Landscape context but not management strategies affects the diversity of native and exotic semi-natural vegetation in Mediterranean agroecosystems of Central Chile

Abstract

Current knowledge on the effects of farming type and landscape heterogeneity on plant diversity is biased towards temperate ecosystems in Europe and North America, while there is a paucity of information for the Mediterranean agroecosystems. In particular, the Mediterranean region of Central Chile concentrates most of the country's population and have experienced the greatest agricultural changes leading to the replacement of native vegetation remnants by monocultures and livestock ranching. This study aims to analyse the effects of farming type (organic versus conventional) and landscape heterogeneity (composition and configuration), in addition with local habitat type, on semi-natural vegetation. We addressed these effects considering both native and exotic herbs at 14 fruit farms and landscape metrics at three spatial scales (0.5, 1 and 2 km). In total, we recorded 32 native and 103 exotic plant taxa. Farming type and local habitat type did not influence the diversity of native and exotic herbs. We showed that increasing landscape compositional heterogeneity (i.e. percentage of grasslands, of woody elements) increased alpha and beta diversity of native herbs at the scale of 0.5 km and 2 km. Gamma diversity of native plants responded negatively to decreasing landscape configurational heterogeneity (i.e. largest patch index) at the scale of 0.5 km. Exotic specis did not respond to landscape context. Our findings suggest that semi-natural elements in the surrounding landscape of fruit farms particularly benefited native plant species. Therefore, agri-environment schemes designed to preserve native biodiversity in Mediterranean agroecosystems must promote landscape heterogeneity through the conservation of semi-natural elements at multiple spatial scales.