1,721,019 research outputs found
An analysis of the diurnal course of growth, carbon dioxide exchange and carbohydrate reserve content of cucumber
No full textA detailed study was made of the diurnal course of carbon dioxide exchange, transpiration and carbohydrate reserve levels in different organs of young cucumberplants, cultivated in climate rooms under 'spring' or 'winter' conditions. Under spring conditions the stomata closed after about 8 hours light, causing a decrease in the rate of CO 2 uptake. This closure could not be ascribed to water shortage. Under winter conditions CO 2 production rapidly decreased after about 12 hours darkness, as a result of carbohydrate depletion. Additional respiration substrates were provided by protein breakdown. Reducing the air temperature during that period from 25 °C to 12 °C caused an increase in rate of plant growth, probably by reducing the amount of protein breakdown. The moment at which starch reserves were depleted was, under the conditions studied, independent of the amounts formed and seems to be 'preprogrammed'. Majority of the carbohydrate reserves formed during the day were used as respiration substrates. A comparison of the measured amounts of CO 2 production with theoretically derived values, showed a discrepancy which may be explained by underestimation of the amount of protein turnover.Furthermore a new method is described for calibration of differential water vapour analysers and also for mixing pure CO 2 with CO 2 -free air to obtain air mixtures with various constant CO 2 -concentrations.<p/
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Biological control of fruit-tree red spider mite
No full textDuring the last decade, integrated pest control systems have been developed for several crops. One of the main fields of research in integrated control has been the control of orchard pests. Experience with modified spraying programmes in apple orchards, the increasing resistance of spider mites to acaricides, and knowledge on the bionomics of many pest species have been major factors in promoting the development of integrated pest control systems. Attempts were made to introduce predatory mites or to improve their effectiveness in the control of the fruit-tree red spider mite, one of the major pests in commercial fruit orchards. These experiments clearly showed how these natural enemies can reduce and maintain spider mite populations below the economic threshold level. At present predacious mites are widely applied in the control of spider mites in apple orchards. However, the resulting changes in the system have still not been quantitatively assessed, and it is only speculation to explain the mode of operation of the system if there is no information about the underlying ecological processes. For a stable pest control system one must know how spider mite and predacious mite populations interact with each other and with the host plant, and how the system is influenced by abiotic factors (temperature, relative air humidity, wind and rain) and by cultivation methods (including the use of fertilizers as well as insecticides and fungicides). In several countries with a developed agriculture, research has therefore been started to monitor the effect of predators on pest populations.This study presents basic models for the fruit-tree red spider mite (Panonychus ulmi) and the native predacious mite, Amblyseius potentillae. The models are constructed according to the state variable approach, as is described in Chapter 3. The models developed with this technique bridge the gap between biological control with predacious mites in the field and the analytical methods of natural sciences, thus assisting in the introduction and management of biological control agents of the fruit-tree red spider mite.The simulation models are based on extensive knowledge of the effect of temperature, humidity, food and daylength on the prey as well as the predator. The relations between rates of development, mortality, oviposition and diapause with temperature and other physical factors were determined from literature studies, estimation and many laboratory experiments, Chapter 5. Many of the temperature responses of rates proved to be linear and reacted momentaneously to temperature fluctuations.The predator-prey interaction (between predacious mite and fruit-tree red spider mite) in these models, which closely approximates the field situation, is based on a detailed analysis of the predation process. This predator-prey interaction is very complex. Five developmental stages of the prey (larva, protonymph, deutonymph, adult male and female), and four developmental stages of the predator (protonymph, deutonymph, adult male and female) are involved. The attractiveness of the different stages of the prey varies and depends partly on the satiation level of the predator. For example, the adult female predator (the most voracious stage) shows a strong preference for the younger stages of the prey, but 'hungry' predators are much less selective. The rate of ingestion and the utilization of a killed prey also depends on the satiation level of the predator. Fransz's detailed analysis of the predation process in the system two-spotted spider mite and predacious mite and the explanatory models he developed for this process showed that a simple system (one standardized predator and a constant number of preys) reaches an equilibrium within a few hours. Hence the degree of filling of the gut of the predator oscillates with a small amplitude, at a level depending on predator and prey density and on the temperature of the system. This enables the complex predation process to be incorporated in a model for a population of higher order by simply expressing relative predation rate and prey utilization as functions of temperature and state of the predator. The satiation level of the predator can be quantified visually, because well-fed predators are dark, while hungry predators are whitish and transparent. A colour scale has been developed which relates the behaviour of the predator expressed in success ratio (number of successful encounters to the total number of encounters) to the quantity of leaf and animal pigments in the predator, which together constitutes its colour.Experiments were carried out to determine the rate of decrease in colour value, which is supposed to equal the digestion rate, the relation between predation rate and prey density, and the relation between predation rate and colour value at various temperatures. The required relations for relative predation rate and prey utilization are easily derived from these functions. Oviposition rate and the development rate from egg to adult of the predator (numerical response) also dependon its satiation level and on temperature. These relations are also experimentally quantified, Section 6.3.The details of information required on the driving variables, temperature and food condition were determined by experiment and simulation. The effect of nutritive condition of the tree on the prey was determined in water culture experiments and related to the nitrogen content of the leaves in commercial apple orchards. It is shown, Section 7.2, that the nutritive condition of the trees in practice do not affect the rates of development and oviposition of the fruit-tree red spider mite. To determine the required details about micro-weather an adapted and verified micro-weather simulator was coupled to the population model. The small differences between simulation results when leaf temperatures are the driving variables and simulations in which air temperature is the driving variable justified further calculations in the field with air temperature, Section 7.3.The assumptions in the model underlying the treatment of the predation process were verified by comparing results of an independent experiment on predation in replacement series of 'prey stages', with simulation results. It is also shown that the procedure, for determining yields of a plant species growing in competition, from sowing density experiments in monoculture, may be applied for calculating predation rates of a species in 'mixed cultures' from its functional response curve in monoculture (see Section 9.2).The models for hatching winter eggs, for population growth throughout the season and for diapause are verified at different levels of integration by independent population experiments. The most simple verification is the measurement of population growth in small ecosystems under controlled conditions in situations with and without predators and then to compare results with those of simulation.Verification in the field is done by comparing simulation results with population measurements in several orchards. The correspondence in general pattern of population fluctuations of prey and predator and the good correspondence between simulated and measured colour values of the predators enables the model to be used for sensitivity analysis and management.Sensitivity analysis showed that particular key factors are absent and that a wide range of initial prey-predator ratio's may be tolerated. It is further shown that the predation activity of the younger stages and the adult males is relatively unimportant and that the female predator is the important regulator due to its high predation capacity, its long lifespan and an increase in rate of oviposition until the predator is well fed. The system is rather sensitive to length of prey's juvenile period, predation rate, and oviposition rate of the adult female predator and the delay in development of the predator due to insufficient food
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dynamics of partial anaerobiosis denitrification, and water in soil : experiments and simulation
No full textDynamic interactions between biological respiration and denitrification, and physical transport processes that modify the abiotic soil environment in which bacteria live, were studied through the development of a new type of experimental respirometer system and an explanatory simulation model.The respirometer system enables one to measure simultaneously the distribution of water, oxygen, nitrate, ammonium, and pH as a function of space and time in an unsaturated, artificially made, homogeneous, cylindrical soil aggregate. The coherent data sets that were obtained by this experimental system served to test the explanatory simulation model.The simulation model comprises four submodels: 1) biological respiration and denitrification, 2) water transport including a description to account for hysteresis, 3) solute transport, and 4) gas transport including a new description to simulate the integral soil atmosphere. Besides evaluation of the integral model with the results of the respirometer system, three of the submodels were also separately tested, either by means of experiments (submodel 1 and 2) or by analytical solutions (a special case of submodel 4).It was found that the new respirometer system yields valuable data to test the simulation model, and that the simulation model gives a fair description of the measured data. However, it appears that only the combined study of the results of experiments and simulations will deepen the understanding of the complicated interactions that occur in this soil biological ecosystem.It was the objective of this study to describe the respirometer system, the explanatory simulation model, and the tests that were done to evaluate the integral model and the separate submodels
The interpretation of remote sensing : a feasibility study
No full textThis thesis describes research done to ascertain the possibilities and limitations of the use of remote sensing observations for agriculture. The topic is defined in Chapter 1. In Chapter 2 the possible applicability of certain existing models for this study is examined. Three models are developed further in Chapter 3. Two of them describe the relation between properties of a crop and its reflective behaviour; the third is a model for soil reflection. Chapter 4 presents calculations on hypothetical crops; in Chapter 5 some calculations based on actual crop data are described.In the early years of the use of remote sensing, the agricultural applications of this technique were almost exclusively qualitative. However, the quantitative applications have been steadily increasing. These applications always require measured electromagnetic radiative energy to be translated into parameters of agricultural interest, such as coverage, leaf area index, biomass, development stage or health conditions of a crop, and in most situations the qualitative information which crop is being grown must also be determined from the observed radiation.The problem is defined in Chapter 1. The conclusion is that the optical behaviour of a crop is determined by a number of more or less independent parameters. This number generally exceeds the number of data measured. Consequently, in many situations it is very difficult to reliably estimate the quantities that cause this behaviour, if these estimations are only based on the observations. Two additional complicating factors are that the relations between the optical and the agricultural properties of a crop are surely not unequivocal, and that the reflection of a crop also depends on the spatial distribution of the incident radiation. This justifies the conclusion that it is useful to study the relations between the agricultural properties of a crop and the upward radiation, measured under different irradiance conditions.In Chapter 2, it is investigated if, and under which conditions, existing models could be used as reflection models. To determine the requirements of reflection models, an existing analytical model (Kubelka & Munk, 1931) is used to calculate the ratio of reflected radiation to absorbed radiation, and a new analytical model is used to ascertain the spatial distribution of the reflected radiation. From the calculations with the Kubelka-Munk model it is concluded that for the calculation of the absorption of incident radiation by a crop the modelling of the spatial distribution of the intercepted and remitted radiation can be strongly simplified, without compromising the quality of the absorption calculations. This justifies that in the models used by plant physiologists for calculating the absorption of photosynthetically active radiation, the spatial distribution of this secondary radiation is strongly simplified. Calculations with the distribution model show that both the crop properties and the spatial distribution of the incoming radiation may strongly influence the reflected radiation in one direction.Four existing models are examined to ascertain their applicability in the situation under consideration. As might be expected, the two absorption models (De Wit, 1965; Goudriaan, 1977) lack the level of detail that is required for the modelling of the reflected radiation. Of the two models that have primarily been developed as reflection models (Suits, 1972; Chen, 1984), the first is a very theoretical model, so if it is applied to a real crop it only permits qualitative statements. The second model should, in principle, be applicable, but its intensive use of computer resources means that a prohibitive number of calculations is required. The conclusion is that it makes sense to develop a new reflection model, incorporating several aspects of the existing models both in its theoretical basis and in its implementation.Chapter 3 is devoted to the three models that are developed in this study: the TURTLE, HARE and SOIL models. TURTLE and HARE describe a crop and SOIL describes a, non-flat soil. Both TURTLE and HARE are based on the description of a crop as 8, stack of thin crop layers. For this description, 46 directions are defined in a semispace. These directions, which are used as representatives of all possible directions, are distributed in such way that each represents an equal solid angle (0.14 sr). The mutual angle between adjacent directions is 0.42 rad. Because each model direction represents all directions within a fairly regular pentagonal or hexagonal conic sector of the space, the angle between a representative and a represented direction never exceeds 0.24 rad. These model directions are used both to represent radiation patterns and to define leaf angle distributions. In the latter case, the directions are used as vectors perpendicular to possible leaf orientations.The optical properties of a single crop layer are derived from the optical properties of the crop components and of the leaf angle distribution of this layer. The optical properties of a crop layer are described in the form of a set of four 46*46 matrices: one for the upperside reflection of the layer, one for the underside reflection, one for the upward transmission and one for the downward transmission through the layer. In the models as described, upperside and underside are assumed to be identical, so only two matrices have to be computed: one for the layer reflection and one for the layer transmission. From these matrices, and in combination with another 46*46 matrix for the soil reflection, one matrix is calculated. This matrix describes the optical behaviour of the total crop. The TURTLE and HARE models differ in the aspect that the TURTLE model allows the radiation pattern and the radiation intensity throughout the complete crop to be calculated. To enable this, in the calculations the layers are stacked one by one, in an upward direction, starting with the soil matrix. In the HARE model, the matrices for stacks of identical model layers are calculated by means of a doubling method. This way of combining layer matrices prohibits the calculation of a radiation pattern throughout the crop, but this limitation is not very drastic in remote sensing applications. The advantage of this method is that it reduces the computer time required by a factor of 5 to 10, compared with the TURTLE model. Also, the incoming radiation is described as a, vector that comprises in the 46 previously mentioned directions. Multiplying this vector by the crop reflection matrix yields the radiation remitted by the crop. The TURTLE model allows the radiation regime within the crop to be calculated in a similar way.The SOIL model is developed to investigate if the influence of a non-flat soil to the reflected radiation is so large that it would be unrealistic to model the soil as a flat reflecting surface. The calculations show that only if the coverage of the crop is very low (In Chapter 4, a large number of calculations with the HARE model are presented. For these calculations, test values based on values that are found in literature are chosen for the parameters that can be varied in the model. These parameters concern the leaf angle distribution, the leaf reflection and the leaf transmission coefficient, the reflective behaviour of the leaves, the soil reflection coefficient, the spatial distribution of the incoming radiation and the direction of observation. The calculations always concern the relation between the upward radiation and the primary crop property, namely the vertically measured coverage. It is investigated how this relation is influenced by variations in the values of the given parameters. Based on these calculations it can be concluded that these variations can be large, but that it may be expected that the relation between the vertical coverage and the ratio between the reflection in the infrared and the red bands (or a derived function such as the normalized difference between these two, the vegetation index), will be much less sensitive to the mentioned variations. For this reason a second series of calculations is done. In these calculations, the sensitivity of the relation between coverage and vegetation index for the same parameter variations is examined. It appears that this relation is indeed much less sensitive, except for changes in the observation direction. The latter phenomenon is investigated separately. The conclusion of the latter investigation is that the commonly used method to reduce the directional dependency that is based on a quadratic regression, only enhances the quality of the interpretation under special conditions, but that in some cases, this correction yields an even worse result than the result that would have been found if the correction had not been applied at all. It is indicated how, by means of the HARE model, the calculations may be improved.Finally, Chapter 5 discusses the interpretation of remote sensing observations applied to winter wheat and sugarbeet. The aim of the wheat calculation is to investigate which variation in the crop can be determined and at which moments. For the calculations, a, normal developing wheat crop was constructed, based on literature data. Some variants with a higher and a lower LAI and also three variants with strongly yellowing leaves were derived from this crop. The calculation indicates that the vegetation index only gives information about the LAI as long as the crop is green and the LAI does not exceed 3.5. Higher LAI-values cannot be distinguished, and if the crop turns yellow, it cannot be distinguished from a crop with a much lower LAI. If, besides the vegetation index the ratio red/green is also applied, the interpretation possibilities increase somewhat. The red/green ratio decreases until the crop reaches an LAI of 6, higher LAI-values cannot be determined. It is also possible, if repeated observations are carried out, to distinguish yellowing in a late growth phase from a decreasing LAI-value. The use of the vegetation index or the red/green ratio causes a drastic decrease in the influence of factors that are of no agricultural interest, but which were present in the reflection in the individual bands.The aim of the calculations with sugarbeet was to ascertain which conditions are most applicable for the detection of places where the crop droops its leaves. For this purpose the spatial pattern of the reflected radiation by a beet crop in different wavelength bands is calculated. These calculations are done both for a healthy crop and for a dehydrated crop. For both crop types the infrared/red ratio is calculated for all possible observation directions, and then the quotient of these ratios is calculated. It appears that the areas where leaf drooping has occurred can easily be identified, providing that the observation direction is chosen well (e.g. facing the sun, and with an inclination that is approximately the complement of the sun's inclination). These areas can be distinguished, even if the observations are carried out under full cloud cover. The latter conclusion is especially important if the observations are done on a small scale by using a micro-light airplane
Mathematical analysis and simulation of crop micrometeorology
No full textIn crop micrometeorology the transfer of radiation, momentum, heat and mass to or from a crop canopy is studied. Simulation models for these processes do exist but are not easy to handle because of their complexity and the long computing time they need. Moreover, up to now such models can only be run on mainframe computers. This study aims at developing a more elegant mathematical analysis that both deepens the understanding of the processes involved, and enables the writing of more efficient computer programs.To model the radiation regime, Goudriaan (1977) divided the crop canopy into several layers. The radiation at each layer was classified into downward and upward flux densities, assigned to nine contiguous zones in a hemisphere. Then a set of equations was derived for these radiation components and an efficient iteration method was developed to solve them. The solutions gave a detailed description of the distribution of the radiation in a canopy, from which the zonal reflectance from a canopy can also be obtained. In addition, by computer experimentation a so- called reciprocity relation was found between a direct light source and the reflected radiance from vegetation. This relation has potential applications in remote sensing techniques. Remaining problems are: (a) the computation of the radiation profiles in a canopy needs much execution time; (b) azimuthal variations of bidirectional reflectance from a canopy cannot be simulated; and (c) the mathematical proof of the reciprocity relation was not found.In Chapters 2 and 3, the downward and upward radiation from all directions in a hemisphere are represented by radiation vectors and the interactions of the radiation with a horizontally homogeneous canopy layer are represented by reflectance and transmittance matrices. In Chapter 2, the physical process of the reflection and transmission of radiation by a multi-layer canopy is examined under vector-matrix notation. The radiation vector incident upon the top of a canopy, may be directly reflected from the first layer forming a component of the reflected radiation vector from the top of the canopy; or it may, for instance, be transmitted through the first layer, reflected from the second layer, and transmitted again through the first layer, forming another component of the reflected radiation vector. Not every reflection-transmission series, called a radiation path, results in a component of the reflected radiation vector but there is an infinite number of such paths. It is proven in Chapter 2 that the reciprocity relation holds if each radiation path contributing to the reflection vector can be reversed and also result in a component of the reflected radiation vector. It is shown that this reversibility of the radiation paths is generally true for reflection whereas for transmission a vertically uniform canopy and a black soil surface are required.In Chapter 3, the radiation equations are rewritten as a set of difference equations with vectors as variables and matrices as coefficients. Then two differential equations for downward and upward radiation vectors are derived, where the coefficients are interception, backward and forward scattering matrices, which are the three basic matrices characterizing the interactions of a horizontally homogeneous canopy with radiation vectors. These two differential equations are, in fact, the vector-matrix version of the Kubelka-Munk equations, which are two scalar differential equations for total downward and upward radiation intensities in a canopy with horizontal Lambertian leaves. The extended Kubelka-Munk equations can describe the directional transfer of radiation in a canopy with non-Lambertian leaves and any leaf inclination distribution. This is more realistic than Suits' (1972) model containing, principally, only vertical and horizontal leaves. The azimuthal variations are included by extending the corresponding vectors and matrices. The analytical solutions for profiles of the downward and upward radiation vectors are found by means of a standard matrix method and also the bidirectional reflectance from a canopy is thus obtained. In spite of the availability of the analytical solution to the bidirectional reflectance from a canopy, however, the azimuthal resolution is still restricted by the execution time. Thus, for leaf canopies without azimuthal preference a special method reducing the dimensions of the relevant matrices, and an approximate method based on the radiation path method presented in Chapter 2 are developed. The approximate method allows the resolution of 10 degrees in azimuth as well as in inclination, and calculates the bidirectional reflectance from a canopy within an acceptable execution time.In Chapters 4 to 7, profiles of temperature, humidity, sensible and latent heat flux densities in a canopy are studied in detail. Because the derived equations for sensible and latent heat flux densities are coupled with each other, they must be solved simultaneously. This leads to the following problems: (a) it costs much execution time and space so the program cannot be executed on a microcomputer; (b) distinction of sunlit and shaded leaves within each layer would require to split each layer into several sublayers according to different irradiation levels and thus increase further the execution time and space; (c) the analytical expressions for total sensible and latent heat flux densities above a canopy are not available so that it is not possible to find relationships between the parameters used in the multi-layer model and those used in the single- layer model (Penman- Monteith approach), viz. the canopy resistance and the excess resistance.In Chapter 4, the sensible and latent heat flux densities are replaced by the enthalpy flux density H, which is the sum of the sensible and latent heat flux densities, and by the saturation heat flux density J, which is a weighted difference between the sensible heat flux density and the latent heat flux density. This weight is done in such a way that the resulting equations for H and J are now mutually independent, so that the computation of the relevant profiles is greatly simplified. Two uncoupled electrical analogues for H and J, respectively, are designed, which are the counterparts of the coupled electrical analogue for the sensible and latent heat. The computation of the J profile is further simplified by recurrent formulas. Moreover, in terms of H and J, the well known Penman's formulas are expressed in a unified form applicable to both single- and multi-layer models, which provides a bridge between these two models.In Chapter 5, a method to distinguish sunlit and shaded leaves is developed based on the two uncoupled electrical analogues for H and J and on the recurrent formulas developed in Chapter 4. Goudriaan's (1977) simulation program MICROWEATHER is then rewritten in BASIC. A complete list of the program and the symbols used in the program is given in the Appendix. This program in BASIC gives the same detailed description of the crop micrometeorology as MICROWEATHER does, while it can be executed on a microcomputer. The agreement between the results of these twoprograms is good.In Chapter 6, Monteith's (1963) extrapolation method to obtain representative surface values of temperature and vapour pressure is extended by replacing the vapour pressure profile by the dew- point temperature profile. Thus, the canopy resistance can be obtained directly by graphical means. Two basic parameters of the single-layer model, the canopy resistance and the excess resistance, are clearly presented in this way.In Chapter 7, the canopy resistance and the excess resistance are calculated from the parameters used in the multi-layer model by means of the unified Penman's formulas developed in Chapter 4. The formulas derived for these two resistances show that both of them contain aerodynamic and physiological components. It is shown that however, for a dense canopy with a dry soil surface, the canopy resistance contains mainly physiological components and is approximately equal to the resistance value calculated as all stomatal resistances of the leaves connected in parallel; the excess resistance contains mainly aerodynamic components and is a simple function of the friction velocity. In this case, therefore, the canopy resistance and the excess resistance can be estimated easily in 'terms of the parameters used in the multi-layer model.In the discussion in Chapter 8, it is emphasized that the method to calculate bidirectional reflectance from a canopy developed in Chapter 3 can have important applications in remote sensing of vegetation, because it allows to study the effects of different leaf inclination distributions and non-Lambertian leaves. The results should be compared with data sets on the bidirectional reflectance from various vegetation canopies to see the practical significance of these two factors. The simulation program for crop micrometeorology developed for microcomputers (Chapter 5) can be used for short grass, where Goudriaan's MICROWEATHER has difficulties with the execution time caused by the small time coefficient of the model. The model can be further developed to simulate the evapo-transpiration from a canopy wetted by rainfall, and it could be incorporated into a pest and plant disease model. The results obtained on the canopy resistance and excess resistance (Chapter 7) justify the applicability of the single-layer model for a dense canopy. But for a sparse canopy the influence of the soil surface cannot be neglected, and the double-layer model one represents the canopy and the other represents the soil surface should be used. This version of the micrometeorological simulation program may be included in a crop growth model such as BACROS (de Wit et al., 1978)
- …
