I am an ecologist enthralled with wild lands, the plant and soil microbial communities that populate them, and the future of their existence. I am passionate about using basic science to create knowledge that can be used to support sustainable restoration and management needs in dryland ecosystems.
I am a Research Ecologist with the U.S. Geological Survey, Pacific Island Ecosystem Research Center in Volcano, HI. Prior to this, I was Post-Doctoral Research Scientist with the U.S. Geological Survey, Southwest Biological Science Center in Moab, UT. I received my PhD in Plant Biology with an emphasis on Ecology from University of California, Riverside and M.S. in Environmental Science from American University.
My research bridges multiple disciplines to build a better understanding of how biotic interactions and global change mediate community assembly of plants and soil microbes to affect emergent ecosystem functions. I integrate community, ecosystem, plant and microbial ecology in my research by using statistical modeling to combine data from a diversity of approaches (field, greenhouse, sensor networks, soil chemistry and molecular biology techniques).
Biological soil crust recovery in a warmer world
Biological soil crusts provide a myriad of ecosystem functions and are highly sensitive to physical disturbance. In addition to physical disturbance, contemporary data suggest that climate change can alter biocrust community composition and function on fast (sub-decadal) timescales. While we have a strong sense of the vulnerability of biocrusts to change, few studies have tracked trajectory of biocrust community composition and function recovery after disturbance. Here, we use long-term physical and climate disturbance experiments to follow recovery of biocrusts in an effort to build a ‘clock’ from which we can better predict how biocrust communities and the processes they regulate fluctuate over the course of recovery. We use a study at three sites on the Colorado Plateau, where we applied climate change and physical disturbance treatments for nearly a decade. We ceased the strongest disturbance factors (physical trampling and altered precipitation) and allowed the communities to recover for five years. I am using Bayesian structural equation models to tease out the trajectory of biocrust constituents following the cessation of physical and climate disturbance, both under ambient and elevated temperatures. Check out our results in Nature Climate Change.
Anthropogenic Nitrogen Deposition on the Colorado Plateau
Nitrogen deposition is significantly altering both community structure and ecosystem processes in terrestrial ecosystems across the globe. However, our understanding of the consequences of N deposition in dryland systems remains relatively poor, despite evidence that drylands may be particularly vulnerable to increasing N inputs. In this study, we use a long-term nitrogen deposition experiment in Arches National Park. We investigate the influence of multiple levels of simulated N deposition on on plant community structure and biological soil crust (biocrust) cover at three semi-arid grassland sites spanning a soil texture gradient. Biocrusts are a surface community of mosses, lichens, cyanobacteria, and/or algae and have been shown to be sensitive to N inputs. Teasing apart the ecosystem effects of N deposition on these vast and heterogenous systems is critical, yet the majority of dryland N deposition research focuses on systems with a Mediterranean climate and highly urbanized areas with large rates of deposition downwind. Check out our results in Oecologia.
Determining successful management and restoration strategies for
maintaining pinyon-juniper communities in the face of change
Pinyon-juniper woodlands are a dominant vegetation type across the Intermountain West and these systems are experiencing significant effects from increasing fire and from treatments designed to reduce the frequency and intensity of fire (e.g., stand thinning). Wildfire occurrence and severity are rising and are expected to continue to rise. Shifts in fire regimes have many consequences for Pinyon-Juniper woodlands that comprise over a million acres of public lands. In particular, losses of Pinyon-Juniper woodlands represent large challenges for land managers tasked with protecting, restoring, and facilitating the use of these vast landscapes. This project was co-developed by managers and researchers from multiple agencies: USGS, Northern Arizona University, National Park Service and the Ute Mountain Ute Tribe. Goals of this project are: (1) Determine the influence of fire and stand thinning on community composition and ecosystem functions; (2) Assess how thinning and fire affect Pinyon-Juniper regeneration; (3) Test innovative restoration actions that facilitate Pinyon-Juniper recovery in burned areas, (4) incorporate strategies into management, fuels treatment, and post-fire recovery plans.
Water-use and phenological strategies of invasive plants
Terrestrial plant invasion is one of the greatest threats to biodiversity and contributors to habitat loss worldwide. Invasion by annual grasses has had wide spread effects on resource availability, disturbance regimes and other ecosystem functions. Invasive annual grasses are drought escapers that may have short-lifespan, fine roots for rapid nutrient uptake. Alternatively, drought tolerant shrubs are highly dependent on seasonal precipitation events for recharge through the soil profile and are likely to possess long-lived relatively less efficient fine roots. To understand how differences in root development relate to soil-water dynamics between a chaparral shrub and an invasive grass, I used soil moisture sensors, manual minirhizotron imagery, stable isotopes (C, N and O), sap flux sensors and normalized difference vegetation index (NDVI) to track activity from the beginning of the rainy season to the onset of the summer drought. Check out the paper in American Journal of Botany.
Fungal community assembly
in response to global change
Fungal community composition in the Anthropocene is driven by rapid changes in environmental conditions caused by human activities. Many fungal functional groups may respond to drivers of global change, including arbuscular mycorrhizal fungi (AM), ectomycorrhizal fungi (EM), saprotrophs and pathogens. AM are plant mutualists, providing host plants with resources (nutrients and water) in exchange for photosynthetically derived carbon. N deposition and invasion of non-native plant species have the potential to shift the structure and function of both AMF and broader fungal communities. I examined the relative importance of two global change drivers – atmospheric nitrogen (N) deposition and annual grass invasion – on structuring fungal communities in a California chaparral ecosystem, with emphasis on arbuscular mycorrhizal fungi. We used molecular markers, functional groupings, generalized linear statistics and joint distribution modeling, to examine how environmental variables structure taxonomic and functional composition of fungal communities. Check out the paper in Fungal Ecology. Further, I explored the effects of invasive-conditioned soils on chaparral seedlings using a greenhouse experiment with invasive, native and sterile inoculum treatments. Check out the paper in Applied Soil Ecology.
Links to publications are provided below.
Please email me if you cannot access the publication and would like a PDF.
Osborne, B. B., Roybal, C. M., Reibold, R., Collier, C. D., Geiger, E., Phillips, M. L., Weintraub, M.N., Reed, S. C. (2022). Biogeochemical and ecosystem properties in three adjacent semi‐arid grasslands are resistant to nitrogen deposition but sensitive to edaphic variability. Journal of Ecology, https://doi.org/10.1111/1365-2745.13896
Collins, C.G., Phillips, M. L., Beals, K., Bailey, L., O'Brian, J., Dhungana, I., Jech, S. (2022) Mentoring is more than a mentor. Frontiers in Ecology and the Environment, https://doi.org/10.1002/fee.2518
Phillips, M. L., Mcnellis, B. E., Howell, A., Lauria, C. M., Belnap, J., & Reed, S. C. (2022). Biocrusts mediate a new mechanism for land degradation under a changing climate. Nature Climate Change, https://doi.org/10.1038/s41558-021-01249-6
Steven, B., Phillips, M.L., Belnap, J., Gallegos-Graves, L.V., Kuske, C.R., Reed, S.C. (2021) Resistance, Resilience, and Recovery of Dryland Soil Bacterial Communities Across Multiple Disturbances. Frontiers in Microbiology, https://doi.org/10.3389/fmicb.2021.648455
Phillips, M.L., Winkler, D.E., Reibold, R.H., Osborne, B.B., Reed, S.C. (2021) Muted responses to chronic experimental nitrogen deposition on the Colorado Plateau. Oecologia, https://doi.org/10.1007/s00442-020-04841-3
Howell, A., Winkler, D., Phillips, M.L., McNellis, B., and Reed, S.C. (2020) Warming shortens
growing season length of the dominant invasive Bromus tectorum (cheatgrass). Frontiers in Plant Science, https://doi.org/10.3389/fpls.2020.570001
Collins, C.G., Spasojevic, M., Alados, C., Aronson, …, Phillips, M.L, …, Diez, J. (2020) Belowground Impacts of Alpine Woody Encroachment are determined by Plant Traits, Local Climate and Soil Conditions. Global Change Biology, https://doi.org/10.1111/gcb.15340
Phillips, M.L., Aronson, E.L., Maltz M.M., Allen, E.B. (2020) Native and invasive inoculation
source can modify fungal community assembly and biomass production of a chaparral shrub. Applied Soil Ecology, https://doi.org/10.1016/j.apsoil.2019.103370
Schmidt, K.T. Maltz, M.R., Ta, P., Khalili, Weihe, C., Phillips, M.L., Aronson, E.A., Lulow, M., Long, J., Kimball, S. (2020) Identifying Mechanisms for Successful Ecological Restoration with Successful Ecological Restoration with Salvages Topsoil in Coastal Sage Scrub Communities. Diversity, https://doi.org/10.3390/d12040150
Phillips, M.L., McNellis, B.E, Allen, M.F., Allen, E.B. (2019) Differences in root phenology and water depletion by an invasive grass explains persistence in a Mediterranean ecosystem. American Journal of Botany,
Phillips, M.L., Weber, S.E., Andrews L.V., Aronson, E.A, Allen, M.F., Allen, E.B. (2019)
Allen, E.B., Williams, K. Beyers, J.L. Phillips M.L., Ma, S., D’Antonio, C.M. “Chaparral Restoration.”
Valuing Chaparral: Ecological, Socio-Economic and Management Perspectives. Springer, Cham, 2018.
Women in Soil Ecology (WISE)
Our network is aimed at connecting women scientists to build a strong community and further the fight for equity of all those identifying as womxn in science. We aim to establish connections among senior and junior ecologists through meetups, workshops, and peer-to-peer mentorship. Our network includes women from across the US and abroad in University, Government, NGOs and Non-profit positions all connected through Soil Ecology! Check out our website for upcoming events and meetings here!