52 CIRCULAR 3 3 3, U.S. DEPARTMENT OF AGRICULTURE 



sectioned off with string or, preferably, with a standard wooden 

 frame. 



Reproduction on quadrats can often be mapped by coordinates 

 (4. 36. Jfl. 50. 73, 78) r 5 This eliminates tagging and sometimes 

 makes field mapping unnecessary. A number of research agencies 

 have found the coordinate system so satisfactory that they haye dis- 

 carded the tagging method entirely. They report that seedlings can 

 be located by this method within half an inch on milacre quadrats. 

 If reproduction is mapped by coordinates, great care is necessary to 

 avoid erroneous location of stems. Where a standard wooden frame 

 is used, mapping by coordinates requires about the same time as 

 tagging. It saves a great deal of time in reexaminations, however, 

 by obviating the necessity of hunting for tags, some of which may 

 have been damaged by animals or covered with debris. 



When detailed mapping of quadrats is necessary, slope areas 

 rather than horizontal areas should be used and the results should 

 be converted to a horizontal-area basis. 



If plant succession is to be studied by repeated mapping of re- 

 production quadrats it is well to make the second and subsequent 

 maps on transparent overlays, so that changes can be brought out 

 without the confusion resulting from marking changes on the orig- 

 inal maps. 26 Except in instances in which the composition or density 

 of the vegetation changes rapidly from one season to the next, many 

 quadrats need not be recharted more often than every 2 or 3 years. 

 Colors may be used to indicate year of origin of the reproduction or 

 area occupied by various plants. Symbols or abbreviations may be 

 used for species, and heights may be written in. 



Maps of surface conditions, such as the depth, character, and 

 density of litter, the exposure of mineral soil or rock, or the color 

 of the soil after fire, are often of sufficient value to justify preparing 

 them. 



Symbols used in sample-plot mapping are shown in the appen- 

 dix '(p. 76). 



Every map should be initialed and dated in the field. 



PLOT DESCRIPTION 



When the trees and reproduction on a sample plot have been 

 measured the plot itself remains to be described. The plot descrip- 

 tion should be carefully written in the field and not left to be pre- 

 pared weeks or months later from hurriedly written field notes. 

 Many facts easily obtained but often overlooked in the field are of 

 inestimable value in working with the data away from the plot, 

 especially to those not familiar with the plot itself. The success 

 of the whole experiment may depend on the completeness of this 

 description. 



The quantity and kind of detail needed and methods to be used 

 vary according to the permanence of the plot and the duration of the 

 study (7, 15. 16. Sip, 72). A long-time study should have a more 

 complete record than a short one. But since short-time studies often 

 merge into long-time ones, in initiating a short-time study it is desir- 



es Toumey, J. W. See footnote 7. 



26 A phvtograph for recording abundance, frequency, size classes, and basal area per 

 acre by species is described by Lutz (44). 



