October 14, 2017

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Tree Spatial Coexistence Determined by Root Fungus Association

Mycorrhizal associations and the spatial structure of an old‐growth forest community.

The Science

Plants alter the composition of the soils that they grow in to either keep plants with negative interactions away or bring plants with positive interactions closer. Most plants and trees also have a symbiotic relationship with fungus that grow on their roots that work together to cycle nutrients in the soil and help each other grow. This paper shows that the root fungus association of plants governs the spatial distribution of both saplings and old-growth trees in mature forests.

The Impact

Prior to this study it had only been shown that saplings had distinct distribution patterns within a forest based on the fungus that grows on their roots. This study shows that there are distinct distributions of old-growth trees as well. Root fungal association along with other important community structure mechanisms like seed dispersal and seed germination can be used to predict future spatial structures of forests.

Summary

It was shown through spatial analysis of saplings and old-growth trees that root fungus association plays a large part in the distribution of plants in a forest. One hypothesis for why this happens is that some fungal associations are prone to pathogens so these plants tend to grow farther away from each other so they’re less likely to spread the pathogens. The other hypothesis is that one type of fungal association has enzymes used to extract nutrients from the soils around them so it is advantageous for these plants to huddle together to better break down soils in the same plot. These hypotheses do not contradict each other and together could explain the community structures.

Principal Investigator

Joshua Fisher
University of California, Los Angeles/NASA Jet Propulsion Laboratory
joshbfisher@gmail.com

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
daniel.stover@science.doe.gov

Funding

U.S. Department of Energy, Office of Biological and Environmental Research, Terrestrial Ecosystem Science Program, and National Science Foundation Ecosystem Science.

References

Johnson, D. J., K. Clay, and R. P. Phillips. "Mycorrhizal associations and the spatial structure of an old-growth forest community". Oecologia 186 (195–204), (2018). https://doi.org/10.1007/s00442-017-3987-0.