Comprehension

Acquisition - The Math Model

Shannon-Wiener Diversity Index

• H’ = ^- P_i (log P_i)
  1. where H’ is the index of diversity,

  2. is the sum of all results,

  3. "i" is the counter,

  4. P_i is the proportion of the species "i",

  5. and "log P_i" is the log function of P_i.

• Assumptions of this model:

  a. The individuals sampled come from an infinitely large population

  b. All species are represented in the sample
        (such that the sample must be a good one)

The second assumption is known to be a significant source of error in Shannon index calculations.

Let us assume that two conditions above are satisfied - so that we can use the model to learn how to calculate the diversity index.

Information

The tables below give the data derived from the plant diversity project conducted in Shiprock.

One set comes from the riparian community along San Juan River.

The second set comes from the desert community above the river level. Here, the water table from the river doesn’t reach the plant roots.

Although we found many more than twenty species from each community, we decided to control the species richness to reflect the relative abundance of each community.

Click here for pictures and descriptions of plants at the following USDA web site. Then adjust the size of the USDA overlay screen so that you can view both the table and the USDA side by side. We suggest that you size the USDA screen so that you can read the both scientific and common name of the plant. The best way is to arrow down to 'scientific name'. Then type in the scientific name. You can also enter the common name and navigate the USDA web site until you find the information that you are seeking.