- Agronomic: sunflower
- Animals: bees
- Education and Training: on-farm/ranch research, workshop
- Production Systems: agroecosystems, holistic management
- Sustainable Communities: sustainability measures
We evaluated the ability of hedgerow restorations to augment hybrid sunflower pollination by the native bee community. We also investigated whether rates of nesting were increased in fields adjacent to hedgerows, as well as whether the presence of hedgerows enhanced the diversity and abundance of the native bee community at different distances into fields.
Pollination is a critical component of the crop production cycle, directly contributing to reproductive success for pollinator-dependent crops. Sufficient pollination enhances seed quantity and quality, which directly correlates to profits. Bees are the most important crop pollinators, providing an estimated $200 billion in pollination services worldwide (1). Drastic declines in honey bee (Apis mellifera) populations due to Colony Collapse disorder and other factors have demonstrated the risk of relying on a single pollinator. Many native bee species are capable of providing pollination services and could act as insurance against fluctuations in honey bee supply (2). However, native bees have also declined in some regions of North America due to agricultural intensification. As a result, there are increasing calls for on-farm management actions that can enhance agroecological resilience by restoring habitats that support pollination services (3). Hedgerows, field edge plantings of native shrubs and forbs, are a common re-diversification technique; however, the efficacy of hedgerows or the scale at which they affect crop yields remains unknown.
Native bees depend on both floral and nesting resources. While floral abundance has been extensively studied, nesting resources are understudied despite their role regulating bee communities. Native bees are predominantly solitary ground-nesters, requiring direct access to open soil. Disturbances, such as irrigation and tillage, in intensively farmed areas can inhibit nest availability. In addition, native bees are central-place foragers, typically foraging within a 300-1000 m radius from their nest site, depending on body size (4). Thus, the proximity of nesting habitat to crops could affect the distribution and evenness of pollination services within agricultural fields. Availability of nesting resources is essential for the success of on-farm habitat enhancement projects targeting native bee conservation. Hedgerow restoration appear to provide more nesting resources than unmanaged field margins (5), however whether this translates into increased rates of nesting bees has not yet been evaluated.
We studied the provision of pollination services associated with hedgerow restoration. Specifically we examined whether native bees pollinating crops also utilized hedgerow resources. We then determined whether abundance and diversity of native bees affected calculating rates of seed set in hybrid sunflower (Helianthus annuus), a mass-flowering pollinator-dependent crop. We then determined where bees nested within the agricultural landscape, and whether hedgerow presence increased nesting rates.
1. Gallai, N et al 2009. Ecol. Econ. 68:810-821 2. Winfree, R et al 2007. Ecol. Let. 10: 1105-1113 3. Garibaldi, LA et al. 2014. Front. in Ecol. and the Env.12(8): 439-447 4. Greenleaf, S 2007. Oecologia 153: 589-596 5. Morandin, LA and C Kremen 2013. Ecol. App.23(4): 829-839.
Project objectives:div style="margin-left:1em;">
- Assess the spatial distribution of pollinators in agricultural fields
- Assess pollination function in fields with and without hedgerows
- Generate an economic model that evaluates the marginal benefits of hedgerow restoration along field edges
- Assess the nesting bee community in hedgerows and fallow field edges
- Correlate habitat features in hedgerows and fallow field edges to nest occurrence