Wednesday, August 6, 2008 - 2:30 PM

COS 62-4: Resilience or rebound? Terrestrial arthropod community response to a catastrophic perturbance in Pacific Northwest poplars

R. Andrew Rodstrom and John J. Brown. Washington State University

Background/Question/Methods

Terrestrial arthropods are an integral part of a well-functioning ecosystem and can be used as indicators of the overall health of an area.  Hybrid poplars are a long rotation (12-15 yr) woody crop grown to meet today’s fiber demands.  In order to meet the recent push towards environmentally friendly management, several poplar plantations in the Pacific Northwest have been certified by the Forest Stewardship Council (FSC), which encourages environmentally responsible management of forest resources.  This project investigated how terrestrial arthropod communities in FSC-certified poplar plantations respond to the planned catastrophe of harvest by examining the community composition before and after harvest and the intermediate (3-7) years. Previous studies show that arthropod communities recover to pre-harvest levels in less than two years.  Based on the Shannon-Weiner diversity index, we hypothesized that terrestrial arthropod community composition during these intermediate years would be unstable and dissimilar to pre-harvest communities.  Terrestrial arthropod communities were surveyed using unbaited pitfall traps, and limited light trapping was conducted to provide a broader understanding of the system community.  Temperature data was recorded in all studied communities to quantify potential abiotic differences between the communities.   

Results/Conclusions

Results indicate that a change in community composition during the intermediate years and we show that resilience noted in earlier studies is only an echo of the pre-harvest community.  Despite these changes, the most common species in the system was found across all communities.  The monospecific dominance of Calathus ruficollis (Coleoptera:  Carabidae) was most noticeable in the fall, with spring and summer communities showing greater evenness.  We also show that temperature initially mirrors the arthropod community’s quick return to pre-harvest species diversity levels, but unlike the arthropod community, remains at pre-harvest levels throughout the intermediate years.