Subsequently, between 1968 and 1974, a series of longterm
monitoring sites were established to study trends in
crown injury to ponderosa and Jeffrey pines from oxidant
air pollution in the San Bernardino Mountains. Over the past
30 years, studies conducted at these sites have contributed to
our understanding of foliar injury and bole growth responses
to ozone exposure in forest systems. More recently, the
scope of research efforts at these sites has expanded to
include studies on nitrogen deposition to ecosystems, and
multiple effects of ozone and N deposition on ecosystem
function