l8p THE FORMATION 



that all charts and photographs must bear the number of the reading as well 

 as that of the transect. Physical factor observations are taken as often as 

 the charts are made, and the results noted on the back of the chart sheet for 

 purposes of ready comparison. 



The Denuded Transect 



223. The denuded transect bears exactly the same relation to a perma- 

 nent one as that which exists between the denuded and the permanent quad- 

 rat. While the permanent transect records the actual mutations due to 

 changing physical factors or to competition, the denuded transect throws 

 needed light upon the mobility and ecesis of the various species, and upon 

 the nature of the competition between them. Denuded transects may be 

 established wherever it seems desirable, after the strip has been properly 

 charted and photographed. The most valuable results, however, are secured 

 by locating each one alongside of a permanent one. The best plan is to lo- 

 cate and chart two permanent transects a meter apart. A single view is then 

 made of the two. One of them is denuded together with a strip 2 decimeters 

 on either side, resulting in a denuded transect 5 decimeters wide. In chart- 

 ing this during succeeding years, the entire width may well be plotted as 

 long as the vegetation is open, but after it has again become well established, 

 it is necessary to save time by confining one's attention to the central deci- 

 meter strip. Photographs can be made either of the permanent and denuded 

 transects singly, or of the two together. The latter method has certain ob- 

 vious advantages. Climatic factor readings can be made for both transects 

 in common, but all those factors which are affected by the exposure of the 

 soil surface must be observed in each. 



The Layer Transect 



224. This is a modification of the line transect, by means of which the 

 vertical relations of plants are also shown, especially the tendency to form 

 layers which is so regular a feature of forest formations. Owing to the dif- 

 ficulty of charting in three planes, belt transects do not lend themselves to 

 this purpose. Because of the greater complexity, layer transects can rarely 

 exceed ten meters in length except in those formations where layering is lit- 

 tle or not at all developed. The simplest method is to establish a line tran- 

 sect in the ordinary way, and then to record the height of each plant as its 

 position is noted. This is done by means of a measuring stick ruled in deci- 

 meters, which can be moved from interval to interval along the tape, or bet- 

 ter, by two such sticks connected by tapes a meter long at every five deci- 



