Physiological Responses of Miscanthus giganteus Under a Short Term Drought Scenario
Miscanthus × giganteus has emerged as a potential high-yield biofuel crop due to its ability to grow in marginal soils. However, water availability is reported as a limiting factor worldwide for biofuel crop production and drought conditions can significantly decrease productivity in Miscanthus. The goals of this study were to understand how Miscanthus responds physiologically to short term drought and whether biochar can alleviate drought stress by improving soil water status. Miscanthus rhizomes were grown for 100 days in either soil only or soil amended with biochar at a rate of 50 t ha-1. Drought was induced on half of the plants by withholding watering and physiological measurements (gas exchange, plant water potential) were made every three days throughout the drought period and during a rewatering event. Biochar was found to play a minimal role in alleviating drought stress, and increased water status was seen only under well-watered conditions. Although volumetric water content began to significantly decrease immediately, most physiological parameters, including leaf water potential, photosynthetic rates and stomatal conductance, did not significantly until water content had reached 35% of control levels 12 days after drought was induced. After rewatering, leaf water potential recovered to within 90% of pre-drought rates within one day, and gas exchange recovered within three days. No significant differences were seen in total aboveground biomass between any treatment combinations. The ability of Miscanthus to recover quickly suggests that drought impacts could be eliminated in a short time, contributing to its ability to grow on marginal soils.
Dept of Biology, Appalachian State University, Boone, NC
115 • Benjamin R. Montgomery, Brittany P. Twitty, Donathan S. Dendy
The role of flower petals as pollinator attractants is clear. However, in some species, petals may also promote pollination upon abscission by causing anthers or pollen to directly contact the stigma. Linum rigidum (stiffstem flax) is an annual of dry prairies with large basally sympetalous petals. Given that the plants apparently invest substantial resources in petals, we were interested in why the petals abscise quickly, typically within several hours of anthesis. To test the hypothesis that petal abscission promotes delayed self pollination, we placed plants either in pollinator exclosures or exposed them to pollinators. Then around the time of typical abscission, we either removed petals or left petals intact to allow for potential petal-mediated self pollination, and we returned all plants to exclosures. Pollen receipt was greater for flowers with petals intact than those with petals removed both among flowers exposed to pollinators and flowers in exclosures. Fruit set was also higher for flowers with intact petals than those with removed petals, both among flowers exposed to and those excluded from pollinators. Intact petals were associated with higher seed set per fruit for flowers in exclosures but not for flowers exposed to pollinators, perhaps indicating that for flowers with few visitors, petal-mediated delayed pollination boosted pollen receipt enough to allow fruit formation but not enough to maximize seed production. Manually self-pollinated flowers exhibited the highest levels of pollen receipt, fruit and seed set. These results indicate that petals act as a mechanism of delayed self pollination in L. rigidum.
Division of Natural Sciences and Engineering, University of South Carolina Upstate, Spartanburg, South Carolina
116 • Pieter A. P. deHart1, Dana J. Morin2
Eating Off the Land: Exploring Regional Variations in Coyote Diets
The conservation and management of local ecosystems is often a daunting task, involving multiple variables ranging from life history characteristics of predators to seasonal climate shifts. This management is made even more difficult by missing or misleading information regarding trophic structure. To address this issue and fill a critical knowledge gap in Appalachian Virginia, we focused on identifying dietary variation in an important and burgeoning opportunistic predator in this system, the eastern coyote (Canis latrans). To investigate the trophic role of the coyote throughout this region, we examined the carbon and nitrogen isotopic signatures from the hairs of coyotes captured across multiple habitats. We found wide variation in signatures of individual coyotes in both isotopes, with differences ranging up to 4.7‰ and 4.4‰ in d15N and d13C, respectively. These differences highlight foraging across multiple trophic levels, and may be dependent on the habitat characteristics of individual home ranges. Furthermore, the observed mean isotopic signatures for all coyotes (d15N = 7.72, d13C = -23.07) are consistent with diets dependent on small mammal communities, suggesting a need to reassess current predation models that assume eastern coyotes persist primarily on livestock and ungulates. However, seasonal dietary differences are difficult to elucidate from current results, as coyote captures are heavily seasonally dependent and may be temporally misleading. This study provides important isotopic evidence for the diet of top predators in this region, and recommends that regional variations in coyote predation be considered to refine current management plans throughout Appalachia.
1 Dept of Biology, Virginia Military Institute, Lexington, VA; 2 Dept of Fish and Wildlife Conservation, Virginia Polytechnic and State University, Blacksburg, VA
