In a wide ranging talk that took the audience from the island of Manhattan to Southeast Asia, Krista McGuire, an associate professor in the Department of Biology at the University of Oregon, presented work on microbial responses to two key types of land use change: urbanization and agriculture.
Most of the world’s population now resides in urban centers, but the microbial ecology of cities remains largely unexplored, she said at JGI’s 13th Annual Genomics of Energy & Environment Meeting in San Francisco, Calif. While at Columbia University, McGuire studied the impact of green infrastructure in New York City—including green roofs, parks, tree pits, and medians—on fungal ecology, though she noted that bacteria reflected similar patterns to those seen with fungi. “We’re trying to understand if we can use basic ecology of plant-microbe function to optimize installation of green infrastructure,” she said.
For instance, her team observed that total microbial biomass was unusually low in unfenced tree pits. The reason, they hypothesized, was that there was a different biotic influence in these ground-level systems: “visitation” by dogs (specifically, their urine). With one dog for every three humans, that’s a huge influx of nitrogen, she pointed out. One of McGuire’s graduate students showed experimentally that urine addition decreased water-holding capacity of the system, microbial biomass, and biodiversity. Fenced tree pits, of course, prevent dogs from “visiting,” but it’s not practical to close all of these systems in, she said, so clever ways to dilute the nitrogen inputs are needed.
Switching gears, she highlighted several ongoing projects related to plant microbial assembly across land use gradients.Tropical rainforests cover only 7 percent of Earth’s land surface but contain half of its biomass and two-thirds of its terrestrial biodiversity. In Malaysia, her group is looking at the effects of land use and the ecology of ectomycorrhizal (ECM) associations in old-growth tropical rainforest, oil palm plantations, and regenerating forest.