Effects of a Fungal Endophyte Symbiosis on Managed Grassland Nutrient Dynamics and Resilience to Climate Change.

Plant-microbe symbioses can be important in governing ecosystem responses to climate change. One example occurs with tall fescue (Schedonorus arundinaceus), a predominant cool season forage in managed grasslands of the eastern U.S., and its leaf fungal endophyte (Epichloë coenophiala). Infection with the common toxic strain of Epichloë improves fescue’s ability to resist environmental stressors, including drought and other likely impacts of climate change, and endophyte infection can increase soil C sequestration, modify greenhouse gas (GHG) fluxes, and alter soil microbial community composition and function. However, toxic alkaloids produced by this strain of the endophyte negatively affect animal production, and have led to the inoculation of fescue with “non-toxic” strains. Whether these non-toxic endophytes confer a similar level of environmental stress resistance or GHG mitigation is unknown.

To address this knowledge gap, we will leverage two existing field projects to accomplish the following objectives: (i) Quantify the effects of fescue-fungal endophyte symbiosis on soil microbial communities, soil C pools, and GHG emissions; (ii) Quantify how different strains of fungal endophytes affect these parameters; and (iii) Determine whether manipulation of fescue-fungal endophyte symbioses can improve the resilience of managed grasslands to elevated temperature and reduced water availability, while simultaneously increasing soil C sequestration and reducing GHG emissions. The proposed work will allow us to assess whether it is possible to improve the resilience of fescue pastures, the base of animal production for much of the eastern US, and mitigate the effects of climate change on these pastures by manipulating grass-endophyte symbioses.

The experimental climate manipulations began on April 29, 2016 and are currently running. The plots originally included tall fescue material from collaborator R.D. Dinkins and Canada Wild Rye material from collaborator Carolyn Young. We added red clover to replace the Canada Wild Rye in March 2018. We are currently measuring a variety of plant and soil parameters. 

 Planting tall fescue seed in the new plots.   

Planting tall fescue seed in the new plots.

 

 Aerial view of the field site.

Aerial view of the field site.

 Climate manipulation in action! Moveable shelters cover half of the plots during precipitation events; precipitation is added at scheduled intervals to mimic a decrease in frequency and increase in intensity in rainfall. Infrared heaters heat plots 5 C above ambient temperatures.

Climate manipulation in action! Moveable shelters cover half of the plots during precipitation events; precipitation is added at scheduled intervals to mimic a decrease in frequency and increase in intensity in rainfall. Infrared heaters heat plots 5 C above ambient temperatures.

 Measuring greenhouse gases.

Measuring greenhouse gases.