The effect of field size on the number of bumble bees Anna-Reeta Aalto
Introduction• Bumble bees have always been important pollinators both in agricultural and natural ecosystems. Due to homogenization of fields and changes in land-use during last decades the number of bumble bees is however decreased.
Introduction• In this research the aim was to study the effect of field size on the number of bumble bees in Estonia• Compared to previous studies in Central and Western Europe, Estonian fields are very heterogenous and smaller surrounded with semi-natural habitats
Methods• Data was collected from 66 farms in Southern- Western- and Mid-Estonia in summer 2007• Bumble bees were counted three times from 400 x 2 m wide transects• Monitoring was done only in dry weather with more than +16 °C and wind speed under 6 m/s
Results• The results show that there is a negative correlation between the number of bumble bees and the field size: the bigger field is, less bumble bees are shown• This result is similar to the previous studies done in 2005 and later in 2009
Discussion• Homogenous fields – The abundance of bumble bees is usually dependent to the amount of food resources (crops and wild flowers) which they need through whole foraging season – Not enough nesting and hypernating places > More undisturbed perennial vegetation along fields
Discussion• Large fields – Bumble bees have a limited foraging range (some species only 450 m) > Smaller field sizes