Bourassa, S.

O'Halloran, John

Oxbrough, Anne

Spence, John R.

Tejero, Sergio

Edge Hill University Research Information Repository

Assessing the effects of human disturbance using ground-dwelling arthropods: does sampling method affect our conclusions? Sergio García-Tejeroa, Stephane Bourassab, John R. Spenceb, John O’Halloranc, Anne Oxbrougha a Department of Biology, Edge Hill University, United Kingdom; b  Department of Renewable Resources, University of Alberta, Canada; c  School of Biological, Earth and Environmental Science, University College Cork, Ireland  tejeros@edgehill.ac.uk CONCLUSIONS  Pitfall and Berlese methods obtained different results on the effect of forestry man-agement on arthropod abundance and diversity. Results were more similar for spe-cies composition analyses.   Relative abundance differed widely between methods except for carabids. Behav-iour may affect catchability: highly mobile surface dwellers may be easily captured with pitfall traps and low mobile species may be better detected with Berlese.   Pitfall traps collected most species, but some were only found with Berlese. Both methods are complementary for biodiversity surveys.   Sampling method bias should be acknowledged when interpreting ecological results. RESULTS Fig. 4. Number (and %) of species found with each sampling method. Table 1. Summary of significant results on the effect of cover type and forestry stage on overall abundan-ce, alpha diversity and species composition of the groups studied. Attribute Group Pitfall Berlese Agree? Fig. # Abundance       Spiders mature < regenerating mature > regenerating  2a  Staphylinids mature < regenerating no differences  2b Diversity       Spiders mature < regenerating mature > regenerating  2c  Carabids deciduous < coniferous no differences  2d Composition      Spiders mature ≠ regenerating mature ≠ regenerating    Staphylinids mature ≠ regenerating mature ≠ regenerating     Staphylinids deciduous ≠ coniferous no differences    Fig. 3. Relative abundance of the three most common species sampled with Berlese and their corresponding relative abundance in pitfall traps.  INTRODUCTION  Pitfall traps are a very popular way of sampling ground dwelling invertebrates for ecology studies. They are cheap, can be left working for several weeks and collect high numbers of individuals.  Berlese-Tullgren funnels (Berlese) extract most mobile individuals found in a known volume of litter or soil sample.  However, sampling accuracy is affected by many factors, including climate and habitat structure for pitfalls, sample volume and funnel characteristics for Berlese and spe-cies mobility and behaviour for both methods (Southwood & Anderson 2000).  Can both sampling methods obtain similar results in ecology-focused studies? OBJECTIVES Do pitfall- and Berlese-sampled data obtain similar patterns of ground-dwelling spider, staphylinid and carabid assemblages in managed boreal forests? Specifically:  Do responses of arthropods to canopy cover type and forestry management in overall abundance, alpha diversity and species composition differ between sampling meth-ods?  Do both methods rank species relative abundance similarly?  Do they collect the same species? METHODS The study was carried out in Canadian boreal mixedwood. A fully replicated 3x2 design was used:  Three cover types: deciduous-dominated (DD), mixed (MX) and coniferous-dominated (CD)  Two forestry stages: mature and regenerating (11 years after clear-cutting)  Three replicates of each cover type x forestry stage combination were sampled:  Three pitfall traps 50-m apart were placed in each replicate for 12 weeks in summer.  Litter samples were collected three times near each pitfall trap.  The effect of cover type and forestry stage on overall abundance, alpha diversity and species composition was tested with PERMANOVA and 9999 permutations. Fig. 1. Sampling sites and methods: a) coniferous-dominated mature stand; b) regenerating stand; c) pitfall trap showing captures; d) soil sample to be pro-cessed in e) Berlese-Tullgren funnel. a c b d e Acknowledgements Spence lab at the University of Alberta; Lindsey Dewart, Jason Edwards, Charlene Hahn for help in the field and laboratory; Fieldwork supported by the EMEND project and co-funders: Daishowa-Marubeni International Ltd.; Canadian Forest  Products Ltd.; Alberta Sustainable Resource Development; Foothills Research Institute; This research was funded through an  IRCSET-Marie Curie International Mobility Fellowship in Science, Engineering and Technology. References Southwood, T.R.E., Anderson, P.A. 2000. Ecological methods. 3rd Edition. Blackwell Science. 575 pp. Fig. 2. Overall abundance per day (a, b) and arthropod alpha diversity (c, d) plots comparing sig-nificant results obtained with pitfall and those obtained with Berlese. 

Assessing the effects of human disturbance using ground-dwelling arthropods: does sampling method affect our conclusions?

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Assessing the effects of human disturbance using ground-dwelling arthropods: does sampling method affect our conclusions?

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