An experimental test of plant canopy reflectance models on cotton

Extensive data on the plant parameters necessary to evaluate any model are presented for a cotton crop. The variation of the bidirectional reflectance function with observer altitude, observer azimuth, and sun altitude angle is presented for a high density cotton crop having leaf index of 19. A comparison with the quantitative behavior obtained from the Suits model is accomplished in the wavelength region from 400 nm to 1050 nm

The Effect of Prescribed Fires on Vernal Herbs

The effects of fire on vernal herbs are little known. David Kem attempted to assess the influences of spring and winter prescribed fires on vernal herbs by collecting abundance data on three sets of research plots located at the WKU Green River Preserve in Hart County, KY, on April 9-10, 2010. On April 10 he conducted spring burns, and on February 22, 2011, he conducted winter burns. He then collected post-fire data on the abundance of the herbs on the 12-19 of March, 2011. He found little influence of fire on overall species richness and the density of common species. In spring of 2015, these plots were re-sampled. Results indicated that there was a change between years in overall stem density and the density of several common vernal herbs, including Dentaria laciniata and Claytonia virginica. There was also a slight change in species richness between years. Fire treatment was found to have little or no effect on herb stem density and species richness. We suspect that changes between years could be caused by differing precipitation amounts for each respective year

A plant canopy light absorption model with application to wheat

From the light absorption model the absorption of light in the photosynthetically active region of the spectrum was calculated for a Penjamo wheat crop for several situations including: (1) the percent absorption of the incident radiation by a canopy having a four layer structure; (2) the percent absorption of light by the individual layers within a four layer canopy and by the underlying soil; (3) the percent absorption of light by each vegetative canopy layer for variable sun angle; and (4) the cumulative solar energy absorbed by the developing wheat canopy as it progresses from a single layer through its growth stages to a three layer canopy. This calculation was also presented as a function of the leaf area index

Seasonal soybean crop reflectance

Data are presented from field measurements of 1980 including 5 acquisitions of handheld radiometer reflectance measurements, 7 complete sets of parameters for implementing the Suits mode, and other biophysical parameters to characterize the soybean canopy. LANDSAT calculations on the simulated Brazilian soybean reflectance are included along with data collected during the summer and fall on 1981 on soybean single leaf optical parameters for three irrigation treatments. Tests of the Suits vegetative canopy reflectance model for the full hemisphere of observer directions as well as the nadir direction show moderate agreement for the visible channels of the MSS and poor agreement in the near infrared channel. Temporal changes in the spectral characteristics of the single leaves were seen to occur as a function of maturity which demonstrates that the absorptance of a soybean single leaf is more a function of thetransmittancee characteristics than the seasonally consistent single leaf reflectance

Multifluid magnetohydrodynamic turbulent decay

It is generally believed that turbulence has a significant impact on the dynamics and evolution of molecular clouds and the star formation which occurs within them. Non-ideal magnetohydrodynamic effects are known to influence the nature of this turbulence. We present the results of a suite of 512-cubed resolution simulations of the decay of initially super-Alfvenic and supersonic fully multifluid MHD turbulence. We find that ambipolar diffusion increases the rate of decay of the turbulence while the Hall effect has virtually no impact. The decay of the kinetic energy can be fitted as a power-law in time and the exponent is found to be -1.34 for fully multifluid MHD turbulence. The power spectra of density, velocity and magnetic field are all steepened significantly by the inclusion of non-ideal terms. The dominant reason for this steepening is ambipolar diffusion with the Hall effect again playing a minimal role except at short length scales where it creates extra structure in the magnetic field. Interestingly we find that, at least at these resolutions, the majority of the physics of multifluid turbulence can be captured by simply introducing fixed (in time and space) resistive terms into the induction equation without the need for a full multifluid MHD treatment. The velocity dispersion is also examined and, in common with previously published results, it is found not to be power-law in nature.Comment: 16 pages, 15 figures, Accepted for publication in Ap

Three Reasons Why

The United States is a great nation not because of its natural water ways, acres of timber, acres of wheat, corn, oats, rye, mines of iron, coal, copper, tin. It is the people who man the water ways, level the trees and run the mills, sow the crops and reap the harvest, operate the mines who make the United States so great a nation. The people of the United States have made this a nation to be proud of because they have kept it growing, kept fighting, and kept the spirit of competition alive

F. [LeMaster] to James (2 October 1962)

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