4. Design changes
The new design is intended to preserve the ability to
use all sites in a spatial surface, while recognizing differences
in species composition, precipitation and soils that
occur across small distances in the San Bernardino Mountains.
This will be accomplished by establishing a network
of sites expanding in two directions along the air pollution
gradient. This two dimensional ‘grid’ of sites will extend
both north and south (perpendicular to air pollution flow)
as well as east and west (parallel to the air pollution flow).
The advantage of this approach is that large-scale comparisons
based on geography, exposure, and species composition
are possible, while accommodating opportunities for
smaller scale studies requiring more homogenous forest
conditions. It should be noted that forest composition
changes are greatest in the west to east direction of the
gradient.