Ridge & Slough Landscape

Ridge and slough (R&S) landscape includes distinct linear sawgrass-dominated ridges that are oriented in the direction of predominant water flow and separated by a network of similarly oriented sloughs with sparse emergent, submerged, and floating-leaved plant species. In the pre-drainage Everglades, the R&S landscape had ridges ≥ 30 cm higher in elevation than the sloughs. A healthy R&S system is characterized by distinctness in vegetation composition, bimodality in elevation, and directionality in landform orientation. A deviation from this vegetation distinctness and elevation bimodality and loss of directionality represents degraded landscape. The degradation process might include the simultaneous decline in both topographic variation and vegetation distinctness, or degradation in one may be the leading indicator of future degradation in the other.

See the results for ridge and slough landscape in the Greater Everglades.

Photo credit: Everglades National Park Service.

How is it measured?

This indicator is measured in the Greater Everglades. For better understanding of the mechanisms involved in formation, maintenance and degradation of patterned R&S landscape, a detailed system-wide assessment of the spatiotemporal patterns in R&S was initiated, as a pilot in 2009, and a full study in 2010. The sampling design was based on the Generalized Random-Tesselation Stratified approach and included 80 2 km by 5 km cells, called Probabilistic Sampling Units (PSUs).

There are six metrics measured for the ridge and slough landscape indicator; microtopography variability, elevation mode differences, site hydrology, vegetation community distinctness, vegetation elevation relation, and Ridge-Slough elevation difference. 

Microtopography variability: Spatial variability of soil elevation represented by standard deviation of mean water depth across all points sampled within each PSU.

Elevation mode differences: Peat surface elevation (water depth) difference between two modes.

Site hydrology: Long-term mean water depth.

Vegetation community distinctness: How distinct the vegetation community is with regard to species distribution.

Vegetation Elevation Relation: Vegetation-elevation correlation represented by Mantel_r.

Ridge-Slough elevation difference: Difference in relative elevation between Ridge & Slough