Effect of green infrastructures on pollinators and pollination in almond orchards

• Autor(a) principal: Pacheco, Inês Jesus Ferreira Leão Ponte
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/36256
• topic: Wild bees; (Semi-)natural habitats; Intensive agricultural landscape; Mass-flowering crop; Fruit set; Prunus spp

Habitat destruction and fragmentation caused by anthropogenic changes in the landscape, agricultural intensification, and inappropriate use of agrochemicals are significant drivers of biodiversity losses of insect pollinators, dramatically impacting pollination ecosystem services. This biodiversity- dependent service contributes to the yield and quality of over 75% of crops worldwide. The area occupied by pollinator-dependent crops has increased significantly over the last decades, and predictions point to a scenario of growing food demands and decreased pollination services. In this context, it is crucial to evaluate the success of management tools, such as implementing new green infrastructures (GIs) or maintaining the existing ones, to promote the stability and sustainability of pollination services. This work evaluates the effect of GIs in pollinator communities and pollination services in almond orchards by testing two alternative hypotheses: GIs work as reservoirs for pollinators that spill over to the crop fields, providing pollination services to the crop (‘exporter’ hypothesis), or GIs create a sink effect on the crop edge, hindering the dispersal of pollinators to the field (‘concentrator’ hypothesis). For this, two intensive and super-intensive almond orchards (around 300 ha each) were selected in an emerging production region in Portugal, Beira Baixa. GIs’ impact on insect pollinators’ abundance and diversity, pollination services, and crop productivity were quantified. Floral visitors and visitation rates were recorded in the GIs and in the crop at specific distances from the GI. Additionally, at the same distances in the crop, pollen tube and fruit production were also quantified. Floral and nesting resources were quantified in the GI and orchard to assess site quality for the pollinators’ community. In total were assessed eight different types of GIs (ditch, pasture, cork oak, temporary crop, water line, water body, mixed forest and scrub). The results obtained show: 1) a diverse community of pollinators within almond orchards and in the surroundings GIs, but almond is mainly visited by honeybees; 2) the resource quality of the GIs explained visitation rates within the orchard, although no relationship was observed with remaining variables; 3) honeybee abundance drive whole pollinator abundance, visitation rates and pollen tubes in almond; 4) diversity of plants in the orchard relate positively with visitation rates and pollen tubes in almond, but not with wild pollinator abundance; 5) the distance to the GI did not affected any of the response variables; 6) GIs harbour a significantly higher abundance of wild pollinators, while honeybees tend to present the opposite pattern. Consequently, the results suggest 1) that GIs behave as a sink effect making it difficult for pollinators to disperse to the field, and 2) that richer GIs harbour more abundant and diverse pollinator assemblages, increasing visitation rates in the orchard, although without clear effects in almond productivity.