Needle retention in Oregon Coast Range Douglas-fir plantations across elevational and disease severity gradients.

Gabriela Ritóková¹,²*, Dave Shaw¹,², Sky Lan², Jeff Hatten², Randy Comeleo³

¹ Swiss Needle Cast Cooperative, College of Forestry, Oregon State University² Forest Engineering, Resources, and Management, College of Forestry, Oregon State University

³ U.S. Environmental Protection Agency, Corvallis, OR

Cooperative Aerial Survey: US Forest Service, Forest Health Protection, Forest Health Aviation, Oregon Department of Forestry, Swiss Needle Cast CooperativeSwiss Needle Cast Cooperative http://sncc.forestry.oregonstate.edu/*Contact: gabriela.ritokova@oregonstate.edu

Swiss Needle Cast (SNC)

Fig 3. Area of Douglas-fir forest in western Oregon with SNC symptoms detected during aerial surveys conducted in April-June, 1996-2018 (2008 area estimated from partial survey consisting of 3 sample blocks). Trend line is 3-year rolling average. Coast Range, Oregon.

Citations Ritóková, G., Shaw, D.C., Filip, G., Kanaskie, A., Browning, J., and D. Norlander. 2016. Swiss Needle Cast in Western Oregon Douglas-Fir Plantations: 20-Year Monitoring Results. Forests 7, 155.

Shaw, D.C.; Filip, G.M.; Kanaskie, A. [and others]. 2011. Managing an epidemic of Swiss needle cast in the Douglas-fir region of Oregon: the role of the Swiss Needle Cast Cooperative. Journal of Forestry.109: 109-119.

Mulvey, L.R., Shaw, D.C., Filip, G., Chastagner, G.A. January 2016. Swiss Needle Cast. Forest Insect & Disease Leaflet 181. U.S. Department of Agriculture, Forest Service.

Shaw, D.C., Woolley, T., and A. Kanaskie. 2014. Vertical foliage retention in Douglas-fir across environmental gradients of the western Oregon coast range influenced by Swiss needle cast. Northwest Science 88: 23-32.

Maguire, D.A., D.B. Mainwaring, and A. Kanaskie. 2011. Ten-year growth and mortality in young Douglas-fir stands experiencing a range in Swiss needle cast severity. Canadian Journal of Forest Research 41: 2064-2076.

Results

Fig 10. Estimated relationship between mean SNC disease severity index and needle retention at mid-crown level in young Douglas-fir plantations in western Oregon southwestern Washington, 2013-2015. Shaded area indicates 95% confidence interval.

Fig 1. Douglas-fir needles affected by Nothophaeocryptopus gaeumannii

Fig 2. Crown of a diseased Douglas-fir with less than 1-year of needle retention

Fig 4. SNC causes Douglas-fir tree crowns to look yellow-brown in spring. Symptomatic Douglas-fir is surrounded by light-green red alder and dark-green Sitka spruce and western hemlock. Photo by Rob Flowers, Oregon Department of Forestry.

Disease severity trends north to south match symptomatic acreage as identified by aerial survey (fig 7, 8c).Unpublished needle retention data indicates that areas with lowest needle retention don’t necessarily have the greatest disease severity, presumably because of pre-sampling casting of needles with the greatest stomatal occlusion (fig 10).

Fig 5. The relationship observed between needle retention and percent volume-growth loss in a ten-year growth impact study of 76 Douglas-fir stands in north coastal Oregon. Each line represents the needle retention-growth loss relationship during a specific measurement period. In general, growth loss peaks at about 50-60% and no growth loss is expected when trees retain more than 3-4 needle cohorts. (Maguire et al., 2011).

Needle RetentionFig 6. Needle Retention = summed proportions of attached needles from

each annual foliar cohort, as in the photos shown.

Fig 9. Trend in plot average needle retention with elevation, with the highly-variable positive relationship reflecting the confounding and interactive effects of topography and climate.

Fig 8. Maps from left to right showing a) needle retention distribution; b) elevation surface; c) SNC disease severity index (higher the number, higher level of SNC infection). Black dots represent the 106 SNCC research plots. Maps are based on existing SNCC plot network data.

← a) 4.0 years

← b) 2.4 years

c) 0.9 years →

SNCC plot networkMethods

• 106 research plots distributed across OR coast and SW WA 50 km from the coast

• Plot size: 1/5 acre • Plantation age: 10-30 year • Douglas-fir TPA: 250-810 • Non-Douglas-fir TPA: 0-765• Avg. needle retention range: 1.15 – 3.9 yrs• Elevation range: 45 – 810 m• Plots were established in fall and foliage

from 5-10 dominant trees collected in the following spring

• Middle crown foliage was used for needle retention and disease severity evaluation

2018

Fig 7. Aerial survey map of SNC distribution in the Oregon Coast Range. Observed symptoms inDouglas-fir. Navarro and Norlander, Oregon Dept. of Forestry.

• Foliage disease of Douglas-fir (Pseudotsuga menziesii) caused by ascomycete fungus Nothophaeocryptopus gaeumannii (fig 1)

• Symptoms include decreased needle retention (fig 2,6bc), yellow to brown discoloration of the needles and tree crowns (fig 4), resulting in sparse crowns (fig 2) and significant reduction of tree diameter and height growth when mean needle retention < 2 years (fig 5)

• In Oregon, aerial survey covers approximately 3 mil. acres• In 2018, 434,000 ac of Douglas-fir forests acres observed

with symptoms (fig 3,4,7)• SNC is most damaging near the coast