Do FSC guidelines work?: Evaluating terrestrial insect communities in Pacific Northwest hybrid poplars and adjacent natural areas

Pacific Northwest hybrid poplars are a Forest Stewardship Council certified short-rotation woody crop (SRWC) grown under drip irrigation on a 12-yr rotation stressing environmental quality and habitat. As management decisions are continually evaluated during the rotation, a premium should be placed on identifying its key components. Terrestrial arthropod communities are often overlooked in SRWC systems although they can act as harbingers of ecosystem health.  By identifying the community′s composition, we can develop integrated pest management strategies that minimize the grower′s environmental impact. We conducted a four-year investigation of the terrestrial arthropod community and its response to harvesting activities.  Terrestrial insect communities were observed using pitfall in newly planted and mature poplar stands and the surrounding riparian and sagebrush habitats.  Abiotic differences were quantified by recording above and below ground temperatures in each habitat.  This community consists of a number of pestiferous and beneficial insects dominated by a small suite of species, including Calathus ruficolis Dejean, (Coleoptera:  Carabidae) and Tetramorium caespitum L, (Hymentoptera:  Formicidae).  Newly planted stands and natural areas had the highest diversity (Poles H′=2.36; Riparian H′=2.52) while mature stands were the least diverse (H′=0.56).  Surface temperatures within each community were closely tied to the stand′s physical structure, with sagebrush and 1-yr old plantings being warmer than mature stands.  These findings suggest that the current management of hybrid poplars in the Pacific Northwest under the FSC guidelines provides suitable habitat for the local terrestrial insect communities.  This increased understanding has led to the development of a more complete integrated pest management strategy within this silvaculture.