32 David L. Penrose, David R. Lenat, K. W. Eagleson 



within the family Chironomidae. Because several of the surveys listed in 

 Table 1 were conducted by our group, reduction in taxa richness 

 between these surveys cannot be accounted for by differences in collec- 

 tion and taxonomic techniques. For example, the low average taxa 

 richness in the Trichoptera for the North Toe River cannot be accounted 

 for taxonomically. 



Abundance (percent of total abundance): Rivers 



Table 3 summarizes average community composition by taxonomic 

 order (as percent of total abundance) for several Appalachian mountain 

 control stations. Differences within watersheds are small for both the 

 French Broad and Mills rivers. However, large differences exist between 

 watersheds, and much of the variability can be attributed to watershed 

 characteristics. 



Average annual water temperature is higher for the French Broad 

 (12.8° C) than for the Mills River (11.3° C) (N.C. Department of Natu- 

 ral Resources and Community Development 1977). The cooler water 

 temperature of the Mills River might favor the development of the Plec- 

 optera community observed there (Baumann 1979). Also, several of the 

 dominant Plecoptera genera in the Mills River are chironomid preda- 

 tors, which may account for the low percentage of Diptera in this area. 

 Average annual water temperature of the North Toe River also is high 

 (14.0° C) and might limit Plecoptera. 



The highest percent abundance for Trichoptera was noted for the 

 North Toe River, and is related to watershed size. The North Toe 

 watershed (193 km 2 ) is substantially larger than either the French Broad 

 (97 km 2 ) or Mills River (43 km 2 ) watersheds. Larger drainage areas 

 result in increased flow (Edington 1968) and increased amount of fine 

 particulate organic matter (Wallace 1975). These variables influence the 

 distribution of hydropsychid Trichoptera (Gordon and Wallace 1975) 

 because of the net building and filter feeding habits of this group. The 

 North Toe River at the sampling site is dominated by hydropsychid 



Table 3. Average percent community composition comparisons by taxonomic 

 order for four Appalachian mountain river studies. Abbreviations as in 

 Table 1. 



Order FB-1 FB-2 MR-1 MR-2 NT-1 LPR 



Ephemeroptera 



40 



46 



39 



37 



40 



20 



Plecoptera 



4 



4 



16 



10 



7 



6 



Trichoptera 



16 



12 



18 



26 



35 



22 



Diptera 



33 



28 



20 



18 



11 



44 



Coleoptera 



5 



3 



5 



5 



6 



4 



Other 



2 



7 



2 



4 



1 



4 



