426 KESER, LARSON, VADAS, AND McCARTHY 



Growth 



At Bailey Marsh the number of new shoots increased in August, 

 forming the typical bimodal pattern that was evident before 1972 

 but was lacking during the second year of thermal stress. The size 

 and numbers of Spartina continued to decline in 1975 because the 

 surface discharge continued until May of that year. The bimodal 

 growth pattern was reestablished in 1976 and 1977, however. The 

 recovery of Spartina was limited to 40% of the marsh, where 

 rhizomes had survived, and the remaining portion has not been 

 recolonized by seeds or rhizomes. Growth patterns for Spartina at 

 Causeway Marsh have not changed over the course of these studies 

 (Fig. 4). Shoot growth began in early May, and by July the majority 

 of plants were in the larger size ranges (50 to 125 cm in length). 



These results suggest that rhizome systems of northern popula- 

 tions of Spartina are intolerant of thermal stress and that revegeta- 

 tion of a marsh is a slow process in northern areas. The sensitivity of 

 rhizomes to stress is not unique. The destruction of marshes through 

 compaction and damage to rhizome systems by walking was 

 described by Teal and Teal (1969). Similarly, Thomas (1973) 

 reported that the mortality of S. alterniflora was most severe the 

 second year after an oil spill because of the demise of the rhizome 

 system. 



Flowering 



Flowering in Spartina at Bailey Marsh during stressed years began 

 in July and continued through September (Vadas et al., 1976). When 

 the stress was ameliorated (in 1975 to 1977), flowering was initiated 

 later and lasted through October (Table 1). The onset of flowering in 

 Causeway Marsh (control) occurred in August throughout both 

 phases of these studies. Plants in the 75- to 100- and 100- to 200-cm 

 size classes flowered at Bailey Marsh, but only plants taller than 100 

 cm flowered at Causeway Marsh. The average height of reproductive 

 plants in the Control Marsh during 1975 to 1977 ranged from 135 to 

 149 cm, whereas average shoot heights at Bailey Marsh ranged from 

 98 to 116 cm. These size ranges were similar to those recorded in 

 1973 and 1974 (Vadas et al., 1976). Plants in the 50- to 75-cm range 

 at Causeway Marsh did not flower in 1975 to 1977 although that size 

 class had flowered previously. Since marsh plants are less fertile at 

 high salinities (Adams, 1963), it is possible that the reduction in 

 flowering at this site was caused by increased salinities. 



