Spatial heterogeneity and domain of scale on the Skallingen salt marsh, Denmark
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Spatial heterogeneity and the domain of scale over which such heterogeneity is observed are fundamental topics in hiogeography. Focusing upon two facets of heterogeneity, or spatial point pattern andspatial texture (i.e. arrangement of patches andgaps), this study quantified how these facets vary across scales on the Skallingen salt marsh, Denmark. We established a 10 m 10 m plot with 2500 cells (20 cm 20 cm) inside. Each cell was surveyed for the presence of vascular plants. Among 12 species identified, we analyzed the spatial pattern of six species that had a probability of occurrence greater than 1%. To examine point pattern and texture, Ripley's K-function and lacunarity analysis were used, respectively. There was a gradient in K and lacunarity values in an order of Halimione portulacoi-des, Plantago maritima, Limonium vulgare, Puccinellia maritima, Triglochin maritima, and Salicornia herbacea. At all scales of our interest (< 5 m), H. portulacoides was randomly distributed due to its frequent occurrence (> 90%), while S. herbacea showed a strong clustering with extensive gaps. Correspondingly, lacunarity values were smallest for H. portulacoides and greatest for S. herbacea. The domain of scale where a lacunarity curve approaches zero was about 1.6 m for most species except for H. portulacoides and S. herbacea with smaller and larger domains, respectively. This domain variability among species was illustrated as a scale of 2.56 m2 (i.e. 1.6 m 1.6 m) in the curve of the species-area relationship. This study makes a quantitative contribution to the body of emerging novel theory that emphasizes scale-dependent complexity in salt marsh ecosystems.
