Many studies of biological populations require estimates of population size or density. Consequently, the focus of several previous chapters has been either estimation of population size or population density. In this chapter, we are again concentrating on estimating population density. Not all populations can be sampled effectively using the techniques presented thus far. For example, suppose we want to estimate the density of a plant population. We know that the plants are sparsely scattered in the region of interest. Quadrat sampling would not be effective because we would need either large quadrats or an excessive number of small quadrats to obtain a precise estimate of density. Capture—recapture methods are not applicable to this problem. An intuitive approach is to walk along a line through the region and count the number of plants that are seen on either side of the line. The line and the area on either side of the line that is searched for plants has been called a transect. If we assume that we can see all plants within w units of the line, we have strip transects. More commonly, we can observe all plants close to the line, but we count only a portion of those farther from the line. These are called line transects, and we can allow for this differential sightability in estimating the population density.
KeywordsLine Transect Perpendicular Distance Detection Function Transect Sampling Circular Plot
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