Radial growth of grand fir and Douglas-fir 10 years after defoliation by the Douglas-fir tussock moth in the Blue Mountains outbreak.

Radial-growth recovery related to amount of tree defoliation was measured 10 years after a severe outbreak of Douglas-fir tussock moth (Orgyia pseudotsugata (McDunnough). For the period 1978-82, growth of qrand fir surpassed and was significantly greater than in the preoutbreak period, 1968-72. Douglas-fir growth during the postoutbreak period showed similar patterns, but it was not significantly different from preoutbreak growth for every defoliation class. Growth of undefoliated trees was also greater during the postoutbreak period, indicating that above-normal precipitation aided tree recovery and masked the thinning effect of tree mortality.