20 CIRCULAR 3 3 3, U.S. DEPARTMENT OF AGRICULTURE ' 



Subplots should be laid out on the slope rather than horizontally, 

 if they are to be mapped. This eliminates the bothersome necessity 

 of allowing for slope in measuring the coordinates of each tree, and 

 the data can be reduced to a horizontal-area basis by the use of a 

 simple converting factor. Furthermore, the vegetation on sub- 

 plots can be mapped more easily if measurements are taken along 

 the slope. For subplots thus laid out slope must be carefully re- 

 corded, in order to facilitate conversion to an acre basis. 



The location of all subplots irregularly placed should be ref- 

 erenced to plot-boundary stations or to regularly placed subplots. 



PLOT CORNER TIE-INS AND WITNESSES 



Each plot corner should be tied in by bearing and distance to 

 1 or 2 witness trees or, if trees suitable for this use are lacking, to 

 witness stakes or large rocks set for the purpose. Numbered trees 

 within the plot are excellent witnesses, if they are to remain in the 

 stand throughout the experiment. If stakes or other artificial 

 markers must be used as witness points, they may be placed one on 

 each side of the corner in such a way that they and the corner 

 form a straight line. Another method is to place the witness 

 markers on the plot boundaries about 20 feet each way from the 

 corner of the plot. In very young stands, shallow ditches extend- 

 ing 3 or 4 feet from the corner along adjacent sides of the plot 

 may be used to indicate the corner's position. 



Blazes on witness trees should face the plot corner. If paint is 

 used to mark witness trees, double bands should be painted around 

 the tree at about eye height, with a vertical stripe crossing these 

 on the side of the tree facing the corner. Small enameled signs 

 bearing the name of the agency responsible for the plot and a blank 

 space for painting in the plot number may be tacked on witness trees. 



NUMBERING PLOTS, SUBPLOTS, AND PLOT SECTIONS 



Where a considerable number of plots are involved, some scheme 

 for designating each individual plot should be worked out in advance 

 and carefully followed. Generally speaking, all plots in a given 

 locality should be numbered consecutively as established, regardless 

 of differences of purpose. Where several parties from one research 

 agency are at work in the same locality at the same time, it may 

 be necessary to use before each plot number a letter designating 

 the party. In order to avoid later confusion, the number of an 

 abandoned plot should not be given to a new plot in the same 

 locality. 



Each group of consecutively numbered plots should be called by 

 some appropriate and distinctive name, such as that of the State, 

 the forest, or the drainage. Each plot should be designated by this 

 name plus the plot number, e.g., Virginia 8, Shasta 5, or Pinto 

 Creek 13. County names, because of duplication between States, 

 often would fail to distinguish the plot groups of an interstate 

 research organization. 13 



13 If the plots established by an interstate organization are numbered serially in each 

 of the States in its territory, the number of the latest plot established in a State is an 

 index of the quantity of sample-plot work under way in that State. This plan is not 

 feasible if the agency has several parties at work establishing plots at the same time. 





