-43- 



Associations of species rarely found together are also of 

 interest, such as northern mountain species occurring together 

 with southern lowland species. This often indicates relict 

 conditions such as hemlock and rhododendron isolates and northern 

 species left in sphagnum bogs adjacent to southern communities 

 of plants. 



Size of Area 



The bigger an area, the greater its diversity of ecosystems, 

 communities and species is likely to be. In smaller isolated 

 areas the larger predators which act as regulators are usually 

 missing and may require intervention by man to prevent too 

 large populations of primary herbivores. 



The minimum size required for a natural area has been 

 discussed almost endlessly and to halt repetitive debate certain 

 arbitrary sizes have been set. The prime function of size as a 

 criteria lies in the viability of the ecosystem to be protected. 

 This varies greatly depending on the ecosystem. A tenth acre 

 bog may be quite defensible with some protecting buffer zone. 

 A small area of mountain top or a small island can be preserved 

 and maintained with relative ease. In addition, a half acre 

 plot of rare tall-grass prairie in a cemetary or along a railroad 

 should be preserved as a natural area. 



On the other hand, pine flatland may require over 1,000 

 acres to provide examples of the usual species expected in such 

 an area. There is no rule for determining the minimum size of an 



