Drought Response of Plant Coexistence are Mediated by Arbuscular Mycorrhizal Fungi
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Date
2024-06
Authors
Tavernier, Austyn
Journal Title
Journal ISSN
Volume Title
Publisher
University of Oregon
Abstract
Climate change is predicted to alter interannual precipitation patterns and increase drought
severity and frequency. Although plant ecologists are actively investigating the impacts of
climate change, we still lack robust and generalizable predictions of future plant community
dynamics in light of novel precipitation regimes. One of the most pressing obstacles for making
these predictions is understanding how the many species in these communities, as well as the
interactions between them, respond to drought. Among the more important biotic players in
structuring herbaceous plant communities are arbuscular mycorrhizal fungi (AMF) which have
been shown to contribute to plant responses to drought at both an individual and community
level. However, the mechanisms of drought-dependent mycorrhizal effects on plant
competition have yet to be empirically assessed. To explore how AMF may modify the effect of
drought on plant competitive dynamics, we conducted a greenhouse competition experiment
within a two-by-two factorial manipulation of soil moisture and AMF presence. We used the
data from this experiment to parameterize population dynamic models for each species
(Clarkia amoena, Collinsia grandiflora, and Plectritis congesta) within each treatment
combination. We used posterior distributions of our parameter estimates to explore how
mycorrhizae and drought singularly and interactively influenced species vital rates, interaction
coefficients, and the niche and fitness differences underlying pairwise species coexistence. We
found that intrinsic growth rates of species generally decreased with drought and increased
with AMF inoculation. The effects of drought and AMF were highly variable between species
pairs. Overall, we found evidence of a three-way interaction between drought, mycorrhizae,
and species pair on niche and fitness differences and the probability of coexistence. Most
species pairs exhibited the highest probability of coexistence when both inoculated with AMF
and exposed to drought conditions. The results of this study suggest that drought and AMF
singularly and/or interactively influence the demographic parameters and interaction
coefficients underlying plant community dynamics. Differences in coexistence probability
between our treatments may implicate AMF as a key factor in whether species are able to coexist during projected increases in drought frequency. Thus, AMF could prove to be a
potentially useful tool for managing plant community resilience to climate change.
However, variable species responses to both drought and mycorrhizae suggest that under
these conditions competitive outcomes might be affected by the strength of species-specific
mycorrhizal mutualisms. Future studies on the interactive effects of mycorrhizae and droughts
on plant competition should focus on identifying axes for plant species variation which may
underlie the complex, species-specific interactions between mycorrhizal mutualisms and water
availability.
Description
16 pages
Keywords
coexistence, arbuscular mycorrhizal fungi, modern coexistence theory, drought, niche differences, fitness inequalities, mutualisms, plant competition