PARENT SESSION
Oral Session # 49: Invasive Species IV: Grasslands; Wetlands.
Presiding: F Hughes
Wednesday, August 6. 8:00 AM to 11:30 AM, SITCC Meeting Room 204.
Phalaris arundinacea invasion potential increases with soil successional changes.
Kellogg, Chev *,1, 2, Bridgham, Scott 3, Craft, Chris4, 1 U.S. Geological Survey, Corvallis, OR2 Oregon State University, Corvallis, OR3 University of Oregon, Eugene, OR4 Indiana University, Bloomington, IN
ABSTRACT- Invasive plants increasingly threaten to disrupt plant communities and ecosystem function worldwide. Of particular concern in North American wetlands is the invasive grass Phalaris arundinacea (reed canary grass). In wetlands this grass can invade and become the dominant member of the plant community, both in restored and undrained wetlands. Although late-successional systems have traditionally been thought to be less invasible, the invasion of undrained wetlands casts doubt on this assumption. A carbon accumulation rate, based on a 47-y chronosequence of restored wetlands, was used to develop a simulated successional gradient to test the effects of soil successional changes on invasibility. We determined the effects of three levels of organic soil on germination of P. arundinacea seeds in three water levels (-4, -1, +2 cm from soil surface). Additionally, the effects of the same organic additions on both intraspecific and interspecific (five species) competition with water levels 1 cm below the soil surface were examined. Germination of P. arundinacea was increased by high levels of organic soil in the driest hydrology and inhibited by intermediate and high levels of organic matter in flooded hydrology. Aboveground biomass, belowground biomass, and number of new shoots of P. arundinacea increased with increasing organic content of the soil. Leersia oryzoides consistently had the greatest competitive effects on P. arundinacea. These results indicate that successional changes in soils is sufficient to increase invasibility of Midwestern marshes by P. arundinacea. From a management standpoint, planting or seeding of L. oryzoides may slow the invasion of P. arundinacea. Additionally, control of hydrology based on organic content of the soil can be effective in reducing germination rates of P. arundinacea.
Key words: invasion, soil, succession, Phalaris arundinacea