VEGETATIONAL ANALYSIS 



39 



ure. Fairly accurate coverage for individual species can be deter- 

 mined from the prints with a planimeter (a mechanical device for 

 determining the area of a surface with irregular boundaries). Such 

 records are particularly useful when the areas are to be studied 

 over a period of time and when they are subject to treatment. 



FlG. 14. A4apping a quadrat by the use of a pantograph, which reduces all 

 details to scale.— U. S. Forest Service. 



When a high degree of accuracy is desired for small plots, a panto- 

 graph 193 can be used with a drawing board, or sketching on co- 

 ordinate paper may be quite satisfactory, especially if the quadrat 

 itself is marked off into a grid pattern, as with strings. For small 

 quadrats of low or matted vegetation, a rigid frame permanently 

 rigged with fine cross wires to form a grid (see Fig. 12) can be 

 used to advantage since it can be moved from place to place, thus 

 saving the time of marking off" each new quadrat. 25 Small quadrats 

 in relatively tall herbaceous vegetation or among shrubs and sap- 

 lings can be laid out more easily with rods or wooden strips cut to 

 proper length than with tapes (see Fig. 11). There are times when 

 the accurate measurement or recording of cover is too time-con- 

 suming or is not actually necessary. Estimation of cover merely 

 by inspection of each plot can be done with considerable accuracy 

 after only a little experience, and such an estimate may be suffi- 

 cient for the objectives. 



