This web tool uses the BEE-STEWARD model to simulate bumble bee pollination services and population growth on blueberry farms with potential locations for grower-specified wildflower patches. The tool predicts how bumble bee pollination services and contribution to blueberry fruit set will change when wildflower patches are added to the farm property. We assume that all other factors affecting fruit set (weather, pruning, etc) are held constant.
BEE-STEWARD is both a population model and a foraging model, and has been widely used to see how pollinator-friendly farm management practices can affect bumble bee survival and pollination rates. BEE-STEWARD is a combination of two previously published models, Bumble-BEEHAVE and BEESCOUT, both of which are available at beehave-model.net. All of these models have been exhaustively validated against data. Full scientific details of the models can be found in the publications listed at the end of this page.
Key Model Assumptions
- Bees forage for either pollen or nectar, on a single type of flower per foraging trip, and forage until a full load of pollen or nectar has been collected.
- Bees initially choose their foraging site based on distance from the nest, and subsequently based on the distance from the nest and the perceived quality of the site. Site quality decreases as other bees visit the site and deplete the nectar and pollen resources there.
- The quantity of pollen and nectar brought back to the nest by foragers affects the population growth of the nest, but the nutritional quality of pollen from different species is not considered.
- The farm habitats are defined by the user and surrounding areas are spatially defined by using data from the Annual Crop Inventory. The simulation takes this information and builds a simplified representation of the landscape in which bee visits to each field are modeled as visits to the centre of the field.
Key Fruit Set/Berry Yield Assumptions
- When a bee visits a flower, there is a 92% (for workers) or 97% (for queens) chance that the flower is successfully pollinated.
- Each flower visit is unique, until there have been more successful flower visits than there are flowers, at which point flowers may be visited more than once.
- All deposited pollen grains are accepted by the flower to calculate pollination and fruit set.
Simulations begin on January 1st. In the spring, hibernating bumble bee queens emerge, and search for nest sites. Queens that successfully find nest sites then forage and provision their nest, lay an initial batch of eggs, and raise the young. Once these young become adults, the queen stays in the nest, and the workers forage and help tend the new eggs laid by the queen. Nests may fail at any point throughout the season, if they are unable to obtain sufficient food resources. At the end of the season, each successful nest will switch to producing males and queens, rather than workers. Males and new queens from different nests will mate, and the queens will enter hibernation. Hibernating queens may die, but in the spring, any surviving queens will emerge and start the cycle again. The simulations run for five years, and provide yearly information about the bumble bee populations, and blueberry flower visits. An extension to the model quantifies the potential contributions of these wild bees to berry yield.
The modelled bees make foraging decisions in response to the flowers available on and around the farm. Naive bees select a foraging location based on the distance from their nest to each flower patch, with nearer patches preferred. If a forage patch is composed of multiple flower types, bees will choose to forage on the most profitable flower type. Bees forage at the same patch, on a single flower species, for either pollen or nectar, for the entire foraging trip. The choice to forage for pollen or nectar is determined at the nest, based on the needs of the nest. Experienced bees remember previously visited patches, and return to the most profitable patch and flower type remembered. The bees will switch flower species or patches between trips once a flower species or patch becomes unprofitable. The flower handling times and the amount of pollen or nectar collected per flower are calculated based on the total amount of pollen or nectar available in the patch, and on bee characteristics such as tongue length. The bees forage until they have collected a full load, defined by species specific characteristics such as body size Thus, the number of flowers visited per trip can vary. The amount of pollen and nectar available for each flower species in each patch is reduced throughout the day as the bees forage, and reset to maximum at the beginning of each day for the duration of bloom. The landscape does not change from one year to the next. All bees have a chance of mortality while foraging, and have a species-specific lifespan.
Potential contribution to fruit set and berry yield are calculated based on the research papers listed below. Each time a bumble bee visits and successfully pollinates a flower, a certain number of grains of pollen are deposited. The number of pollen grains deposited correlates with the berry weight.
Citations
Bee-Steward References M. A. Becher, V. Grimm, J. Knapp, J. Horn, G. Twiston-Davies, and J. Osborne. BEESCOUT: A model of bee scouting behavior and a software tool for characterizing nectar/pollen landscapes for BEEHAVE. Ecological Modelling, 340:126-133, 2016
M. A. Becher, G. Twiston-Davies, T. D. Penny, D. Goulson, E. L. Rotheray, and J. L. Osborne. Bumble- BEEHAVE: A systems model for exploring multifactorial causes of bumblebee decline at individual, colony, population and community level. Journal of Applied Ecology, 55:2090-2801, 2018
Berry Yield References R. Isaacs and A. K. Kirk. Pollination services provided to small and large highbush blueberry fields by wild and managed bees. Journal of Applied Ecology, 47:841-849, 2010
S. K. Javorek, K. E. Mackenzie, and S. P. Vander Kloet. Comparative pollination effectiveness among bees (hymenoptera: Apoidea) on lowbush blueberry (ericaceae: Vaccinium angustifolium). Annals of the Entomological Society of America, 95(3):345-351, 2002
H. Qu and F. Drummond. Simulation-based modelling of wild blueberry pollination. Computers and Electronics in Agriculture, 144:94-101, 2018