Tall fescue pastures cover extensive acreage in the eastern half of the United States and contribute to important ecosystem services, including the provisioning of forage for grazing livestock. Yet little is known concerning how these pastures will respond to climate change. Tall fescue's ability to persist and provide forage under a warmer and wetter environment, as is predicted for much of this region as a result of climate change, will likely depend on a symbiotic relationship the plant can form with the fungal endophyte, Epichloë coenophiala. While this symbiosis can confer environmental stress tolerance to the plant, the endophyte also produces alkaloids toxic to insects (e.g., lolines) and mammals (ergots; which can cause “fescue toxicosis” in grazing animals). The negative animal health and economic consequences of fescue toxicosis make understanding the response of the tall fescue symbiosis to climate change critical for the region. We experimentally increased temperature (+3°C) and growing season precipitation (+30% of the long-term mean) from 2009–2013 in a mixed species pasture, that included a tall fescue population that was 40% endophyte-infected. Warming reduced the relative abundance of tall fescue within the plant community, and additional precipitation did not ameliorate this effect. Warming did not alter the incidence of endophyte infection within the tall fescue population; however, warming significantly increased concentrations of ergot alkaloids (by 30–40%) in fall-harvested endophyte-infected individuals. Warming alone did not affect loline alkaloid concentrations, but when combined with additional precipitation, levels increased in fall-harvested material. Although future warming may reduce the dominance of tall fescue in eastern U.S. pastures and have limited effect on the incidence of endophyte infection, persisting endophyte-infected tall fescue will have higher concentrations of toxic alkaloids which may exacerbate fescue toxicosis.

Background and aims Infection of tall fescue with the common toxic fungal endophyte Epichloë coenophiala harms livestock via toxic alkaloid production; therefore, non-toxic 'novel' strains of the endophyte have been developed and released. How different endophyte strains impact biological nitrogen fixation (BNF) in mixed species pastures is unknown. We asked whether novel endophyte or common toxic endophyte-infected (NE+; CTE+) tall fescue affects symbiotic and nonsymbiotic BNF, and utilization of biologically-fixed nitrogen in tall fescue. Methods Tall fescue was planted either endophyte-free (E-), infected with CTE, two non-toxic strains AR542 NE, AR584 NE, or a blend of endophyte treatments. We measured natural abundance of 15 N in plant and soil samples, and conducted soil acetylene reduction assays. Results Endophyte presence and strain significantly affected the δ 15 N of tall fescue. Near red clover, CTE+ and AR584 NE+ tall fescue were most 15 N-depleted; but away, E-tall fescue was most 15 N-depleted. Endophyte strain significantly influenced N concentration in red clover, but not symbiotic or non-symbiotic BNF.Conclusions Endophyte strains produce different effects on tall fescue's competitive ability and nitrogen utilization. In mixed pastures, deployment of NE strains for decreased alkaloid toxicity will differentially impact use of biologically fixed nitrogen in tall fescue and nitrogen concentration in red clover. Abbreviations CTE+common toxic endophyte-infected Eendophyte-free BNF biological nitrogen fixation NE+ novel endophyte-infected EMix equal mix of E-, CTE+, AR542 NE+, and AR584 NE+ treatments within plot PDF pasture demonstration farm RC red clover TF(+RC) tall fescue plant located close to red clover TF(-RC) tall fescue plant located away from red clover CF-IRMS continuous flow isotope ratio mass spectrometer ARA acetylene reduction assay Plant Soil

Grasslands in North America are increasingly threatened by land conversion and ecological degradation, prompting restoration efforts to increase native plant species diversity and improve wildlife habitat. A major challenge is the removal and management of nonnative invasive species such as tall fescue (Schedonorus arundinaceus), which has a symbiotic association with a fungal endophyte (Epichloë coenophiala) that modifies its ecological interactions. Using transplanted clumps of the cultivar Kentucky‐31, we tested the effects of endophyte infection on tall fescue's survival and performance (tiller production, flowering, and basal area) for 5 years in a central Kentucky reconstructed prairie. We predicted that endophyte infected (E+) clumps would have increased performance compared to endophyte‐free (E−) clumps. Overall, E+ clumps had greater survival, tiller production, flowering tiller production, and basal area, but not reproductive effort (proportion of tillers flowering) as compared to E− clumps. However, survival and trends in tiller number and basal area over the 5‐year period suggested experimental tall fescue populations were in decline in the reconstructed prairie, although the E− population declined more rapidly. Our study provides evidence that endophyte infection improved tall fescue's growth and survival in a postreconstruction plant community, at least in the early years following reconstruction, and may increase the invasive potential of this nonnative species in prairie restorations.

A constitutive, host-specific symbiosis exists between the aboveground fungal endophyte Epichloë coenophiala (Morgan-Jones & W. Gams) and the cool-season grass tall fescue (Lolium arundinaceum (Schreb.) Darbysh.), which is a common forage grass in the United States, Australia, New Zealand, and temperate European grasslands. New cultivars of tall fescue are continually developed to improve pasture productivity and animal health by manipulating both grass and E. coenophiala genetics, yet how these selected grass-endophyte combinations impact other microbial symbionts such as mycorrhizal and dark septate fungi remains unclear. Without better characterizing how genetically distinct grass-endophyte combinations interact with belowground microorganisms, we cannot determine how adoption of new E. coenophiala-symbiotic cultivars in pasture systems will influence long-term soil characteristics and ecosystem function. Here, we examined how E. coenophiala presence and host × endophyte genetic combinations control root colonization by belowground symbiotic fungi and associated plant nutrient concentrations and soil properties in a 2-year manipulative field experiment. We used four vegetative clone pairs of tall fescue that consisted of one endophyte-free (E−) and one E. coenophiala-symbiotic (E+) clone each, where E+ clones within each pair contained one of four endophyte genotypes: CTE14, CTE45, NTE16, or NTE19. After 2 years of growth in field plots, we measured root colonization of arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE), extraradical AMF hyphae in soil, total C, N, and P in root and shoot samples, as well as C and N in associated soils. Although we observed no effects of E. coenophiala presence or symbiotic genotype on total AMF or DSE colonization rates in roots, different grass-endophyte combinations altered AMF arbuscule presence and extraradical hyphal length in soil. The CTE45 genotype hosted the fewest AMF arbuscules regardless of endophyte presence, and E+ clones within NTE19 supported significantly greater soil extraradical hyphae compared to E− clones. Because AMF are often associated with improved soil physical characteristics and C sequestration, our results suggest that development and use of unique grass-endophyte combinations may cause divergent effects on long-term ecosystem properties.

Climate change will significantly impact the world’s ecosystems, in part by altering species interactions and ecological processes, such as herbivory and plant community dynamics, which may impact forage quality and ecosystem production. Yet relatively few field experimental manipulations assessing all of these parameters have been performed to date. To help fill this knowledge gap, we evaluated the effects of increased temperature (+3°C day and night, year-round) and precipitation (+30% of mean annual rainfall) on slug herbivory and abundance and plant community dynamics biweekly in a pasture located in central Kentucky, U.S.A. Warming increased slug abundance once during the winter, likely due to improving conditions for foraging, whereas warming reduced slug abundance at times in late spring, mid-summer, and early fall (from 62–95% reduction depending on month). We found that warming and increased precipitation did not significantly modify slug herbivory at our site, despite altering slug abundance and affecting plant community composition and forage quality. Climate change will alter seasonal patterns of slug abundance through both direct effects on slug biology and indirect effects mediated by changes in the plant community, suggesting that pasture management practices may have to adapt.