Estimating scattered and absorbed radiation in plant canopies by remote sensing

Several research avenues are summarized. The relationships of canopy characteristics to multispectral reflectance factors of vegetation are reviewed. Several alternative approaches for incorporating spectrally derived information into plant models are discussed, using corn as the main example. A method is described and evaluated whereby a leaf area index is estimated from measurements of radiation transmitted through plant canopies, using soybeans as an example. Albedo of a big bluestem grass canopy is estimated from 60 directional reflectance factor measurements. Effects of estimating albedo with substantially smaller subsets of data are evaluated

Estimation and Validation of Land Surface Broadband Albedos and Leaf Area Index From EO-1 ALI Data

The Advanced Land Imager (ALI) is a multispectral sensor onboard the National Aeronautics and Space Administration Earth Observing 1 (EO-1) satellite. It has similar spatial resolution to Landsat-7 Enhanced Thematic Mapper Plus (ETM+), with three additional spectral bands. We developed new algorithms for estimating both land surface broadband albedo and leaf area index (LAI) from ALI data. A recently developed atmospheric correction algorithm for ETM+ imagery was extended to retrieve surface spectral reflectance from ALI top-of-atmosphere observations. A feature common to these algorithms is the use of new multispectral information from ALI. The additional blue band of ALI is very useful in our atmospheric correction algorithm, and two additional ALI near-infrared bands are valuable for estimating both broadband albedo and LAI. Ground measurements at Beltsville, MD, and Coleambally, Australia, were used to validate the products generated by these algorithms.This work was supported in part by the National Aeronautics and Space Administration under Grant NCC5462 and by funding provided by the Australian Federal Government to the Commonwealth Scientific and Industrial Research Organization and the Cooperative Research Centre for Sustainable Rice Production, Project 1105

Effects of Anacetrapib in Patients with Atherosclerotic Vascular Disease

BACKGROUND: Patients with atherosclerotic vascular disease remain at high risk for cardiovascular events despite effective statin-based treatment of low-density lipoprotein (LDL) cholesterol levels. The inhibition of cholesteryl ester transfer protein (CETP) by anacetrapib reduces LDL cholesterol levels and increases high-density lipoprotein (HDL) cholesterol levels. However, trials of other CETP inhibitors have shown neutral or adverse effects on cardiovascular outcomes. METHODS: We conducted a randomized, double-blind, placebo-controlled trial involving 30,449 adults with atherosclerotic vascular disease who were receiving intensive atorvastatin therapy and who had a mean LDL cholesterol level of 61 mg per deciliter (1.58 mmol per liter), a mean non-HDL cholesterol level of 92 mg per deciliter (2.38 mmol per liter), and a mean HDL cholesterol level of 40 mg per deciliter (1.03 mmol per liter). The patients were assigned to receive either 100 mg of anacetrapib once daily (15,225 patients) or matching placebo (15,224 patients). The primary outcome was the first major coronary event, a composite of coronary death, myocardial infarction, or coronary revascularization. RESULTS: During the median follow-up period of 4.1 years, the primary outcome occurred in significantly fewer patients in the anacetrapib group than in the placebo group (1640 of 15,225 patients [10.8%] vs. 1803 of 15,224 patients [11.8%]; rate ratio, 0.91; 95% confidence interval, 0.85 to 0.97; P=0.004). The relative difference in risk was similar across multiple prespecified subgroups. At the trial midpoint, the mean level of HDL cholesterol was higher by 43 mg per deciliter (1.12 mmol per liter) in the anacetrapib group than in the placebo group (a relative difference of 104%), and the mean level of non-HDL cholesterol was lower by 17 mg per deciliter (0.44 mmol per liter), a relative difference of -18%. There were no significant between-group differences in the risk of death, cancer, or other serious adverse events. CONCLUSIONS: Among patients with atherosclerotic vascular disease who were receiving intensive statin therapy, the use of anacetrapib resulted in a lower incidence of major coronary events than the use of placebo. (Funded by Merck and others; Current Controlled Trials number, ISRCTN48678192 ; ClinicalTrials.gov number, NCT01252953 ; and EudraCT number, 2010-023467-18 .)

Effects of Nitrogen Nutrition on the Growth, Yield and Reflectance Characteristics of Corn Canopies

An experiment was conducted in which spectral and agronomic measurements were collected from corn (Zea mays L.) canopies under four nitrogen treatment levels (0, 67, 134, and 202 kg/ha) at the Purdue Agronomy Farm, W. Lafayette, IN, on 11 dates during 1978 and 12 dates during 1979. Spectral measurements over the 0.4 to 2.4 µm wavelength region were acquired with a spectroradiometer and used to compute reflectance factor. Agronomic data collected included biomass, leaf area index, plant height, crop development stage, and percent soil cover. Data were analyzed to determine: (1) the relationship between the spectral responses of canopies and their agronomic characteristics and (2) the spectral separability of the four treatments. Red reflectance was increased, while the near infrared reflectance was decreased for canopies under nitrogen deprivation. Spectral differences between treatments were seen throughout each growing season. The near infrared/red reflectance ratio increased spectral treatment differences over those shown by single band reflectance measure. The spectra of the four nitrogen treatments were significantly different on August dates; however, early and late in the season only two spectral classes were resolved. Of the spectral variables examined, the near infrared/red reflectance ration most effectively separated the treatments. Differences in spectral response between treatments were attributed to varying soil cover, leaf area index, and leaf pigmentation values, all of which changed with N treatment. The results further confirm the potential of remote sensing for monitoring the growth and condition of crops

Spectral Estimates of Agronomic Characteristics of Crops

If agronomic variables related to vigor and yield of crops could be reliably estimated from multispectral data, then crop growth and yield models could be implemented for large areas. The objectives of these experiments were to determine relationships of key agronomic characteristics and spectral properties of crops and to integrate spectral and meteorological data for forecasting crop yields. Reflectance data of corn, wheat, and soybeans were acquired with radiometers that simulate Landsat MSS and TM sensors. The spectral indices, greenness, and normalized difference were highly correlated with leaf area index (LAI) and absorbed photosynthetically active radiation (APAR). Grain yields were more highly related to APAR cumulated during the growing season than to maximum LAI or LAI duration. A model which simulated the daily effects of weather and APAR on growth accounted for 85% of the variation in corn yields. The concept of estimating agronomic characteristics using spectral data represents a viable approach for merging spectral and meteorological data for crop forecasting models