Canopy reflectance, photosynthesis and transpiration
24 Feb 1985-International Journal of Remote Sensing (Taylor & Francis Group)-Vol. 6, Iss: 8, pp 1335-1372
TL;DR: In this paper, a two-stream approximation model of radiative transfer was used to calculate values of hemispheric canopy reflectance in the visible and near-infrared wavelength intervals.
Abstract: A two-stream approximation model of radiative transfer is used to calculate values of hemispheric canopy reflectance in the visible and near-infrared wavelength intervals. Simple leaf models of photosynthesis and stomatal resistance are integrated over leaf orientation and canopy depth to obtain estimates of canopy photosynthesis and bulk stomatal or canopy resistance. The ratio of near-infrared and visible reflectances is predicted to be a near linear indicator of minimum canopy resistance and photosynthetic capacity but a poor predictor of leaf area index or biomass.
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TL;DR: In this paper, the authors evaluated the performance and validity of the MODIS vegetation indices (VI), the normalized difference vegetation index (NDVI) and enhanced vegetation index(EVI), produced at 1-km and 500-m resolutions and 16-day compositing periods.
6,563 citations
Cites background from "Canopy reflectance, photosynthesis ..."
...They serve as intermediaries in the assessment of various biophysical parameters, such as green cover, biomass, LAI, and fraction of absorbed photosynthetically active radiation (fAPAR) (Asrar, Fuchs, Kanemasu, &Hatfield, 1984; Sellers, 1985; Tucker, 1979)....
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...Generally, vegetation indices approach a saturation level asymptotically in high biomass regions and for a certain range of LAI (Sellers, 1985)....
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TL;DR: In this article, a transformation technique was presented to minimize soil brightness influences from spectral vegetation indices involving red and near-infrared (NIR) wavelengths, which nearly eliminated soil-induced variations in vegetation indices.
5,450 citations
TL;DR: In this paper, satellite data from the Advanced Very High Resolution Radiometer sensor have been processed over several days and combined to produce spatially continuous cloud-free imagery over large areas with sufficient temporal resolution to study green-vegetation dynamics.
Abstract: Red and near-infrared satellite data from the Advanced Very High Resolution Radiometer sensor have been processed over several days and combined to produce spatially continuous cloud-free imagery over large areas with sufficient temporal resolution to study green-vegetation dynamics. The technique minimizes cloud contamination, reduces directional reflectance and off-nadir viewing effects, minimizes sun-angle and shadow effects, and minimizes aerosol and water-vapor effects. The improvement is highly dependent on the state of the atmosphere, surface-cover type, and the viewing and illumination geometry of the sun, target and sensor. An example from southern Africa showed an increase of 40 percent from individual image values tothe final composite image. Limitations associated with the technique are discussed, and recommendations are given to improve this approach.
2,760 citations
TL;DR: The use of the NDVI in recent ecological studies is reviewed and its possible key role in future research of environmental change in an ecosystem context is outlined.
Abstract: Assessing how environmental changes affect the distribution and dynamics of vegetation and animal populations is becoming increasingly important for terrestrial ecologists to enable better predictions of the effects of global warming, biodiversity reduction or habitat degradation. The ability to predict ecological responses has often been hampered by our rather limited understanding of trophic interactions. Indeed, it has proven difficult to discern direct and indirect effects of environmental change on animal populations owing to limited information about vegetation at large temporal and spatial scales. The rapidly increasing use of the Normalized Difference Vegetation Index (NDVI) in ecological studies has recently changed this situation. Here, we review the use of the NDVI in recent ecological studies and outline its possible key role in future research of environmental change in an ecosystem context.
2,493 citations
TL;DR: In this paper, a simple radiative transfer model with vegetation, soil, and atmospheric components is used to illustrate how the normalized difference vegetation index (NDVI), leaf area index (LAI), and fractional vegetation cover are dependent.
2,429 citations
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TL;DR: In this paper, the authors take up the concepts of altruistic and selfish behaviour; the genetical definition of selfish interest; the evolution of aggressive behaviour; kinship theory; sex ratio theory; reciprocal altruism; deceit; and the natural selection of sex differences.
Abstract: Science need not be dull and bogged down by jargon, as Richard Dawkins proves in this entertaining look at evolution. The themes he takes up are the concepts of altruistic and selfish behaviour; the genetical definition of selfish interest; the evolution of aggressive behaviour; kinship theory; sex ratio theory; reciprocal altruism; deceit; and the natural selection of sex differences. Readership: general; students of biology, zoology, animal behaviour, psychology.
10,880 citations
TL;DR: Various aspects of the biochemistry of photosynthetic carbon assimilation in C3 plants are integrated into a form compatible with studies of gas exchange in leaves.
Abstract: Various aspects of the biochemistry of photosynthetic carbon assimilation in C3 plants are integrated into a form compatible with studies of gas exchange in leaves. These aspects include the kinetic properties of ribulose bisphosphate carboxylase-oxygenase; the requirements of the photosynthetic carbon reduction and photorespiratory carbon oxidation cycles for reduced pyridine nucleotides; the dependence of electron transport on photon flux and the presence of a temperature dependent upper limit to electron transport. The measurements of gas exchange with which the model outputs may be compared include those of the temperature and partial pressure of CO2(p(CO2)) dependencies of quantum yield, the variation of compensation point with temperature and partial pressure of O2(p(O2)), the dependence of net CO2 assimilation rate on p(CO2) and irradiance, and the influence of p(CO2) and irradiance on the temperature dependence of assimilation rate.
7,312 citations
TL;DR: In this paper, the second edition of the Second edition, the authors present a list of symbolic symbols for the field of environmental physical sciences, including the following: 1.GAS LAWS Pressure, volume and temperature Specific heats Lapse rate Water and water vapour Other gases 3. TRANSPORT LAWS General transfer equation Molecular transfer processes Diffusion coefficients Radiation laws 4. RADI ENVIRONMENT Solar radiation Terrestrial radiation Net radiation 5. MICROCLIMATOLOGY OF RADIATION (i) Interception Direct solar radiation Diffuse radiation Radiation in
Abstract: PREFACE TO THE SECOND EDITION LIST OF SYMBOLS 1. SCOPE OF ENVIRONMENTAL PHYSICS 2. GAS LAWS Pressure, volume and temperature Specific heats Lapse rate Water and water vapour Other gases 3. TRANSPORT LAWS General transfer equation Molecular transfer processes Diffusion coefficients Radiation laws 4. RADIATION ENVIRONMENT Solar radiation Terrestrial radiation Net radiation 5. MICROCLIMATOLOGY OF RADIATION (i) Interception Direct solar radiation Diffuse radiation Radiation in crop canopies 6. MICROCLIMATOLOGY OF RADIATION (ii) Absorption and reflection Radiative properties of natural materials Net radiation 7. MOMENTUM TRANSFER Boundary layers Wind profiles and drag on uniform surfaces Lodging and windthrow 8. HEAT TRANSFER Convection Non-dimensional groups Measurements of convection Conduction Insulation of animals 9. MASS TRANSFER (i) Gases and water vapour Non-dimensional groups Measurement of mass transfer Ventilation Mass transfer through pores Coats and clothing 10.MASS TRANSFER (ii) Particles Steady motion 11.STEADY STATE HEAT BALANCE (i) Water surfaces and vegetation Heat balance equation Heat balance of thermometers Heat balance of surfaces Developments from the Penman Equation 12.STEADY STATE HEAT BALANCE (ii) Animals Heat balance components The thermo-neutral diagram Specification of the environment Case studies 13.TRANSIENT HEAT BALANCE Time constant General cases Heat flow in soil 14.CROP MICROMETEOROLOGY (i) Profiles and fluxes Profiles Profile equations and stability Measurement of flux above the canopy 15.CROP MICROMETEOROLOGY (ii) Interpretation of measurements Resistance analogues Case studies: Water vapour and transpiration Carbon dioxide and growth Sulphur dioxide and pollutant fluxes to crops Transport within canopies APPENDIX BIBLIOGRAPHY REFERENCES INDEX
4,087 citations
TL;DR: Under optimal conditions, the most outstanding genotype was ICS-1, both in plant height, number of leaves, and stomatal conductance, this being proof that this genotype develops excellently and stands out if it has the right conditions and water availability.
Abstract: This research is part of an effort that the ICT (Institute of Tropical Cultivation) has been doing for several years tending to develop superior genotypes of cocoa (Theobroma cacao L.). That is why this study aims to find tolerant or moderately tolerant cocoa genotypes and accessions to water stress with resistance to pests and diseases and high production and industrial quality. Twenty genotypes of cocoa seedlings were investigated, during the period of 6 months, in a soil with sandy-loam texture under nursery conditions, of controlled irrigation. A split plot design was used, with 40 treatments and 3 repetitions. In addition, daily data of the micro climatic characteristics (T °, HR) were taken, in which different indicators of variable were evaluated such as the stomatal conductance (CE) that is greatly influenced by the T ° and HR. The results obtained indicate that the genotypes that showed moderate tolerance to water stress were UNG - 77, UNG - 53, ICT - 1281 and ICT - 1112; the non-tolerant ones were PAS - 93, CEPEC - 2002, ICT - 2142, ICT - 1092, CP - 2005 - C10, TSH - 1188, CCN - 51, IMC - 67, PH - 17, AYP - 15, ICS - 6, BN - 34, ICT - 1506, PAS - 91, PH - 990 and ICS - 1. Under optimal conditions, the most outstanding genotype was ICS-1, both in plant height, number of leaves, and stomatal conductance, this being proof that this genotype develops excellently and stands out if it has the right conditions and water availability.
3,693 citations
TL;DR: The efficiency of crop production is defined in thermodynamic terms as the ratio of energy output (carbohydrate) to energy input (solar radiation). Temperature and water supply are the main climatic constraints on efficiency as mentioned in this paper.
Abstract: The efficiency of crop production is defined in thermodynamic terms as the ratio of energy output (carbohydrate) to energy input (solar radiation). Temperature and water supply are the main climatic constraints on efficiency. Over most of Britain, the radiation and thermal climates are uniform and rainfall is the main discriminant of yield between regions. Total production of dry matter by barley, potatoes, sugar beet, and apples is strongly correlated with intercepted radiation and these crops form carbohydrate at about 1.4 g per MJ solar energy, equivalent to 2.4% efficiency. Crop growth in Britain may therefore be analysed in terms of ( a ) the amount of light intercepted during the growing season and ( b ) the efficiency with which intercepted light is used. The amount intercepted depends on the seasonal distribution of leaf area which, in turn, depends on temperature and soil water supply. These variables are discussed in terms of the rate and duration of development phases. A factorial analysis of efficiency shows that the major arable crops in Britain intercept only about 40 % of annual solar radiation and their efficiency for supplying energy through economic yield is only about 0.3%. Some of the factors responsible for this figure are well understood and some are immutable. More work is needed to identify the factors responsible for the large differences between average commercial and record yields.
3,304 citations