Scale-Dependent Patterning of Wetland Depressions in a Low-Relief Karst Landscape

Abstract

Thousands of small wetland depression features (cypress domes) dot the low-relief karst of Big Cypress National Preserve (BICY) in South Florida, USA. We hypothesized that these wetland depressions are organized in a regular pattern, which is atypical of wetlandscapes elsewhere. Regular patterning implies the existence of coupled feedbacks operating at different spatial scales, with local wetland depression expansion (facilitation via karst dissolution) limited by competition among adjacent depressions for finite water resources (inhibition). We sought to test the hypothesis that wetlands in BICY exhibit regular patterning, and to quantify pattern properties to evaluate competing genesis mechanisms. We tested four predictions about landscape structure and geometry using high-resolution Light Detection and Ranging elevation data from six 2.25-km2 domains across BICY. Specifically, we predicted (1) feature overdispersion resulting from competition between adjacent basins; (2) truncated wetland area distributions due to growth inhibition feedbacks; (3) periodicity in surface elevation indicating a characteristic pattern wavelength; and (4) elevation bimodality indicating distinct upland and wetland states. All four predictions were strongly supported. Depressions were significantly overdispersed and efficiently fill the landscape, generating hexagonal patterning. Wetland areas followed truncated power law scaling, indicating incremental constraints on basin expansion, in contrast to depression areas elsewhere. Variogram and radial spectrum analyses revealed clear periodicity (~150- to 250-m wavelength) in surface elevations. Finally, surface elevations were consistently bimodal with elevation divergence of 10 to 40 cm. Regular patterning of wetland depressions across BICY is clear, implying long-term biogeomorphic control on landform structure in this karst landscape.