178 THE FORMATION 



changes in arrangement are taking place rapidly. They are especially 

 adapted to the study of minute alternations and to the zonation of small 

 ponds, streams, ditches, roads, blowouts, etc. Longer transects can not fur- 

 nish the same detail, on account of the amount of time necessary, but they 

 are invaluable for the zonation and alternation of larger areas, such as the 

 consocies, formation, and formation series. They are of particular impor- 

 tance for the record of zonation, since they aftord a clue to the topographic 

 symmetry of the area. The location of a transect depends upon the area to 

 be studied, though it should always run through a portion as typical as pos- 

 sible. The general direction is ascertained by means of the compass, and 

 when there is a measurable difference in elevation it is taken by the barometer 

 or otherwise. 



The points at which ecotones cross the transect are carefully indicated 

 upon the chart. They serve as stations for simultaneous readings of phys- 

 ical factors, though in the majority of cases water-content readings alone will 

 determine the reason for the ecotone. Photographs of line transects should 

 be made while the tape is in position, in order that the superficies of the series 

 may be as evident as possible. 



The Belt Transect 



220. Details. This differs from the line transect in that it is wider, and 

 consequently affords a more accurate record of the arrangement of plants. 

 While both give the actual facts of distribution, the line transect necessarily 

 ignores the minor lateral deviations in position. These are brought out in a 

 strip of some width, and the belt transect thus gives a more correct view of 

 the variations which result from competition in an area physically homo- 

 geneous. The width of such transects depends upon the length, and the 

 character of the vegetation. The standard width is one decimeter in herba- 

 ceous formations, and one meter in the long transects which are used in 

 woodlands. In open vegetation, especially in the initial stages of succes- 

 sions, the width may often be increased to advantage, but ordinarily the 

 amount of work necessary to run a belt transect of some length limits the 

 width to one decimeter. 



The location of a belt transect, the choice of landmarks, the determination 

 of direction and elevation are made exactly as for the line transect. The 

 topographic map is made in precisely the same way also, the scale used de- 

 pending upon the length. Two tapes, however, are employed, and these are 

 placed so that they mark off a strip just one decimeter wide. Every few 

 meters, or oftener if need be, they are checked by a decimeter rule, and fixed 

 firmly in place by quadrat stakes. The arrangement of the plants is recorded 



