Hall Sarah L, McCulley Rebecca L, Barney Robert J, Phillips Timothy D
Department of Plant and Soil Sciences, University of Kentucky, Lexington, Kentucky, United States of America ; Community Research Service, Kentucky State University, Frankfort, Kentucky, United States of America.
Department of Plant and Soil Sciences, University of Kentucky, Lexington, Kentucky, United States of America.
PLoS One. 2014 Jan 31;9(1):e86904. doi: 10.1371/journal.pone.0086904. eCollection 2014.
Invasive species may owe some of their success in competing and co-existing with native species to microbial symbioses they are capable of forming. Tall fescue is a cool-season, non-native, invasive grass capable of co-existing with native warm-season grasses in North American grasslands that frequently experience fire, drought, and cold winters, conditions to which the native species should be better-adapted than tall fescue. We hypothesized that tall fescue's ability to form a symbiosis with Neotyphodium coenophialum, an aboveground fungal endophyte, may enhance its environmental stress tolerance and persistence in these environments. We used a greenhouse experiment to examine the effects of endophyte infection (E+ vs. E-), prescribed fire (1 burn vs. 2 burn vs. unburned control), and watering regime (dry vs. wet) on tall fescue growth. We assessed treatment effects for growth rates and the following response variables: total tiller length, number of tillers recruited during the experiment, number of reproductive tillers, tiller biomass, root biomass, and total biomass. Water regime significantly affected all response variables, with less growth and lower growth rates observed under the dry water regime compared to the wet. The burn treatments significantly affected total tiller length, number of reproductive tillers, total tiller biomass, and total biomass, but treatment differences were not consistent across parameters. Overall, fire seemed to enhance growth. Endophyte status significantly affected total tiller length and tiller biomass, but the effect was opposite what we predicted (E->E+). The results from our experiment indicated that tall fescue was relatively tolerant of fire, even when combined with dry conditions, and that the fungal endophyte symbiosis was not important in governing this ecological ability. The persistence of tall fescue in native grassland ecosystems may be linked to other endophyte-conferred abilities not measured here (e.g., herbivory release) or may not be related to this plant-microbial symbiosis.
入侵物种在与本地物种竞争和共存方面取得的一些成功，可能归功于它们能够形成的微生物共生关系。高羊茅是一种冷季型、非本地的入侵性草种，能够在北美草原与本地暖季型草种共存，而北美草原经常经历火灾、干旱和寒冷的冬季，在这些条件下，本地物种应该比高羊茅更能适应。我们假设高羊茅与一种地上真菌内生菌——内生真菌共生的能力，可能会增强其在这些环境中的环境胁迫耐受性和持久性。我们进行了一项温室实验，以研究内生菌感染（感染内生菌E+ 与未感染内生菌E-）、规定火烧（1次火烧与2次火烧与未火烧对照）和浇水制度（干燥与湿润）对高羊茅生长的影响。我们评估了处理对生长速率以及以下响应变量的影响：总分蘖长度、实验期间招募的分蘖数、生殖分蘖数、分蘖生物量、根生物量和总生物量。水分状况显著影响所有响应变量，与湿润条件相比，干燥水分条件下的生长和生长速率较低。火烧处理显著影响总分蘖长度、生殖分蘖数、总分蘖生物量和总生物量，但各参数的处理差异并不一致。总体而言，火烧似乎促进了生长。内生菌状态显著影响总分蘖长度和分蘖生物量，但其影响与我们的预测相反（E- > E+）。我们的实验结果表明，高羊茅对火烧具有相对耐受性，即使与干燥条件相结合也是如此，并且真菌内生菌共生关系在控制这种生态能力方面并不重要。高羊茅在本地草原生态系统中的持久性可能与这里未测量的其他内生菌赋予的能力（例如，免受食草动物侵害）有关，或者可能与这种植物 - 微生物共生关系无关。
