Elisabeth Ward – Harper Prize Shortlist

Throughout April, we are featuring the articles shortlisted for the 2021 Harper Prize. The Harper Prize is an annual award for the best early career research paper published in Journal of Ecology.

Elisabeth Ward’s article ‘Ericoid mycorrhizal shrubs alter the relationship between tree mycorrhizal dominance and soil carbon and nitrogen‘ was one of those shortlisted for the award.

⭐️About me:

My professional work has always been linked to plants both through academic research and through the lens of a practitioner. I am currently a fourth-year Ph.D. candidate jointly affiliated with the New York Botanical Garden and the Yale School of the Environment, where I also completed a Master of Forest Science degree in 2018. My undergraduate research at Brown University and my Masters work at Yale focused on urban forest ecology in Boston and New York City, respectively, where I had the opportunity to engage with the public in the field on a daily basis. Before graduate school, I worked as a horticulturist at a public garden and in a land management position focused on plant conservation with the U.S. government. Together these positions, along with my training at a professional forestry school, taught me the value of integrating research into land management and communicating my work to the public—practices which I am committed to carrying forward in my academic career.

🔎About the shortlisted article

The shortlisted study is my first published dissertation chapter, which investigates how interactions between understory ericoid mycorrhizal (ErM) plants (e.g. species of heather, rhododendron, and laurel) and overstory tree mycorrhizal associations influence carbon and nitrogen dynamics in forests. Recent interest in the ecosystem biogeochemical effects of plant-mycorrhizal associations has primarily focused on the relative abundance of arbuscular (AM) versus ecto- (EcM) mycorrhizal trees, particularly in temperate forests in which these two groups account for the majority of plant biomass. Our study extends this framework by considering the effects of ErM shrubs, which are also common in temperate forests (Fig. 1) but are less often studied than AM and EcM trees. Because ErM shrubs occupy a different vertical niche, they can co-occur and hence interact with AM and EcM trees. Work conducted in boreal forests has shown that the effects of ErM shrubs in EcM-dominated forests can be substantial, yet the biogeochemical effects of co-occurring ErM shrubs with AM and EcM trees have seldom been explored in temperate forests.

Fig. 1 Plants that associate with ericoid mycorrhizal fungi are common in the understory of temperate forests in the eastern U.S. and include: (b) mountain laurel (Kalmia latifolia), (c) great laurel (Rhododendron maximum), and (d) black huckleberry (Gaylussacia baccata). Photo credits: (b) Elisabeth Ward, (c) Ken Thomas/Wikimedia commons (Burke County, North Carolina, U.S.), (d) Mary Ward (Suffolk County, New York, U.S.).

This study used data collected across an AM versus EcM tree relative abundance gradient with varying levels of ErM plant cover to test hypotheses regarding the combined effects of ErM shrubs and AM versus EcM trees on soil organic matter dynamics (Fig. 2). Given the relative scarcity of data on ErM shrubs, we also analyzed two regional datasets from the eastern United States to estimate the abundance and richness of ErM plants in forests in this region as well as the extent to which they co-occur with AM versus EcM trees.

We found that ErM shrubs strongly altered tree mycorrhizal effects on soil carbon and nitrogen, and contrary to our expectations, the effects of ErM shrubs and EcM trees were functionally distinct (Fig. 1). Specifically, ErM shrubs were positively associated with soil organic matter, carbon, and nitrogen concentrations, whereas EcM trees were negatively associated with these variables. Additionally, tree mycorrhizal effects on soil carbon and organic matter were contingent on the presence of ErM shrubs, and the positive association between ErM and EcM plants suggests that the largely unmeasured presence of ErM shrubs could confound tree mycorrhizal dominance effects in studies that do not account for their presence. Altogether, this study bolsters the large body of work highlighting the importance of plant-fungal associations for predicting soil biogeochemical processes and extends the prevailing mycorrhizal dominance framework by including subdominant ErM shrubs.

Fig. 2 Alternative hypotheses and graphical summary of results on how understory ericoid mycorrhizal (ErM) plants could alter the relationship between arbuscular (AM) versus ecto- (EcM) mycorrhizal tree dominance and soil organic matter (SOM) content. Solid red and gray dashed lines show the hypothesized effect of EcM relative basal area on SOM with and without ErM plants, respectively.

🌳About my research

I am a forest ecologist interested in plant-microbial-soil interactions and their effects on biogeochemical processes. After I finish my Ph.D., I plan on working as a postdoctoral associate to expand the breadth of my research skills by developing new collaborations. Currently, my research focuses on basic and applied questions related to shifts in plant dominance driven by factors of global change and how they influence soil carbon and nitrogen dynamics. This work includes three interconnected topic areas: (1) interactions between under- and over-story plant-fungal associations and soil biogeochemical processes, (2) feedbacks between invasive plants, soil nutrient availability, and forest disturbance, and (3) the effects of forest management and restoration practices on soil biogeochemical processes. The systems that I work in are strongly influenced by human use, such as urbanization, land management, and logging, and I am particularly interested in applications of my research for conservation, restoration, and land management.

Find Elisabeth on Twitter and Google Scholar.

Read the full list of articles shortlisted for the 2021 Harper Prize here.

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