Effects of Invasive Grass on Soil Composition Differ Based on Tree Root Fungus Association

Impacts of an invasive grass on soil organic matter pools vary across a tree-mycorrhizal gradient.

The Science

Most trees associate with one of the two main types of root fungus or the other. The relationship between tree and fungus affects how a tree gains nutrients and alters and processes the soil around it. Invasive plants that invade wide-ranging habitats, accumulate biomass rapidly, and contribute copious amounts of carbon to soil can have significant effect on soil composition. This study shows that these grasses change soil organic matter of trees differently based on their fungal association.

The Impact

Although this study focuses on the impact of invasive grasses, the ability of these invasive species to deposit carbon was used as a tool to observe how non-specific sources of foreign carbon inputs into soil causes plants and microbes to alter their nutrient acquisition strategies. The results of this study emphasize the importance of resolving the long-term and global effects of enhanced carbon inputs in natural systems.


An invasive grass that had a particular carbon isotope signature was observed in plots of plants with a different carbon signature such that the carbon contributions to the soil from the invasive species could be measured and compared to pre-invasion measurements. It was found that one of the root-fungal association, arbuscular mycorrhizal (AM), was generally unresponsive to invasion while the other type, ectomycorrhizal (ECM), altered the composition of its soil presumably to access more nitrogen. This alteration of soil organic matter may cause long term or global effects to carbon cycling that needs to be studied further.

Principal Investigator

Joshua Fisher
University of California, Los Angeles/NASA Jet Propulsion Laboratory

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science


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


Craig, M. E., N. Lovko, S. L. Flory, et al. "Impacts of an invasive grass on soil organic matter pools vary across a tree-mycorrhizal gradient". Biogeochemistry 144 (2), (2019). https://doi.org/10.1007/s10533-019-00577-2.