Riparian Vegetation and Arthropod Responses to Dam Removal and Habitat Restoration Along the Kalamazoo River, Michigan, <scp>USA</scp>

ABSTRACT Riparian ecosystems harbor diverse biota and provide numerous services to rivers including mitigating sediment run‐off, regulating temperature, and contributing food‐web subsidies. Dams are a major threat to riparian communities, but dam removal and riparian restoration efforts have the potential to restore these communities and the services they provide. The goal of this study was to understand how the removal of small run‐of‐river dams and habitat restoration may change riparian community composition both taxonomically and functionally. We sampled the riparian vegetation and arthropod communities of three sites with dams, two sites where dams were removed, and one free‐flowing reference site along the Kalamazoo River in Michigan, USA. Considering the difference in river conditions created upstream and downstream of dams, we sampled reaches both within the reservoir/former reservoir and below the dam/former dam location. Ordinations revealed that dam sites were characterized by more facultative upland trees, while dam‐removed sites and the reference site had more facultative wetland forbs and grasses. Vegetation community composition at the species level was not different among sites. Riparian arthropod communities did not differ between dam and dam‐removed sites, but reaches within the reservoir/former reservoir were characterized by significantly more detritivorous isopods than below dam/former dam reaches. Moreover, vegetation richness, percent cover of non‐native species, canopy cover, and riparian zone width predicted arthropod richness and Shannon diversity, regardless of site classification. We conclude that dam removal results in subtle changes in riparian functional composition, but long‐term monitoring is essential in evaluating the full extent of stream restoration on these habitats.