Ground-Dwelling Arthropod Distribution and Movement Across a Fragmented Riparian Forest

The ability to predict patterns of species dispersal across habitat edges takes on increasing conservation relevance as land-scapes become more fragmented. We assessed edge responses for four ground-dwelling arthropod taxa by measuring their distribution and movement patterns across a forest edge associated with a forested riparian buffer and an adjacent upslope clearcut at a single site. We used Spatial Analysis by Distance Indices to describe the spatial distribution of arthropods, habitat variables, and the associations between them across a 49 × 63 m pitfall trapping grid with 80 trapping stations. We used mark-release-recapture techniques to measure the distance, rate, and direction of arthropod movement within and between habitat types. Scaphinotus angusticollis (Coleoptera; Carabidae) was restricted to the cool, moist portion of the riparian buffer and was not observed to cross the forest edge. The carabids Pterostichus lattini and Scaphinotus marginatus had more eurytopic distributions across all habitats. Higher overall mobility for S. marginatus may explain, in part, the greater frequency of movement for this species across the forest/clearcut edge. Lycosid spiders, strongly associated with the clearcut, also moved into one portion of the riparian buffer that was warmer and drier. They had a relatively high frequency of movement across the clearcut/forest boundary. These results suggest that ground-dwelling arthropod taxa are likely to respond differently to habitat edges, and that their habitat affinities and mobility strongly influence movement patterns across the landscape. Understanding these patterns of distribution and movement will aid the sustainable management of forest and riparian arthropod taxa in fragmented landscapes.