TY - JOUR
ID - bastiaanssen2000
AU - Bastiaanssen, Wim G. M.
AU - Molden, David J.
AU - Makin, Ian W.
TI - Remote sensing for irrigated agriculture: examples from research and possible applications
UR - http://www.sciencedirect.com/science/article/pii/S0378377400000809
DO - 10.1016/s0378-3774(00)00080-9
T2 - Agricultural Water Management
PY - 2000
SN - 0378-3774
VL - 46
IS - 2
SP - 137-155
AB - Researchers in various international programs have studied the potential use of remotely sensed data to obtain accurate information on land surface processes and conditions. These studies have demonstrated that quantitative assessment of the soil-vegetation-atmosphere-transfer processes can lead to a better understanding of the relationships between crop growth and water management. Information on land surface can now be obtained at a wide range of spatial (5â5000 m) and temporal resolutions (0.5â24 days). However, even though considerable progress has been made over the past 20 years in research applications, remotely sensed data remain underutilized by practicing water resource managers. This paper seeks to bridge the gap between researchers and practitioners, first, by illustrating where research tools and techniques have practical applications and, second, by identifying real problems that remote sensing could solve, albeit with additional research and development. As freshwater becomes an increasingly scarce resource, all opportunities to better manage water uses, particularly in irrigated agriculture, must be taken. An important challenge in the field of water resources is to utilize the timely, objective and accurate information provided by remote sensing.
KW - Remote sensing
KW - Irrigated farming
KW - Land management
KW - Water resources management
KW - Crop yield
KW - Water use efficiency
KW - Water rights
ER -
TY - JOUR
ID - ceccato2001
AU - Ceccato, Pietro
AU - Flasse, Stéphane
AU - Tarantola, Stefano
AU - Jacquemoud, Stéphane
AU - Grégoire, Jean-Marie
TI - Detecting vegetation leaf water content using reflectance in the optical domain
UR - http://www.sciencedirect.com/science/article/pii/S0034425701001912
DO - 10.1016/s0034-4257(01)00191-2
T2 - Remote Sensing of Environment
PY - 2001
SN - 0034-4257
VL - 77
IS - 1
SP - 22-33
AB - This paper outlines the first part of a series of research studies to investigate the potential and approaches for using optical remote sensing to assess vegetation water content. It first analyzes why most methods used as approximations of vegetation water content (such as vegetation stress indices, estimation of degree of curing and chlorophyll content) are not suitable for retrieving water content at leaf level. It then documents the physical basis supporting the use of remote sensing to directly detect vegetation water content in terms of Equivalent Water Thickness (EWT) at leaf level. Using laboratory measurements, the radiative transfer model PROSPECT and a sensitivity analysis, it shows that shortwave infrared (SWIR) is sensitive to EWT but cannot be used alone to retrieve EWT because two other leaf parameters (internal structure and dry matter) also influence leaf reflectance in the SWIR. A combination of SWIR and NIR (only influenced by these two parameters) is necessary to retrieve EWT at leaf level. These results set the basis towards establishing operational techniques for the retrieval of EWT at top-of-canopy and top-of-atmospheric levels.
KW - Leaf water content
KW - Fuel moisture content
KW - Optical domain
KW - Shortwave infrared
ER -
TY - JOUR
ID - ceccato2002
AU - Ceccato, Pietro
AU - Gobron, Nadine
AU - Flasse, Stéphane
AU - Pinty, Bernard
AU - Tarantola, Stefano
TI - Designing a spectral index to estimate vegetation water content from remote sensing data: Part 1: Theoretical approach
UR - http://www.sciencedirect.com/science/article/pii/S0034425702000378
DO - 10.1016/s0034-4257(02)00037-8
T2 - Remote Sensing of Environment
PY - 2002
SN - 0034-4257
VL - 82
IS - 2â3
SP - 188-197
AB - This paper describes the methodology used to create a spectral index to retrieve vegetation water content from remotely sensed data in the solar spectrum domain. A global sensitivity analysis (GSA) using radiative transfer models is used to understand and quantify vegetation water content effects on the signal measured at three levels: leaf, canopy, and atmosphere. An index is then created that optimises retrieval of vegetation water content (in terms of water quantity per unit area at canopy level) and minimises perturbing effects of geophysical and atmospheric effects. The new index, optimised for the new SPOT-VEGETATION sensor, is presented as an example. Limitations and robustness of the index are also discussed.
ER -
TY - JOUR
ID - cibula1992
AU - Cibula, W. G.
AU - Zetka, E. F.
AU - Rickman, D. L.
TI - Response of thematic mapper bands to plant water stress
UR - http://dx.doi.org/10.1080/01431169208904236
DO - 10.1080/01431169208904236
PR - Taylor & Francis
T2 - International Journal of Remote Sensing
PY - 1992
DA - 1992-07-01
SN - 0143-1161
VL - 13
IS - 10
SP - 1869-1880
AB - Abstract Changes in leaf reflectance as water content decreases have been hypothesized to occur in the 1 55-1.75 and 2.08-2.35 ?m wavelength regions. To evaluate this hypothesis, studies were conducted on ryegrass (Lolium muitiflorum Lam.) and oats (Avena saliva L.), which were grown in a controlled, outdoor situation. Both fully-watered control beds and water-stressed beds were periodically examined with a spectroradiometer calibrated against a reflectance reference of polytetrafluoroethylene. The observed changes correspond to those predicted by stochastic leaf models employed by other investigators (leaf reflection increases in the l.55-l.75?m region as leaf water content decreases). Although the percentage changes in TM bands 1-3 are nearly as great as those found in TM bands 5 and 7, the absolute values of reflectance change are much lower. We believe that these patterns are probably characteristic of a broad range of vegetation types. In terms of phenomena detection, these patterns should be considered in any practical remote sensing sensor scenario.
ER -
TY - JOUR
ID - curran1989
AU - Curran, Paul J.
TI - Remote sensing of foliar chemistry
UR - http://www.sciencedirect.com/science/article/pii/0034425789900692
DO - 10.1016/0034-4257(89)90069-2
T2 - Remote Sensing of Environment
PY - 1989
SN - 0034-4257
VL - 30
IS - 3
SP - 271-278
AB - Remotely sensed data are being used to estimate foliar chemical content as a result of our need for the information and our increasing ability to understand and measure foliar spectra. This paper reviews how stepwise multiple regression and deconvolution have been used to extract chemical information from foliar spectra, and concludes that both methods are useful, but neither is ideal. It is recommended that the focus of research be modeling in the long term and experimentation in the short term. Long-term research should increase our understanding of the interaction between radiation and foliar chemistry so that the focus of research can move from leaf model to canopy model to field experiment. Short-term research should aim to design experiments in which remotely sensed data are used to generate unambiguous and accurate estimates of foliar chemical content.
ER -
TY - JOUR
ID - datt1999
AU - Datt, Bisun
TI - Remote Sensing of Water Content in Eucalyptus Leaves
DO - http://dx.doi.org/10.1071/BT98042
T2 - Australian Journal of Botany
PY - 1999
VL - 47
IS - 6
SP - 909-923
AB - The spectral reflectance of leaves from several Eucalyptus species was measured over the 400â2500 nm wavelengths with a laboratory spectroradiometer. The relationship of reflectance with the gravimetric water content and equivalent water thickness (EWT) of the leaves was analysed. The results showed that EWT was strongly correlated with reflectance in several wavelength regions. No significant correlations could be obtained between reflectance and gravimetric water content. It was also possible to confirm theoretically that reflectance changes of leaves could be directly linked to changes in EWT but not to changes in gravimetric water content. Several existing reflectance indices were evaluated for estimation of leaf water content and some new indices were developed and tested. Two semi-empirical indices developed in this study, (R850 - R2218)/(R850 - R1928) and (R850 - R1788)/(R850 - R1928), were found to show significantly stronger correlations with EWT than all other indices tested. It was also shown that these new indices were least sensitive to the effects of radiation scatter. The indices (R850 - R2218)/(R850 - R1928) and (R850 - R1788)/(R850 - R1928) are therefore proposed as two new indices for the remote estimation of vegetation water content.
ER -
TY - JOUR
ID - gao1996
AU - Gao, Bo-cai
TI - NDWIâA normalized difference water index for remote sensing of vegetation liquid water from space
UR - http://www.sciencedirect.com/science/article/pii/S0034425796000673
DO - 10.1016/s0034-4257(96)00067-3
T2 - Remote Sensing of Environment
PY - 1996
SN - 0034-4257
VL - 58
IS - 3
SP - 257-266
ER -
TY - JOUR
ID - glenn2008
AU - Glenn, Edward
AU - Huete, Alfredo
AU - Nagler, Pamela
AU - Nelson, Stephen
TI - Review - Relationship Between Remotely-sensed Vegetation Indices, Canopy Attributes and Plant Physiological Processes: What Vegetation Indices Can and Cannot Tell Us About the Landscape
UR - http://www.mdpi.com/1424-8220/8/4/2136/
DO - doi:10.3390/s8042136
T2 - Sensors
PY - 2008
VL - 8
IS - 4
SP - 2136-2160
ER -
TY - JOUR
ID - hunt_jr1989
AU - Hunt Jr, E. Raymond
AU - Rock, Barrett N.
TI - Detection of changes in leaf water content using Near- and Middle-Infrared reflectances
UR - http://www.sciencedirect.com/science/article/pii/0034425789900461
DO - 10.1016/0034-4257(89)90046-1
T2 - Remote Sensing of Environment
PY - 1989
SN - 0034-4257
VL - 30
IS - 1
SP - 43-54
AB - Detection of plant water stress by remote sensing has been proposed using indices of Near-Infrared (NIR, 0.7â1.3 µm) and Middle-Infrared (MIR, 1.3â2.5 µm) wavelengths. The first objective of this study was to test the ability of the Leaf Water Content Index (LWCI) to determine leaf Relative Water content (RWC) of different species with different leaf morphologies. The second objective was to determine how the Moisture Stress Index (MSI; MIR / NIR) varies with RWC and the Equivalent Water Thickness (EWT). Reflectance factors at 0.82 µm and 1.6 µm were measured on leaves of Quercus agrifolia (sclerophyllous leaves), Liquidambar styraciflua (hardwood deciduous tree leaves), Picea rubens and Picea pungens (conifer needles), and Glycine max (herbaceous dicot leaves) as they dried on a laboratory bench. RWC and EWT were measured concurrently with the reflectance measurements. The results showed that LWCI was equal to RWC for the species tested. However, the results of a sensitivity analysis indicated the reflectances at 1.6 µm for two different RWC must be known for accurate prediction of unknown RWC; thus the LWCI is impractical for field applications. MSI was linearly correlated to RWCwith each species having a different regression equation and to log10 EWT with data of all species falling on the same regression line. Because EWT is correlated with leaf area index, MSI should also be correlated with leaf area index. Assuming that the linear regression equation of MSI to EWT can be applied to canopies, then the minimum significant change of RWC that can be detected is 52%. For most plants, the natural variation in RWC from water stress is only about 20%, so that we conclude that indices derived from NIR and MIR reflectances cannot be used to remotely-sense water stress.
ER -
TY - GEN
ID - hunt_jr1987
AU - Hunt Jr, Raymond E.
AU - Rock, Barrett N.
AU - Nobel, Park S.
TI - Measurement of leaf relative water content by infrared reflectance
UR - http://www.sciencedirect.com/science/article/pii/0034425787900940
DO - 10.1016/0034-4257(87)90094-0
T2 - Remote Sensing of Environment
PY - 1987
SN - 0034-4257
VL - 22
IS - 3
SP - 429-435
AB - From basic considerations and Beer's law, a leaf water content index incorporating reflectances of wavelengths from 0.76 to 0.90 μm and from 1.55 to 1.75 μm (Landsat Thematic Mapper Bands TM4 and TM5, respectively) was developed that relates leaf reflectance to leaf relative water content. For the leaf succulent, Agave deserti, the leaf water content index was not significantly different from the relative water content for either individual leaves or an entire plant. Also, the relative water contents of intact plants of Encelia farinosa and Hilaria rigida in the field were estimated by the leaf water content index; variations in the proportion of living to dead leaf area could cause large errors in the estimate of relative water content. Thus, the leaf water content index may be able to estimate average relative water content of canopies when TM4 and TM5 are measured at a known relative water content and fraction of dead leaf material.
ER -
TY - JOUR
ID - nagler2005
AU - Nagler, Pamela L.
AU - Scott, Russell L.
AU - Westenburg, Craig
AU - Cleverly, James R.
AU - Glenn, Edward P.
AU - Huete, Alfredo R.
TI - Evapotranspiration on western U.S. rivers estimated using the Enhanced Vegetation Index from MODIS and data from eddy covariance and Bowen ratio flux towers
UR - http://www.sciencedirect.com/science/article/pii/S0034425705001616
DO - 10.1016/j.rse.2005.05.011
T2 - Remote Sensing of Environment
PY - 2005
SN - 0034-4257
VL - 97
IS - 3
SP - 337-351
AB - We combined remote sensing and in-situ measurements to estimate evapotranspiration (ET) from riparian vegetation over large reaches of western U.S. rivers and ET by individual plant types. ET measured from nine flux towers (eddy covariance and Bowen ratio) established in plant communities dominated by five major plant types on the Middle Rio Grande, Upper San Pedro River, and Lower Colorado River was strongly correlated with Enhanced Vegetation Index (EVI) values from the Moderate Resolution Imaging Spectrometer (MODIS) sensor on the NASA Terra satellite. The inclusion of maximum daily air temperatures (Ta) measured at the tower sites further improved this relationship. Sixteen-day composite values of EVI and Ta were combined to predict ET across species and tower sites (r2 = 0.74); the regression equation was used to scale ET for 2000â2004 over large river reaches with Ta from meteorological stations. Measured and estimated ET values for these river segments were moderate when compared to historical, and often indirect, estimates and ranged from 851â874 mm yr- 1. ET of individual plant communities ranged more widely. Cottonwood (Populus spp.) and willow (Salix spp.) stands generally had the highest annual ET rates (1100â1300 mm yr- 1), while mesquite (Prosopis velutina) (400â1100 mm yr- 1) and saltcedar (Tamarix ramosissima) (300â1300 mm yr- 1) were intermediate, and giant sacaton (Sporobolus wrightii) (500â800 mm yr- 1) and arrowweed (Pluchea sericea) (300â700 mm yr- 1) were the lowest. ET rates estimated from the flux towers and by remote sensing in this study were much lower than values estimated for riparian water budgets using crop coefficient methods for the Middle Rio Grande and Lower Colorado River.
KW - Evapotranspiration
KW - Riparian
KW - Water balance
KW - MODIS
KW - Saltcedar
KW - Remote sensing
ER -
TY - JOUR
ID - penuelas1993
AU - Penuelas, J.
AU - Filella, I.
AU - Biel, C.
AU - Serrano, L.
AU - Save, R.
TI - The reflectance at the 950â970 nm region as an indicator of plant water status
UR - http://dx.doi.org/10.1080/01431169308954010
DO - 10.1080/01431169308954010
PR - Taylor & Francis
T2 - International Journal of Remote Sensing
PY - 1993
SN - 0143-1161
VL - 14
IS - 10
SP - 1887-1905
AB - We present new remote sensing indices of plant water status: the ratio between the reflectance at 970 nm, one of the water absorption bands, and the reflectance at a reference wavelength, 900 nm (R970/R9000; the first derivative minimum in this near-infrared region (dNIRminimum ) and the wavelength where this minimum is found ( ?NIRminimum). In order to evaluate them, we carried out three experiments. Daily irrigated gerbera plants were allowed to dry until almost wilting and then daily irrigation was restarted; pepper and bean plants were grown for four months submitted to two different irrigation treatments; and bean detached leaves were submitted to progressive dehydration whereas pressure-volume curves were being carried out. In gerbera plants, the trough about 950?970 nm decreased as the drought was increasing. Therefore, the R970/R900 index and the dNIRminimum closely tracked the changes in relative water content (RWC), leaf water potential, stomatal conductance and the foliage-air temperature differences. The ?dNIRminimum tracked even better these changes in gerberas. However, these water status indices began to be significant when the water stress was already well developed, at RWC smaller than 85 per cent. The same happened to detached leaves of beans which did not present differences above ?1·55 MPa water potential. Beans and peppers growing at soil matric potentials larger than ?0·04 MPa presented higher R970/R900 values than those growing at soil matric potentials only larger than ?0·01 MPa. In all the cases, the maximum response of these indices was found in the varieties or the species that lost cell wall elasticity in response to drought stress. This could indicate an important structural component in these indices changes. Relative water content itself seemed to be, however, the most important factor as shown by the highest correlation coefficients with these spectral indices. These spectral signals were more evident at canopy level than at leaf level. They seem to be useful as water status indicators at ground level, especially when there are not important changes of LAI and when plants wholly cover the soil.
ER -
TY - JOUR
ID - penuelas1997
AU - Penuelas, J.
AU - Pinol, J.
AU - Ogaya, R.
AU - Filella, I.
TI - Estimation of plant water concentration by the reflectance Water Index WI (R900/R970)
UR - http://dx.doi.org/10.1080/014311697217396
DO - 10.1080/014311697217396
T2 - International Journal of Remote Sensing
PY - 1997
DA - 1997/09/01
SN - 0143-1161
VL - 18
IS - 13
SP - 2869-2875
AB - Abstract Water Index WI (R900/R970) was used for the estimation of plant water concentration (PWC) by ground-based, reflectance measurements. Reflectance and PWC were measured for adult plants growing in the field throughout an annual cycle and in potted seedlings submitted to progressive desiccation. The species studied were characteristicly Mediterranean: Pinus halepensis, Quercus ilex, Quercus coccifera, Arbutus unedo, Cistus albidus, Cistus monspeliensis, Phillyrea angustifolia, Pistacia lentiscus and Brachypodium retusum . WI was significantly correlated with PWC when all the species were considered together, and with almost all the species considered individually, especially when a wider range of PWC was obtained by extreme dessication of experimental plants. The correlations increased when normalizing WI by NDVI. The wavelength of the trough corresponding to water absorption band tended to shift from 970-980 nm to lower wavelengths 930-950 nm with decreasing PWCs. Infrared measurement of plant temperature and T leaf - T air provided worse assessment of PWC. A simple radiometer measuring plant reflectance at 680, 900, and 970nm could speed up the measurement of PWC, and be useful in wildfire risk evaluation and drought assessment.
ER -
TY - JOUR
ID - pe_uelas1998
AU - Peñuelas, J.
AU - Filella, I.
TI - Visible and near-infrared reflectance techniques for diagnosing plant physiological status
UR - http://dx.doi.org/10.1016/S1360-1385(98)01213-8
DO - 10.1016/S1360-1385(98)01213-8
T2 - Trends in Plant Science
PY - 1998
SN - 13601385
VL - 3
IS - 4
SP - 151-156
ER -
TY - JOUR
ID - pe_uelas1994
AU - Peñuelas, J.
AU - Gamon, J. A.
AU - Fredeen, A. L.
AU - Merino, J.
AU - Field, C. B.
TI - Reflectance indices associated with physiological changes in nitrogen- and water-limited sunflower leaves
UR - http://www.sciencedirect.com/science/article/pii/0034425794901368
DO - 10.1016/0034-4257(94)90136-8
T2 - Remote Sensing of Environment
PY - 1994
SN - 0034-4257
VL - 48
IS - 2
SP - 135-146
AB - We followed diurnal and seasonal changes in physiology and spectral reflectance of leaves throughout the canopies of sunflower plants grown in control, nitrogen (N)-limited, and water-stressed plots. Leaves from control sunflower plants had significantly higher levels of nitrogen, chlorophyll (chl), ribulose bis phosphate carboxylase / oxygenase (RuBPCase) activity and photosynthetic rates and lower starch content and leaf thickness than N-limited plants. Water-stressed plants had the highest N and chl contents (on an area basis). They also had the lowest water potential and photosynthetic rates, in spite of maintaining high RuBPCase activities. Leaves from stressed plants (especially N-limited) had significantly higher reflectances in the visible wavelengths and lower in the near IR than leaves from control plants. The only clear trend across canopy levels was the higher reflectance at all wavelengths but especially in the visible of the lower (oldest) leaves. NDVI-like parameters were useful in distinguishing stress and control leaves over the growing season. However, several narrow-band indices provided better physiological information than NDVI. The physiological reflectance index (PRI) (R550 - R530 / R550 + R530) followed diurnal changes in xanthophyll pigments and photosynthetic rates of control and N-limited leaves. The maximum of the first derivative of reflectance in the green (dG) was correlated with diurnal photosynthetic rate, and with seasonal chl and N changes. The normalized pigment chlorophyll ratio Index (NPCI) (R680 - R430 / R680 + R430) varied with total pigments / chl. The water band index (WBI) (R970 / R902) followed water status. The normalized ratio between the maxima of the first derivatives of reflectances at the red edge and green regions (EGFN) was correlated with chl and N content. Principal components analysis yielded several indicators of physiological status. The first principal component was higher in control leaves, the second was higher in N-limited leaves, and the third was higher in water-limited leaves. Discriminant analysis based on the combination of several narrow-band spectral indices clearly separated leaves into the three treatment groups. These results illustrate the promise of narrow-band spectroradiometry for assessing the physiological state of vegetation.
ER -
TY - JOUR
ID - pinter2003
AU - Pinter, P. J.
AU - Hatfield, J. L.
AU - Schepers, J. S.
AU - Barnes, E. M.
AU - Moran, M. S.
AU - Daughtry, C. S. T.
AU - Upchurch, D. R.
TI - Remote sensing for crop management
UR - ://WOS:000221193400006
T2 - Photogrammetric Engineering and Remote Sensing
PY - 2003
DA - Jun
SN - 0099-1112
VL - 69
IS - 6
SP - 647-664
N1 - ISI Document Delivery No.: 817RA
Times Cited: 88
Cited Reference Count: 256
Pinter, PJ Hatfield, JL Schepers, JS Barnes, EM Moran, MS Daughtry, CST Upchurch, DR
Amer soc photogrammetry
Bethesda
AB - Scientists with the Agricultural Research Service (ARS) and various government agencies and private institutions have provided a great deal of fundamental information relating spectral reflectance and thermal emittance properties of soils and crops to their agronomic and biophysical characteristics. This knowledge has facilitated the development and use of various remote sensing methods for non-destructive monitoring of plant growth and development and for the detection of many environmental stresses which limit plant productivity. Coupled with rapid advances in computing and position-locating technologies, remote sensing from ground-, air-, and space-based platforms is now capable of providing detailed spatial and temporal information on plant response to their local environment that is needed for site specific agricultural management approaches. This manuscript, which emphasizes contributions by ARS researchers, reviews the biophysical basis of remote sensing; examines approaches that have been developed, refined, and tested for management of water, nutrients, and pests in agricultural crops; and assesses the role of remote sensing in yield prediction. It concludes with a discussion of challenges facing remote sensing in the future.
KW - water-stress index
KW - spectral-biophysical data
KW - soil heat-flux
KW - infrared
KW - aerial photography
KW - laser-induced fluorescence
KW - constant leaf
KW - temperature
KW - adjusted vegetation index
KW - surface-energy balance
KW - clover-seed production
KW - gossypium-hirsutum l
ER -
TY - JOUR
ID - pu2003
AU - Pu, R.
AU - Ge, S.
AU - Kelly, N. M.
AU - Gong, P.
TI - Spectral absorption features as indicators of water status in coast live oak ( Quercus agrifolia ) leaves
UR - http://dx.doi.org/10.1080/01431160210155965
DO - 10.1080/01431160210155965
T2 - International Journal of Remote Sensing
PY - 2003
DA - 2003/01/01
SN - 0143-1161
VL - 24
IS - 9
SP - 1799-1810
AB - A total of 139 reflectance spectra (between 350 and 2500 nm) from coast live oak ( Quercus agrifolia ) leaves were measured in the laboratory with a spectrometer FieldSpec?Pro FR. Correlation analysis was conducted between absorption features, three-band ratio indices derived from the spectra and corresponding relative water content (RWC, %) of oak leaves. The experimental results indicate that there exist linear relationships between the RWC of oak leaves and absorption feature parameters: wavelength position (WAVE), absorption feature depth (DEP), width (WID) and the multiplication of DEP and WID (AREA) at the 975 nm, 1200 nm and 1750 nm positions and two three-band ratio indices: RATIO 975 and RATIO 1200, derived at 975 nm and 1200 nm. AREA has a higher and more stable correlation with RWC compared to other features. It is worthy of noting that the two three-band ratio indices, RATIO 975 and RATIO 1200, may have potential application in assessing water status in vegetation.
ER -
TY - JOUR
ID - serrano2000
AU - Serrano, Lydia
AU - Ustin, Susan L.
AU - Roberts, Dar A.
AU - Gamon, John A.
AU - Peñuelas, Josep
TI - Deriving Water Content of Chaparral Vegetation from AVIRIS Data
UR - http://www.sciencedirect.com/science/article/pii/S0034425700001474
DO - 10.1016/s0034-4257(00)00147-4
T2 - Remote Sensing of Environment
PY - 2000
SN - 0034-4257
VL - 74
IS - 3
SP - 570-581
AB - Spectral imaging data acquired with Advanced Visible Infrared Imaging Spectrometer over Point Dume (Los Angeles County, CA, USA) were used to assess the ability of hyperspectral reflectance data to estimate canopy Relative Water Content (RWC) at the landscape level. The study was performed on 23 vegetation stands comprised of three characteristic chaparral plant communities, with contrasting phenological stages and canopy cover. Several estimates of water content based on the near-infrared (NIR; reflectance indices and water thickness derived from reflectance and radiance data) and shortwave infrared (SWIR) water absorption bands were compared to measurements of vegetation structure and water content made on the ground. The Water Index (WI) and Normalized Difference Water Index (NDWI), reflectance indices formulated from the NIR water absorption bands, were the best indicators of canopy RWC estimated from combining leaf relative water content with measures of canopy structure. A stepwise multiple regression revealed that canopy structure explained 36% and 41% of the variation in WI and NDWI, respectively. The explained variance in WI and NDWI increased to 44% and 48% when leaf relative water content was included in the model. By contrast, the inclusion of leaf relative water content did not contribute significantly to the explained variance in indices formulated using SWIR water absorption bands and in those based on water thickness. The relationship between WI and the canopy RWC significantly improved when only data from plots with green vegetation cover >70% were considered (r2=0.88, p<0.001). All the indices studied had an important structural component (as indicated by the strong correlation with NDVI), yet only the indices WI and NDWI additionally responded to water content. These results indicate that the WI and NDWI are sensitive to variations in canopy relative water content at the landscape scale.
ER -
TY - JOUR
ID - thenot2002
AU - Thenot, F.
AU - Méthy, M.
AU - Winkel, T.
TI - The Photochemical Reflectance Index (PRI) as a water-stress index
UR - http://dx.doi.org/10.1080/01431160210163100
DO - 10.1080/01431160210163100
T2 - International Journal of Remote Sensing
PY - 2002
DA - 2002/01/01
SN - 0143-1161
VL - 23
IS - 23
SP - 5135-5139
AB - Measurements of leaf reflectance in two narrow wavelength bands centred around 531 and 570 nm were carried out during withering of two contrasting functional and structural plant types: Chenopodium quinoa (Willd.) and Arbutus unedo (L.). The Photochemical Reflectance Index (PRI)=( R 531 - R 570 )/ ( R 531 + R 570 ) was calculated. The results showed that PRI could be used as a reliable water-stress index. However, some limits to the use of PRI have to be emphasized, e.g. the wilting of leaves during dry periods. If such limits are under control, PRI could be a non-destructive and low cost method for assessing plant water status.
ER -
TY - JOUR
ID - underwood2003
AU - Underwood, Emma
AU - Ustin, Susan
AU - DiPietro, Deanne
TI - Mapping nonnative plants using hyperspectral imagery
UR - http://www.sciencedirect.com/science/article/pii/S0034425703000968
DO - 10.1016/s0034-4257(03)00096-8
T2 - Remote Sensing of Environment
PY - 2003
SN - 0034-4257
VL - 86
IS - 2
SP - 150-161
AB - Nonnative plant species are causing enormous ecological and environmental impacts from local to global scale. Remote sensing images have had mixed success in providing spatial information on land cover characteristics to land managers that increase effective management of invasions into native habitats. However, there has been limited evaluation of the use of hyperspectral data and processing techniques for mapping specific invasive species based on their spectral characteristics. This research evaluated three different methods of processing hyperspectral imagery: minimum noise fraction (MNF), continuum removal, and band ratio indices for mapping iceplant (Carpobrotus edulis) and jubata grass (Cortaderia jubata) in California's coastal habitat. Validation with field sampling data showed high mapping accuracies for all methods for identifying presence or absence of iceplant (97%), with the MNF procedure producing the highest accuracy (55%) when the classes were divided into four different densities of iceplant.
KW - AVIRIS
KW - Hyperspectral
KW - Invasive plants
KW - Nonnative plants
KW - Iceplant
KW - Carpobrotus edulis
KW - Jubata grass
KW - Cortaderia jubata
KW - Mapping
ER -
TY - JOUR
ID - zarco-tejada_p_j_sepulcre-cant_2007
AU - Zarco-Tejada P.J.
AU - Sepulcre-Cantó, G.
TI - REMOTE SENSING OF VEGETATION BIOPHYSICAL PARAMETERS FOR DETECTING STRESS CONDITION AND LAND COVER CHANGES
T2 - Estudios de la Zona No Saturada del Suelo
PY - 2007
VL - 8
ER -
TY - JOUR
ID - zarco-tejada2003
AU - Zarco-Tejada, P. J.
AU - Rueda, C. A.
AU - Ustin, S. L.
TI - Water content estimation in vegetation with MODIS reflectance data and model inversion methods
UR - http://www.sciencedirect.com/science/article/pii/S0034425702001979
DO - 10.1016/s0034-4257(02)00197-9
T2 - Remote Sensing of Environment
PY - 2003
SN - 0034-4257
VL - 85
IS - 1
SP - 109-124
AB - Statistical and radiative-transfer physically based studies have previously demonstrated the relationship between leaf water content and leaf-level reflectance in the near-infrared spectral region. The successful scaling up of such methods to the canopy level requires modeling the effect of canopy structure and viewing geometry on reflectance bands and optical indices used for estimation of water content, such as normalized difference water index (NDWI), simple ratio water index (SRWI) and plant water index (PWI). This study conducts a radiative transfer simulation, linking leaf and canopy models, to study the effects of leaf structure, dry matter content, leaf area index (LAI), and the viewing geometry, on the estimation of leaf equivalent water thickness from canopy-level reflectance. The applicability of radiative transfer model inversion methods to MODIS is studied, investigating its spectral capability for water content estimation. A modeling study is conducted, simulating leaf and canopy MODIS-equivalent synthetic spectra with random input variables to test different inversion assumptions. A field sampling campaign to assess the investigated simulation methods was undertaken for analysis of leaf water content from leaf samples in 10 study sites of chaparral vegetation in California, USA, between March and September 2000. MODIS reflectance data were processed from the same period for equivalent water thickness estimation by model inversion linking the PROSPECT leaf model and SAILH canopy reflectance model. MODIS reflectance data, viewing geometry values, and LAI were used as inputs in the model inversion for estimation of leaf equivalent water thickness, dry matter, and leaf structure. Results showed good correlation between the time series of MODIS-estimated equivalent water thickness and ground measured leaf fuel moisture (LFM) content (r2=0.7), demonstrating that these inversion methods could potentially be used for global monitoring of leaf water content in vegetation.
KW - Radiative transfer
KW - Water content
KW - Leaf fuel moisture
KW - Equivalent water thickness
KW - MODIS
KW - Reflectance
KW - Model inversion
ER -
TY - ELEC
ID - idb
AU - Henrich, V.
AU - Krauss, G.
AU - Götze, C.
AU - Sandow, C.
TI - The IndexDatabase
UR - https://www.indexdatabase.de/
CY - Bonn
PY - 2011
DA - 2011
ER -