Competitive effect of an invasive grass, Phalaris arundinacea L., on the growth of a rhizomatous sedge, Carex stricta lam

Includes bibliographical references (pages [52]-56).Phalaris arundinacea is a rhizomatous grass that invades northern Illinois wetlands and sedge meadows. Carex stricta. a rhizomatous sedge, is a common native species in these habitats. Field and laboratory studies were conducted to examine the competitive effect of E. arundinacea on £. stricta. The field site was located at Boyle Grassland, Lynnville Township, De Kalb County, Illinois. Soil samples were collected where the species grew alone and together at a wet and moist site and analyzed for nine soil nutrients. No soil nutrients varied significantly among sites or species. To examine the competitive ability of C. stricta when grown with E. arundinacea. C. stricta was transplanted on 29 April 1994 into E. arundinacea monocultures in a randomized block design with four treatments: 1) no interspecific competition (control), 2) above-ground competition, 3) below-ground competition, 4) and above-and-below-ground competition. In the absence of interspecific competition, £. stricta transplants produced new tillers throughout the experiment. However, in all treatments involving competition with E. arundinacea. £. stricta transplants lost tillers. Between May and September 1994, £. stricta experiencing above-ground competition lost tillers faster than £. stricta grown in the other two types of competition, possibly due to the method of isolating above-ground competition. Between September 1994 and May 1995, £. stricta experiencing belowground competition lost tillers faster than £. stricta grown in above-ground or above-and- below-ground competition. To examine the effect of water level on competition among and between these two species, a greenhouse experiment was conducted from 1 September to 15 November 1994. Seedlings were transplanted into a 3 x 2 x 2 randomized block factorial design (type of competition, water level, initial density). Intraspecific competition reduced the above-ground and below-ground biomass of £. arundinacea. Flooded conditions interacted with intraspecific competition to cause lower below-ground biomass in E. arundinacea. High initial density decreased the number of E. arundinacea tillers per original seedling in all treatments by increasing the intensity of intraspecific competition. The intensity of interspecific competition incurred by C. stricta depended on the water level. Whereas the number of tillers and biomass of £. stricta were greatest in moist, intraspecific conditions, they were the least in moist, interspecific conditions and intermediate in flooded, interspecific conditions. Since flooding decreased the intensity of competition with _E. arundinacea. £. stricta was able to grow moderately in flooded conditions. Based on these field and greenhouse competition experiments, C. stricta growth is significantly reduced when in competition with E. arundinacea; the magnitude of reduction decreases when grown under flooded conditions.M.S. (Master of Science