Insect diversity and abundance measured two decades after farmland conversion to forest using different human-assisted restoration strategies in Gede, Kenya

Abstract

Abstract. We present a field study aimed at better understanding how different types of human-assisted restoration of farmland may affect insect diversity and abundance in a dry tropical forest. We report on the first survey measuring insect diversity and abundance in restored forest plots in Gede National Monument, Kenya, conducted 20 years after plantings were done across a gradient of human-assistance (natural regeneration, seed scattering, and high-density tree planting). We found that insect diversity and abundance within restored areas with different initial planting strategies and differing local ground vegetation characteristics varied highly among different insect taxa. For instance, seed scattered plots had a significantly greater leaf litter depth than natural regeneration plots; and we found that leaf litter depth had a negative effect on hymenopteran diversity. We also found negative relationships between dead ground cover and overall insect abundance, and bare ground cover and coleopteran diversity. Overall, we found that farmland restored to forest harbored similar levels of insect diversity as that of a nearby reference forest. Our preliminary survey reveals that taxon-specific habitat requirements of different insect groups needs to be carefully considered in order to understand the effects of human-assisted restoration on insect biodiversity.