The Line Intercept Method for Studying Plant Cuticles from Rumen and Fecal Samples

Abstract

Several methods are available for estimating the proportion, by area, of leaf cuticles of a given species in a rumen or fecal sample. They all involve choosing a line transect on a microscope slide and noting the cuticles that intercept the line. In this paper estimates based on lengths or squared lengths of intercept are compared. When there are several transects a jackknife method of combining the data is recommended. Simulation experiments indicate that this method provides satisfactory estimates, as far as bias and precision are concerned. J. WILDL. MANAGE. 43(4):916-925 A common problem in ecology is that of estimating the proportion, by area, of leaf cuticles that belong to a given plant species by examining slides of rumen or fecal samples under a microscope. Several procedures have been suggested and they all involve choosing a line transect on the slide and noting the cuticles that intercept the line. The most common method, which might be called the hit or miss method or the count method, consists of simply counting the number of cuticles of each species that intersect the line (Anthony and Smith 1974, Anthony 1976, Staines 1976). Another method, commonly called the line intercept method, consists of measuring the lengths of intercept of all the cuticles that intercept the line. This method has been applied to plant populations and shrub canopies (McIntyre 1953, Eberhardt 1978): a general theory for the method is given by Lucas and Seber (1977). A 3rd method, which we shall call the squared-intercept method, consists of using the squares of the lengths of the intercepts (cf. Dunnet et al. 1973). The aim of this paper is to compare these methods both theoretically and empirically (using simulation), and to show that the line intercept method should be used in most situations. LINE INTERSECT METHOD