c. Sand Accumulation . Volumes of sand accumulated during the 

 initial 3 months (Table 13) were largely due to sand accumulation by the 

 0.61-meter fence (Fig, 10), not the planted vegetation. After 3 months, 

 the bitter panicum plots had as much or more sand than the other 

 experimental plots except the American beachgrass plots 1 and 2 (NJ-327 

 and Cape, respectively). These values had no uniform correlation with 

 the 15- and 27-month values. For example, plots 1, 2, 4, and 6 liad 

 higher values after 3 months than the other replicate plots (12, 14, 8, 

 and 10) in the respective treatments, but lower values after 27 

 months (Table 13) . These results indicate that the sand fence did 

 not significantly influence the 15- and 27-month values whicli were 

 primarily due to the differential sand-trapping potentials of the 

 vegetation. 



After 27 months, the three American beachgrass treatments had 

 trapped more sand than all other treatments, and over twice as much 

 as the bitter panicum treatment (Table 13, Fig. 16). The Hatteras 

 beachgrass treatment accumulated slightly more sand over the 24-month 

 period, June 1973 to June 1975, than the other two American beachgrass 

 treatments. Over this same period, the bitter panicum treatment 

 averaged about 1 cubic meter of sand accumulation per linear meter of dune 

 which is about one-fifth as much sand as any other treatment. Even if the 

 best replicate of the bitter panicum treatment is considered, sand accumu- 

 lation during this period was only 1.9 cubic meters per linear meter or 

 one-third the sand accumulated by other treatments. 



All three mixed species treatments accumulated over 5 cubic meters 

 of sand per meter of dune over the 24-month period. AltJiougli the 

 bitter panicum plus sea oats treatment accumulated more sand than the 

 other two mixed species treatments, American beachgrass or sea oats 

 planted with bitter panicum accumulated more sand than did bitter 

 panicum alone. 



Three treatments (Hatteras beachgrass, bitter panicum plus sea oats, 

 and Hatteras beachgrass plus bitter panicum plus sea oats) trapped over 

 1 cubic meter of sand per meter of dune more in June 1973 to June 1974, 

 than in June 1974 to June 1975. Only the NJ-327 American beachgrass 

 treatment accumulated more than one-half meter of sand per meter of 

 dune during the second 12-month period. If the supply of moving sand 

 was equal over both years, the vegetation should have caught more sand 

 during the second year since the vegetation was more dense at that time. 



Cross-section profiles indicate that the dune crest in all 

 treatments moved seaward about 3 meters from June 1973 to June 

 1975 (Fig. 16) . The dune crest in the Hatteras beachgrass treatment 

 moved the most, about 5 meters. We have observed other experimental 

 American beachgrass dunes move seaward more rapidly than those 

 of sea oats. This movement is due partially to American beachgrass' 

 tremendous vegetative growth (by rhizomes) potential under conditions 



37 



