Summary
Effective pest control requires a better understanding of natural enemy ecology, particularly how their distribution responds to landscape structure and local management. Agricultural intensification has simplified landscapes, reducing biodiversity and constraining pest control. Landscape-scale surveys are therefore needed to identify strategies that support natural enemies in agricultural systems. From 2021 to 2022, over three seasons, we surveyed 25 clementine orchards across a gradient of landscape complexity in Corsica. We modelled the tree-level occurrence of four natural enemy species in relation to ecological context across multiple spatial and temporal scales. Site-level evenness, reflecting differences in species occurrence frequencies, was also estimated to assess how natural enemy assemblages vary across local management and landscape gradients. Climate and local management were the primary drivers of species occurrence, with additional contributions from landscape factors. Species displayed distinct responses, while model performance increased with the number of sampled trees, plateauing at around half of the sampling effort. Site-level evenness was higher in organic orchards than in conventional orchards. In conventional orchards, it responded to landscape structure in a scale-dependent manner, increasing at the larger scale with the heterogeneity and spatial continuity of semi-natural habitats. Synthesis and applications. Organic farming enhances natural enemy presence and diversity in Corsican citrus orchards, while the naturalness and complexity of surrounding landscape can mitigate species scarcity in conventional orchards. We recommend continued long-term monitoring of arthropod communities in these systems, prioritizing the number of sampling sites and years while reducing the number of trees sampled per site to optimize effort.
Outcomes reported
Effective pest control requires a better understanding of natural enemy ecology, particularly how their distribution responds to landscape structure and local management. Agricultural intensification has simplified landscapes, reducing biodiversity and constraining pest control. Landscape-scale surveys are therefore needed to identify strategies that support natural enemies in agricultural systems. From 2021 to 2022, over three seasons, we surveyed 25 clementine orchards across a gradient of landscape complexity in Corsica. We modelled the tree-level occurrence of four natural enemy species in relation to ecological context across multiple spatial and temporal scales. Site-level evenness, reflecting differences in species occurrence frequencies, was also estimated to assess how natural enemy assemblages vary across local management and landscape gradients. Climate and local management were the primary drivers of species occurrence, with additional contributions from landscape factors. Species displayed distinct responses, while model performance increased with the number of sampled trees, plateauing at around half of the sampling effort. Site-level evenness was higher in organic orchards than in conventional orchards. In conventional orchards, it responded to landscape structure in a scale-dependent manner, increasing at the larger scale with the heterogeneity and spatial continuity of semi-natural habitats. Synthesis and applications. Organic farming enhances natural enemy presence and diversity in Corsican citrus orchards, while the naturalness and complexity of surrounding landscape can mitigate species scarcity in conventional orchards. We recommend continued long-term monitoring of arthropod communities in these systems, prioritizing the number of sampling sites and years while reducing the number of trees sampled per site to optimize effort.
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