56 



THE FORESTER. 



March, 



pie plots: four near Clackamas, four in 

 the Santiam Valley near Shelburne, and 

 one between Detroit and Permelia Lake. 

 The measurements of the trees which 

 were analyzed on the various plots are 

 summarized in Table No. I. 



The annual growth of each tree in 

 diameter and height was worked out 

 separately from the stem analyses, and 

 the average of all obtained by entering 

 the values on cross-section paper and 

 drawing normal curves through them. 

 The rate of growth for each decade was 

 then read directly from the curves. 

 These values are given in Table No. 2. 



TABLE No. 2. 



Rate of Growth in Height and Diameter. 



Average of Nine Trees. 



From this table it will be seen that 



the tree reaches its maximum rate of 

 growth in height between its twentieth and 

 thirtieth years, during which period it is 

 shooting up two and four-tenths feet per 

 annum. The mean annual growth in 

 height for the first thirty years is one and 

 nine tenths feet, or slightly less than the 

 current annual growth. The rate of 

 growth in diameter is very regular. It 

 reaches its maximum at about the thirtieth 

 year and continues at the rate of twenty- 

 four one-hundredths of an inch per 

 annum until the tree is about fifty years 

 old, when it begins to decrease. It 

 must be borne in mind that these figures 

 of growth do not represent what an in- 

 dividual tree is capable of doing if given 

 favorable conditions of light and grow- 

 ing space, but are the average for all 

 trees both large and small, in a dense 

 forest. 



The chief purpose in taking the meas- 

 urements of sample plots was to deter- 

 mine the number of trees per acre and 

 the total contents at different ages. 

 Table No. 3 gives a summary of the 

 nine valuation surveys, and shows for 

 each plot the number of trees, the aver- 

 age and maximum diameters, the average 

 height, age and density, and the total 

 contents in cubic feet and cords. No 

 computation of board feet was made be- 

 cause, with the exception of a few speci- 

 mens on Plot No. g, the trees were not 

 of a merchantable size. 



