Tue, Aug 16, 2022: 5:00 PM-6:30 PM
ESA Exhibit Hall
Background/Question/MethodsEctomycorrhizal (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/ConclusionsPreliminary 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.
Results/ConclusionsPreliminary 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.