A comparison of three trapping methods used to survey forest-dwelling Coleoptera

Abstract

Abstract. Sampling of insect communities is very challenging and for reliable interpretation of results the effects of different sampling protocols and data processing on the results need to be fully understood. We compared three different commonly used methods for sampling forest beetles, freely hanging flight-intercept (window) traps (FWT), flight-intercept traps attached to trunks (TWT) and pitfall traps placed in the ground (PFT), in Scots pine dominated boreal forests in eastern Finland. Using altogether 960 traps, forming 576 sub-samples, at 24 study sites, 59760 beetles belonging to 814 species were collected over a period of a month. All of the material was identified to species, with the exception of a few species pairs, to obtain representative data for analyses. Four partly overlapping groups were used in the analyses: (1) all, (2) saproxylic, (3) rare and (4) red-listed species. In terms of the number of species collected TWTs were the most effective for all species groups and the rarer species the species group composed of (groups 1-2-3-4) the larger were the differences between the trap types. In particular, the TWTs caught most red-listed species. However, when sample sizes were standardized FWTs and TWTs caught similar number of species of all species groups. PFTs caught fewer species of all species groups, whether the sample sizes were standardized or not. In boreal forests they seem to be unsuitable for sampling saproxylic, rare and red-listed species. However, the PFTs clearly sampled different parts of species assemblages than the window traps and can be considered as a supplementary method. The abundance distribution of saproxylic species was truncated lognormal in TWT and pooled material, whereas unclassified material failed to reveal lognormal distribution in all the trap types and pooled material. The results show that even in boreal forests sample sizes of at least thousands, preferably tens of thousands of individuals, collected by a high number of traps are needed for community level studies. Relevant ecological classification of material is also very important for reliable comparisons. Differences in the performance of trap types should be considered when designing a study, and in particular when evaluating the results.

Colonisation of ephemeral forest habitats by specialised species: beetles and bugs associated with recently dead aspen wood

“…Traps attached to dead trees usually capture more saproxylic beetles than traps situated away from trees (Hyvärinen et al 2006; Sverdrup-Thygeson and Birkemoe 2009; see however Saint-Germain et al 2006), which means that the capture in trunk window traps at least to some extent reflect what is attracted by the trees. In each pile, one trap was attached to the standing log (Fig.…”

How we improved a landscape study of species richness of beetles in woodland key habitats, and how model output can be improved

“…2 in Franc et al, 2007) per site, four in each plot: one attached to a newly dead oak tree; one attached to an oak that had been dead from about 2 to 5 years; one attached to downed oak; and one freestanding trap at least 3 m away from any dead oak. Such traps are efficient in catching saproxylic beetles, including redlisted ones (Hyvärinen et al, 2006), and traps placed on specific substrates or no substrate catch different parts of the saproxylic oak beetle community (Franc, 2007;Sverdrup-Thygeson and Birkemoe, 2009). The traps on substrates had panes 0.2 Â 0.3 m in size and were placed on the southern side of dead trunks.…”

Saproxylic beetle assemblages in the Mediterranean region: Impact of forest management on richness and structure

“…We used 48 flight-interception traps with crossed panels of plexiglass (50 cm  30 cm) to survey the flight-active beetle fauna of the different woodlands (see Hyvä rinen et al, 2006). The traps were placed in the lower canopy ca.…”