Year of Publication

2011

Degree Name

Doctor of Philosophy (PhD)

Document Type

Dissertation

College

Agriculture

Department

Crop Science

First Advisor

Dr. Rebecca McCulley

Second Advisor

Dr. Timothy Phillips

Abstract

Tall fescue, a cool-season grass native to Europe, central Asia, and northern Africa, has been widely distributed throughout the U.S. for use as turf and forage. Following its widespread planting, its ability to associate with a toxic fungal endophyte, Neotyphodium coenophialum, was discovered. Research has linked this fescue-endophyte association with increased biotic and abiotic stress resistance in endophyte-infected (E+) versus endophyte-free (E-) plants, and these differences may affect the ability of land managers to eradicate tall fescue and restore native grasslands. I conducted three studies to examine whether E+ tall fescue plants respond differently to management than E- plants, and whether the success of planted native species might be impacted via indirect soil effects. My overall hypotheses were that E+ plants would recover from restoration/eradication efforts better than E- plants, and that E+ fescue would reduce microbial symbionts in the soil needed by planted native species.

I first conducted a field study of a tall fescue pasture consisting of four sub-units being restored with different combinations of prescribed burns and/or herbicide applications, as well as an unmanaged control. I found no evidence of E+ plants preferentially surviving restoration management; however this field had unusually low endophyte infection rates to begin with. The second study was a greenhouse experiment in which I measured growth of E+ and E- plants exposed to different watering regimes (wet, dry) and prescribed burn treatments (none, one, or two burns). Watering regime significantly affected all measured growth parameters (wet>dry), but few endophyte effects were found and when present were opposite the hypothesis (E->E+). All burned plants quickly re-grew tiller lengths comparable to the unburned control, with recovery occurring faster following the second burn compared to the first. My final study examined growth and arbuscular mycorrhizal colonization of native species planted by seed into soil from beneath E+ and E- tall fescue. I observed few differences in mycorrhizal colonization or biomass for seedlings between soil from E+ and E- tall fescue. Taken together, my results indicate endophyte status of tall fescue pastures being restored to native grassland species may not be important in governing restoration success.

Share

COinS