Spatiotemporal Patterns of Leymus arenarius Nebkhas during Early Primary Succession on the Sub-Arctic Coastal Sand Plains of Iceland


Ecology, Evolution, and Organismal Biology

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A spatiotemporal analysis of phytogenic mounds (nebkhas) of the pioneer dune building grass Leymus arenarius was assessed during primary succession on three coastal sand plains in Iceland. Extensive sand plains were formed on the study sites due to catastrophic glacial river floods associated with sub-glacial volcanic activities. Present and past spatial patterns of Leymus-nebkhas were examined by the use of satellite images and high resolution aerial photographs and confirmation through field work. The colonization patterns of the nebkhas were studied from the initial phases and up to a maximum period of 54 years on the sand plains Skeidararsandur, Myrdalssandur, and Skogarsandur. The hypothesis was that nebkhas would be clustered and nonrandom in early phases of the primary succession but would have random configurations at later stages. Average density of nebkhas was low within 10 years of colonization on Skeidararsandur (0.55-0.67 dunes ha-1) and the spatial configuration was found to be highly nonrandom (clumped). Following the initial colonization of L. arenarius, the increase of nebkha density with time followed a similar nonrandom pattern on Myrdalssandur with final average density of 6.12 nebkha ha-1. On Skogarsandur, the spatial configuration of nebkhas was random with final average density of 7.08 nebkha ha-1. Nonlinear cubic polynomial regression analysis showed a very strong relationship (R2 = 0.989) for the average density of nebkha for 60 years on Skogarsandur. On the coastal sand plains, the spatial configuration of nebkha was observed to progress with time from nonrandom towards random distribution. This study supports the view of deterministic spatiotemporal pattern of nebkhas during early primary succession on the coastal sand plains. The nebkha density was most likely a function of sand drift on the plains, significantly decreasing (R2 = 0.93) away from the sand source of the glacier river Jökulsa on Skogarsandur. The results are discussed in relation to ecological restoration.

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Journal of Coastal Research

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