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 wasexamined. Fire treatments for hazard reduction were initiatedin 1976,and growth was evaluated in 1988 for fire rotations of 1, 2, 4, 6, 8, and 10 years. Dendroecological analysis shows that there were only small changes in treegrowth (compared tocontrols) in the first few years after the initial fire treatment despite large fuel reductions and thinning, and that annual precipitation was positively correlated with growth. Moderate changes in growth relative to that of control trees were apparent after 1984.The 1-,2-,8-,and 10-year treatments had lower growth than controls after this date, while 4and 6-year treatments had slightly higher growth. Although additionaldataareneeded todetermine long term growth effectsin the longer firerotations,a fire treament interval of 4 to 6 years appears to provide adequate fuel reduction without reducing long term growth in Southwestern P. ponderosa forests.