Abstract

Efficient sampling design in field studies is important for economical and statistical reasons. We compared two ways to distribute sampling effort over an area, either randomly or subjectively. We searched for red-listed saproxylic (wood-living) beetles in 30 spruce stands in boreal Sweden by sifting wood from dead trees. We randomly selected positions within each stand with a geographic positioning system and sampled the nearest dead tree (random sample). In the same stand we also sampled dead trees that, based on literature, were likely to host such species (subjective sampling). The subjective sampling (two to five samples per stand, depending on stand size) was compared with the higher, random sampling effort (fixed level of 12 samples/stand). Subjective sampling was significantly more efficient. Red-listed species were found in 36% of the subjective samples and in 16% of the random samples. Nevertheless, the larger random effort resulted in a comparable number of red-listed species per stand and in 13 detected species in total (vs. 12 species with subjective sampling). Random sampling was less efficient, but provided an unbiased alternative more suitable for statistical purposes, as needed in, for example, monitoring programs. Moreover, new species-specific knowledge can be gained through random searches.

Keywords

biodiversity inventories; monitoring; random sampling; subjective sampling; species abundance; sampling methods

Published in

Conservation Biology
2008, Volume: 22, number: 1, pages: 212-215
Publisher: BLACKWELL PUBLISHING

SLU Authors

• Hedgren, Per Olof

  • Department of Entomology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Zoology
Environmental Sciences related to Agriculture and Land-use


Publication identifier

DOI: https://doi.org/10.1111/j.1523-1739.2007.00848.x

Permanent link to this page (URI)

https://res.slu.se/id/publ/78167