CLUSTER ANALYSIS 

 74 - 75 



REVEGETATED AND UNTREATED AREAS 



U - Untreated (11 Tubes) 

 R - Revegetated (21 Tubes) 



n 



2.967 



37 40 3 4 32 1 8 

 U U R R U R R 



6 12 39 26 42 22 41 25 30 36 17 10 34 14 33 24 16 28 38 31 35 9 7 29 10 

 RRURURURRURRURURRRURURRRR 



Figure 1.— Dendrogram of soil-water samplers on the revegetated and untreated areas, 1974-75. 



Cophenetic correlation = 0.92. 



For these data the "objects" were the ceramic 

 cup soil-water samplers and the variable for each 

 object was the mean ionic concentration of cop- 

 per, iron, and sulfate. The analysis was to deter- 

 mine which of the soil-water smaplers are similar 

 and which dissimilar. This information can be 

 visualized in dendrograms, or trees. A way to 

 conceptualize a dendrogram is to imagine how 

 objects look as one gets progressively farther 

 away from them. Up close, dy. = 0, every sampler is 

 seen individually. As the distance increases, indi- 

 vidual samplers become progressivley more dif- 

 ficult to discern and the observer sees only groups 

 of samplers. Finally, at the greatest distance, no 

 individuals are seen, and only one large group 

 comprising the entire set of objects can be dis- 

 cerned. This distance abstraction is evident in the 

 following dendrograms. 



Revegetated vs. Untreated 

 Areas, 1974-75 



The dendrogram of soil-water samplers on the 

 revegetated and untreated areas for this period 

 does not indicate strong similarities between 

 samplers within either area (fig. 1). The decision 

 about where to cut the tree is subjective and is 

 analogous to distance abstraction. If we cut the 

 tree at about one-fourth of the total Euclidian 

 distance, we divide the samplers into seven 

 groups of similar soil-water samplers (table 2). 



In the total set of samplers, 21 are on the 

 revegetated area and 1 1 on the untreated area. 

 The distribution of the samplers (table 2) does not 

 suggest any strong degree of grouping within 

 either the revegetated or untreated area. 



3 



