Biodiversity

Average Size Measure all trees in a transect or quadrat. Produce a size-frequency histogram to show the size distribution. Can also calculate the average size tree.

Quadrat Sampling Randomly select plots and count all individuals in that plot. Each quadrat = 200m 2. Can calculate density as #/m 2 then multiply by total area to estimate the total # of trees. 60,703 m 2 = 15 acres

Transect Sample Randomly select a transect of known area and count every tree in that transect. Each transect = 90m 2. Can calculate density for each tree species. 60,703 m 2 = 15 acres

Measuring Biodiversity The simplest measure of biodiversity is the number of species – called species richness. –Usually only count resident species, and not accidental or temporary immigrants Another concept of species diversity is heterogeneity: Community 1Community 2 Species A9950 Species B150 Heterogeneity is higher in a community where there are more species and when the species are more equally abundant.

Diversity Indices A mathematical measure of species diversity in a community. Reveals important information regarding rarity and commonness of species in a community.

Shannon-Wiener Diversity Index (H) Variables associated with the Shannon-Weiner Diversity index:  S – total number of species in the community (richness)  p i – proportion of S made up of the i th species  H max = ln(S)  E H – equitability (evenness; b/t 0 and 1) = H / H max H = -  p i (lnp i )  Larger H = more diversity

Species richness and equitability affect the Shannon Wiener index.

Simpson’s Index N = total number of individuals p i = proportion of each species Simpson’s Index of Diversity = 1 – D –Ranges from 0 to 1  Low to high diversity D =D = 1 -  p i 2 ranges from 0 to 1

Species richness and equitability affect Simpson’s index.