Experimental warming decreases arbuscular mycorrhizal fungal colonization in prairie plants along a Mediterranean climate gradient.
BACKGROUND
Arbuscular mycorrhizal fungi (AMF) provide numerous services to their plant symbionts. Understanding climate change effects on AMF, and the resulting plant responses, is crucial for predicting ecosystem responses at regional and global scales. We investigated how the effects of climate change on AMF-plant symbioses are mediated by soil water availability, soil nutrient availability, and vegetation dynamics.


METHODS
We used a combination of a greenhouse experiment and a manipulative climate change experiment embedded within a Mediterranean climate gradient in the Pacific Northwest, USA to examine this question. Structural equation modeling (SEM) was used to determine the direct and indirect effects of experimental warming on AMF colonization.


RESULTS
Warming directly decreased AMF colonization across plant species and across the climate gradient of the study region. Other positive and negative indirect effects of warming, mediated by soil water availability, soil nutrient availability, and vegetation dynamics, canceled each other out.


CONCLUSIONS
A warming-induced decrease in AMF colonization would likely have substantial consequences for plant communities and ecosystem function. Moreover, predicted increases in more intense droughts and heavier rains for this region could shift the balance among indirect causal pathways, and either exacerbate or mitigate the negative, direct effect of increased temperature on AMF colonization.
Department of Biology, University of Oregon , Eugene, Oregon , United States.
Hannah
H
Wilson
Department of Landscape Architecture, University of Oregon , Eugene, Oregon , United States.
Bart R
BR
Johnson
Institute of Ecology and Evolution, University of Oregon , Eugene, Oregon , United States.
Brendan
B
Bohannan
Institute of Ecology and Evolution, University of Oregon , Eugene, Oregon , United States.
Laurel
L
Pfeifer-Meister
Department of Biology, University of Oregon , Eugene, Oregon , United States.
Rebecca
R
Mueller
Institute of Ecology and Evolution, University of Oregon , Eugene, Oregon , United States.
Scott D
SD
Bridgham
Arbuscular mycorrhizal fungi; Climate change; Experimental warming; Mediterranean; Nutrient availability; Pacific Northwest; Plant-nutrient interactions; Structural equation models