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1.
Labor productivity is a major component of agricultural development. Boserup is the scholar most associated with the view that labor productivity declines with intensification of agriculture. This paper reviews the theoretical argument and empirical support for the decline thesis. An empirical test is conducted by means of a comparative study of traditional rice agriculture in Southeast Asia. The decline thesis is rejected. The implications for agricultural development are discussed.  相似文献   

2.
This paper reviews the theoretical and empirical literature on labor productivity in shifting cultivation systems, and relationships between labor productivity and production parameters are analyzed in two case studies of Iban communities in Sarawak, Malaysia, during two farming seasons. In addition, the labor productivity in shifting cultivation compared to off-farm wage labor opportunities is explored. Establishing firm relationships between labor productivity and production parameters, such as fallow length, fertilizer use, and herbicide use was not possible. We are thus unable to verify or reject the thesis that more labor is required for managing fields after short fallow compared to long fallow periods. We do demonstrate that shifting cultivation of hill rice can compete economically with common off-farm employment opportunities, and conclude that farmers’ decisions to maintain their practices is based as much on economic rationales as on tradition.  相似文献   

3.
Goal, Scope and Background  Green Productivity (GP) is a new paradigm in sustainable manufacturing where resource conservation and waste minimization constitute the strategy in simultaneously enhancing environmental performance and productivity. This productivity approach to the sustainability of industries requires the adoption of clean production technology and the development of appropriate indicators and instruments to measure environmental performance in a continuous improvement strategy that focuses on the manufacturing stage of the product life cycle. The analysis may be expanded to include the entire life cycle with increasing details on impacts, improvement strategies and indicators. Methods  The study proposes a methodology for GP assessment that integrates the essential components of life cycle assessment (LCA) and multicriteria decision analysis specifically the analytic hierarchy process (AHP). LCA provides a systematic and holistic perspective for GP analysis that spans inventory, impact and improvement assessment. The AHP is utilized as a decision framework and valuation tool for impact and improvement assessment to come up with priority weights. Indicators are derived and measured from a streamlined LCA focused on a number of parameters within the gate-to-gate analysis to demonstrate the GP concept in relation to resource utilization and waste minimization. An input-output approach using a suitable material balance in a scenario analysis provides the basis of GP performance measurement. Results and Conclusion  The diagnostic model is applied on a semiconductor assembly/packaging operation. From the streamlined life cycle inventory, impact factors were derived for water resource depletion (WRD), energy resource depletion (ERD), human toxicity-air (HTA), human toxicity-land (HTL), human toxicity-water (HTW), aquatic ecotoxicity (ETA) and terrestrial ecotoxicity (ETT). Valuation of impact factors using the AHP showed the high significance of ETT, HTL, WRD and ERD. This especially reflects the impact of the industry on the solid waste problem as a result of emissions to land associated with human toxicity and ecotoxicity effects and the intensive use of water and energy resources. Using scenario analysis, the effect of implementing a process-based improvement technique on a product-specific operation was determined and the highest values in GP are for energy utilization, water utilization and terrestrial ecotoxicity. Recommendation and Perspective  Expert system technology was explored in developing a diagnostic prototype that emulates how human experts diagnose green productivity of manufacturing processes. The aim was to investigate how such a diagnosis could be performed in an intelligent fashion that it is also easily accessible as a decision support for industries. The expert system model will provide flexibility in testing the relationships of environmental performance and productivity parameters as well as in preserving and disseminating valuable human expertise in GP program implementation. This is a continuing research effort that is building the knowledge base for GP assessment. It will include case studies over a wider range or level of detail regarding the impacts and improvement techniques and the other stages of the product life cycle.  相似文献   

4.
Despite extensive research efforts, the controversy over diversity–productivity (D–P) patterns in natural communities still looms large. Recent meta‐analyses suggest that unimodal D–P relationships tend to pre‐dominate in plant studies, while positively linear relationships are more common in animal studies. These patterns, however, are based on studies in which productivity is estimated either directly, based on the biomass or energy of the studied organisms, or indirectly, according to the productivity of lower trophic levels, and various surrogates. Our analysis shows that the distribution of D–P patterns is sensitive to the directness of productivity estimates in animal studies but not in plant studies. Analysis of D–P patterns should be based on direct productivity estimates of the studied organisms, especially in comparative meta‐analyses of communities from multiple trophic levels, where productivity is often affected nonlinearly by indirect factors or when complex feedback interactions are expected between productivity and diversity.  相似文献   

5.
Duarte  P.  Ferreira  J. G. 《Hydrobiologia》1993,260(1):183-189
This paper presents a combined approach for parameter estimation in models of primary production. The focus is on gross primary production and nutrient assimilation by seaweeds.A database of productivity determinations, biomass and mortality measurements and nutrient uptake rates obtained over one year for Gelidium sesquipedale in the Atlantic Ocean off Portugal has been used. Annual productivity was estimated by harvesting methods, and empirical relationships using mortality/wave energy and respiration rates have been derived to correct for losses and to convert the estimates to gross production. In situ determinations of productivity have been combined with data on the light climate (radiation periods, intensity, mean turbidity) to give daily and annual productivity estimates. The theoretical nutrient uptake calculated using a Redfield ratio approach and determinations of in situ N and P consumption by the algae during incubation periods have also been compared.The results of the biomass difference and incubation approaches are discussed in order to assess the utility of coefficients determined in situ for parameter estimation in seaweed production models.  相似文献   

6.
The influence of pore size and surface chemistry upon the productivity in affinity chromatography of three silica-based solid phases, Sorbsil C-200, C-500, and C-1000 (40-60 mum particle diameter and the corresponding pore diameters of 20, 50, and 100 nm), was studied using three model ligand/biomolecule systems of varying molecular masses. These studies revealed two unique parameters, biochemical productivity and maximum physical capacity, of the matrix as generically essential in the successful design and operation of productive affinity chromatography systems. Biochemical productivity, the molar ratio of the amount of product recovered per unit volume of adsorbent and ligand concentration, utilized the expected stoichiometry of binding of the two molecules to assess the efficacy of the adsorbent. This parameter, determined by equilibrium binding in batch suspensions and by saturation binding capacities and recoveries in fixed beds, yielded the optimum ligand concentration required for maximal performance. Maximum physical capacity, of the adsorbent to accommodate the biomolecules, was calculated from pore and molecular dimensions assuming that there was no steric hindrance to access. Using an immobilized human-IgG (Hu-IgG)/anti-Hu-IgG monoclonal antibody (MCAB) system, in which both the ligand and the product are of the same size (150 kDa), it was shown that the physical capacity of C-200 was only 16% of the theoretically expected amount. This capacity increased to 70 and 90% of the expected value with C-500 and C-1000, respectively, as the steric hindrance to protein penetration induced by pore dimensions decreased. The distribution of immobilized Hu-IgG within individual particles, visualized by immunofluorescence and immunogold labeling, showed that the ligand was restricted to the peripheral 3 mum of the C-200 particles (12% radius). In contrast, it was present throughout the C-1000 particles, indicating that there was no hindrance to access in this solid phase. The C-200 was suitable for use in a small ligand/biomolecule system studied (immobilized trypsin-inhibitor binding trypsin; 22.1 and 23.3 kDa, respectively) for which more than 60% of the maximum physical capacity was available for interactions. The C-500 proved satisfactory for the Hu-IgG/MCAB model system but showed steric limitations when an immobilized anti-beta-galactosidase MCAB (anti-beta-gal) was used to purify a larger product (beta-galacosidase; 460 kDa). The binding capacity and overall productivity of Hu-IgG- and anti-beta-gal-C-1000 was equivalent to that of Sepharose CL-4B. Selection of matrices with pore sizes appropriate to the dimensions of the ligand and product was, therefore, important. Finally, the Sorbsil silicas packed easily into beds and were used successfully with conventional chromatography equipment for low-pressure affinity chromatography. They therefore offer an ideal alternative to silica-based high-performance liquid affinity chromatography and soft-gel supports. (c) 1992 John Wiley & Sons, Inc.  相似文献   

7.
The allocation and cycling of carbon (C) within forests is an important component of the biospheric C cycle, but is particularly understudied within tropical forests. We synthesise reported and unpublished results from three lowland rainforest sites in Amazonia (in the regions of Manaus, Tapajós and Caxiuanã), all major sites of the Large‐Scale Biosphere–Atmosphere Programme (LBA). We attempt a comprehensive synthesis of the C stocks, nutrient status and, particularly, the allocation and internal C dynamics of all three sites. The calculated net primary productivities (NPP) are 10.1±1.4 Mg C ha−1 yr−1 (Manaus), 14.4±1.3 Mg C ha−1 yr−1 (Tapajós) and 10.0±1.2 Mg C ha−1 yr−1 (Caxiuanã). All errors bars report standard errors. Soil and leaf nutrient analyses indicate that Tapajós has significantly more plant‐available phosphorus and calcium. Autotrophic respiration at all three sites (14.9–21.4 Mg C ha yr−1) is more challenging to measure, with the largest component and greatest source of uncertainty being leaf dark respiration. Comparison of measured soil respiration with that predicted from C cycling measurements provides an independent constraint. It shows general good agreement at all three sites, with perhaps some evidence for measured soil respiration being less than expected. Twenty to thirty percent of fixed C is allocated belowground. Comparison of gross primary productivity (GPP), derived from ecosystem flux measurements with that derived from component studies (NPP plus autotrophic respiration) provides an additional crosscheck. The two approaches are in good agreement, giving increased confidence in both approaches to estimating GPP. The ecosystem carbon‐use efficiency (CUEs), the ratio of NPP to GPP, is similar at Manaus (0.34±0.10) and Caxiuanã (0.32±0.07), but may be higher at Tapajós (0.49±0.16), although the difference is not significant. Old growth or infertile tropical forests may have low CUE compared with recently disturbed and/or fertile forests.  相似文献   

8.
Scientists predict that global agricultural lands will expand over the next few decades due to increasing demands for food production and an exponential increase in crop‐based biofuel production. These changes in land use will greatly impact biogeochemical and biogeophysical cycles across the globe. It is therefore important to develop models that can accurately simulate the interactions between the atmosphere and important crops. In this study, we develop and validate a new process‐based sugarcane model (included as a module within the Agro‐IBIS dynamic agro‐ecosystem model) which can be applied at multiple spatial scales. At site level, the model systematically under/overestimated the daily sensible/latent heat flux (by ?10.5% and 14.8%, H and λE, respectively) when compared against the micrometeorological observations from southeast Brazil. The model underestimated ET (relative bias between ?10.1% and –12.5%) when compared against an agro‐meteorological field experiment from northeast Australia. At the regional level, the model accurately simulated average yield for the four largest mesoregions (clusters of municipalities) in the state of São Paulo, Brazil, over a period of 16 years, with a yield relative bias of ?0.68% to 1.08%. Finally, the simulated annual average sugarcane yield over 31 years for the state of Louisiana (US) had a low relative bias (?2.67%), but exhibited a lower interannual variability than the observed yields.  相似文献   

9.
This work represents an attempt to assess the relative contribution of the factors limiting productivity ofSpirulina platensis in open raceways throughout the year. Temperature of the culture during daylight exerted the predominant effect on productivity and elevating the temperature resulted in a significant rise in productivity even in summer. Photoinhibition had a decisive role in summer in determining productivity ofSpirulina in open raceways in that growth almost ceased after mid-day. Contamination by other microorganisms, particularlyS. minor andChlorella sp. was estimated to reduce the net biomass yield by at least 15 to 20%, but measures to curtail the establishment of these species in the raceway have been devised. The effect of harvest time during the day on the yield of dry mass was examined: no conclusion could be drawn except in mid-summer, when evening harvesting resulted in a significant increase in the output rate of dry weight over morning harvesting.It was estimated that in a subtropical climate with little cloudiness, it should be readily possible to obtain an annual output rate of dry mass of ca. 60 to 70 t ha–1. Such output, however, which would reduce very substantially the cost of production to-date, is possible only if the optimal temperature forSpirulina can be maintained throughout daylight, photoinhibition essentially controlled, harvesting in summer performed in the evening, and night-loss of dry mass as well as the extent of contamination by other cyanobacteria or microalgae can be kept low. The pronounced daily fluctuations in the output rate at peak productivity in summer suggest that when environmental limitations of growth are minimal, other limitations become dominant. These should be identified to facilitate an even greater increase in the productivity ofSpirulina in outdoor cultures.  相似文献   

10.
As resources become scarcer measuring resource productivity (RP) is more important. Quantifying the value of natural resources is challenging but the ecological footprint (EF) concept provides one method of uniformly describing a variety of natural resources. Current assessments of RP mainly revolve around output efficiency of resources, namely the ratio of GDP to natural resource usage.This paper develops a new method of calculating the RP by using the EF as an indicator of the natural resource input and gross domestic product (GDP) as the output in the equation of RP = GDP/EF. A regression analysis is carried out using GDP per capita and RP of China from 1997 to 2011, and a comparative analysis with the members of the G20 countries according to their RP and per capita GDP in 2008. The results indicate that RP correlates with the per capita GDP, showing that RP is a valid indicator which can be used to measure a country’s level of economic development.  相似文献   

11.
Carbon dioxide and oxygen exchange procedures for measuring community metabolism (two open stream methods and three chamber methods) were compared on the same reach of a third-order stream. Open stream methods were complicated by high diffusion rates and yielded net community primary productivity estimates lower than those obtained with chamber methods. Chamber methods yielded variable productivity and respiration data. However, when normalized for chlorophyll a, productivity estimates from the chamber methods were within an expected range for the system. Balances of photosynthesis and respiration from the chamber methods were similar between methods and indicated that autotrophic or heterotrophic processes could dominate the system. Considerations in applying the various procedures are discussed.  相似文献   

12.
Evaluation of maize productivity under different climatic conditions was made by determination of the amount of the incident solar radiation energy in the PAR range, which can be potentially used by plants for photosynthesis. An irradiance, which can be stored in primary photosynthesis, designated as photosynthetic energy, W ph, was estimated taking into account the action spectra of photosynthesis. Limitation of the W ph usage, owing to unfavorable environmental factors was considered. Quantitative evaluation of limitations by two such factors, air temperature and soil water potential, was made by means of the coefficients F(i), which were defined as the ratio between the photosynthetic rate at a given value of a particular environmental factor and that at the optimal value for this factor. The coefficients F(i), were determined from the dependencies of the photosynthesis rate on air temperature and soil water potential as obtained in chamber and field experiments. In general terms, the fraction of W ph, which can be utilized under a given climatic condition, was named bioclimatic potential, W pc. In our model, the effect of monodominancy, when strong action of one factor suppresses the influence of any other factor, was considered. In this case, the bioclimatic potential, designated Wpc, was calculated by multiplying W ph times the coefficient F, for the factor which was most limiting during the period of measurement. There was close correlation between values of bioclimatic potential for the period of vegetation, Wpc,v, and total dry matter. Wpc,v use efficiency in the maize crop was also evaluated for five variants of mineral nutrition. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

13.
Biomass, net primary productivity, energetics and energy efficiencies were estimated in an age series of Alnus-cardamom plantations in the eastern Himalaya. The impact of stand age (5, 10, 15, 20, 30 and 40 years) on the performance of mixtures of N2-fixing (Alnus nepalensis) and non-N2-fixing (large cardamom) plants was studied. Large cardamom (Amomum subulatum) is the most important perennial cash crop in the region and is cultivated predominantly under Alnus trees. Net primary productivity was lowest (7 t ha(-1) per year) in the 40-year-old stand and was more than three times higher (22 t ha(-1) per year) in the 15-year-old stand. Agronomic yield of large cardamom peaked between 15 and 20 years of age. Cardamom productivity doubled from the 5- to the 15-year-old stand, and then decreased with plantation age to reach a minimum in the 40-year-old stand. Performance of cardamom in association of N2-fixing Alnus remained beneficial until 20 years of age. Annual net energy fixation was highest (444 x 10(6) kJ ha(-1) per year) in the 15-year-old stand, being 1.4 times that of the 5-year-old stand and 2.9-times that of the 40-year-old stand. Inverse relationships of production efficiency, energy conversion efficiency and energy utilized in N2-fixation against stand age, and a positive relationship between production efficiency and energy conversion efficiency suggest that the younger plantations are more productive. The Alnus-cardamom plantation system will be sustainable by adopting a rotational cycle of 15 to 20 years.  相似文献   

14.
Abstract It is shown how root : shoot ratios can be derived from two plant characteristics, (i) the nitrogen productivity (amount of biomass produced per unit of nitrogen in the biomass and per unit of time) and (ii) the relationship between photo-synthetic rate and internal nitrogen concentration. Derived root: shoot ratios are compared with experimental data for seedlings of seven tree species grown with stable internal nitrogen concentrations. Agreement is good but more exact knowledge of the relationship between nutrient status and photosynthesis is needed. It is shown that a formula derived for the root: shoot ratio can also be applied under non-steady-state conditions.  相似文献   

15.
Chromatographic and non‐chromatographic purification of biopharmaceuticals depend on the interactions between protein molecules and a solid–liquid interface. These interactions are dominated by the protein–surface properties, which are a function of protein sequence, structure, and dynamics. In addition, protein–surface properties are critical for in vivo recognition and activation, thus, purification strategies should strive to preserve structural integrity and retain desired pharmacological efficacy. Other factors such as surface diffusion, pore diffusion, and film mass transfer can impact chromatographic separation and resin design. The key factors that impact non‐chromatographic separations (e.g., solubility, ligand affinity, charges and hydrophobic clusters, and molecular dynamics) are readily amenable to computational modeling and can enhance the understanding of protein chromatographic. Previously published studies have used computational methods such as quantitative structure–activity relationship (QSAR) or quantitative structure–property relationship (QSPR) to identify and rank order affinity ligands based on their potential to effectively bind and separate a desired biopharmaceutical from host cell protein (HCP) and other impurities. The challenge in the application of such an approach is to discern key yet subtle differences in ligands and proteins that influence biologics purification. Using a relatively small molecular weight protein (insulin), this research overcame limitations of previous modeling efforts by utilizing atomic level detail for the modeling of protein–ligand interactions, effectively leveraging and extending previous research on drug target discovery. These principles were applied to the purification of different commercially available insulin variants. The ability of these computational models to correlate directionally with empirical observation is demonstrated for several insulin systems over a range of purification challenges including resolution of subtle product variants (amino acid misincorporations). Broader application of this methodology in bioprocess development may enhance and speed the development of a robust purification platform. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 31:154–164, 2015  相似文献   

16.
A simple ‘big leaf’ ecosystem gas exchange model was developed, using eddy covariance data collected at an undisturbed tropical rainforest in south-western Amazonia (Brazil). The model used mechanistic equations of canopy biochemistry combined with an empirical stomatal model describing responses to light, temperature and humidity. After calibration, the model was driven using hourly data from a weather station at the top of the tower at the measurement site, yielding an estimate of gross primary productivity (annual photosynthesis) in 1992/1993 of about 200 mol C m?2 year ?. Although incoming photon flux density emerged as the major control on photosynthesis in this forest, at a given PAR CO2 assimilation rates were higher in the mornings than in the afternoons. This was attributable to stomatal closure in the afternoon in response to increasing canopy-to-air vapour pressure differences. Although most morning gas exchange was clearly limited by the rate of electron transport, afternoon gas exchange was generally observed to be very nearly co-limited by both Rubisco activity (Vmax) and electron transport rate. The sensitivity of the model to changes in nitrogen allocation showed that the modelled ratio of Vmax to electron transport (Jmax) served nearly to maximize the annual carbon gain, and indeed, would have resulted in almost maximum annual carbon gain at the pre-industrial revolution atmospheric CO2 concentration of 27 Pa. Modelled gross primary productivity (GPP) was somewhat lower at 27 Pa, being about 160 mol C m?2 year?1. The model suggests that, in the absence of any negative feedbacks on GPP, future higher concentrations of atmospheric CO2 will continue to increase the GPP of this rainforest, up to about 230 mol C m?2 year?1 at 70 Pa.  相似文献   

17.
Globalization induces changes in the combinations of productions and activities within farming systems in all parts of the world. These changes can only be apprehended through an in-depth understanding of the mechanisms and diversity of these farming systems. Labor, as a major technical determinant of differences in competitiveness, is central in these transformations. The technical and economic analysis of labor in Andean dairy production in this paper illustrates this issue. Combining various scales of analysis of labor and productivity highlights the technical obstacles faced by Andean dairy farmers, demonstrates the technical and economic principles of these production systems, and puts them in a competitive context. This analysis also discusses the benefits of a labor-centered approach of farming systems.
Charles -Henri MoulinEmail:
  相似文献   

18.
The relationship between investments of labor to agricultural production and environmental degradation in rural areas of the developing world is complex. This paper reports on qualitative and quantitative research focused on the effects of labor availability and its compensation on the way in which cattle are herded in the Maasina region of Central Mali. Within this particular region, two social relationships determine the level and form of herder compensation: that between herd patriarch and cattle owner, and that between herd patriarch and herder. Both the nature of these relationships and variations in herding practice are described prior to a presentation of statistical analyses of the effects of household labor availability and cattle wealth on travel and grazing management decisions. Reductions in both the availability of herding labor and in the economic security of Fulsse households are shown to lead to reduced herd mobility and more constricted grazing patterns with significant environmental implications.  相似文献   

19.
Several methods for the estimation of the reaeration coefficient were compared by determining the ability of the methods to recover the correct K value from a computer-simulated stream oxygen record affected by a variety of non-ideal conditions. Noisy data and long observation intervals were not a serious problem for most methods. Saturating photosynthesis, fluctuating light intensity, afternoon depression and temperature variation caused failures by some methods but were well handled by others. Serious impairment of all methods occurred with low productivity or high K. In general, the best-performing methods were the modified hysteresis, nighttime regression, daytime regression, Odum and Hornberger-Kelly daytime methods.  相似文献   

20.
This is the second of a series of four articles aimed at providing a general analysis of the dynamic of rural intensification in China in view of sustainability, with a particular focus on the area considered in our project. Data provided in this article confirms the analysis given in the previous article about global trends for agricultural changes. In the last decades, the agricultural sector of the Hubei province managed to cope with the dramatic increase in demographic pressure by increasing more than proportionally agricultural yields. This was paid for in terms of higher environmental stress and higher reliance on external inputs. The challenge for future decades will refer to the need of matching an increasing socioeconomic pressure (=boosting the productivity of labor of farmers to get them a higher income and to make available surplus of food for the growing urban population) while limiting the environmental loading generated by agriculture. Data describing the evolution of cropping patterns, production techniques, mix and intensity of inputs used in production in the last decades seem to indicate that this would represent a formidable challenge. The nature of this challenge implies that the entire Chinese society must be involved in order to negotiate viable compromises between the need of: guaranteeing food security for China; raising the standard of living for rural populations; preserving natural resources and ecological systems for future generations.  相似文献   

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