Research Accomplishment Reports 2007

Endophyte Effects on the Structure and Function of Tall Fescue Pasture

R.L. McCulley
Department of Plant and Soil Sciences

 

Project Description

Tall fescue occurs on >15 million hectares within the United States and is considered invasive in some native grasslands (Stubbendieck et al. 1994, Uva et al. 1997, Rudgers et al. 2005). As a forage species it has significant agronomic and economic importance to our nation. The endophyte-tall fescue relationship has received considerable attention because of the negative animal health consequences of eating high concentrations of fungal-produced ergot alkaloids. However, recent research has begun to demonstrate that this symbiotic relationship can have other significant ecological impacts, such as altering productivity-diversity relationships, community invasibility (Rudgers et al. 2004), trophic dynamics (Clay et al. 2005), and carbon sequestration rates (Franzluebbers et al. 1999).

Ecosystem effects of the endophyte-plant symbiosis are known to vary depending on environmental factors, particularly drought, which is significant given that climate models predict alterations in precipitation and temperature resulting from global change for much of the range in which tall fescue is currently grown.

The proposed research will determine if reported ecosystem effects of endophyte infection on soil nutrient pools and microbial communities in tall fescue pastures in Georgia are observed across a broader geographic range of sites. In addition, this research will determine whether endophyte infection status alters the ability of tall fescue to respond to changes in climate. These objectives will help clarify the complicated relationships between climate, endophyte infection status, and tall fescue pasture structure and function. As such, this research will further our understanding of the endophyte-plant symbiosis and its effect on the environment, and help the scientific community predict the consequences of climate change on forage production.

This past year we identified and sampled ~14 sites, located throughout the southeastern U.S., with extant, paired stands of endophyte-infected and endophyte-free tall fescue. We sampled the vegetation (for % tall fescue cover and endophyte infection frequency) and the soils (0-10 cm depth) at all these locations during the summer of 2007. We have completed all the lab work on these samples (including soil nutrient and microbial community composition analyses). We are currently analyzing the data and writing the results up. We have presented the data at two national meetings, and will contribute results to extension led field days this coming summer.

Significant and interesting new knowledge on the ecosystem-level effects of the tall fescue-endophyte symbiosis has resulted from this work. Furthermore, this work has led to new proposal development (one was recently submitted to the USDA-NRI Soil Processes Program, and a second was funded by DOE-NICCR in November 2007).

Impact

This project will contribute to an increased knowledge of how the fungal endophyte-tall fescue sybmiosis impacts environmental health and quality in southeastern pastures. It may have some implications for retaining endophtye infected tall fescue within pasture systems, despite the known animal health consequences.

Publications

Siegrist, J.A. and McCulley, R.L. (2007) Endophyte effects on soil nutrient pools, microbial communities, and litter decomposition rates in tall fescue pasture. ASA-CSSA-SSSA Annual Meeting Abstract, New Orleans, LA.

Siegrist, J.A. and McCulley, R.L. (2008) Endophyte effects on soil nutrient pools, microbial communities, and litter decomposition rates in tall fescue pasture. AFGC-SRM Joint Annual Meeting Abstract, Louisville, KY.