c. Rhizome Extension . 



(1) Dunes . All of the major plant species on Nauset Splt-Eastham are 

 rhizomatous and rely primarily on vegetative reproduction. Ammophila brevi- 

 ligulata has the capability of extending its rhizomes both vertically in 

 response to sand burial and horizontally to colonize new areas. Measuring 

 the rate of natural sand accretion in North Carolina, Woodhouse and Hanes 

 (1967) documented that Ammophila breviligulata can recover from as much as 120 

 centimeters of burial in 1 year. Ranwell (1975) stated that while Amnophil a 

 breviligulata can recover from 90 centimeters of gradual burial, the plant would 

 probably be unable to recover from an instantaneous deposition of 90 centi- 

 meters of sand. Overwash activity may, in low dune areas, bury Ammophila 

 breviligulata by large amounts of sediment (sometimes approaching 1 meter). 



To test the ability of Ammophila breviligulata to recover from sand 

 burial, a 55-gallon drum, with open ends, was placed over a healthy stand 

 of Ammophila breviligulata on an accreting dune in early April 1979. From 

 inspection of the base of tillers, it appeared that approximately 25 centi- 

 meters of sand had naturally accumulated during the previous winter. Thirty- 

 eight tillers were present in the area that was experimentally buried. The 

 barrel was filled to the top (90 centimeters), and sand was mounded around the 

 base. The first tiller visible on the surface was recorded 5 weeks after the 

 beginning of the experiment (Fig. 78). Vertical rhizomes extended through a 

 total of 115 centimeters of sand in 35 days for a rate of 3.3 centimeters per 

 day. 



Measurements taken during the height of the growing season have shown that 

 Ammophila breviligulata rhizomes can grow horizontally as much as 2 centi- 

 meters per day (Brodhead and Godfrey, 1979). The Ammophila front can expand 

 seaward in favorable areas at a rate of 4 to 5 meters per year. Rhizome 

 extension into washovers was not visible during the first growing season after 

 overwash. Since buds along rhizomes do not break dormancy until the year 

 following their formation, there may be no visible evidence of plant growth, 

 although rhizomes may exist below the sand surface. Excavations of dunes 

 adjacent to site 1 revealed that Ammophila breviligulata plants had extended 

 as much as 2 meters into the washover fan. 



During the second growing season (1979), the location of Ammophila brevi- 

 ligulata was recorded in relation to the remnant dune line. An 800-meter 

 transect was established along the back side of the Nauset Spit-Eastham dune 

 line paralleling an off-road vehicle trail. At a 2-meter interval, the loca- 

 tion of the marshward edge of the established dune vegetation was noted, and 

 the distance of newly emergent plants from the dune edge was recorded. Plants 

 were excavated to distinguish tillers resulting from rhizome extension from 

 fragments regenerating in drift lines. Only a few tillers were evident in the 

 road in 1978; these plants were undoubtedly from rhizomes that had extended 

 into the road before the 1978 storm. Ammophila breviligulata tillers in 

 1979 were located as far as 4.6 meters from the rhizome origin, but these 

 tillers had not formed a closed population 2 years after the storm. Ammophila 

 breviligulata tillers, however, had become well established on washover sub- 

 strate above former salt-marsh vegetation. A map of the outgrowth of dune 

 vegetation from the western edge of the dune line shows that the greatest 

 expansion occurred along areas downwind of washovers (Fig. 79). The prevail- 

 ing, sand-transporting northwest winds added sediment to the dune line south- 

 east of washovers. 



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