Influence of Low Density Garlic Mustard Presence and Hardwood Leave Litter Composition on Litter Dwelling Arthropod Diversity

Abstract

Garlic mustard (Alliaria petiolata (M. Bieb.) Cavara & Grande) is a non-native plant that
commonly invades hardwood forest understory plant communities. Such invasions have the potential of
restructuring forest communities and influencing community function. Litter dwelling arthropods were
collected from areas with and without garlic mustard, and were identified to family. Forest characteristics,
including canopy cover, forest basal area, litter depth, and soil moisture, were also measured. Plot locations
with and without garlic mustard did not differ in the forest characteristics. However, arthropod richness was
significantly reduced in areas with garlic mustard compared to areas without. Arthropod richness and
diversity were positively related to leaf litter species diversity. In nonmetric multidimensional scaling
ordination, mature garlic mustard density influenced a few arthropod taxonomic groups. However, it is
likely that forest characteristics that facilitate the intensity of garlic mustard colonization (i.e., canopy cover,
moisture) may be part of that influence. Additionally, leaf litter species richness provided a strong
relationship with the majority of taxonomic groups. While garlic mustard presence may have a minor
influence on the litter dwelling arthropod community, leaf litter richness and diversity play a major role in
defining the arthropod community diversity and individual taxonomic group abundances. Management to
control garlic mustard in forests may have little impact on leaf litter dwelling arthropods, especially if the
litter layer remains intact.