Five-Year Impacts of Swiss Needle Cast on Douglas-fir in Interior Forests of Oregon, USA

northern Cascade Mountain foothills in Oregon, USA. Mean 5-year-dbh growth was 6.1 cm and total-height growth was 3.6 m. Mean needle-retention index increased by 3.4 over 5 years, and mid-crown retention increased by 1.2 years. Mean percentages of stomata occluded by pseudothecia of Phaeocryptopus gaeumannii were 13.6 % for 2000-(2-year-old) needles and 1.7 % for 2001-(1-year-old) needles sampled in 2002, and 13.3 % for 2004 (2-year-old) needles sampled in 2006. Mean crown-length to sapwood-area ratio was 5.2 cm/cm2 in 2006. There were poor correlations (R2 <0.3) among all variables except for a moderate correlation between stand elevation and either 2000-stomata occluded (R2 = 0.43) or 2004-stomata occluded (R2 = 0.50), where there were fewer pseudothecia at the higher elevations. Either 5 years is not enough time to evaluate the affects of Swiss needle cast on Douglas-fir growth in the Oregon Cascades or there was no significant effect of Swiss needle cast during the latest outbreak on Douglas-fir growth. Based on our results and their interpretation, forest managers may need not alter their current practices in the northern Oregon Cascades, and managing a mix of Douglas-fir and western hemlock at lower elevations and noble fir at higher elevations will help offset any future stand-growth declines due to Swiss needle cast. Phaeocrytopus gaeumannii / Pseudotsuga menziesii / tree growth loss Kivonat – A svájci tűhullás ötéves hatása a duglászfenyőre Oregon belső erdeiben. 2001-ben é