Measuring Canopy Coverage with Digital Imaging

Abstract

Sampling plant canopies for their ability to intercept sunlight has traditionally been done with destructive or time‐consuming methods. Although nondestructive methods are available, they are either time consuming or subject to large variation. A commercially available software was utilized to analyze digital images of a cotton (Gossypium hirsutum L.) canopy in an effort to quantify canopy coverage. Digital images were obtained from a vertical perspective using a stationary camera stand. Images were analyzed using Adobe Photoshop 4.0 (Adobe Systems, Inc., Seattle, WA) software. Using functions within the software, plant material in the image was separated from the soil and converted to black. The soil surface was converted to white. The resulting black and white image was analyzed with Javascript software developed at North Carolina State University that counts the black and white pixels in each image. The resulting percentage of black pixels in the image was termed percent ground cover for the canopy. Percent ground cover was well correlated with leaf area index (LAI) over a low range of LAI with r2=0.74. This method provides a reasonable estimation of canopy coverage and proved to be a simple and efficient method of sampling a plant canopy. As image processing software becomes more refined, this and other techniques will become powerful tools for plant science research.