Relationship Between Grassland Corridor Characteristics and Flying Insect Biomass in Forest Plantations in a Grassland Context

Abstract

The expansion of human land use has led to significant loss of natural habitats. In forest plantations established in grassland ecosystems,remnants of native habitats persist as linear structures, such as roadsides, firebreaks, and stream margins, commonlyreferred to as ‘corridors’. Insects are highly sensitive to environmental changes, and their body size can serve as an indicator ofhabitat quality. We hypothesised that corridors within forest plantations that exhibit greater native vegetation cover, resemblingnatural environments, provide sufficient resources for insect development, resulting in increased insect biomass. According tothe environmental filtering model, habitat characteristics in human-modifiedlandscapes and biotic interactions act as filters,promoting the loss of certain species and convergence in functional traits. We posited that environmental filtering is the primarymechanism structuring flying insect assemblages in these corridors, and that its influence diminishes with increasing corridorwidth and native vegetation cover. To test this, we quantified insect biomass through body size and abundance and analyzed variationin body size among collected flying insects in forest plantation corridors and larger patches (representing the natural environment).Also, we measured vegetation cover and corridor width, and we evaluated their relationship with insect biomass andits components. Our results indicate that intensive land use impacts insect biomass primarily by influencing insect abundance:larger patches support greater insect biomass and abundance than forest corridors. Additionally, we observed that most corridorshad less variation in insect body size than expected by chance, a pattern consistent with the environmental filtering hypothesis.