Effects of Water Level and Temperature on Competitive Interaction between Invasive and Native Wetland Plants

Abstract

Riparian areas are vulnerable to invasion because regular floods decrease the competitive interaction and provide many kinds of microhabitats for species. Lythrum salicaria is a well-known aggressive invader of wetlands in North America but is a native species in Korea. There are reports about natural habitats of Lythrum salicaria at the riparian area in some parts of Korea, however, none of them reports that it dominates the community. Panicum dichotomiflorum is invasive in Korea but native in North America and Phragmites australis is native in Korea. I compared the characteristics of three species among different treatments to measure fitness of each species at several flooding conditions and elevated temperature. I hypothesize that Lythrum salicaria will most sensitive to different condition and have the lowest position in competition. To compare different properties on different environmental condition, I divided experimental sets to two temperature and three water level conditions. The sets at elevated temperature were placed in the greenhouse and the mean temperature inside the greenhouse was about 2℃ higher than outside. The height of Panicum dichotomiflorum wasnt affected by temperature change while the height of Lythrum salicaria and Phragmites australis were significantly higher in elevated temperature than in ambient temperature. Three different water levels (dry, wet and flooding condition) were set for studying water supply and flooding effects. There was no difference between wet treatment and flooding treatment but plants at dry treatment didnt grow up well than other water treatments. Lythrum salicaria and Phragmites australis showed significant difference between dry and other conditions while Panicum dichotomiflourum didn't. It indicates that two species are more sensitive to water condition, especially at elevated temperature. Three species were investigated separately or planted together to watch the competitive effects. Lythrum salicaria was affected most by competition. There was no difference between the kinds of which species it competes with. The interaction between climate factors and competition had different influences with species. Panicum dichotomiflorum showed more competitive properties than other two species. In conclusion, Lythrum salicaria was most sensitive to environmental variations and Panicum dichotomiflorum and Phragmites australis were less sensitive to environmental factors. The stable precipitation pattern of the United States could affect to the wide distribution of Lythrum salicaria. If climate changes, however, Panicum dichotomiflorum and Phragmites australis which showed more competitive ability than Lythrum salicaria may replace the wetlands community and alter the plant distribution in wetlands.