THE VALVE OF EDGES 



175 



in terms of gross coziiposition rather than the mosaic of vegetation which may be produced 

 by cuhural operations. 



Reviewing the whole, the picture takes shape. \^Tiere the soil and the other site condi- 

 tions are poor, both the variety and interspersion of plants suffer accordingly. Here edges 

 are important in that they add diversity to the cover. Where the soil is good, the land not 

 too dry and the environment has not been heavily impoverished by man or by natural agen- 

 cies such as fire. Nature encourages a wide variety of plant species. In such situations the 

 individual types usually provide within their borders the conditions that strongly attract grouse 

 thereto. Thus there is less inclination to frequent the edges. When fresh desire or seasonal 

 changes draw them to another type, good grouse habitats are usually so well broken up that 

 the birds find no particular reason to stop at the edges. This, probably, explains the pres- 

 ence of many birds scattered throughout, rather than along, the edges of a type on the three 

 study areas characterized bv a favorable and frequent interspersion of cover. 



^Air>. ,■• 



THE T.liTHKR PRE.SERVK IS REFORESTED WITH BLOCKS OF CONIFERS WHICH 

 OFTEN ADJOIN NATURAL WOODLANDS 



Throughout this discussion we have used the word "edges' advisedly. Plotted on the cover 

 maps are all the major vegetative groups occupying more than a tenth of an acre which are 

 sufficiently distinct to make recognition of edges practical. Within these are found subdi- 

 visions in infinite variety. Here, in a wet spot, a patch of jewelweed has established itself; 

 there, where the winds have tipped over a widespreading beech, letting in a shaft of sunlight, 

 a patch of briers is springing up. Such spots cannot be mapped and measured as one does 

 the cover types. Yet each potentially may fulfill some grouse need. Each has an edge which 

 may be meaningful to a grouse even though too small to map. The more varied the patch- 

 work, the greater the chance for the cover to fulfill the wants of the bird. 



