5. Pinyon is capable of fully recovering from rather severe suppression. 



6. Stand basal area increment had been remarkedly constant on all but the youngest 

 plot for the past 60 years or more. The only plots with any indication that 

 stand basal area increment might have been beginning to decline were, surpris- 

 ingly, two of the younger plots. Because of its constancy and direct relation- 

 ship to productivity, stand basal area increment appears to be a good index of 

 site quality in closed stands. 



7. Total aboveground biomass accumulation rates follow a pattern similar to stand 

 basal area increment, but, because of continued height growth, there is a tend- 

 ency for the rates to continue to increase even in the oldest stands. Since 

 competition rarely kills larger pinyon and juniper, biomass accumulation can be 

 expected to continue at nearly constant or slightly increasing rates for several 

 centuries, barring tree cutting, fires, or epidemics. 



These conclusions are tentative and subject to modification when more data are 

 acquired. The conclusions pertaining to juniper are rather tenuous because few junipers 

 were on the plots. Conclusions concerning effects of age on growth should be tested 

 by measuring old stands on better sites, if such stands can be found. 



11 



