DUNE: A COMPUTER MODEL OF AMMOPHILA GROWTH AND THE DEVELOPMENT OF VEGETATED FOREDUNES IN THE NORTHEASTERN UNITED STATES.

摘要

This study was initiated to increase our understanding of the processes affecting Ammophila foredunes of the Northeast. The two phenomena most responsible for their formation are movement of sand by wind and the colonization of A. breviligulata and its response to wind-blown sand. The goal of this study was to develop a computer model, based on the interaction of wind-blown sand and plant growth, of dune formation.; Measurements of standing crop, leaf area, plant height, and total chlorophyll all indicate that the growth of A. breviligulata is enhanced with increasing amounts of sand burial up to 39 cm. A study of plant cover in 1979 nd 1980 showed that most of the increases in cover were found on quadrats where deposition occurs. A multiple regression of 1980 cover on 1979 cover, surrounding cover, and sand burial accounted for 57% of the variance associated with the data. A multiple regression of accretion on the exponential plant height, elevation, the interactive effects of elevation, plant height, and distance from the beach, and the number of onshore winds with speeds greater than 36 m/s accounted for 54% of the observed variance. The maximum, potential sand burial is ultimately related to plant height.; A computer model, DUNE, was developed based on the observations described above. Initial simulations, with average conditions, show that the model mimicked the accretion pattern on 75% of the foredune. The sometimes greater amount of deposition on those other quadrats has been attributed to a lack of adjustment in the model to the flexibility of grass blades, lack of precipitation measurements, and a general time lag inherent in the model computations. Long-term simulations indicated that the dunes on Site 1 are younger than the dunes of Site 2 and that they will take on the shape of the Site 2 dunes. A dynamic equilibrium shape is reached within 15 years. A simulation of driftline establishment followed the bi-weekly accretion patterns and provided a profile very similar to the dunes on Site 2.