A GROWTH COMPARISON OF SPARTINA ALTERNIFLORA LOISEL. ECOPHENES UNDER AEROBIC AND ANAEROBIC CONDITIONS

Spartina alterniflora Loisel. culms were collected from tall (creekbank), short (highmarsh) and dieback sites in a North Carolina salt marsh and grown in aerobic and anaerobic simulated marsh systems in the greenhouse. There were no significant differences between density, aerial live biomass, height, leaf width or root biomass and sprig source. All variables were significantly different between aeration treatments. Aerated systems had an average of 6.3 times more biomass than the unaerated treatments. There was a significant interaction between sprig source and aeration treatments based on a multivariate analysis of variance representing overall plant performance. These results demonstrated that pioneer sprigs from the dieback sites had an advantage over the other sprigs when exposed to unaerated systems. Tall plants performed better than plants from short or dieback zones in the aerobic systems. LINTHURST AND SENECA (1980b) have investigated the dieback of short (highmarsh) Spartina alterniflora Loisel. and recolonization of these sites. Since these areas were characterized by standing water, several studies to evaluate the effects of drainage-aeration regimes on the growth of S. alterniflora have been conducted (Linthurst, 1979; Linthurst and Seneca, 1980a; Linthurst and Seneca, 1980c). The results of these experiments suggested, as did those of Mendelssohn andSeneca (1980), that impeded drainage inhibited S. alterniflora growth. Linthurst (1979) and Linthurst and Seneca (1980a) found that standing water or poor drainage per se was not responsible for the inhibition since aeration and/or mixing of the water removed any detrimental effects. However, none of these experiments utilized pioneer plants responsible for the recolonization of the dieback sites or made comparisons between sprig sources. Numerous authors have investigated the productivity differences between tall (creekbank) and short (highmarsh) S. alterniflora (Turner, 1976). Since these S. alterniflora height forms are genetically similar (Mooring, 'Received for publication 4 September 1979; revision accepted 8 March 1980. Research was supported by Carolina Power and Light Company under contract number 99227. Appreciation is extended to Drs. E. D. Seneca, Udo Blum, and E. J. Kamprath of N.C.S.U. for their assistance, support and critical review of the manuscript. Special thanks is extended to Dr. J. 0. Rawlings of N.C.S.U. for assistance with multivariate analysis and his review of the manuscript. L. L. Hobbs and A. Hines are gratefully acknowledged for their technical assistance. Paper No. 6135 of the Journal of the North Carolina Agricultural Research Service, Raleigh, North Carolina 27650. Cooper and Seneca, 1971; Shea, Warren and Niering, 1975), environmental gradients are presumed to be responsible for the productivity differences. Since the dieback sites were recolonized by seed from natural marsh unaffected by dieback (Linthurst and Seneca, 1980b), these plants are also assumed to be genetically the same as those of the surrounding natural marsh. However, unlike the natural marsh, the pioneer plants responsible for recolonization of dieback sites in the lower Cape Fear River Estuary of North Carolina colonized an area which was flooded with 10 to 15 cm of standing water during most of the year. It was hypothesized that these plants may have some adaptive advantage for growth in standing water. The purpose of this experiment was to examine the growth of S. alterniflora from tall, short and dieback zones, in standing aerated and unaerated water-substrate. An assessment of resultant data would provide: 1) additional evidence to support or reject the concept that biomass and height differences between tall and short plants are a result of environmental factors, 2) evidence to suggest whether or not the response to aeration is independent of S. alterniflora ecophenes and 3) data to confirm or reject the possibility of short-term adaptive advantages based on original habitat. METHODS-Twenty-four white plastic containers (23 x 23 cm, depth x diameter) were filled with 4.5 1 of salt marsh creek delta, silt loam substrate collected from Oak Island, North Carolina. This substrate did not acidify upon oxidation and the interstitial water salinity was 15%o. The experiment was a randomized complete