Salton Sea microbiomes
My work with Emma Aronson in Microbiology and David Lo in Biomedical Sciences at UC Riverside, funded through the National Institute of Health and the University of California Office of the President, examines the sediment, playa, seawater, and aeolian microbiomes of the Salton Sea, with associated implications for human health and conservation.
Our recently published manuscript (invited; co-first author with graduate student Hannah Freund) to California Agriculture investigates the ecological and biomedical implications of this drying lakebed on microbial proliferation and regional health disparities. Another of our papers, published in the same issue of Cal Ag, provides greater perspective into the drying Salton Sea and asthma, and explores the extent of this “natural” disaster on human health and asthmatic inflammatory responses.
Regeneration-phase microbial inoculation in post-fire systems
In 2021, as Primary Investigator, I was was awarded the Wildlife Conservation Society’s Climate Adaptation Fund. In this work, in collaboration with Point Blue Conservation Science, UC Riverside (Sydney Glassman’s Lab) and others, we aim to optimize microbial inoculation approaches post-fire by conducting experimental manipulations across a western U.S. climate gradient.
Since 2019, I have investigated methods for promoting microbial diversity and ecosystem multifunctionality in fire-affected ecosystems. One multi-factorial experiment investigates microbial inoculation post-fire, and is supported by a federal grant from the Bureau of Land Management, awarded to Sydney Glassman’s Fungal Ecology Lab, for work in the Stephens’ Kangaroo Rat (Dipodomys stephensi) Preserve, at Lake Mathews Estelle Mountain Reserve.
Other fungi and fire projects are supported by Metabolic Studio and CoRenewal, a 501(c)3 non-profit organization that I co-founded.
In spring and summer 2020, CoRenewal offered a Fungi and Fire study group via Zoom, which invited global participation from fire-affected communities worldwide, including those from Ecuador, Australia, and Butte County, California.
Soil microbiomes and ecological restoration
My work investigating community assembly of soil fungal communities was previously funded by the Natural Communities Coalition in Orange County. This research, in collaboration with researchers from the University of California Irvine’s Center for Environmental Biology investigated the effects of ecological restoration techniques on microbial communities. For these projects, I evaluated how fungal functional groups respond to disturbance and influence ecosystems to support restoration outcomes. I presented the findings from this research as an invited speaker in special sessions at the Ecological Society of America‘s annual meeting in Portland, the International Conference on Mycorrhizae in Prague, and the California Invasive Plant Council Symposium in Riverside, California. Moreover, findings from my research have already been used by land managers and directly incorporated into best practices for restoring degraded landscapes.
Fungal pathogens and restoration ecology
At UC Riverside, through the Center for Conservation Biology, I collaborated with Edie Allen and Mike Allen to explore the potential for Ustilago species (smut fungi) to control exotic annual brome grasses. I investigate dispersal limitations and host specificity dynamics for these smut fungal pathogens. Moreover, I examine constraints and challenges associated with promoting this fungal pathogen as a biocontrol of exotic grasses in degraded ecosystems.
Dispersal of airborne fungi
Southern Sierra Critical Zone Observatory
I aim to link fungal functional traits with dispersal patterns observed in airborne fungi within the aeolian microbiome. In my collaborative research with Emma Aronson, I compare fungal pathogens from dust, rain, and snow within an elevation gradient in the Southern Sierra Critical Zone Observatory (CZO). At the Southern Sierra CZO, I examine how dispersal influences dust-associated fungal communities. Specifically, I sequence aeolian dust and soil fungal communities, paired with isotopic analyses of dust particles, to document fungal communities introduced at each elevation over time, while also determining the source location from where these fungi are passively dispersing.
My findings suggest that compositionally distinct fungal communities are dispersing temporally to each elevation in the Sierra Nevada (Maltz et al. in prep). Moreover, the origin of aeolian materials may depend on either regional (Central Valley) or long-distance (Gobi Desert, China) patterns of drought or precipitation regimes, as detailed in Aciego et al. 2016, Nature Communications and Aarons et al. 2019, Aeolian Research. The National Science Foundation’s EarthCube and RAPID grants supported our research examining the role of drought in determining the community structure of dust-associated airborne microbial communities. Check out this comic by Michelle Gilmore on our work in the Sierra Nevada Mountains, entitled: A Tale of Two Dust Specks
Aeolian microbes and the lung microbiome
We are exploring the response of the aeolian microbiome to increased erosion of material previously covered by Salton Sea. These aeolian inputs may alter microbial dispersal and increase aerosolized toxins, which will likely impact air quality and human health. I examine low-impact methods for reducing airborne pathogen burdens and minimizing dust emissions.
Moreover, exposure to soil or airborne fungal pathogens and aeroallergans influences the lung microbiome upon inhalation. Using a novel environmental exposure chamber, I expose mice to collected aeolian materials to interrogate the direct effect of inoculation of single or multiple microbial taxa on the mouse-lung microbiome and their immune responses. My preliminary results suggest that chronic exposure to aerosolized suspensions of fungal allergens, such as the airborne fungus Alternaria alternata, can shift the lung microbiome and induce lung allergic inflammatory responses in naïve mice within only 96 hours, while the commonly used intranasal exposure did not produce as large a response. Our group received a U54 Center Grant from the NIH to support our work on health disparities, air pollution, and the lung microbiome. This work also resulted in my fellowship from the University of California’s Office of the President (UC President’s Postdoctoral Fellowship).
Dispersal of soil fungi
My postdoctoral research disentangles the effects of dispersal from biotic or environmental filtering. Using greenhouse assays, microscopy, and molecular techniques, I characterize the plant seed and fungal spore bank across intact and degraded sites. Specifically, by transplanting salvaged topsoil, which contains plant seed and fungal spore banks from intact ecosystems, into degraded recipient sites, I simulate regional dispersal and manipulate propagule pressure to monitor community assembly in landscape-scale field restoration experiments. In collaboration with the University of California’s Center for Environmental Biology, I use a randomized-block design to examine the relative importance of local interactions among co-existing species, priority effects, propagule pressure, and abiotic factors in driving differences in plant and fungal communities. Along with an undergraduate honors student co-first-author, in affiliation with the Center for Environmental Biology, we published a manuscript detailing these findings in a special issue of Diversity (invited) dedicated to Microbial interactions with invasive plants.
Fungal biogeochemical cycling
Carbon cycling
I am interested in how microbes mediate important biogeochemical reactions relevant to global change, especially within extreme environments. My collaborative research with Exequial Ezcurra at UC Riverside and Matthew Costa at UC San Diego investigates whether fungal biogeochemical reactions are fundamental to carbon stabilization within mangrove sediments in La Paz, Mexico. Our research about microbial communities in deep mangrove sediments and fungal carbon cycling was presented at both ESA in Portland, OR and in Mérida, Yucatán, Mexico at the meeting of the Association for Tropical Biology and Conservation.
Ectomycorrhizal inoculation may promote plant and soil recovery in forested ecosystems. My recently published paper in the special issue of Fungal Ecology, dedicated to the Ecology of Mycorrhizas in the Anthropocene, examines the role of ectomycorrhizal inoculation in ameliorating the impact of acid rain on soil properties and microbial communities associated with Pinus massoniana seedlings. In this study, we found that ectomycorrhizal inoculation increased soil organic matter and altered both fungal and microbial community composition in severely-acidic treatment plots.
Nitrogen cycling
In addition to the role of fungi in carbon cycling, I investigate feedbacks associated with fungal nitrogen cycling. Fungal traits, such as mycorrhizal exploration type, or hydrophobic versus hydrophilic mycelium, may influence resource diffusion from fungal hyphae. Abiotic factors such as depth, NH4+, CO2, O2, and water availability may also alter N mobilization or N diffusion. In cases where deep fungal geobiological weathering is increased, I expect more available surficial N, if mycorrhizal fungi deliver more N to their plant hosts or potentially emit more N into terrestrial environments. A majority of this N could be acquired directly from the soil by plant roots,
or it could be used to fuel biogeochemical N transformation processes mediated by soil microbes.
This research on fungal geobiological weathering of nitrogen from the deep lithosphere, in collaboration with Kathleen Treseder at UC Irvine, Ben Houlton at UC Davis, Jennifer Pett-Ridge at Lawrence Livermore National Labs and Seulgi Moon at UCLA, provides insight about feedbacks between global change and ecosystem processes at multiple scales.
Microbial facilitation of soil and ecosystem health
My overarching research goal is to determine how microbial groups respond to environmental stress, and whether their responses are correlated with their effect on important ecosystem processes. Along with my collaborators, I focus primarily on fungi, to identify taxa that perform critical ecosystem services such as facilitation of native plant biodiversity, soil stabilization, and carbon sequestration. This research aims to determine the responses of these fungal taxa to environmental characteristics such as dominance by invasive plant species, distribution of plant functional groups, and restoration practices. I just submitted a USDA NIFA AFRI proposal aimed at evaluating the role of microbial groups in promoting soil and ecosystem health in sustainable agro-ecosystems, including the Irvine Ranch Conservancy Native Seed Farm. Moreover, it provides new insight into basic biological questions related to microbial biogeography, controls over fungal community dynamics and biodiversity, and the ecological consequences of disturbance.