed microstructure of ferrite and pearlite, with cementite randomly distributed on ferrite grain boundaries and the grains interiors. EBSD images of grain boundaries demonstrate that high angle grain boundaries （HAGBs） are dominant in both of the deformation induced microstructures occurring below and above A（e3） , with only a few low angle grain boundaries （LAGBs） existing in the grain interiors. It implies that the dynamic strain-induced transformation （DSIT） happens above and below A（e3） temperature and has the same phase transition mechanisms. The refinement of ferrite is the cooperative effect of DSIT and continuous dynamic recrystallization （CDRX） of ferrite. Besides, DSIT is deemed as an incomplete carbon diffusion phase transition through the analysis of microstructure and the previous simulated results. The strengths of the Q（235） steel with refined ferrite and pearlite structure get doubled than the initial state without treated by DSIT and the residual stress in the refined structure is partly responsible for the ductility loss.

A novel oscillator based on heterogeneous carbon@ MoS2 nanotubes

Oscillatory behavior of novel heterogeneous oscillators composed of carbon and molybdenum disulfide nanotubes （CNT@MST） was investigated for the first time, by using the methods of classical molecular dynamics. In the proposed oscillators, a molybdenum disulfide nanotube （MST） was set as an outer tube, leading to better compatibility with the semiconductor industry standards. A smooth and stable oscillator with a frequency reaching 20 GHz was obtained based on a double-walled CNT@MST hetero-nanotube for a wide range of gap widths, indicating that the proposed oscillators perform much better than those built from double-walled carbon nanotubes （CNTs） that require a narrow range of gap widths. In addition, the oscillation characteristics of CNT@MST oscillators containing different inner and outer tube chirality were significantly better than those of CNT@MST oscillators containing two tubes with the same chirality.

Extrapolating plot-scale CO_(2) and ozone enrichment experimental results to novel conditions and scales using mechanistic modeling

Introduction:The Aspen-FACE experiment was an 11-year study of the effect of elevated CO_(2) and ozone(alone and in combination)on the growth of model aspen communities(pure aspen,aspen-birch,and aspen-maple)in the field in northern Wisconsin,USA.Uncertainty remains about how these short-term plotlevel responses might play out over broader temporal and spatial scales where climate change,competition,succession,and disturbances interact with tree-level responses.In this study,we used a new physiologybased approach(PnET-Succession v3.1)within the forest landscape model LANDIS-II to extrapolate the FACE results to broader temporal scales(and ultimately to landscape scale)by mechanistically accounting for the globally changing drivers of temperature,precipitation,CO_(2),and ozone.We added novel algorithms to the model to mechanistically simulate the effects of ozone on photosynthesis through ozone-induced impairment of stomatal control(i.e.,stomatal sluggishness)and damage of photosynthetic capacity at the chloroplast level.Results:We calibrated the model to empirical observations of competitive interactions on the elevated CO_(2) and O_(3) plots of the Aspen-FACE experiment and successfully validated it on the combined factor plots.We used the validated model to extend the Aspen-FACE experiment for 80 years.When only aspen clones competed,we found that clone 271 always dominated,although the ozone-tolerant clone was co-dominant when ozone was present.Under all treatments,when aspen clone 216 and birch competed,birch was always dominant or co-dominant,and when clone 216 and maple competed,clone 216 was dominant,although maple was able to grow steadily because of its shade tolerance.We also predicted long-term competitive outcomes for novel assemblages of taxa under each treatment and discovered that future composition and dominant taxa depend on treatment,and that short-term trends do not always persist in the long term.Conclusions:We identified the strengths and weaknesses of PnET-Succession v3.1 and conclude that it can generate potentially robust predictions of the effects of elevated CO_(2) and ozone at landscape scales because of its mechanistically motivated algorithms.These capabilities can be used to project forest dynamics under anticipated future conditions that have no historical analog with which to parameterize less mechanistic models.

Effect of wood density and water permeability on wood decomposition rates of 32 bornean rainforest trees

Aims a better understanding of wood litter decomposition is essential for predicting responses of forest ecosystems to global climate change.recent studies suggest that chemical properties of wood litters,rather than physical ones such as wood density,are more important for inter-specific differences in wood decomposition rates.However,empirical data are still limited,especially for tropical trees.In addition,decom-position rate of wood litter often varies with time,which makes inter-specific comparison difficult.We studied the wood decomposition of 32 rainforest trees to elucidate(i)the degree of interspecific variation in wood decomposition rate of a given size and configuration and(ii)if initial wood density and water permeability are consistent predictors of the overall decomposition rate and its pattern over time.Methods a common garden decomposition experiment was conducted in a tropical rainforest in malaysian borneo for 32 native tree species.small wood sticks were set on the forest floor and the weight loss was monitored monthly for 2.7 years.Important Findings We found large variation in the wood decomposition rate(a 49-fold range),suggesting that we need to consider this variation when cal-culating community-level carbon dynamics of tropical rain forests.the physical traits of wood,i.e.wood density and water permeability,were related to wood decomposition rate and its pattern over time.Decomposition half-time related positively and negatively to initial wood density and water permeability,respectively.the time-dependentrate model fitted better for 18 species(56%of the study species)that had higher water permeabilities than the others,suggesting that micelle porosity in wood relates to temporal changes in decomposition rate.

An Introduction to Advanced Hot-Formed Steel for Automobile

A recently developed advanced hot-formed （AHF） steel for automobile is introduced and three physical metallurgy concepts based on which the AHF steel was designed are reviewed, they are dynamic carbon partitioning （DCP）, flash copper precipitation and bake toughening. AHF steel is an upgrade of the existing hot-formed steel especially suitable for making components with superior crashworthiness; it can be processed by regular hot stamping equipment and process. A kinetics model for DCP is expressed in detail, which can be used to calculate the volume fraction of retained austenite based on four materials and processing parameters. The flash copper precipitation used as an additional strengthening mechanism for AHF steel is also discussed and its ultrafast kinetics can be attributed to the enhancement of quenched-in vacancies on copper diffusion. Also, the bake toughening of AHF steel is addressed; the mechanism of which may be related to the elimination of the less stable block-like retained austenite.

Compact fluidized bed sorber for CO_2 capture

Multiphase CFD is used to design a compact fluidized bed sorber for CO2 removal from flue gases using sodium or potassium carbonate pellets. The sorber sizes are much smaller than commercial amine absorbers and smaller than other proposed dry adsorbers. The size reduction is due to the elimination of dilute regions that cause bypassing. With proper solids feeding we eliminated the usual core-annular regime found in circulating fluidized beds.