PS 30-108 - Soil microbes and diversity maintenance in Asian dipterocarp forests: preliminary results from a plant-soil feedback experiment

Tuesday, August 16, 2022

5:00 PM – 6:30 PM EDT

Located in: ESA Exhibit Hall

Presenting Author(s)

AS

Akshay Surendra

PhD Candidate
School of the Environment, Yale University
New Haven, Connecticut, United States

Coauthor(s)

LC

Liza S. Comita

Professor
Yale School of the Environment
New Haven, Connecticut, United States

Background/Question/Methods

Ectomycorrhizal (EcM) fungi often provide host tree species with a competitive advantage by aiding in nutrient acquisition and reducing pathogen infection, which could lead to their increasing dominance and a loss of tree diversity. However, in Asian rainforests, EcM-host tree species co-occur with arbuscular mycorrhiza (AM) host tree species, and high tree diversity is maintained despite the expectation that EcM species should outcompete AM species.

To help resolve this “paradox”, we conducted a plant-soil feedback experiment with five common tree species from lowland mixed dipterocarp forests of South-West Sri Lanka. Seedlings of three EcM-host species and two AM-host species were grown in soils collected from beneath adult trees of each of the five species in a shadehouse. We predicted that (i) AM-host species will experience an away-site advantage consistent with pathogen escape and (ii) EcM-host trees will experience a home-site advantage consistent with EcM-benefit exceeding costs of pathogen escape. We modelled log-response ratio of growth against soil source to test our predictions.

Results/Conclusions

Preliminary results (three months since the start of the experiment) indicate no consistent, statistically discernible home- or away-site advantage for EcM-host and AM-host trees, respectively. Instead, individual species varied in their response to home versus away soils. For example, an away-site advantage was more common than a home-site advantage in Shorea congestiflora (all four away soils) and Bhesa ceylanica (three of four away soils). On the other hand, a home-site advantage was more common in Dipterocarpus zeylanicus (three of four away soils) as well as Horsfieldia irya (all four away soils). Home- and away- site advantages were equally frequent in Shorea trapezifolia.

Taken together, our preliminary results indicate that soil microbe-mediated (de-) stabilization may not be driven by mycorrhizal type alone. We anticipate stronger effect sizes over time as mortality and growth differences heighten over time – we will also corroborate patterns in the shadehouse with an ongoing field plant-soil feedback experiment and a census of seedlings in a nearby forest. This project is part of a comprehensive first step towards understanding soil microbe-mediated tree diversity in Asian rainforests.