Relative growth ofSpartina patens (Ait.) Muhl. andScirpus olneyi gray occurring in a mixed stand as affected by salinity and flooding depth

Abstract

Mixed stands ofSpartina patens andScirpus olneyi occur in brackish marshes along the Gulf Coast of Louisiana.Scirpus olneyi is considered to be an important wildlife food, and marshes are often managed to favor its dominance overS. patens. Two environmental factors that affect growth of the two species are salinity and water regime. The objectives of this study were to determine the effects of salinity and water depth, under controlled greenhouse conditions, on relative dominance of the two species, chemical properties of soil interstitial water, and nutrient concentrations in the plant tissue. Treatments imposed in a factorial design were salinities of 0, 5, 10, 15 and 20 ppt and water depths of −10, +10, and +30 cm relative to the soil surface. Results indicated that salinity treatments above 10 ppt reduced growth of both species, butS. olneyi was more drastically affected thanS. patens. Increased flooding depth reduced growth ofS. patens but had little effect onS. olneyi. Concentrations of inorganic ions (Na+, K+, Mg+2, Ca+2, Cl−1) in plant tissue were greater inS. olneyi thanS. patens, indicating that ion accumulation may be the principal salt tolerance mechanism ofS. olneyi. Extrapolated to field conditions, these results indicate that increasing salinity favors productivity ofS. patens relative toS. olneyi, while increased depth of flooding favorsS. olneyi.