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 Metrics > Human Stressors > Metric Map (p_load), Quantile, Methodology and Interpretation
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Natural Breaks
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Methodology and Interpretation

P_LOAD - Phosphorus loading ( kg / ha / yr )
The phosphorus nutrient load is calculated by multiplying a contribution factor by the the area of certain land cover types known to produce phosphorus. Default contribution factors are based on literature (Reckhow et al. 1980), but may be changed by the user.

Reckhow, K.H., Beaulac, M. N., and Simpson, J. T. (1980). Modeling Phosphorus Loading and Lake Response Under Uncertainty: A Manual and Compilation of Export Coefficients. USEPA 440/5-80-011. Washington, DC: Office of Water Regulations and Standards, U.S. Environmental Protection Agency.

Metric Map (p_load), Quantile Metric Map (p_load), Natural Breaks

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.

Natural Breaks: Classes are based on natural groupings of data values. Natural break points are identified by looking for groupings and patterns inherent in the data. The features are divided into classes whose boundaries are set where there are relatively large jumps in the distribution of data values.

* EMAP-West Landscape Metrics Metadata (FGDC)


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