Effects of Traditional Orchard Abandonment and Landscape Context on the Beneficial Arthropod Community in a Mediterranean Agroecosystem

SIMPLE SUMMARY: Agricultural abandonment is a very relevant process in Europe and its consequences on biodiversity are not yet clear. Moreover, abandonment is focused on marginal areas, characterized by traditional agricultural landscapes, with high cultural and biodiversity values, which are particularly vulnerable to this process. Although increasing attention has been paid to agricultural abandonment in recent years, studies focused on traditional orchards are scarce. In our study, we analyzed how abandonment and landscape complexity (measured as the percentage of semi-natural habitats) affected three groups of beneficial arthropods (spiders, bees and hymenopteran parasitoids) in almond orchards established on the border between Spain and Portugal. Our results showed that traditional and abandoned orchards harbor different arthropod communities, with the latter favoring these beneficial arthropods in simple landscapes (with a low percentage of semi-natural habitats). However, abandoned orchards lose relevance as the percentage of semi-natural habitat in the landscape increases, highlighting the important role that these habitats play in traditional agricultural landscapes. While abandoned orchards provide valuable habitats and alternative resources, they do not substitute semi-habitats nor traditional orchards. From a conservation management perspective, both traditional almond orchards and semi-natural habitats should be conserved to protect the rich biodiversity associated with these traditional cultural landscapes. ABSTRACT: Agricultural abandonment is one of the main land-use changes in Europe, and its consequences on biodiversity are context- and taxa-dependent. While several studies have worked on this topic, few have focused on traditional orchards, especially in different landscapes and under a Mediterranean climate. In this context, we aimed to determine the effects of almond orchard abandonment on the communities of three groups of beneficial arthropods and the role of the landscape context in modulating these effects. Between February and September 2019, four samplings were carried out in twelve almond orchards (three abandoned and three traditional (active orchards under traditional agricultural management) located in simple landscapes as well as three abandoned and three traditional in complex landscapes). Abandoned and traditional almond orchards harbor different arthropod communities and diversity metrics that are strongly conditioned by seasonality. Abandoned orchards can favor pollinators and natural enemies, providing alternative resources in simple landscapes. However, the role that abandoned orchards play in simple landscapes disappears as the percentage of semi-natural habitats in the landscape increases. Our results show that landscape simplification, through the loss of semi-natural habitats, has negative consequences on arthropod biodiversity, even in traditional farming landscapes with small fields and high crop diversity.