How do you determine if a site is fully occupied (stocked) by pinyon and or juniper?

The amount of lateral leader growth on understory sapling-size trees is a good indicator of understory competition between overstory trees.  Compare leader length in closed stands to trees growing in the open or at the edge of a stand or adjacent to a road. 

In this Phase II woodland, leader growth on these tree saplings indicate that: 1) this ecological site is relatively productive; 2) there is little intraspecific competition among trees; and 3) the shrub layer has little effect on tree growth. Although leader growth is shorter on less productive sites, the length of leaders on younger trees becomes severely reduced under intraspecific competition from the tree overstory, indicating a near closed stand of trees. (Photo from Grand Staircase, Utah, by Rick Miller)