THE EFFECTS OF REPEATED PRESCRIBED BURNING ON PINUS-PONDEROSA GROWTH

The effect of repeated prescribed burning on long term growth of Pinus ponderosa in northern Arizona was examined. Fire treatments for hazar d reduction were initiated in 1976, acid growth was evaluated in 1988 for fire rotations of 1, 2, 4, 6, 8, and 10 years. Dendroecological an alysis shows that there were only small changes in tree growth (compar ed to controls) in the first few years after the initial fire treatmen t despite large fuel reductions and thinning, and that annual precipit ation was positively correlated with growth. Moderate changes in growt h relative to that of control trees were apparent after 1984. The 1-, 2-, 8-, and 10-year treatments had lower growth than controls after th is date, while 4- and 6-year treatments had slightly higher growth. Al though additional data are needed to determine long term growth effect s in the longer fire rotations, a fire treatment interval of 4 to 6 ye ars appears to provide adequate fuel reduction without reducing long t erm growth in Southwestern P. ponderosa forests.