%0 Journal Article
%T Development of a Rapid and Precise Method of Digital Image Analysis to Quantify Canopy Density and Structural Complexity
%A Anne E. Goodenough
%A Andrew S. Goodenough
%J ISRN Ecology
%D 2012
%R 10.5402/2012/619842
%X Estimation of canopy density is necessary for ecological research and woodland management. However, traditional manual methods are time consuming and subject to interobserver variability, while existing photographic methods usually require expensive fish-eye lenses and complex analysis. Here we introduce and test a new method of digital image analysis, CanopyDigi. This allows user-defined threshold to polarise the 256 grey shades of a standard monochrome bitmap into dark ¡°canopy¡± and light ¡°sky¡± pixels (the threshold being selected using false-colour images to ensure its suitability). Canopy density data are calculated automatically and rapidly, and, unlike many other common methods, aggregation data are obtainable using Morisita¡¯s index to differentiate closed (diffuse light) and open (direct light) canopies. Results were highly repeatable in both homogeneous and heterogeneous woodland. Estimates correlated strongly with existing (nondigital) canopy techniques, but quicker and with significantly lower interobserver variability (CV = 3.74% versus 20.73%). We conclude that our new method is an inexpensive and precise technique for quantifying canopy density and aggregation. 1. Introduction Vegetation structural complexity comprises several parameters including the density and height of different vegetation layers, the percentage coverage of each layer, and species composition [1].In a woodland ecosystem, one of the most important aspects of overall structural complexity is the canopy density and aggregation [2, 3]. These parameters influence stand productivity and species composition, as well as the density and growth of the understorey, which is a key determinant of habitat [4]. Estimation of canopy coverage is important in studies of species-habitat relationships (e.g., [5¨C10]) and also for land managers given the increasing emphasis on sustainable woodland management. The effective use of canopy data in ecological research, or to inform woodland management, demands that measurements are accurate, precise, and obtainable using a quick, easy, and inexpensive method [11]. Estimates also need to have a high consistency and low interobserver variability to avoid generation of erroneous results [12¨C14]. 1.1. Canopy Measurements: Coverage and Density Somewhat surprisingly given its importance, there is no standard method of measuring canopy on a relatively small scale (e.g., for specific woodland plots). Jennings et al. [15] distinguish two basic types of measurement of forest canopies; the percentage of canopy coverage¡ªthe area of ground covered by a
%U http://www.hindawi.com/journals/isrn.ecology/2012/619842/