THE MEDITERRANEAN AGROFORESTRY SYSTEMS

Dehesas and montados are the most well-known traditional agroforestry systems in the Mediterranean (Iberian Peninsula): they are open wood pastures, occasionally also cultivated with annual crops, dominated by sparse oak trees. For their high biological diversity, these systems are protected by the European Habitats Directive. Indeed, Moreno et al. (2016) found dehesa wood pastures hosting more species of vascular plants compared with open pastures, which also applied to bees (although not significantly more).

‘Dehesa type’ systems also exist in the eastern part of the Basin: they are savanna-like structures similar to the Iberian ones, dominated by different tree species including oak, terebinth, sweet chestnut and even particular species, like mastic trees. Olive and carob groves, traditional almond and fig orchards, as well as combinations with other fruit trees (pear, apple, pomegranate etc.), can be also added to the list. Most of these systems originated from natural scrub communities or from sparsely occurring trees, which were gradually transformed through management.

Traditional management (occasional and light ploughing, organic manuring, conserved field margins, sheep grazing) allow a diversity of wild annual plants to sustain pollinator resources, in favor of both the cultivated trees and the combined annual crops, if any. This is also the case of Lesvos, Greece, where traditionally cultivated olive groves proved to be richer in annual plants (Dalaka and Petanidou unpublished data) and in wild bee species (Potts et al. 2006) compared with abandoned olive groves. Yet, on the same island, considered as one of the world hot spots for bees (Nielsen et al. 2011, Petanidou, unpublished data), bee diversity maximized in traditionally managed agroforestry systems dominated by oak (Potts et al. 2006) and chestnut (Petanidou, unpublished data). In fact, induced wild bee diversity in agroforestry systems benefits cultivated fruit trees which may not need honeybee pollination at all, as evidenced for almond trees cultivated in southern Sinai, Egypt (Norfolk et al. 2016).

Carob groves, densely or sparsely planted, constitute a Mediterranean uniqueness. Carob tree (Ceratonia siliqua) is native to the Mediterranean where it has been cultivated historically for its pods used as foodstuff for domesticated animals and as supplement to human diet (gum extracted from endosperm, carob powder and syrup). Carob is a dioecious and, more rarely, gynodioecious plant, implying that pollination is important for its fruit set. Even though it is characterized by ambophily (it is both insect- and wind-pollinated), the plant requires insect pollination. Indeed, in the Mediterranean, the carob tree is serviced by a high variety of flower visiting insects, both diurnal (mainly bees, flies, wasps) and nocturnal (mainly settling moths) (Dafni et al. 2012). Because it flowers late in the year and has a prolonged flowering period (September – December), carob is a highly valued provider of floral rewards (nectar and pollen); this makes the plant indispensable not only for late pollinator flyers when floral resources are scarce, but also for co-flowering plant species with minor floral display. Overall, it is an important species contributing to the system’s conservation of pollination resources.