Analysis of radiant environment in forest canopies
Subtitle: technique and application
By: by George Palmer Miller.
Published: 1981
Language: eng
Format: Hardcover
Number of pages: 36
Subjects: Plants -- Effect of solar radiation on.; Solar radiation -- Physiological effect.
Notes: Thesis (M.S.)--Washington State University, 1981.

Bibliography: leaf 34.

WSU:"Department of Agronomy and Soils."
Table of contents: title: Thesis for partial fulfillment of requirements for degree of Master of Science in Soils from Washington State University, Department of Agronomy and Soils; title: Chairman: Gaylon S. Campbell; title: ABSTRACT; title: Solar radiation is the main source of energy for plants. Therefore, it is necessary to obtain accurate measurements of light interception by foliage to determine the amount of energy available. The use of hemispherical photographs taken with a fisheye lens is a valuable technique for obtaining such measurements. Two comparisons were made using this technique. First, two methods of analyzing the hemispherical photographs were compared. One was a visual analysis using a grid system, and the other was a mechanical method involving a computer with interfacing plotter. Each was used to acquire transmission coefficients from photographs taken for these comparisons. Second, two film bypes, HC-135 high contras copy and Tri-X were compared. Linear correlations between the results of the two methods for each film type showed significant correlations with r=0.93 for HC-135 and r=-.96 for Tri-X. Analyses of variance showed that there was no significant difference between the film types or the methods of analysis. The conclusion was drawn that the computer analysis is at least as accurate as the visual method. The computer method is preferred over the visual since it is more convenient, takes less time, and causes no eye strain. Since the films also showed no significant differences, the Tri-X is preferred over the HC-135 because it can be used more easily under diffuse light conditions in which the photographs must be taken for maximum sky-canopy contrast.; title: Hemispherical photographs were used to determine the effect of solar energy interception on the growth of forest understory and overstory. The research site was a seventy year old ponderosa pine stand in the Upper Methow Valley of eastern Washington. Plots had been established in this location in 1959 as part of a long-term study on understory and overstory productivity. The study area was composed of three regions of four plots each. Three plots per region were thinned to spacings of 4.0,  5.7, and 8.0 m. The remaining plots were left as unthinned controls with an average tree spacing of 1.3 m. Subplots were established within the spacing plots for collection of understory samples and for taking hemispherical photographs of the forest canopy. Samples of understory were collected, oven dried, and weighed. Measurements of height and DBH were taken on the overstory. Average height, DBH, basal area, and volume annual growth increments were determined from these and similar measurements made by researchers at the beginning of the long-term study. The results showed significant correlations between understory productivity and radiant energy penetration, and between overstory rates of growth and canopy interception. Analysis of the variance and multiple comparisons for the penetration factors from the photographs and for total understory productivity showed that only unthinned and thinned plots differed significantly. Since the thinned spacings all had average light penetration values greater than 50%, it was concluded that canopy transmission greater than this does not affect understory productivity appreciably. On an individual tree basis, rates of growth of the overstory increased with decreasing canopy closure and decreased overall light interception. However, total overstory biomass increased with light interception by the overall canopy.