Normal and AcHial Forest, Etc. 155 



fiilly stocked stands. (What is "ful!}^ stocked" cannot be dis- 

 cussed at this time or place.) 



This yield table is not fixed. Just as the farmer changes his 

 standard or measure in keeping v.'ith progress in agriculture, so 

 the forester changes his measure, his normal }4cld table, as he 

 leams more of silviculture. Schwappach's tables of 1902 are 

 not the same as his earlier tables, and we may expect considerable 

 change as the years go by. 



But his tables are now standard, made so by acceptance; they 

 are the best measure we have, they are useful and used; hundreds 

 of stands are judged every year by them and they saj^ whether a 

 given stand is good or poor, 60 per cent or 85 per cent norrrial. 



The normal stand is a measure; it is based on a number of actual 

 though selected, stands, it is not m.erely an ideal; it is a result 

 actually obtained with a given species and site in a given time. 



As a measure it serves to judge the actual stands as they occur 

 in the forests. Mistakes, accidents, etc., prevent, ordinarily, 

 that the many stands on a large property should all be normal. 

 In m.ost good forests, som.e stands are better than normal, i. e., 

 they have larger or more timber than is called for by the normal 

 yield table. But the majority fall below normal so that in the 

 Bavarian instructions, it is considered satisfactory when stands 

 of spruce 80-100 years old arc .8 normal. The farmer is no 

 better off; he, too, is satisfied if his crops are .8 "good," when 

 ten years average is taken. 



The normal yield table, stating as it does, the size of trees 

 and the volume per acre at the age of 10, 20, 30, etc., years is 

 also a table of grozvih from which may be computed current 

 growth, average growth, etc., of any stand or of a series of stands, 

 and the results thus obtained are figures of normal growth, or the 

 growth of a stand of timber which we accept as standard, as 

 m.easure, or as normal. 



The nomial yield table then serves, among other things, to 

 (g) judge, or measure, an actual stand before us, as to size of 

 trees and vcltmie per acre, by comparing it to a normal stand; 

 (6) estimate the crop v,'hich may be grov/n on a given site by 

 assuming that luider the given conditions (method, care and 

 probable injuries), we may secure, say, .8 as much timber as was 

 produced by the stands (of the same species on similar land) 

 which were used to make the yield table, or our standard. 



