An evaluation of Israeli forestry trees and shrubs as potential forage plants for bees

Loss and fragmentation of foraging habitats, and extreme seasonality in the flowering phenology of wild plants, limit honeybee populations in Israel. This problem can be alleviated by the planting of bee forage plants in forests, parks, and along roadsides. To provide recommendations for such planting, we combined a literature survey and qualitative evaluations of experts to compile a list of 266 local wild plant species that have high food potential for bees. We also quantitatively evaluated the food potential of 32 species of trees and shrubs planted by Keren Kayemeth LeIsrael-Jewish National Fund (KKL-JNF). We recorded the following parameters of each species: main flowering season; flower morphology; type of food reward; number of flowers per plant; nectar standing crop; hourly nectar production rate; type of insect visitors; and frequency of insect visits. We ranked the surveyed species according to their potential importance as food plants, assigning high ranks to species that (a) bloom between July and February (the period of dearth in flowering natural vegetation), (b) produce large amounts of nectar, and (c) are highly attractive to honeybees. Of the species surveyed, Amygdalus communis, Eucalyptus camaldulensis, Ceratonia siliqua, and Ziziphus spina-christi best combined these benefits. A regression model indicated that high nectar production rates increased insect visitation rates, while long flowers reduced them, in an inter-specific analysis. Our study highlights the importance of diversified forestry planting to address agricultural, conservation, and recreational needs.