Sw. Broome et al., RELATIVE GROWTH OF SPARTINA-PATENS (AIT) MUHL AND SCIRPUS-OLNEYI GRAYOCCURRING IN A MIXED STAND AS AFFECTED BY SALINITY AND FLOODING DEPTH, Wetlands, 15(1), 1995, pp. 20-30
Mixed stands of Spartina patens and Scirpus olneyi occur in brackish m
arshes along the Gulf Coast of Louisiana. Scirpus olneyi is considered
to be an important wildlife food, and marshes are often managed to fa
vor its dominance over S. patens. Two environmental factors that affec
t growth of the two species are salinity and water regime. The objecti
ves of this study were to determine the effects of salinity and water
depth, under controlled greenhouse conditions, on relative dominance o
f 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 i
ndicated that salinity treatments above 10 ppt reduced growth of both
species, but S. olneyi was more drastically affected than S, patens. I
ncreased flooding depth reduced growth of S. patens but had little eff
ect on S. olneyi. Concentrations of inorganic ions (Na+, K+, Mg+2, Ca2, Cl-1) in plant tissue were greater in S. olneyi than S. patens, ind
icating that ion accumulation may be the principal salt tolerance mech
anism of S. olneyi. Extrapolated to held conditions, these results ind
icate that increasing salinity favors productivity of S. patens relati
ve to S. olneyi, while increased depth of flooding favors S. olneyi.