Restoration ecology and habitat fragmentation studies in Massachusetts woodlands

Biological communities in urban areas need to be conserved and restored to prevent loss of native plant communities and wildlife. To monitor the success of plant reintroduction carried out at the Upper Charles River Reservation (UCRR) in metropolitan Boston, reintroduced populations of four native shrubs species (Aronia melanocarpa, Viburnum acerifolium, Cornus amomum and Clethra alnifolia) were compared to natural populations growing either at the nearby Webster Conservation Area (WCA) in Newton or at UCRR. Vegetative stem growth, reproduction, pollinator activity, light levels, soil nitrogen status and gravimetric soil moisture were compared between the sites. The movements of bumblebee pollinators (Bombus spp.) were examined across roads and railroads, and across artificial gaps simulating two-lane roads at the WCA.; Transplant sites had significantly higher light levels, lower soil nitrogen mineralization and nitrification rates, and lower soil moisture than natural sites. However, relative stem growth was higher in reintroduced populations compared to natural populations for all species except Cornus. This was the only species with both natural and reintroduced populations located at the UCRR. Sizes and densities of inflorescences, fruits and seeds were also significantly higher in reintroduced populations in all species except Cornus, while seed germination rates were higher in reintroduced than natural populations. The dominant insect orders visiting inflorescences at both sites included Hymenoptera, Coleoptera and Diptera. Average similarity in floral visitors ranged from 60–98% at the level of insect order and from 20–75% for hymenopteran families. Floral visitor abundance was greater in reintroduced populations, but visitation rates of insects were higher in natural populations due to lower inflorescence densities. Overall, reintroduced plants were growing and reproducing as well as or better than plants at control sites.; Tagged bumblebee pollinators displayed high site fidelity and rarely crossed roads and railroads unless there were no longer flowers to visit. Bees experimentally displaced across roads and a railroad up to distances of 500 m returned to their respective forage patches. In an experimentally fragmented purple loosestrife population, bees stayed predominantly within one habitat fragment. Thus, fragmentation of plant populations may further reduce the naturally low frequency of bee movements between patches.