QUADRATS 



171 



a labeled stake at one corner of the quadrat, and locating the latter definitely 

 in relation to a conspicuous landmark. When one is in residence for several 

 years, practically all chart quadrats are converted into permanent ones, since 

 the work already done in the chart quadrat is so much accomplished towards 

 the permanent one. This is not necessary when one wishes merely to com- 

 pare different areas of stable formations. As a rule, however, some change 

 is constantly being wrought by invasion or competition, and the amount and 

 direction of this can only be revealed by the permanent quadrat. The latter 

 has a fundamental value for all kinds of invasion, but it is absolutely indis- 



Fig. 53. Permanent quadrat, Polygon He (Polygonum bistortoides) 

 Ruxton Park; mapped and photographed July 22, denuded September 

 8. 1903. 



pensable in studying complete invasion or succession, and in discovering and 

 recording the gradual effects of competition. It is in the detailed investiga- 

 tion of these dynamic phenomena that the paramount importance of the 

 quadrat is most evident. If the experience of several years be taken as con- 

 clusive, no other method is capable of revealing the minute changes as they 

 are occurring. 



The permanent quadrat is regularly i meter square, a size determined both 

 by the exigencies of charting and photographing. When ecograph batteries 

 are used, the quadrat is located as close to the latter as is possible. Other- 



