Methodology and Interpretation

Percent grassland adjacent to wetlands
The amount of grassland on the periphery of wetlands may indicate the amount of upland herbaceous plant habitat for organisms that might travel relatively short distances to and from nearby upland grassland and wetland areas for breeding, water, forage, or shelter. Also, the affect of runoff on wetlands from areas nearby (e.g., agricultural land) may be ameliorated by biogeochemical processes that occur in herbaceous areas that are on the periphery of the wetland. Thus, the percentage of grassland adjacent to wetlands is calculated by summing the total number of grassland land cover cells directly adjacent to wetland land cover cells in the reporting unit and dividing by wetland total area in the reporting unit. Other buffer distances may be more appropriate for habitat analyses, depending on the type of organism; for runoff analyses the chemical constituent(s), flow dynamics, soil conditions, position of wetland in the landscape, and other landscape characteristics should be carefully considered.

Quantile: Each class contains an approximately equal number (count) of features. A quantile classification is well-suited to linearly distributed data. Because features are grouped by the number within each class, the resulting map can be misleading, in that similar features can be separated into adjacent classes, or features with widely different values can be lumped into the same class. This distortion can be minimized by increasing the number of classes.

Metric input GIS data:

• United States Hydrologic Units (8-digit HUCs) - Metadata

• United States Coastal Change Analysis Program (CCAP) - Metadata