Production Decomposition Research Articles

Global change alters peatland carbon cycling through plant biomass allocation

Global change is shown to significantly affect the C storage function of peatlands; however, a majority of previous research is focused on a single environmental stressor such as the increased temperature. As a result, little is known about the interactive effect of multiple environmental stressors on peatland C storage, especially in sedge-dominated fen peatlands. We performed a full factorial experiment of increased temperature and elevated atmospheric CO2 concentration on minerotrophic, sedge-dominated fen monoliths to experimentally examine the individual and interactive effects of simulated future climate conditions on peatland plant biomass, CO2 exchange, and pore water dissolved organic carbon (DOC) over one full growing season. Our study demonstrates that warming and elevated atmospheric CO2 significantly increased aboveground and belowground biomass, respectively, as well as the gross ecosystem production (GEP), while the DOC concentrations and respired CO2 from peatland soils only increased under warming Our results suggest that global change will increase both plant production and microbial decomposition, but with altered plant biomass allocation between aboveground and belowground. Our study provides experimental evidence for shifts in ecosystem-level carbon dynamics under global change for a sedge-dominated peatland, and suggests that while carbon stores may weaken, the carbon sink will be maintained in these types of northern peatlands if hydrological conditions are largely maintained.

On-line analysis and in situ pH monitoring of mixed acid fermentation by Escherichia coli using combined FTIR and Raman techniques

We introduce an experimental setup allowing continuous monitoring of bacterial fermentation processes by simultaneous optical density (OD) measurements, long-path FTIR headspace monitoring of CO2, acetaldehyde and ethanol, and liquid Raman spectroscopy of acetate, formate, and phosphate anions, without sampling. We discuss which spectral features are best suited for detection, and how to obtain partial pressures and concentrations by integrations and least squares fitting of spectral features. Noise equivalent detection limits are about 2.6 mM for acetate and 3.6 mM for formate at 5 min integration time, improving to 0.75 mM for acetate and 1.0 mM for formate at 1 h integration. The analytical range extends to at least 1 M with a standard deviation of percentage error of about 8%. The measurement of the anions of the phosphate buffer allows the spectroscopic, in situ determination of the pH of the bacterial suspension via a modified Henderson-Hasselbalch equation in the 6–8 pH range with an accuracy better than 0.1. The 4 m White cell FTIR measurements provide noise equivalent detection limits of 0.21 μbar for acetaldehyde and 0.26 μbar for ethanol in the gas phase, corresponding to 3.2 μM acetaldehyde and 22 μM ethanol in solution, using Henry’s law. The analytical dynamic range exceeds 1 mbar ethanol corresponding to 85 mM in solution. As an application example, the mixed acid fermentation of Escherichia coli is studied. The production of CO2, ethanol, acetaldehyde, acids such as formate and acetate, and the changes in pH are discussed in the context of the mixed acid fermentation pathways. Formate decomposition into CO2 and H2 is found to be governed by a zeroth-order kinetic rate law, showing that adding exogenous formate to a bioreactor with E. coli is expected to have no beneficial effect on the rate of formate decomposition and biohydrogen production.

Urbanisation affects ecosystem functioning more than structure in tropical streams

Urbanisation poses a clear threat to tropical freshwater streams, yet fundamental knowledge gaps hinder our ability to effectively conserve stream biodiversity and preserve ecosystem functioning. Here, we studied the impact of urbanisation on structural and functional ecosystem responses in low-order streams in Singapore, a tropical city with a mosaic landscape of protected natural forests, managed buffer zones (between forest and open-country habitats), and built-up urban areas. We quantified an urbanisation gradient based on landscape, in-stream, and riparian conditions, and found an association between urbanisation and pollution-tolerant macroinvertebrates (e.g. freshwater snail and worm species) in litter bags. We also found greater macroinvertebrate abundance (mean individuals bag−1; forest: 30.3, buffer: 70.1, urban: 109.0) and richness (mean taxa bag−1; forest: 4.53, buffer: 4.75, urban: 7.50) in urban streams, but similar diversity across habitats. Higher levels of primary productivity (measured from algal accrual on ceramic tiles) and microbial decomposition (measured from litter-mass loss in mesh bags) at urban sites indicate rapid microbial activity at higher light, temperature, and nutrient levels. We found that urbanisation affected function 32% more than structure in the studied tropical streams, likely driven by greater algal growth in urban streams. These changes in ecological processes (i.e. ecosystem functioning) possibly lead to a loss of ecosystem services, which would negatively affect ecology, society, and economy. Our results point to possible management strategies (e.g. increasing vegetation density through buffer park creation) to reduce the impacts of urbanisation, restore vital ecosystem functions in tropical streams, and create habitat niches for native species.

Ojos que no ven... ¿Qué podemos hacer para incluir más a la fracción subterránea en estudios de vegetación?

Conocer la estructura y el funcionamiento de la fraccion subterranea de la vegetacion es fundamental para comprender numerosos procesos que ocurren en distintos niveles de organizacion. Sin embargo, dicha fraccion fue menos estudiada que su contraparte aerea, principalmente por el gran esfuerzo que demanda muestrearla a campo y procesarla en el laboratorio. En la XXVIII Reunion Argentina de Ecologia (Mar del Plata, 2018) se realizaron dos simposios sobre la importancia de conocer las raices en estudios ecologicos. De los simposios surgio la necesidad de 1) cuantificar los estudios que hayan evaluado las fracciones subterranea y aerea de la vegetacion, y 2) determinar las metodologias empleadas y las variables de la fraccion subterranea registradas en sistemas naturales (i.e., pastizales, estepas, bosques, arbustales y desierto) y antropizados (i.e., pasturas y cultivos) en seis provincias fitogeograficas de la Argentina y en dos regiones geomorfologicas de Uruguay. Se registraron 933 estudios publicados entre 1990 y 2019. El 57% y el 23% correspondieron a estudios exclusivos de la fraccion aerea y de la subterranea, respectivamente, con un incremento exponencial en el tiempo de ambas fracciones. En la actualidad existe una tendencia a incorporar el compartimiento subterraneo en estudios ecologicos. Mediante un analisis sistematico se encontro que se emplearon seis metodos de muestreo (barreno, ruleros, planta entera, monolitos, rhizotron y estimacion de la biomasa subterranea a partir de la biomasa aerea) para evaluar cuatro variables (biomasa subterranea, productividad primaria neta subterranea, algunos atributos radicales y tasa de descomposicion radical). El metodo mas empleado fue el del barreno y la variable mas evaluada fue la biomasa subterranea. Proponemos fomentar la colaboracion entre equipos de investigacion y establecer comparaciones metodologicas para comprender los alcances de los resultados y obtener estimaciones mas confiables sobre las consecuencias del cambio en el uso del suelo.

The life cycle of cyclotides: biosynthesis and turnover in plant cells

Key messageTurnover rates have implications for understanding cyclotide biology and improving plant cell culture-based production systems.Cyclotides are a family of polypeptides recognized for a broad spectrum of bioactivities. The cyclic, cystine knot structural motif imparts these peptides with resistance to temperature, chemicals and proteolysis. Cyclotides are found widely distributed across the Violaceae and in five other plant families, where their presumed biological role is host defense. Violets produce mixtures of different cyclotides that vary depending on the organ, tissue or influence of environmental factors. In the present study, we investigated the biosynthesis and turnover of cyclotides in plant cells. Viola uliginosa suspension cultures were grown in media where all nitrogen containing salts were replaced with their 15N counterparts. This approach combined with LC–MS analysis allowed to separately observe the production of 15N-labelled peptides and decomposition of 14N cyclotides present in the cells when switching the media. Additionally, we investigated changes in cyclotide content in V. odorata germinating seeds. In the suspension cultures, the degradation rates varied for individual cyclotides and the highest was noted for cyO13. Rapid increase in production of 15N peptides was observed until day 19 and subsequently, a plateau of production, indicating an equilibrium between biosynthesis and turnover. The developing seedling appeared to consume cyclotides present in the seed endosperm. We show that degradation processes shape the cyclotide pattern present in different tissues and environments. The results indicate that individual cyclotides play different roles—some in defense and others as storage proteins. The turnover of cyclotides should be accounted to improve cell culture production systems.

Sulfur promoted n-π* electron transitions in thiophene-doped g-C3N4 for enhanced photocatalytic activity

Expanding the optical absorption range of photocatalysts is still a key endeavor in graphitic carbon nitride (g-C3N4) studies. Here, we report on a novel thiophene group extending the optical property, which is assigned to n-π* electronic transitions involving the two lone pairs on sulfur (TLPS). The as-prepared samples, denoted as CN-ThAx (where x indicates the amount of ThA added, mg), showed an additional absorption above 500 nm as compared to pristine g-C3N4. Further, the thiophene group enhanced charge carrier separation to suppress e−/h+ pair recombination. The experimental results suggest that the thiophene group can obstruct the polymerization of melem to generate a large plane, thus exposing the lone electron pairs on the sulfur. The photocatalytic activity was evaluated in the decomposition of bisphenol A and H2 evolution. Compared with g-C3N4, the optimized CN-ThA30 sample led to a 6.6- and 2-fold enhancement of the degradation and H2 generation rates, respectively. The CN-ThA30 sample allowed for synchronous H2 production and BPA decomposition.

Measuring productivity of healthcare services under environmental constraints: evidence from China

BackgroundDespite the growing literature on the efficiency and productivity of the Chinese healthcare system, less attention has been given to examining the undesirable outputs linked to healthcare services, including environmental pollution. Taking the atmospheric environmental pollution resulting from the incineration of medical waste as an undesirable output of the healthcare system, this study analyzed the growth and decomposition of Total Factor Productivity (TFP) of healthcare services across 31 Chinese provinces during the period 2005–2016.MethodsThe Meta-frontier undesirable super-efficiency slack-based measure (SBM) model and the Global Malmquist-Luenberger (GML) Index were employed to analyze the growth and decomposition of TFP using the Max DEA software.ResultsThe results revealed that the years 2009 and 2015 marked significant changes in TFP of healthcare services in Chinese provinces. During the study period, the rate of technological change (TC) slowly declined, whereas the rate of efficiency change (EC) steadily increased. With the national average being the benchmark, the results indicated that: the TFP of 17 provinces and cities exceeded the average, the EC of 16 provinces and cities exceeded the average, the TC of 9 provinces and cities exceeded the average, and the value in the Technology Gap Ratio (TGR) changes of 13 provinces and cities were above the national average.Conclusions(1) The TFP of the healthcare services across China continued to decline slowly during the study period. (2) The effect of technical catch-up in the eastern, central, and western regions of China was significant across the three regions, whereas the effect of technical innovation was negative. (3) The TFP varied considerably among the Chinese provinces. These findings suggest that, under existing environmental constraints, relevant government departments should improve technical innovation in the supply of healthcare services and medical waste treatment, increase technical efficiency in the factor of healthcare production, strengthen regional health planning, and balance the development of regional healthcare.

Enhancing anaerobic digestion for rural wastewater treatment with granular activated carbon (GAC) supplementation

Notwithstanding many efforts to increase the efficiency of anaerobic digestion at low-temperature (winter) conditions, a cost-effective and efficient method is lacking. This study proposes a low-cost method of low-temperature (<35 °C) anaerobic digestion of wastewater, involving supplementation with granular activated carbon (GAC). Supplementation with GAC was found to reduce the lag time by 29.8% (from 15.1 to 10.6 days) and increase the maximum methane production rate by 23.4% (from 6.4 to 7.9 mL/day) at 25 °C. Network analysis demonstrated a strong co-occurrence of Syntrophobacteriales and hydrogenotrophic methanogens (Methanobacteriaceae; WSA2; Methanoregulaceae). GAC supplementation can drastically reduce the time required for organic matter decomposition and methane production, thereby increase the efficiency of wastewater treatment.

Insight into the Ex Situ Catalytic Pyrolysis of Biomass over Char Supported Metals Catalyst: Syngas Production and Tar Decomposition.

Ex situ catalytic pyrolysis of biomass using char-supported nanoparticles metals (Fe and Ni) catalyst for syngas production and tar decomposition was investigated. The characterizations of fresh Fe-Ni/char catalysts were determined by TGA, SEM–EDS, Brunauer–Emmett–Teller (BET), and XPS. The results indicated that nanoparticles metal substances (Fe and Ni) successfully impregnated into the char support and increased the thermal stability of Fe-Ni/char. Fe-Ni/char catalyst exhibited relatively superior catalytic performance, where the syngas yield and the molar ratio of H2/CO were 0.91 Nm3/kg biomass and 1.64, respectively. Moreover, the lowest tar yield (43.21 g/kg biomass) and the highest tar catalytic conversion efficiency (84.97 wt.%) were also obtained under the condition of Ni/char. Ultimate analysis and GC–MS were employed to analyze the characterization of tar, and the results indicated that the percentage of aromatic hydrocarbons appreciably increased with the significantly decrease in oxygenated compounds and nitrogenous compounds, especially in Fe-Ni/char catalyst, when compared with no catalyst pyrolysis. After catalytic pyrolysis, XPS was employed to investigate the surface valence states of the characteristic elements in the catalysts. The results indicated that the metallic oxides (MexOy) were reduced to metallic Me0 as active sites for tar catalytic pyrolysis. The main reactions pathway involved during ex situ catalytic pyrolysis of biomass based on char-supported catalyst was proposed. These findings indicate that char has the potential to be used as an efficient and low-cost catalyst toward biomass pyrolysis for syngas production and tar decomposition.

The Influence of Trade Agglomeration on Technology Diffusion in Coastal Cities in Different Time and Space

Shan, Q., 2020. The influence of trade agglomeration on technology diffusion in coastal cities in different time and space. In: Yang, Y.; Mi, C.; Zhao, L., and Lam, S. (eds.), Global Topics and New Trends in Coastal Research: Port, Coastal and Ocean Engineering. Journal of Coastal Research, Special Issue No. 103, pp. 543–547. Coconut Creek (Florida), ISSN 0749-0208.In order to realize the coordinated economic development of coastal cities, the influence of trade agglomeration on technology diffusion effect of coastal cities in different time and space is put forward. This paper analyzes the influence of main factors and technological factors on the diffusion effect of technology in coastal cities, and obtains the influence of internal factors of trade agglomeration on the diffusion effect of technology. Based on the analysis of economic environment and policy environment of city agglomeration, the influence of external factors of trade agglomeration on technology diffusion effect is obtained. The relationship between trade agglomeration and economic efficiency was tested by systematic GMM and panel regression. Trade agglomeration in each city has a significant promoting effect on scale efficiency, and has a significant difference on total factor productivity and other decomposition index. Therefore, some suggestions are put forward, such as taking the market as the core of the reform, strengthening the reform of the trade supply side, “moving from the virtual to the real”, promoting innovation-driven development and expanding trade opening.

Effects of Fe-Mn-modified biochar addition on anaerobic digestion of sewage sludge: Biomethane production, heavy metal speciation and performance stability

This study investigated the effects of MnFe2O4-biochar on sludge anaerobic digestion performance, methane production and heavy metal stabilization. The highest cumulative methane yield was achieved when the MnFe2O4-biochar dose was 1.50 g, which was 55.86% higher than control. A suitable dose of MnFe2O4-biochar stimulated methanogenic activities and improved methane yield, whereas excessive addition shows an inhibitory effect on anaerobic digestion. MnFe2O4-biochar addition significantly enhanced the biodegradation of organic matter, as the average volatile fatty acids degradation rate increased by 35.44%, compared to the control. Chemical speciation analyses demonstrated that MnFe2O4-biochar addition was more helpful for immobilization and risk reduction of heavy metals in sewage sludge. Simultaneously, microbial community analysis indicated that MnFe2O4-biochar obviously enriched acetoclastic methanogens Methanosarcina that capable of participating in direct interspecies electron transfer, which could accelerate substrate decomposition and methane production. These findings supply useful information for the resource utilization of sewage sludge.

Experimental demonstration of the importance of keystone communities for maintaining metacommunity biodiversity and ecosystem functioning.

As local communities within a metacommunity may differ considerably in their contributions to biodiversity and ecosystem functioning, it has been suggested that conservation priority should be given to disproportionately important local communities (i.e., keystone communities). However, we know little about what characterizes a keystone community. Using laboratory protist microcosms as the model system, we examined how the environmental uniqueness and location of a local community affect its contributions to the metacommunities. We found that the removal of local communities with unique environmental conditions, which supported endemic species, reduced regional-scale diversity, qualifying them as regional-scale keystone communities. In addition, the local communities possessing unique environmental conditions had greater impacts on ecosystem functions, including biovolume production and particulate organic matter decomposition. We also found that keystone communities for biovolume production were not keystone for organic matter decomposition, and vice versa. Our study, therefore, demonstrates the important role of keystone communities in maintaining biodiversity and functioning of metacommunities.

Quantitative Food Webs Indicate Modest Increases in the Transfer of Allochthonous and Autochthonous C to Macroinvertebrates Following a Large Wood Addition to a Temperate Headwater Stream

Headwaters suffer from reduced leaf and wood inputs and retention capacity from historical land actions like watershed logging and agriculture. When in-stream wood is reduced, stream retention capacity declines and subsequent changes in streamwater flow-paths and patterns of deposition alter decomposition and primary production that influence secondary invertebrate production via modified habitat and resources. Wood additions are commonly used as stream restoration tools for habitat improvements that can restore or strengthen food web connections; however, changes in carbon (C) flow through food webs are rarely measured because of time and expense. We quantified allochthonous and autochthonous C flow through aquatic macroinvertebrate communities one year before and two years after an experimental addition of large wood, compared to macroinvertebrates in an upstream control, in a temperate headwater stream. We predicted wood additions increase macroinvertebrate consumption and assimilation of allochthonous and autochthonous C through retention of leaves and altered flow-paths that expose more gravel and cobble for periphyton colonization. Macroinvertebrate allochthonous C assimilation tended to increase in years with greater organic matter retention and autochthonous C increased with more exposed gravel and cobble across seasons and between reaches. While the effect of wood addition on C flow through the macroinvertebrate community was minimal, it increased by ~20% relative to the control from an increase in production and C assimilation of common mayfly and caddisfly scrapers, Baetis and Glossossoma. Because the amount of organic matter retained and coarse substrate exposed corresponded with C form and amount consumed, restoration of large wood has the potential to increase organic matter C trophic transfer.

Self-assembled heterojunction of metal sulfides for improved photocatalysis

Due to its high redox potential, zinc sulfide (ZnS) is considered an excellent semiconductor photocatalyst. However, the rapid recombination rate of the photogenerated electron-hole pairs limits the efficiency of ZnS for photocatalytic reactions. Herein, we suggest a design rule of heterojunction structure of ZnS for improvement of its photocatalytic performance. Two specific properties are specially emphasized: phase immiscibility and the different growth rates of the component materials. The phase immiscibility not only guarantees a well-separated interface, it also enables the technical convenience of one-pot synthesis. The different growth rates help form wide heterojunctions that foster the efficient consumption of materials. We found that the ZnS/NixSy composite not only meets the aforementioned requirements but also has proper band alignment. Ready-to-use heterojunction photocatalysts (ZnS/NixSy) were obtained via one-pot synthesis, thanks to the different growth rates and the immiscibility of the two sulfides. Combining ZnS with NixSy resulted in substantially improved photocatalytic activity in regard to dye decomposition and H2 production via water splitting. Both band position measurements and DFT simulations indicated that NixSy is a co-catalyst for ZnS, allowing sufficient band offset for electron-hole separation. Abundant and mass-producible, the ZnS/NixSy composite can effectively substitute for noble metal photocatalysis when it comes to organic pollutant degradation and water splitting.

Productivity Growth in Chinese Medical Institutions during 2009–2018

China is the most populous nation and considerations of economic efficiency in the social sectors is important for maintaining the wellbeing of such a large population. This is especially true when gauging the performance of the healthcare sector treating the population. In this paper, we examine the total factor productivity (TFP) growth in Chinese medical institutions during the period 2009–2018, which experienced a systemic healthcare reform. In order to identify the contribution from each component of TFP indicators and from each provincial or regional medical institutions, a generalized decomposition of productivity gains is applied to analyze hospital operations based on an aggregate directional distance function (DDF). The results show that the annual average TFP growth rate in Chinese medical institutions is 1.87% that is mainly driven by technological progress (0.75%, per annum), while less contributed by technical efficiency change (0.65%, p.a.) and scale efficiency change (0.47%, p.a.). Disparities of provincial hospital performances are observed that may provide policy implications for decision makers.

Misallocation and reallocation of resources in Vietnamese manufacturing firms

PurposeThis research identifies the level of misallocation in Vietnamese manufacturing sector for the period 2000–2015. Meltiz and Polanec dynamic productivity decomposition is used to compare the relative productivity contributions from surviving, entering and exiting firms to aggregate productivity change by the type of ownership. Heckman's two-step model is used to examine the effect of misallocation and industry- and firm-level factors on entry or exit decision and market share of firms in Vietnamese manufacturing sector.Design/methodology/approachThe level of misallocation and efficiency gains in total factor productivity (TFP) are assessed using Hsieh and Klenow (2009) productivity decomposition framework for the period 2000–2015. The dynamic productivity decomposition of Meltiz and Polanec (2015) is used to compare the relative contributions from surviving, entering and exiting firms to aggregate productivity change. The effects of misallocation and other factors on entry or exit decisions and market share of firms are determined by using Heckman choice model.FindingsThe results indicate three main points. Firstly, resource misallocation is found to be highest among state-owned enterprise (SOEs) and low technology industries. TFP is found to 81.2% greater if there is no resource misallocation among firms. Secondly, the aggregate productivity change for the entering, exiting and surviving firms is 35% due to productivity reallocation among three groups. Finally, the decision of entry or exit as well as the market share of firms are influenced by misallocation and industry- and firm-level factors such as Vietnam's WTO entry, tax policy, financial frictions, industrial concentration, technology gap, capital intensity, human capital, scale of firm, time entry and FDI spillovers. The result finds the higher misallocation level is, the lower the probability and market share for a new firm to enter in the industry is.Research limitations/implicationsThe main limitation of the study is that the market is assumed perfectly competitive and the method has only decomposed misallocation of resources to those arising from output and capital distortions. The results of Heckman choice model only clarify on the sub-sample of state-owned enterprises and low technology firms.Originality/valueThe focus of many previous research papers on resource misallocation was generally to look at the level of misallocation in developed countries. However, knowledge about the effect of misallocation and other factors on entry or exit decisions and market share of firms is limited, particularly in the context of developing countries. This paper clarifies the level of misallocation in Vietnamese manufacturing sector and the effect of misallocation and other factors on entry or exit decisions and market share of firms.

Comparison of Carbon, Nitrogen, and Sulfur in Coastal Wetlands Dominated by Native and Invasive Plants in the Yancheng National Nature Reserve, China

The rapid invasion of the plant Spartina alterniflora in coastal wetland areas can threaten the capacity of their soils to store carbon (C), nitrogen (N), and sulfur (S). In this study, we investigated the spatial and temporal distribution patterns of C, N and S of both soil and (native and invasive) plants in four typical coastal wetlands in the core area of the Yancheng National Nature Reserve, China. The results show that the invasive S. alterniflora greatly influenced soil properties and increased soil C, N and S storage capacity: the stock (mean ± standard error) of soil organic carbon (SOC, (3.56 ± 0.36) kg/m3), total nitrogen (TN, (0.43 ± 0.02) kg/m3), and total sulfur (TS, (0.69 ± 0.11) kg/m3) in the S. alterniflora marsh exceeded those in the adjacent bare mudflat, Suaeda salsa marsh, and Phragmites australis marsh. Because of its greater biomass, plant C ((1193.7 ± 133.6) g/m2), N ((18.8 ± 2.4) g/m2), and S ((9.4 ± 1.5) g/m2) storage of S. alterniflora was also larger than those of co-occurring native plants. More biogenic elements circulated in the soil-plant system of the S. alterniflora marsh, and their spatial and temporal distribution patterns were also changed by the S. alterniflora invasion. Soil properties changed by S. alterniflora’s invasion thereby indirectly affected the accumulation of soil C, N and S in this wetland ecosystem. The SOC, TN, and TS contents were positively correlated with soil electrical conductivity and moisture, but negatively correlated with the pH and bulk density of soil. Together, these results indicate that S. alterniflora invasion altered ecosystem processes, resulted in changes in net primary production and litter decomposition, and increased the soil C, N and S storage capacity in the invaded ecosystems in comparison to those with native tallgrass communities in the coastal wetlands of East China.

Producción y tasa de descomposición de hojarasca en acahuales de Tabasco, México

La dinámica entre la caída y descomposición de hojarasca forma parte del funcionamiento de los ecosistemas. Se evaluó la producción, pérdida y tasa de descomposición de la hojarasca de selva y vegetación secundaria en unidades ecogeográficas (UE) de laderas de montañas, terrazas y planicies fluviales en la subregión de los Ríos de Tabasco en México. En cada UE se establecieron seis conglomerados con cuatro parcelas de 10 m × 40 m y en tres parcelas de cada conglomerado se distribuyeron 6 trampas de 1 m2 (n = 144), las cuales se recogieron de marzo 2014 a marzo 2015. Para determinar el peso remanente y la tasa de descomposición se utilizó el método de bolsas de descomposición, inicialmente con 10 g de hojarasca por bolsa (n = 384). El periodo para determinar la descomposición estuvo comprendido de junio 2014 a marzo 2015 y mensualmente se recogieron cuatro bolsas por conglomerado, las cuales se secaron a peso constante. La producción de hojarasca en los acahuales de las UE fue similar a la de las zonas de vegetación primaria, excepto a la de una sola de estas últimas, que presentó mayor producción. La pérdida de peso y la tasa de descomposición fueron ligeramente mayores para vegetación primaria que para los acahuales. Los resultados encontrados sobre producción y degradación de la hojarasca pueden ser significativos por la inexistencia de trabajos en acahuales a escala de unidad ecogeográfica, lo que puede servir para darle mucha mayor importancia a este tipo de vegetación que asegure su conservación en el estado de Tabasco.

English

A study was conducted in the Guinea and Sudan Savannah zones in the Upper East Region of Ghana to investigate the effects of Faidherbia albida on some important soil fertility indicators. Soil sampling and analysis, litter trap, and litter bag techniques were employed to determine the soil’s content of major nutrients, the rate of litterfall production and litter decomposition, respectively. Analysis of variance (ANOVA) was performed to determine differences among treatment means, while Tukey’s highest significant difference (HSD) was used to perform post hoc tests among means within the same sample set. Soils under F. albida tree canopies were found to contain significantly higher organic carbon and total nitrogen than those outside the canopies. Peak leaf litter production occurred during the first three months of the onset of the rainy season. Annual leaf litterfall was 340 g m-2 year-1 in the Guinea Savannah zone and 264 g m-2 year-1 in the Sudan Savannah zone. The high leaf litterfall, followed by high decomposition and mineralization at the beginning of the cropping season, the high nutrient content of its leaves, coupled with its nitrogen fixing ability, make F. albida a potential candidate for soil improvement and improved productivity of major crops in smallholder farming systems. About 37 and 59 adult F. albida trees will be required to supply significant amounts of nitrogen in the Guinea and Sudan Savannah zones, respectively. Key words: Litter bag technique, litter decomposition, litter fall, litter trap technique, soil organic carbon, soil

한·중·일 제조업의 총요소생산성 분해 요소와 수출간의 관계에 대한 연구 : 한국의 수출 주력산업을 중심으로

본 연구는 한국 제조업의 생산성 향상을 통한 수출경쟁력 강화를 위해 한·중·일 3국의 제조업 생산성 수준을 파악하고 생산성이 수출에 미치는 영향에 대한 분석을 목적으로 한다. 이를 위해 먼저 확률적 변경생산함수를 추정한 후 총요소생산성(TFP)을 기술진보(TC), 기술적 효율성 변화(TEC), 규모 효과(SE)로 분해하여 각 분해 요소와 수출 간의 관계를 조명하였다.<BR> TFP를 TC, TEC, SE로 분해한 결과, 3개국 모두 TFP에서 TC가 차지하는 비중이 가장 높은 반면, TEC의 비중은 매우 낮게 나타났다. 국가별 TFP와 TC는 중국, 한국, 일본 순으로 높게 나타났으며 이는 현재 한·중·일 3국의 경제성장 단계를 반영한 것이라고 할 수 있다. 이에 반해 TEC는 한국이 중국보다 높게 나타났으며, SE의 경우 일본의 변동성이 가장 크고 중국의 변동성이 가장 낮은 것으로 확인되었다. 한편, 2008년 글로벌 금융위기 당시 한국의 TC와 SE가 중국과 일본에 비해 급격히 하락하며 TFP도 크게 하락했지만 2년 정도 후 원상태를 회복한 것으로 나타났다.<BR> 그리고 TFP 분해 요소가 한·중·일 3국의 수출에 미치는 영향을 분석한 결과, TC와 SE는 3국 모두 수출에 유의적인 정(+)의 영향력이 있으며, TEC는 일본에서만 유의적인 정(+)의 영향력이 있는 것으로 나타났다. 또한 한국의 수출 비중과 대세계 무역특화지수(TSI)가 높은 4개 산업(정유, 화학, 전자, 수송)에 대해 분석한 결과, TC는 한국의 화학과 전자 산업에서, SE는 한·중·일의 정유 산업, 한국의 화학산업, 한국 및 일본의 전자 산업, 일본의 수송 산업에서 유의적인 정(+)의 영향력이 있는 것으로 나타났다.<BR> 현재 한국은 세계 시장을 대상으로 제조업 상품을 수출하고 있으며 시간이 갈수록 중국, 일본과의 경쟁이 더욱 심화되고 있다. 이러한 상황에서 한국의 제조업이 생산성 향상과 수출 증대라는 두 가지 목표를 달성하기 위해서는 기술진보를 위한 연구개발(R&D) 투자와 규모 효과를 누리기 위한 생산시설 투자 등의 확대가 필요함은 명확하다. 특히 규모 효과의 경우 기술진보에 비해 변동성이 높은 것으로 나타나 재고 및 투자 관리를 철저히 할 필요가 있다고 판단된다. 이와 함께 기술적 효율성의 경우 아직은 생산성 향상과 수출 증대에 미치는 영향이 미미하지만 장기적인 관점에서 꾸준히 개선해 갈 필요가 있다.