Landscape heterogeneity increases the spatial stability of pollination services to almond trees through the stability of pollinator visits

Abstract

High pollinator reliability is essential to maintain a stable and predictable crop production. However, still few studies have considered landscape effects on the stability (low variability) of the pollination service to crops. The stability of pollination services may increase in heterogeneous landscapes with high availability and diversity of alternative habitats. By using data on pollinator visitation and fruit production in 18 almond tree fields in Mallorca Island, we related landscape heterogeneity (richness, evenness and diversity of land-cover classes) at 1 and 2 km-radius buffer zone to the spatial (among-tree) stability of their pollination services (total visit rates, wild pollinators’ visit rates, pollinator richness and fruit set). Overall, landscape heterogeneity increased the spatial stability (i.e., decreased spatial variability) of pollination services to almond trees. Interestingly different components of heterogeneity influenced diverse components of this service. Thus, increasing landscape evenness at the 2 km buffer zone increased the spatial stability of both total pollinator visitation and fruit set. However, the stability of wild-pollinators’ visit rate as well as the stability of pollinator richness increased instead with the percentage of natural habitat in the buffers, as the abundance of wild pollinators might depend on the total availability of habitat in the field surroundings. The stability in pollinator richness had a further positive effect on the stability of fruit set, indicating the importance of diversity maintaining stable crop production. Lastly, fruit set was also negatively affected by landscape richness, probably because of a loss of pollinator source habitat when the number of land uses is too high. Preserving a heterogeneous habitat of high quality in the surroundings of crop fields may help to maintain a stable fruit production.