On a stand basis, biomass growth follows trends similar to those of the individual 

 large trees (figs. 14, 15, and 16). On the Green Creek plot (fig. 14), growth rates of 

 all three components--foliage, wood, and total—continued to increase until 1975. As 

 mentioned earlier, the slight decline in growth rates from 1975 to 1977 was probably due 

 to the combined effects of the drought during that period and the measurement of the 

 trees before current season growth was completed; the decline does not necessarily in- 

 dicate a change in trend of growth rates. 



In contrast, rates of biomass increment on the Cattle Trough plot (fig. 15) have 

 been essentially constant since about 1920. The growth pattern on the Monte Cristo 

 plot (fig. 16) is intermediate between the other two plots, although biomasses are 

 greater. Growth rates at Monte Cristo were essentially constant from 1910 to 1950, but 

 growth rates tended to increase from 1950 to the time the plot was measured. 



120 



Figure 14. — Foliage, wood, and above-stump biomasses in metric tons per hectare on the 

 Green Creek plot from 1860 to 1977. 



The differences in growth patterns among these plots were caused mainly by differ- 

 ences in tree density and age structure. The Green Creek plot had a young stand, only 

 five trees in the plot were more than 100 years old (table 2) . The Cattle Trough plot 

 had a dense stand essentially 80 years more advanced than Green Creek; 43 trees on this 

 plot were more than 100 years old. The Monte Cristo plot had the greatest diversity of 

 ages but, unlike Cattle Trough, the density was not great and many of the younger trees 

 were not subject to competition from the older trees. 



17 



