EFFECTS OF SOIL INVERTEBRATES ON MICROBIAL COMMUNITIES AND CARBON AND NUTRIENT CYCLING IN MANAGED URBAN GRASS SYSTEMS
Soil invertebrates have been shown to exert strong controls on microbial community composition, activity and biomass through fragmentation and mixing of organic matter, microorganism dispersal and grazing on bacteria and fungi. There are still many unknowns surrounding the relative importance of invertebrates for predicting and managing soil microbial processes under different soil conditions, suggesting that invertebrates have the potential to influence soil biogeochemical processes. Here, we seek to better understand how soil invertebrates influence microbial communities and carbon and nutrient cycling in managed urban grass systems as there is growing interest in managing and enhancing microbiomes to promote ecosystem services in urban soils. First, we reviewed the roles of invertebrates in the urban soil microbiome and suggest future directions for research on this topic. Then, we aimed to elucidate how soil macroinvertebrates, a unique invertebrate functional group, affect soil microbial community composition and function. We demonstrated that the presence of soil macroinvertebrates created distinct microbial communities and altered both microbial biomass and function. Our results suggest that macroinvertebrate activity can be an important control on microbially-mediated processes in the rhizosphere such as nitrogen mineralization and soil organic matter formation. Third, we aimed to assess the importance specifically of macroinvertebrates in the structuring of aggregates and in determining the fate of recently-derived organic matter from living roots using stable isotopes. We found that macroinvertebrates increase carbon and nitrogen incorporation into macroaggregates, microaggregates and coarse particulate organic matter. With evidence that invertebrates can alter soil microbial communities and carbon and nitrogen cycling in managed urban soils, we examined how invertebrates and microbial community structure and function respond to different pest management strategies. We found that insecticide chemistry and rate of application can have differential effects on non-target soil biota and soil moisture was an important driver of soil biotic responses and pesticide residues in soils.
Urban; grass; invertebrates; microbial communities; Soil; Entomology
Wickings, Kyle G.
Fahey, Timothy James; Kao-Kniffin, Jenny T.; English-Loeb, Gregory M.
Doctor of Philosophy
dissertation or thesis