HELP

 My computer will not let me use count plots!

OK, let's be nice if possible. Don't shoot your compiler person right away. Have a chat with them, and ask them to change the program. Perhaps the program can do it, and you just do not know how to ask for it, or perhaps there is a simple way to fool the program into doing the work without any programming changes. If the compiler person helps you, make sure they get plenty of personal credit for doing so.

Just to be careful, after they do the adjustments run the program with and without the count plots to make sure that the values do change, and the compilations were actually using the count plots. If they will not change the program, what can you do? Well, you could do the changes by hand, and it is not hard.

The program has no choice but to do the equivalent of multiplying the average basal area/acre (BA/acre) times the average VBAR (no matter what it thinks it is doing). We have no quarrel with the VBAR, since the counts would only change the BA/acre. Manipulate the basal area per acre.

For example: the measured plots give a basal area of 100 ft2/acre, which you can see from the printout. What do the measured and counted plots indicate? This is easy to get with a hand calculator or a spreadsheet. Suppose the average BA/acre using all the plots (measured and count) is actually 90 ft2/acre. All you do is multiply the basal area per acre by (90/100). The same is true of volume/acre and many of the other values from the compilation.
You can do this by species, using the individual species tree counts on all plots, and it should greatly improve your results, especially for rare species.

If you are working with a single species, there is a trick you can use. Assuming that we calculate that the basal area should be 92% of the simple value for that species (by the method just explained) we can rerun the program with a different BAF. Change the BAF to 92% of what was actually used, and rerun the program. All the calculations will be done automatically. Essentially, you are just forcing the basal area/acre to be smaller by changing the BAF (as well as whatever flows from the BA, such as the number of trees per acre, volume, etc).

You might not get credit in the statistics when the numbers are recompiled and improved this way, but the output will have the right changes made and printed on the usual reports. This certainly works for BA, volume, trees per acre and most of the standard compilations. If in doubt about the other values, check with a biometrician just to make sure. It should work with virtually any reported item.

Better yet, get them to fix the darn thing and use count plots directly.


To read more about count plots, check the home page, and put "count plot" into the search utility. For articles that are not reproduced there, check the full list of titles. If you have the book with the first 50 issues, check the table of contents.

Originally published January 2002

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