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• Leaf litter management impacts on insect communities

• Leaf litter management impacts on nutrient cycling and decomposition

• Insect behaviors and life cycles in urban areas

• The role of native plants in supporting biodiversity in suburban landscapes

Funding: NSF GRFP

People: Max Ferlauto

Autumn leaf litter management in suburbia is an understudied disturbance to overwintering insects. Litter removal may harm insect communities by directly removing organisms such as moths that overwinter in leaves or by stressing belowground communities by reducing the capacity of the soil to buffer temperatures. To test this, we removed or retained leaf litter from quadrats in twenty suburban properties in Maryland in December. We collected from emergence traps placed on these treatments every 10 days from March to July. Preliminary results show that removing leaf litter reduces moth emergence by up to 67 percent.

We are also using a large-scale tree biodiversity experiment (BiodiversiTREE) to assess if canopy diversity mitigates the effect of litter manipulation on overwintering insects. Here, we used two additional treatments (leaf shredding and leaf piles) to test the effects of common management techniques. Preliminary results show that litter removal and mulching cuts the number of emerging moths almost in half. We did not find an effect of tree diversity, but we are still processing data.

At BiodiversiTREE, we manipulated leaf litter in treatments of “retain,” “remove,” “shred,” or “pile” for three years. Because these treatments were nested within the design of the long-term experiment, we can ask questions about how canopy tree diversity interacts with litter management. Preliminary results indicate that diverse mixtures of tree species have increased soil moisture and less soil temperature variation, which can benefit decomposition rates.

People: Lauren Schmitt

There are many ways in which urban environments might alter insect behavior, but there is very little research exploring how this is or isn’t actually happening. We highlighted existing research and the key research gaps in a review published in Current Opinions in Insect Science. One figure from the paper is included here and described below:

Insect herbivore behaviors (a) are key to the successful completion of insect life cycles within both natural and urbanized habitats. Urbanized environmental conditions (b) likely alter many aspects of these habitats. Herbivore-specific attributes of life cycles include (1) the length of time spent in each life stage (2) the location in the urban environment where that life stage is spent (e.g. leaf, bark, soil surface), and (3) the seasonal timing of each stage. The latter is crucial for determining which stages are spent either overwintering or in aestivation. The life-cycle structure of a species determines which urbanized conditions the species is most likely to come in contact with. For example, species that overwinter in a rolled up leaf on the soil surface (such as the luna moth, Actias luna [Linneaus 1758], illustrated here) are more likely to be negatively affected by fall leaf removal or shredding in urbanized areas. Therefore, conspecifics living in different environments along a gradient of urbanization may experience different selective pressures on the same basic life cycle structure and behaviors. While global change intensity will generally increase along this gradient, management occurs in different forms in the vast majority, if not all, environments. Important insect herbivore behaviors (a) include: host-finding, feeding, oviposition/egg placement, pupation, and anti-predator defense. The primary life stages associated with each behavior are noted in parentheses (A = adult, L = larva, P = pupa).

We also organized a symposium at the 2022 Eastern Branch Entomological Meeting to synthesize research being done on insect conservation in urban areas and highlight non-pest, non-pollinator urban insect ecology.