A comparison of some population density sampling techniques for biodiversity, conservation, and environmental impact studies

Abstract

Twelve terrestrial and marine studies were conducted at various sites in Malaysia, Brazil, and the United States between April 1999 and February 2004. These data were analyzed using five density estimate techniques for stationary (non-motile) organisms including Stratified Random Sampling, Point-Center Quarter, Third Nearest Object, Weinberg, and Strong. The Strong method gave the most accurate density estimates of stationary animals and plants. Stratified Random Sampling ranked second best and the Third Nearest Object the third best. Belt or strip transects may be preferable but can be restrictive in some situations because of logistics and associated time constraints. Straight line measurements on reefs were 3–27% more accurate than reef slack line and reef contour measurements. Most study areas measured with the standardized Morisita index of dispersion were moderately aggregated. Results from the Third Nearest Object and Point-Center Quarter techniques indicate that the addition of more data to establish a density correction factor does not necessarily give more accurate estimates of density.

Appendix

 

Table 3 Density of subtidal hard corals at Pulau Pemanggil, Malaysia in April 1999^a

Table 4 Density of subtidal corals at Pulau Pemanggil (April 1999) and Pulau Langkawi (October 1999), Malaysia^a

Table 5 Density of intertidal invertebrates at Royal Palms State Beach, Palos Verdes Peninsula, southern California in February and March 2001^a

Table 6 Density of the subtidal sponge Polymastia janeirensis (Boury-Esnault, 1993) from Praia Brava, Buzios, Brazil in March 2001^a

Table 7 Density of Ponderosa Pine (Pinus ponderosa Laws.) and Coulter Pine (Pinus coulteri D. Don) trees at Charleton Flats, Angeles National Forest, San Gabriel Mountains, southern California, in April and May 2001^a

Table 8 Density of trees in Alhambra Park, Alhambra, California in May 2001^a

Table 9 Density of white fir trees (Abies concolor [Gordon & Glend.] Lindley) on Mt. Ashland, southern Oregon in June 2001 and June 2002^a

Table 10 Density of Joshua trees (Yucca brevifolia Engelm.) and Mormon Tea (Ephydra? nevadensis S. Watson) in Joshua Tree National Park, southern California, in February and March 2002^a

Table 11 A simulation study on the density of circular dots in different distribution patterns within rectangular sampling plots (from Krebs, 1999), December 2002^a