Different Plot Sizes

In recent analysis of the initial FIA data, we have learned that the trees are not evenly distributed within their fifth-acre plots as we once suspected. If the trees were distributed evenly, a histogram of the distance r from the center of the FIA plot would have followed a straight line from 0.0 at the point r=0(the center of the plot) to about 12.5 at the point r=16.05 (the radius of a fifth-acre plot).

Graph 2.3 shows, however, that this is not the case. At about r=11 the distribution falls off dramatically, and very few trees are located between 11.3 and 16.05 meters from the center. Graph 2.4 shows the physical location of all trees in all the plots (plots are all superimposed). Within a radius of about 11.3 meters the tree density increases dramatically. The area of this inner circle is, coincidentally, a tenth-acre.

One (untested) hypothesis is that many of the plots are actually tenth-acre plots instead of fifth-acre plots. No decision has been made yet as to what should be done about this problem. If it is true that many of the plots are only tenth-acre in size, the final population will be much less than the original 10.8 hectares.