Disentangling the Benefits of Organic Farming for Beetle Communities (Insecta: Coleoptera) in Traditional Fruit Orchards

Abstract

The conversion of traditional land-use systems into more intensive agriculture forms plays a main role in biodiversity loss. Within this framework, organic management has received widespread attention since it is assumed to enhance multiple taxa, including different groups of insects and plants. However, its contribution to the promotion of organism diversity is still controversial. We developed a study in traditional cherry orchards from the Jerte Valley (western Spain) to examine how coleopteran and plant assemblages are driven by farming system (organic vs. conventional), topographic features, and seasonality. The coleopteran community was examined on the basis of its taxonomic and trophic guild response. Organic orchards supported a higher number of beetle families and a greater plant species richness. Additionally, beetle and plant communities were highly correlated; conventional orchards were more homogeneous in terms of both plant and beetle composition, while organic orchards were more heterogeneous, their composition being also shaped by the hillside aspect. From a more functional approach, the different coleopteran trophic guilds exhibited varying responses to the factors analyzed. The benefits of organic farming were notable even when working in traditional systems: highly valuable habitats for overall biodiversity. Therefore, we highlight the potential of organic orchards for conservation purposes.

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

“…Both parasitoid richness and abundance, as well as spider abundance, were higher in abandoned orchards exclusively in mid–late summer (July–September). Mediterranean ecosystems experience dramatic changes throughout the year, with strong disparity in resources availability between seasons and an expected reduction in plant and host accessibility during the summer drought [ 29 , 30 ]. The consequences of this severe seasonality are exacerbated in traditional almond orchards, where the annual vegetation dries up earlier than in the shrub-dominated abandoned orchards, reducing vegetation complexity and thus hampering the diversity of resources that benefit spiders (i.e., anchoring points, prey abundance [ 67 , 92 ]) and parasitoids (i.e., floral resources, alternative hosts, refuge [ 44 , 91 ]).…”

“…Furthermore, the results observed in central Europe may differ in Mediterranean areas given the extreme changes that ecosystems suffer under this climate, with a strong variability in resource availability between seasons [ 29 ]. This severe seasonality can affect plant and arthropod communities and could interact with crop management changes [ 30 , 31 ].…”