A COMPUTER METHOD FOR DETERMINING UPPER CANOPY CLOSURE AT EL VERDE, PUERTO RICO

• Main Author: Desmarais, A. Paul
• Format: Report
• Language: English
• Subjects: AREA COVERAGE; Biology; COMPUTER ANALYSIS; Computer Programming and Software; COMPUTER PROGRAMS; ECOLOGY; FORTRAN; MATHEMATICAL ANALYSIS; PLANTS(BOTANY); PUERTO RICO; RAIN FORESTS; SAMPLING; SITE SELECTION; TERRAIN; TREES; TROPICAL REGIONS; VISIBILITY

Coverage of tree crowns (canopy closure) was studied along with other basic structural attributes of El Verde, Puerto Rico, test sites where canopy closure approaches a maximum (100 percent) in the dense rain forest. There are several methods of determining closure values. Any of these can be used in determining percent coverage by species or by structural type, or on any other basis. The fact that tree crowns overlap, sometimes quite extensively, makes it difficult to obtain coverage values by mathematical analysis because computations involving overlapping circles are mathematically complicated. To resolve the difficulty, a computer method was devised that converts the circular crown areas into squares of approximate equivalent area and calculates crown coverage and canopy closure on this basis. The method is described, and the results are compared with the more tedious manual methods. Three groups of plants were used as bases for closure determinations and comparisons. They were (a) all plants at the El Verde sites above 5 m in height; (b) all plants of the two most predominant species, Dacryodes excelsa Vahl and Sloanea berteriana Choisy, 5 to 13 m in height; and (c) all plants of the same species 13 m or more in height. The mathematical approach used to write the computer program is included as Appendix A. (Author)