THE EFFECTS OF LEAF LITTER MANAGEMENT PRACTICES ON OVERWINTERING INSECT COMMUNITIES AND ECOSYSTEM FUNCTION: IMPACTS AND APPLICATIONS IN RESIDENTIAL LANDSCAPES

Abstract

Fallen leaf management is a widespread landscaping practice in urban areas that not only influences soil health but also affects the overwintering individuals of subsequent year's aboveground arthropod communities. There has been considerable public and scientific interest in the ecological effects of this disturbance, yet little experimental research making it difficult to provide evidence-based landscaping recommendations to stakeholders. This dissertation aims to narrow this knowledge gap, provide information for the creation of best management practices, and encourage further research on this critical topic. In Chapter 2, I compare spring arthropod emergence in residential areas where fallen leaves were removed or retained across different levels of maintenance intensity. In Chapter 3, I focus on the legacies of long-term leaf removal to soil organic carbon dynamics. And in Chapter 4, I examine the efficacy of alternative leaf management practices—such as shredding and leaf piling—on soil microclimates, arthropod biodiversity, and decomposition rates while exploring if tree canopy diversity mitigated impacts to these ecosystem functions. The results of these three experimental studies were consistent across years and habitat types. Leaf removal reduced the spring emergence of Lepidoptera by about 35-45% and reduced spiders by about 50-67%, altered parasitic wasp community composition, reduced soil moisture and temperature buffering, and ultimately led to legacy effects in the soil of reduced decomposition and soil organic carbon. The context in which leaves were managed also mattered, as unique resources attracted overwintering arthropods more when they were scarce in the environment. Despite the potential for high plant diversity in leaf-managed areas to create ecosystem traps for arthropods, tree diversity actually mitigated some negative effects of fallen leaf disturbance to ecosystem function. Overall, I find that some practices like leaf removal and shredding degrade ecosystem processes while others like piling leaves and planting a diverse tree canopy can support ecosystem services. This dissertation is the first to quantify the ecological impacts of leaf management as an urban disturbance and addresses critical questions necessary for developing urban best management practices.