Maintaining high vegetation structural diversity in the landscape promotes arthropod diversity in dynamic production areas

Abstract

Species occurrence in transformed areas (or matrix) can be enhanced by reducing the contrast in vegetation structure between the matrix and remnant natural patches. Contrast depends on both structural features of remnants and that of the matrix, which can be dynamic and determined by harvesting practices. We assess whether structurally equivalent vegetation, as determined by structural features of the matrix relative to that of remnants in the landscape, promotes species diversity and abundance in the matrix. Furthermore, we assess the relative importance of structurally equivalent vegetation compared to features of the immediate adjacent remnant patch. Arthropods were sampled from 34 sites situated in alien forestry plantation blocks of different ages, dissected by corridors of natural grassland and/or closed canopy woody habitats. We analysed how arthropod assemblages within plantations were influenced by structural features of remnant vegetation in the landscape, and that of remnant patches directly adjacent. The amount of structurally equivalent vegetation at the landscape level promoted arthropod abundance and diversity within plantations and was more important than either the structural contrast or biotope type of the immediate adjacent patch for promoting diversity in the forestry blocks. Landscapes composed of a mosaic of structurally distinct vegetation best contribute to promoting diversity within dynamic production areas. Harvesting practices that radically change the structural features of the entire plantation should be avoided. We recommend use of rotational harvesting, so creating a variety of plantation tree ages for improved arthropod spillover from both natural grassland and woody habitats.