Comparing the impacts of autumn leaf litter management and canopy diversity on overwintering insect communities in rural and urban landscapes

Urban autumn litter management is an understudied disturbance to overwintering insects. Litter removal may harm insect communities by directly removing organisms, such as Lepidoptera, that overwinter in leaves or by reducing the capacity of the soil to buffer temperatures. However, a diverse tree canopy may mitigate the effects of disturbance by providing a source community with a diversity of overwintering strategies. To examine this we used two experimental approaches. We removed or retained leaf litter from 1x1m quadrats in 20 suburban properties in Maryland. We collected from emergence traps placed on these treatments every 10 days until July. Over the same collection period, we used a large-scale tree biodiversity experiment to assess if canopy diversity mitigates litter disturbance. Here, we used two additional treatments (leaf shredding and addition) to test the effects of other common management techniques. Treatments were implemented using a randomized block design (24 blocks) within experimental monoculture or polyculture plots. In both sites, we tracked the difference between soil and air temperature (temperature buffering). Preliminary data from the tree diversity experiment shows that the number of Lepidoptera emerging from removal plots was 0.55 [0.35, 0.84] times the number emerging from the control (on log scale: B = -0.59, z= -2.715, p=0.006) Diversity treatment had no effect. Quantifying the ecological effects of litter management will guide landowners to preserve (sub)urban biodiversity.