Intensification of Dwarf Mistletoe on Southwestern Douglas-fir

Washington D.C.

1990

S. 955-969

1 Abb., 6 Tab., 4 Lit. Ang.

Bandaufführung

64616

From a sample of 445 Douglas-fir trees infected with dwarf mistletoe (Arceuthobium douglasii), three models for predicting mistletoe are developed. Two models relate the mean rate of intensification since the tree became infected to initial and current tree conditions; the third one describes the proportion of trees that increased by 0, 1, 2, or more classes of dwarf mistletoe infection (DMR) in the past 10 years. The models suggest that the rate of intensification is most rapid (2 DMR classes per decade) for severely infected trees of small diameter and slowest (0.5 DMR classes per decade) for lightly infected trees of larger diameter. Intensification within a tree increases with the abundance of mistletoe in nearby, larger trees and with stand basal area. No other significant relations were found between rates of intensification and site or stand factors such as habitat type, site productivity, or stand composition. A comparison of mistletoe ratings for standing tree and ratings for carefully examined felled trees indicates that trees can be correctly rated by standard procedures about 75% of the time.