Akihiro Koyama

Akihiro Koyama

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Assistant Professor, Soil Microbiology and Biogeochemistry
Department of Forestry



Ph. D., Natural Resources, University of Idaho, 2007

M. Sci., Forest Resources, University of Idaho, 2002

B. Sci., Forest Science, Tokyo University of Agriculture and Technology, 1995

Research Interests

My research goal is to better understand plant-microbe interactions in the rhizosphere and their roles in ecosystem processes. Specifically, I want to study how interactions between plants and soil microbes shape ecosystem-level processes, such as nutrient cycling and plant community dynamics, across space and time, in response to changing environments. My current and past research projects focus on:

  • The roles of soil and root microbiomes in plant community dynamics (e.g. plant invasion) through plant-soil feedbacks using Next-Generation Sequencing (e.g. Illumina)
  • Responses of soil microbial communities to global change factors (e.g., warming, elevated CO2, altered precipitation regime) and consequent dynamics of greenhouse gases (CO2, CH4 and N2O), and
  • Effects of disturbances (e.g. forest fires, N deposition, warming and drought) on nutrients and energy cycling mediated by soil microbes and plants.

In summary my research is centered at the interface between below-ground microbiology, biogeochemistry and ecosystem ecology.



Fahey, C., Koyama, A., Antunes, P.M., Dunfield, K. & Flory, S.L. (2020). Plant communities mediate the interactive effects of invasion and drought on soil microbial communities. The ISME Journal. DOI: 10.1038/s41396-020-0614-6 

Koyama, A., H. Maherali, and P. M. Antunes. 2019. Plant geographic origin and phylogeny as potential drivers of community structure in root-inhabiting fungi. Journal of Ecology 107:1720-1736.

Koyama, A., Harlow, B., Evans, R.D., 2019. Greater soil carbon and nitrogen in a Mojave Desert ecosystem after 10 years exposure to elevated CO2. Geoderma 355, 113915.

Dukes, A.E., A. Koyama, K.E. Dunfield, P.M. Antunes (2018). Enemy of my enemy: Evidence for variable soil biota feedbacks of Vincetoxicum rossicum on native plants. Biological Invasions. doi: 10.1007/s10530-018-1804-2

Tfaily, M.M., N.J. Hess, A. Koyama, R.D. Evans. (2018) Changes in organic matter composition and substrate diversity under elevated [CO2] in a Mojave Desert ecosystem. Geoderma. 330:1-8

Koyama, A., B. Harlow, C.R. Kuske, J. Belnap, R.D. Evans. (2018) Mechanisms of soil organic carbon and nitrogen accumulation in a Mojave Desert ecosystem after 10 years exposure to elevated carbon dioxide. Soil Biology and Biochemistry. 120:48-57


Koyama, A., J.M. Steinweg, M.L. Haddix, J.S. Dukes, M.D. Wallenstein. (2018) Soil bacterial community structured by plants in response to altered precipitation and temperature regimes in an old field grassland. FEMS Microbiology Ecology. 94:fix156-fix156

Koyama, A., O. Pietrangelo, L. Sanderson, P.M. Antunes (2017) An empirical investigation of the possibility of adaptability of arbuscular mycorrhizal fungi to new hosts. Mycorrhiza. DOI: 10.1007/s00572-017-0776-x


Wang, X., E. Agathokleous, L. Qu, S. Fujita, M. Watanabe, Y. Tamai, Q. Mao, A. Koyama, T. Koike. (2017) Effects of simulated nitrogen deposition on ectomycorrhizae community structure in hybrid larch and its parents grown in volcanic ash soil: the role of phosphorous. Science of the Total Environment. DOI: 10.1016/j.scitotenv.2017.08.283


Carrillo, Y., C. Bell, A. Koyama, A. Canarini, C.M. Boot, M. Wallenstein, E. Pandel. (2017) Plant traits, stoichiometry and microbes as drivers of decomposition in the rhizosphere in a temperate grassland. Journal of Ecology. DOI: 10.1111/1365-2745.12772


Thompson, M.T.C., A. Koyama*, K.L. Kavanagh. (2016). Wildfire effects on physiological properties in conifers of central Idaho forests, USA. Trees – Structure and Function. DOI: 10.1007/s00468-016-1489-z


Alster, C. J., A. Koyama, N. G. Johnson, M. D. Wallenstein, J. C. von Fischer (2016). Temperature sensitivity of soil microbial communities: an application of macromolecular rate theory to microbial respiration. Journal of Geophysical Research: Biogeosciences:2016JG003343. DOI: 10.1002/2016JG003343


Judd, C.R., A. Koyama, M.P. Simmons, P. Brewer, J.C. von Fischer (2016) Co-variation in methanotroph community composition and activity in three temperate grassland soils. Soil Biology and Biochemistry. DOI: 10.1016/j.soilbio.2015.12.014


Stephan, K., K. L. Kavanagh, A. Koyama. (2015) Influence of fire on watershed nitrogen cycling using 15N natural abundance in terrestrial and aquatic ecosystem components. PloS ONE 10:e0119560.


Wang, X., L. Qu, Q. Mao, M. Watanabe, Y. Hoshika, A. Koyama, K. Kawaguchi, Y. Tamai, T. Koike. (2015) Ectomycorrhizal colonization and growth of the hybrid larch F1 under elevated CO2 and O3. Environmental Pollution. 197:116-126.


Koyama, A., Wallenstein, M.D., Simpson, R.T., and Moore, J.C. (2014). Soil bacterial community composition altered by increased nutrient availability in Arctic tundra soils. Frontiers in Microbiology 5. DOI: 10.3389/fmicb.2014.00516


Evan, R.D., A. Koyama, D. Sonderegger, T.N. Charlet, B. Newingham, L.F. Fenstermaker, B. Harlow, V.L. Jin, K. Ogle, S.D. Smith, R.S. Nowak. (2014) Greater ecosystem carbon in the Mojave Desert after ten years exposure to elevated CO2. Nature Climate Change. DOI:10.1038/NCLIMATE2184.


Moore, J.C., R.B. Boone, A. Koyama, K. Holfelder. (2014) Enzymatic and Detrital Influences on the Structure, Function, and Dynamics of Spatially-Explicit Model Ecosystems. Biogeochemistry: 1-23. DOI: 10.1007/s10533-013-9932-3


Koyama, A., M.D. Wallenstein, R.T. Simpson and J.C. Moore. (2013). Carbon-degrading enzyme activities stimulated by increased nutrient availability in Arctic tundra soils. PLoS ONE 8: e77212. DOI: 10.1371/journal.pone.0077212.

Stephan, K., K.L. Kavanagh, A. Koyama. (2012). Effects of spring prescribed burning and wildfires on watershed nitrogen dynamics of central Idaho headwater areas. Forest Ecology and Management. 263: 240-252. DOI: DOI:10.1016/j.foreco.2011.09.013.

Koyama, A., K. Stephan, K. L. Kavanagh. (2011). Fire effects on gross inorganic N transformation in riparian soils in coniferous forests of central Idaho, USA: Wildfires vs. prescribed fires. International Journal of Wildland Fire. 21(1) 69-78.

Koyama, A., K.L. Kavanagh, K. Stephan. (2010). Wildfire effects on gross nitrogen transformation rates in mineral soils in coniferous forests of central Idaho, USA. Ecosystems 13(7): 1112-1126. DOI: 10.1007/s10021-010-9377-7.

Koyama A., K.L. Kavanagh, A. Robinson. (2005). Marine nitrogen in central Idaho riparian forests: evidence from stable isotopes. Canadian Journal of Fisheries and Aquatic Sciences 62: 518-526.