Junipers tended to have lower height growth rates than pinyon, but the two junipers 

 in plot S4 show that juniper is capable of height growth rates comparable to pinyon. 

 A post had been cut from the main stem of juniper No. 20 on this plot about 100 years 

 ago and the present top is a lateral branch that took over. Its height growth rate 

 equaled that of the much younger juniper No. 29. 



Diameter Growth 



As reported for the 1977 plots, diameter growth rates did not decrease appreciably 

 with age in truly dominant trees. Reductions in diameter growth were caused by compe- 

 tition . 



Tree No. 5 on plot S4 (fig. 2) is particulary interesting. In 1750, it was 

 severely suppressed, about 200 years old, only 26 dm tall, only 8 cm diameter at stump 

 height, and nearly dead. It was gradually released from suppression sometime between 

 1750 and 1800. It recovered slowly and eventually became one of the fastest growing 

 dominants in the stand. What happened to the suppressing overstory back in the 18th 

 century is unknown; there was no evidence of fire damage to the surviving trees. Simi- 

 lar, but less spectacular, responses to release have been observed in other pinyons. 



Stand Basal Area 



Radial growth of the individual trees on the plots fluctuated and generally de- 

 creased as competition increased, but, once the trees fully dominated, stand basal 

 area growth on each plot became remarkably constant (fig. 3). The magnitude of this 

 constant rate is determined by site quality. 



Theoretically, there is a maximum basal area for each stand, and, as this maximum 

 is approached, stand basal area increment decreases through reduction in growth of in- 

 dividual trees and through mortality. Other than seedlings and a few saplings, there 

 has been no evident mortality on six of the plots in the past 100 years or so. The 

 other two plots, S4 and P2, each had one pinyon snag. These trees were 220 and 280 

 years old at time of death and had stump diameters of 25 and 30 cm. Both had been 

 growing very slowly for more than 100 years prior to death and apparently died because 

 of localized overcrowding. 



All of the sampled stands, even the oldest ones, are well below maximum basal 

 area. There are no indications of impending reduction in basal area increment on any 

 of the plots, except possibly two of the younger plots, S2 and P3. 



The four younger plots all have higher basal area growth rates than the four older 

 plots. This is because they are on better sites, not because young stands grow faster 

 than old ones. All available evidence indicates that basal area growth rates on the 

 older plots were no greater when they were young. It would be desirable to sample older 

 stands on better sites, but none have been found so far. Virtually all accessible good 

 sites must have been cut over in the 19th century. 



7 



