Manejo innovador del ganado y enfoques metodológicos para el control de plagas en ecosistemas agroforestales

Zusammenfassung

Ecological intensification proposes profiting from the ecosystem services that some organisms within the system may provide. This Doctoral Thesis addresses this subject within the context of pest control in Holm oak Quercus ilex dehesas. It was experimentally demonstrated that leaf-feeding caterpillars (Lepidoptera) reduce acorn production. In addition, acorn losses by pre-dispersal predators were quantified: in the study dehesas these insects were Curculio elephas (Coleoptera) and, in a lesser extent, Cydia fagiglandana (Lepidoptera). At the crop level, although Curculio elephas was the dominant species, certain changes in the climate (longer summer droughts) may reduce its incidence and increase that of Cydia. Acorns attacked by insects are prematurely dropped. After that, Curculio elephas larvae spend 20 days within the acorns. In that period many are killed by livestock, which feeds on sound and infested acorns alike. The results of the Thesis show that a correct livestock management may serve to control oak pests. Within the farms, livestock should be concentrated in certain plots when C. elephas larvae are more vulnerable. In parallel, arthropod biodiversity assessments performed by means of molecular species delimitation, show that species richness decreases when livestock is present, but recovers soon after excluding it. Hence, an optimal strategy would consist in combining and rotating within the farms plots of intensified grazing with short-term ungulate exclosures. By doing this, the increase of productivity and biodiversity conservation would become compatible in an agroecosystem with a high natural value like is the case of dehesas.