Fire history and moisture influences on historical forest age structure in the sky islands of southern Arizona, USA
The authors examined synchrony of stand age and structure between geographically separated sites, or sky islands, to determine the influence of moisture and/or drought variability versus fire frequency on historic stand development.
The authors found that fire frequency appeared to be the primary influence on tree age structure in the sky island communities. Fire free periods were related to age peaks. The authors suggest that climate did not limit tree establishment and regeneration, however, climate did influence fire frequency and thus indirectly influenced age structure pattern in these stands. Within the study sites, age peaks occurred synchronously in the early 19th century, coinciding with a period of increased moisture within the ENSO cycle that reduced fire activity.