ROLE OF FIRE AND PLANT-DERIVED SMOKE IN SEED GERMINATION AND SEEDLING EMERGENCE IN FESCUE PRAIRIE

Fire, a natural disturbance, regulates species composition in Fescue Prairie. However, little is known about the contribution of different regeneration strategies in altering species composition after burning in Fescue Prairie. The present study was conducted to determine if and how fire and associated fire cues regulate species composition in Fescue Prairie through their effects on seedling recruitment. The effects of fire and various fire cues, including smoke, ash, and smoke plus ash on seedlings emerging in the field and/or from litter, 0-1 cm, and 1-5 cm layers of the soil seed banks were therefore examined. These studies were complimented by a study of testing effects of smoke originated from different plant materials on seed germination and seedling growth of species from Fescue Prairie. Chemical analyses were also conducted to determine whether different active compounds existed in smoke made from different materials, which in turn affect germination and seedling growth differently. Burning increased densities, richness, and diversity of seedlings emerging in the field. This was possibly attributed to direct fire cues of burning. Seedling densities of native forbs and non-native graminoids emerging from the soil seed bank were increased and decreased by burning, respectively. Ash and smoke plus ash increased density of forbs emerging from the soil seed bank. Species composition of seedlings emerging in the field and from the soil seed bank was altered by burning. Complex responses were observed for the effects of smoke on seedling establishment, which depended on the type and dilution of smoke solutions, as well as germination conditions. Smoke solutions partly substituted light requirement for germination of Artemisia ludoviciana. Germination of Cirsium arvense and Conyza canadensis only responded to smoke solutions at 25/15°C, but not at 10/0 °C. Diluted smoke solutions increased radical length of Artemisia ludoviciana. Karrikinolide (KAR1) was in the smoke made from prairie hay and wheat straw, but not in that made from alfalfa. This is the first report that different active compounds existed in smoke made from different materials. Highly concentrated smoke solutions made from alfalfa increased germination and radical length of Conyza canadensis, while the same concentrated smoke solutions made from prairie hay and wheat straw reduced germination of Conyza canadensis at 25/15 °C in darkness. Priming in KAR1 solutions and active fractions obtained from prairie hay and/or wheat straw increased germination of Artemisia frigida, Artemisia ludoviciana, and Conyza canadensis at certain germination conditions. In summary, fire and direct fire cues, smoke and ash specifically, stimulated recruitment of some species, especially early seral species and native forbs, contributing to potential changes in species composition of the Fescue Prairie. Different compounds existed in smoke solutions made from alfalfa as compared with those from prairie hay and wheat straw, showing different effects on seed germination and seedling growth. KAR1, the most important active compound discovered in smoke, was present in the smoke made from prairie hay and wheat straw, but was not in that made from alfalfa