Anisotropic Wetland Patterns

"Effects of Anisotropy on Pattern Formation in Wetland Ecosystems"
Yiwei Cheng, Mark Stieglitz, Greg Turk and Victor Engel
Geophysical Research Letters
Vol. 38, 2011
Full Paper (PDF, 0.46 Mbytes).


Wetland ecosystems are often characterized by distinct vegetation patterns. Various mechanisms have been proposed to explain the formation of these patterns; including spatially variable peat accumulation and water ponding. Recently, short‐range facilitation and long‐range competition for resources (a.k.a scale dependent feedback) has been proposed as a possible mechanism for pattern formation in wetland ecosystems. We modify an existing, spatially explicit, advection‐reaction‐diffusion model to include for a regional hydraulic gradient and effective anisotropy in hydraulic conductivity. This effective anisotropic hydraulic conductivity implicitly represents the effect of ponding: a reduction in the long‐range inhibition of vegetation growth in the direction perpendicular to the prevailing hydraulic gradient. We demonstrate that by accounting for effective anisotropy in a simple modeling framework that encompasses only a scale dependent feedback between biomass and nutrient flow, we can reproduce the various vegetation patterns observed in wetland ecosystems: maze, and vegetation bands both perpendicular and parallel to prevailing flow directions. We examine the behavior of this model over a range of plant transpiration rates and regional hydraulic gradients. Results show that by accounting for the effective x‐y anisotropy that results from biomass‐water interaction (i.e., ponding) we can better understand the mechanisms that drive ecosystem patterning.

This material is based in part upon work supported by the National Science Foundation under grant EAR-1027870. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

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