Invertebrate community sampling of woodland field layers: Trials of two techniques involving enclosures

Abstract

The use of enclosures in invertebrate sampling can circumvent or lessen many of the biases associated with open traps. Removing only a relatively small proportion of the community, enclosed traps avoid impacting too severely on populations that may be of conservational concern, so may have applications in protected areas. Two sampling techniques using enclosures, developed for use in woodland field layers, are presented and assessed by way of comparisons with traditional techniques. A novel, portable ‘tent trap’ is described and broadly compared to a Burkard Univac suction sampler in terms of efficiency and insect numbers taken. The main advantage of the tent trap is that samples are free of troublesome organic debris, which is plentiful in the suction samples. When more than one tent trap is used, this method was more efficient in terms of individuals per unit sampling and processing time, than the Burkard. The tent also took groups missed by the Burkard. A pitfall enclosure suited to remote field-work applications is also described, and compared to single external traps, in terms of number of different taxa taken by each method. The enclosure proved more efficient at taking nearly every invertebrate group investigated, and was more effective at catching smaller species of ground beetle. Despite more rigorous testing being advised, both pieces of equipment would seem to be effective and practical, and an asset to quantitative invertebrate sampling.