The physiology of the invasive grass, Cortaderia selloana, in response to variations in water table depth and soil nitrogen content

Cortaderia selloana, or pampas grass, is a serious invader of disturbed, coastal and riparian ecosystems in Southern California. The purpose of this study was to determine how the growth and physiology of C. selloana respond to various combinations of soil nitrogen and water table depth. Growth factors examined included plant biomass, plant height and width, number of tillers per plant and specific leaf area (SLA). Physiological factors examined included water use, photosynthesis and tissue nitrogen and phosphorous contents. These response variables were examined in a manipulative study using a 2 x 3 random factoral design with two water table and three nitrogen levels. Water, nitrogen and the interaction between the two were found to have a significant influence on many of the growth and physiological factors of Cortaderia selloana. Added nitrogen caused increases in plant biomass that were 5 to 9 times higher than plants exposed to ambient nitrogen. Both water and nitrogen influenced the number of tillers per plant, where a lower water table and higher nitrogen availability caused an increase in the number of tillers. C. selloana also responded to increased water and nitrogen with greater average plant height and reduced plant width. By examining which plant response factors are enhanced by the various combinations of water and nitrogen treatments, we hope to gain insight into the invasive nature and success of C. selloana in order to ultimately find less destructive methods to control and prevent the invasion of this invasive grass in the future. Keywords: Biomass, Cortaderia selloana, Disturbed ecosystems, Invasive species, Pampas grass, Riparian ecosystems, Specific leaf area