Pollinator diversity and pollination services provided to urban garden and turf-based vacant lot ecosystems

Midwestern urban areas have witnessed population and economic declines resulting in an increased amount of vacant land. In Cleveland, OH citizen groups are redesigning some of these lots to construct community gardens. Little is known about the pollinator communities and the pollination services they provide within urban vacant lands or how they may be impacted by the conversion of these lands to agricultural production. As pollination is an important component of urban ecosystems and critical to the success of urban farming, information regarding the status of this service is needed. Our goal was to determine if and how bee (Anthophila) communities and the pollination services they provide are affected by a shift in land use from vacant land to urban agriculture. We established 16 sites (8 vacant lots and 8 urban gardens) within Cleveland in 2010-11. Bee abundance and diversity were measured three times in both years using pan traps Two treatments of sunflower plants (Helianthus annuus var Sunspot) were placed in sites for seven days to measure pollination services: unbagged plants allowing for insect visitation, and bagged plants excluding pollinators. Floral diversity and area were also measured, and floral observations were conducted to elucidate specific plant-pollinator interactions. The pollinator community in both lots and gardens consisted primarily of solitary, ground-nesting bees. Sunflower seed set and weight did not differ between lots and gardens. However, both increased at least threefold in unbagged plants when compared to pollinator-excluded plants, indicating significant pollination services were available.