Annual Carbohydrate Variation in Culms and Rhizomes of Smooth Cordgrass (Spartina alterniflora Loisel.)1

Abstract The productivity and stability of northeastern Atlantic tidal salt marshes depend largely upon the growth and persistence of the tall and short ecophenes of smooth cordgrass ( Spartina alterniflora Loisel.). While the annual energy balance upon which perennial grass persistence depends has been studied in the tall form, no such information is available for the short form. The seasonal energy relations of the two morphological forms were compared based upon changes in the nonstructural carbohydrate content of rhizomes and culm tissues. Grass stands growing on a tidal marsh composed of sandy sulfaquents with occasional histic epipedons were sampled at 2‐week intervals during 3 years. Lipids, sample sugars, long chain fructosans, and starch were extracted in chloroform, ethanol, water, and perchloric acid, respectively. Carbohydrates were quantified by standard spectrophometric methods. Sucrose was the major carbohydrate extracted from culms and rhizomes throughout the year. Rhizomes never contained more than 4% starch while ethanol extractable sugars were 20% of dry weight in early spring and autumn. Almost no fructosans were detected in these tissues. During flowering and gram filling in August, the simple sugar content of tall culms was about 10% of dry weight but declined sharply between September and October which was coincident with carbohydrate accumulation in rhizomes. Short plants flowered less and continued Vegetative growth into autumn. Culm tissues of short plants retained a relatively high simple sugar content through October and rhizome carbohydrate levels increased gradually during autumn and early winter. It is proposed that the persistent vegetative growth of the short ecophene may result in less annual rhizome turnover than occurs in the tall form.