66 CARNEGIE INSTITUTION OF WASHINGTON. 



has been prepared for examination in the same manner. The combination of 

 longitudinal and transverse sections has made it possible to secure a set of 

 precise measurements with which to compare the rate of growth of these 

 trees at different heights from the ground, as well as to investigate the corre- 

 lation between growth and rainfall. 



An examination has been made of the relative growth performances of 

 different portions of the trunk in the pine. The greatest diameter increment 

 in a single year was 3.3 cm,, which took place at a height of 5 meters at a time 

 when the pine was 7 meters high and 8 years old. This rate was equaled and 

 approached at about the same age and horizon in other cases. During the 

 first 16 years of the life of this 38-year-old tree the maximum growth for 

 each year took place from 2 to 5 meters below the top. After the attainment 

 of a height of 17 meters, which is near the total of 20 meters, the region of 

 maximum growth in diameter fell to a zone from 5 to 9 meters below the top. 

 In comparing the 19 cross-sections of the trunk, taken at 1-meter intervals, 

 the maximum growth at each of these horizons is almost invariably found at 

 the center or within 4 years of it. In comparing the growth in thickness for 

 a single year at all of the 19 horizons, a very pronounced irregularity is found. 

 This was greatest after the tree had reached a height of 15 meters and an age 

 of 17 years. Correlations between growth and any environmental condition 

 would differ widely if based on growth as measured in a stump section or 

 measured at some other horizon. 



For the purpose of correlating growth and rainfall two sets of growth data 

 were used: (1) the increments shown by the stump-section, and (2) the 

 average increments of the 10 lowest transverse sections. The former is the 

 commonly used datum, the latter should give a much more accurate measure 

 of the total growth performance of a tree. A comparison of graphs of annual 

 growth as determined by the two methods shows that in 22 out of 32 years 

 there was the same behavior on the part of the stump and the trunk as a 

 whole. 



The redwood exhibits a march of growth which is much more orderly than 

 that of the pine. The increments of any two years, when followed up the 

 tree, sustain the same general relation to each other. There is a complete 

 agreement between graphs showing growth at the stump and for the 10 

 trunk-sections. The maximum diameter increase in a single year was 2.3 

 cm. As in the pine, the maximum growth in each year was within a zone 

 2 to 3 meters from the top, and at each horizon was found from 2 to 4 years 

 from the center of the section. 



With a view to determining the degree to which rainfall may be responsible 

 for the fluctuations in growth-rate from year to year, several sets of qualita- 

 tive correlations were made for the pine and the redwood. Growth data 

 have been used from stump alone and from the average of 10 trunk-sections 

 in each tree. Correlations have been made with the total annual rainfall 

 and with four sets of seasonal rainfall data covering different groups of months. 

 The results indicate: a closer correlation of growth with rainfall in the red- 

 wood than in the pine; a much closer correlation in the pine from 20 to 40 

 years of age than from 1 to 20 years; a closer correlation for both trees with 

 the rainfall of the months from December of the preceding year to September 

 than for any of the groups of months more closely coinciding with the growing 



