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Transportability of fixed‐precision level sampling plans
Author(s) -
Trumble J. T.,
Brewer M. J.,
Shelton A. M.,
Nyrop J. P.
Publication year - 1989
Publication title -
population ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 59
eISSN - 1438-390X
pISSN - 1438-3896
DOI - 10.1007/bf02513209
Subject(s) - entomology , library science , biology , ecology , computer science
Detailed knowledge of insect distributions and the primary factors affecting how insect populations utilize their available resources are critical to the development of accurate sampling plans in agroecosystems and integral to the study of population and community ecology of insects (TRuMBLE et al., 1987). Although few scientists question the value of sampling as a method for determining the need for control action, documenting the within-field and within-plant distributions of arthropod pests is often prohibitively expensive in both time and effort. This problem would be alleviated to a large extent if sampling plans created at one location could be utilized in other locations. In spite of the expense, and perhaps in response to a lack of success in transporting sampling programs between locations, a meaningful data base on insect distribution has appeared in the literature over the past 70 years. TAYLOR'S Power Law (TPL) (TAYLOR, 1961), a widely reported measure of dispersion, is often used to provide baseline information on insect distribution for sampling plans. According to TAYLOR (1984), the intercept of TPL is variable with sampling procedures, while the slope is characteristic of a species in a given environment. Regression coefficients from TPL are frequently used to generate fixed-precision level sequential sampling plans as developed by KUNO (1969) and extended using GREEN'S (1970) formula. This formula is responsive to variation in the intercept of TPL, which could be expected to change with the sample unit or the sampler, and to the slope of TPL, which would fluctuate with any changes in within-field distribution. These effects were reported for fixed-precision level estimation plans for Trichoplusia ni (Hi)BNER) on cabbage where the same cabbage cultivar, sampling, and cultural practices were used between widely separated geograpic areas (TRUMBLE et al., 1987). TPL regression statistics for small and large larvae differed between location, with a trend for increasing aggregation from Louisiana to Texas to California. Consequently, more larvae needed to be counted in California before the population density could be estimated with a given precision. To study the impact of variability in TPL regression coefficients on GREEN'S for-