Measuring slope-slope aspect, horizontal configuration, and slope posi- 

 tion can present problems in coulees and on ridges, which are not bottom or 

 top slope positions. This can be explained in field notes but does not make 

 for neat summaries. 



SPECIES DIVERSITY 



A rough measure of species diversity has been formulated for the com- 

 munity types using reconnaissance data. The data were collected between 

 mid-June and late August in 1976. Although diversity can change notice- 

 ably from spring to summer (Munshower and De Puit, 1975), the data are ade- 

 quate for comparing community types. 



Diversity was expressed three ways. Richness is simply the number of 

 plant species encountered in standard size plots. Means and standard devia- 

 tions are given. 



The Simpson index is basically a measure of dominance: 



C = Z ^2 

 N 



where C = index of dominance; 



•^i - value (coverage) for the ith species; and 



N = total value (coverage) for all species. 



Resulting values are between zero and one, and high values indicate that 

 most coverage is concentrated in one or a few species. 



The Shannon-Wiener index can be thought of as a measure of equitability: 



H = -I (P^- log Pi) 



where H = index of equitability; and 



P. = n^ as in the preceding equation. 



W 

 This scale is open-ended and high values indicate that similar coverages 

 are shared by many species. 



STRUCTURE 



Plant community structure is useful in comparing community types and 

 for making reclamation baseline. Structure is often related to animal 

 abundance and diversity and these data have been used in the wildlife 

 study. Raunkier's (1934) life forms were used as primary structure cat- 

 egories. 



16 



