Modeling crown structural responses to competing vegetation control, thinning, fertilization, and Swiss needle cast in coastal Douglas-fir of the Pacific Northwest, USA

Experimental treatments of logging-debris retention (0%, 40%, or 80% surface coverage) and competing vegetation control (initial or annual applications) were installed at two sites in the Pacific Northwest following clearcutting Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco var. menziesii) stands to assess short-term effects on tree N acquisition, soil N supply, and total soil N. Vegetation control treatments began in the first year after harvest, and logging-debris manipulations were installed 2 years after harvest. Annual vegetation control increased foliar N concentration and content in most years at both sites, which was associated with higher available soil N and increased soil water content. Logging-debris retention treatments had no detectable effect on any of the foliar variables or soil available N at either site. There were no treatment effects on total soil N at the site with relatively high soil N, but total soil N increased with logging-debris retention when annual vegetation control was applied at the site with a low initial soil N pool. Competing vegetation control is an effective means to increase tree N acquisition in the initial years after planting while maintaining soil N pools critical to soil quality. The effect of logging-debris retention on tree N acquisition appears to be limited during early years of stand development, but increased soil N with heavy debris retention at certain sites may be beneficial to tree growth in later years.

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Phytophthora pluvialis Studies on Douglas-fir Require Swiss Needle Cast Suppression

Plant Disease ◽

10.1094/pdis-12-16-1738-re ◽

2017 ◽

Vol 101 (7) ◽

pp. 1259-1262 ◽

Cited By ~ 3

Author(s):

Mireia Gómez-Gallego ◽

Martin Karl-Friedrich Bader ◽

Peter Matthew Scott ◽

Sebastian Leuzinger ◽

Nari Michelle Williams

Keyword(s):

New Zealand ◽

Pacific Northwest ◽

Radiata Pine ◽

Douglas Fir ◽

Needle Cast ◽

The Pacific ◽

Swiss Needle Cast ◽

Phytophthora Pluvialis ◽

Red Needle Cast ◽

Ubiquitous Presence

Phytophthora pluvialis is associated with early defoliation and shoot dieback in Douglas-fir in Oregon and New Zealand. In 2013, P. pluvialis was described from mixed tanoak-Douglas-fir forests in the Pacific Northwest and concurrently recognized as the main causal agent of red needle cast (RNC) in New Zealand radiata pine plantations. Little is known about its infection cycle and impact on host physiology. P. pluvialis studies in Douglas-fir are challenging due to the ubiquitous presence of the endophyte Phaeocryptopus gaeumannii, which produces similar symptoms and premature defoliation with persistent needle wetness, known as Swiss needle cast (SNC). Nonetheless, our study showed P. pluvialis infection in the presence of SNC. Exclusive expression of P. pluvialis is difficult to achieve as both diseases are promoted by high humidity. Here we established a ‘dry leaf’ strategy to suppress SNC when inoculating Douglas-fir needles for RNC studies. Sheltering plants along with drip irrigation to avoid needle wetness during the P. gaeumannii sporulation period suppressed its development in the new season flush. The diminished endophyte inoculum enabled bias-reduced studies of P. pluvialis impacts on Douglas-fir without the confounding effects of stomatal blockage and premature defoliation caused by P. gaeumannii.

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Associations between Swiss Needle Cast Severity and Foliar Nutrients in Young-Growth Douglas-Fir in Coastal Western Oregon and Southwest Washington, USA

Forest Science ◽

10.1093/forsci/fxz022 ◽

2019 ◽

Vol 65 (5) ◽

pp. 537-542

Author(s):

Yung-Hsiang Lan ◽

David C Shaw ◽

Gabriela Ritóková ◽

Jeff A Hatten

Keyword(s):

Pacific Northwest ◽

Disease Incidence ◽

Douglas Fir ◽

Cooperative Research ◽

Foliar Nutrition ◽

Needle Cast ◽

The Pacific ◽

Foliage Nutrients ◽

Swiss Needle Cast ◽

Plot Network

Abstract Swiss needle cast (SNC) is a foliage disease of Douglas-fir (Pseudotsuga menziesii) caused by Nothophaeocryptopus gaeumannii, an ascomycete fungus (Mycosphaerellaceae) that causes tree growth reductions in the Pacific Northwest. The epidemiology of the fungus is generally well known, but the relations between disease expression and foliar nutrition are unclear. In this study, we used data from the Swiss Needle Cast Cooperative research and monitoring plot network in western Oregon and SW Washington to assess associations between SNC severity, carbon, and nine foliage nutrients (nitrogen, Na, K, P, Ca, Mg, Mn, Al, S). Foliage samples were collected from midcrown of selected Douglas-firs from each plot. SNC severity was determined on 2-year-old needles by multiplying disease incidence and fungal reproductive (pseudothecia) density. Disease severity and nutrient relations were determined using linear mixed models. SNC severity showed statistically significant positive trends with concentrations of carbon, nitrogen, Na, K, and S, no relation with concentrations of Ca, Mg, or Al, and slightly negative trends that were not significant for P and Mn. This is the first such analysis of associations between a conifer foliage disease and foliage nutrients across a landscape; subsequently, there is little published literature on how or why these nutrients may interact with disease.

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Predicting Swiss Needle Cast Disease Distribution and Severity in Young Douglas-Fir Plantations in Coastal Oregon

Phytopathology ◽

10.1094/phyto.2003.93.7.790 ◽

2003 ◽

Vol 93 (7) ◽

pp. 790-798 ◽

Cited By ~ 32

Author(s):

Pablo H. Rosso ◽

Everett M. Hansen

Keyword(s):

Prediction Model ◽

Disease Severity ◽

Pacific Northwest ◽

Regression Tree ◽

Douglas Fir ◽

Slope Aspect ◽

Disease Prediction ◽

Needle Cast ◽

Swiss Needle Cast ◽

The Relationship

Swiss needle cast (SNC), caused by the fungus Phaeocryptopus gaeumannii, is producing extensive defoliation and growth reduction in Douglas-fir forest plantations along the Pacific Northwest coast. An SNC disease prediction model for the coastal area of Oregon was built by establishing the relationship between the distribution of disease and the environment. A ground-based disease survey (220 plots) was used to study this relationship. Two types of regression approaches, multiple linear regression and regression tree, were used to study the relationship between disease severity and climate, topography, soil, and forest stand characteristics. Fog occurrence, precipitation, temperature, elevation, and slope aspect were the variables that contributed to explain most of the variability in disease severity, as indicated by both the multiple regression (r 2 = 0.57) and regression tree (RMD = 0.27) analyses. The resulting regression model was used to construct a disease prediction map. Findings agree with and formalize our previous understanding of the ecology of SNC: warmer and wetter conditions, provided that summer temperatures are relatively low, appear to increase disease severity. Both regression approaches have characteristics that can be useful in helping to improve our understanding of the ecology of SNC. The prediction model is able to produce a continuous prediction surface, suitable for hypothesis testing and assisting in disease management and research.

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Soil phosphorus fractions vary with harvest intensity and vegetation control at two contrasting Douglas-fir sites in the Pacific northwest

Geoderma ◽

10.1016/j.geoderma.2019.04.038 ◽

2019 ◽

Vol 350 ◽

pp. 73-83 ◽

Cited By ~ 1

Author(s):

Daniel G. DeBruler ◽

Stephen H. Schoenholtz ◽

Robert A. Slesak ◽

Brian D. Strahm ◽

Timothy B. Harrington

Keyword(s):

Pacific Northwest ◽

Soil Phosphorus ◽

Douglas Fir ◽

Phosphorus Fractions ◽

Vegetation Control ◽

Soil Phosphorus Fractions ◽

Harvest Intensity ◽

The Pacific

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Susceptibility of Intermountain Douglas-Fir to Rhabdocline Needle Cast When Grown in the Pacific Northwest

Plant Health Progress ◽

10.1094/php-2001-1029-01-rs ◽

2001 ◽

Vol 2 (1) ◽

pp. 2 ◽

Cited By ~ 3

Author(s):

Gary A. Chastagner

Keyword(s):

Pacific Northwest ◽

Rio Grande ◽

Coastal Areas ◽

Douglas Fir ◽

National Forest ◽

Santa Fe ◽

High Susceptibility ◽

Needle Cast ◽

Christmas Trees ◽

The Pacific

Douglas-fir are traditionally grown as Christmas trees in the Pacific Northwest (PNW). Intermountain (IM) provenances of Douglas-fir are less likely to be injured after harvest by exposure to subfreezing temperatures than the coastal provenances. However, planting IM Douglas-fir in the coastal areas of the PNW is currently not recommended because of their high susceptibility to Rhabdocline needle cast. During a three-year period, needle cast severity was rated (0 to 100 scale) on trees in a replicated planting of IM Douglas-fir near Puyallup, WA. In 1997, needle cast ratings ranged from 0.8 to 70. Trees from the Cibola National Forest (NF) had significantly higher needle cast ratings (70.0) than trees from Carson NF (17.3), Coconino NF (15.7), Rio Grande NF (5.0), and Upper Clearwater, ID (0.8). Trees from the Apache NF (51.4), San Isabel NF (32.3), two collections representing the Lincoln NF (25.4-30.2), and the Santa Fe NF (21.3) had intermediate levels of needle cast. This study shows that certain sources of IM Douglas-fir can be grown in the PNW with minimal Rhabdocline needle cast problems. Applications of chlorothalonil also provided effective needle cast control on all but the most susceptible provenance. Accepted for publication 15 October 2001. Published 29 October 2001.

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Contrasting the Pathogen Loads in Co-Existing Populations of Phytophthora pluvialis and Nothophaeocryptopus gaeumannii in Douglas Fir Plantations in New Zealand and the Pacific Northwest United States

Phytopathology ◽

10.1094/phyto-12-18-0479-r ◽

2019 ◽

Vol 109 (11) ◽

pp. 1908-1921 ◽

Cited By ~ 3

Author(s):

Mireia Gómez-Gallego ◽

Jared M. LeBoldus ◽

Martin Karl-Friedrich Bader ◽

Everett Hansen ◽

Lloyd Donaldson ◽

...

Keyword(s):

United States ◽

New Zealand ◽

Pacific Northwest ◽

Spatial Scales ◽

Douglas Fir ◽

The Pacific ◽

Foliar Pathogen ◽

Swiss Needle Cast ◽

Phytophthora Pluvialis ◽

Foliar Pathogens

The emergence of Phytophthora pluvialis as a foliar pathogen of Douglas fir in New Zealand and the Pacific Northwest United States has raised questions about its interaction with the widespread Swiss needle cast (SNC) disease. During Spring 2017, we repeatedly sampled 30 trees along an environmental gradient in each region and 292 additional trees in a longitudinal transect to assess the P. pluvialis epidemic and the association between P. pluvialis and Nothophaeocryptopus gaeumannii, which are causal agents of SNC. Both pathogens were consistently more abundant in the host’s exotic environment in New Zealand. In both areas, the two pathogens co-exist in different spatial scales for regions and needles. The relative abundance of both pathogens was negatively correlated in the Pacific Northwest, where both presumably have co-existed for longer. Our findings confirmed the interaction of P. pluvialis and N. gaeumannii as foliar pathogens of Douglas fir and suggest a within-site spatial variation in the Pacific Northwest.

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Soil carbon and nutrient pools in Douglas-fir plantations 5years after manipulating biomass and competing vegetation in the Pacific Northwest

Forest Ecology and Management ◽

10.1016/j.foreco.2011.07.021 ◽

2011 ◽

Vol 262 (9) ◽

pp. 1722-1728 ◽

Cited By ~ 15

Author(s):

Robert A. Slesak ◽

Stephen H. Schoenholtz ◽

Timothy B. Harrington

Keyword(s):

Soil Carbon ◽

Pacific Northwest ◽

Douglas Fir ◽

Nutrient Pools ◽

Competing Vegetation ◽

The Pacific

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Persistence of the Swiss Needle Cast Outbreak in Oregon Coastal Douglas-Fir and New Insights from Research and Monitoring

Journal of Forestry ◽

10.1093/jofore/fvab011 ◽

2021 ◽

Author(s):

David C Shaw ◽

Gabriela Ritóková ◽

Yung-Hsiang Lan ◽

Doug B Mainwaring ◽

Andrew Russo ◽

...

Keyword(s):

Climate Change ◽

Regional Scale ◽

Emerging Diseases ◽

Douglas Fir ◽

Landscape Patterns ◽

Needle Cast ◽

Plantation Management ◽

Environmental Controls ◽

Swiss Needle Cast ◽

Improvement Programs

Abstract Swiss needle cast (SNC), caused by Nothophaeocryptopus gaeumannii, is a foliage disease of Douglas-fir (Pseudotsuga menziesii), that reduces growth in native stands and exotic plantations worldwide. An outbreak of SNC began in coastal Oregon in the mid-1990s and has persisted since that time. Here we review the current state of knowledge after 24 years of research and monitoring, with a focus on Oregon, although the disease is significant in coastal Washington and has recently emerged in southwestern British Columbia. We present new insights into SNC distribution, landscape patterns, disease epidemiology and ecology, host-pathogen interactions, trophic and hydrologic influences, and the challenges of Douglas-fir plantation management in the presence of the disease. In Oregon, the SNC outbreak has remained geographically contained but has intensified. Finally, we consider the implications of climate change and other recently emerged foliage diseases on the future of Douglas-fir plantation management. Study Implications: Douglas-fir tree growers need to consider Swiss needle cast (SNC) and other emerging foliage diseases as SNC has not abated over the past 24 years, and along with other emerging diseases, it continues to pose a threat to Douglas-fir plantation productivity. Douglas-fir management in western Oregon remains important, such that a knowledge of disease impacts and effective silvicultural responses is key. Managers should carefully consider whether alternative species may be ecologically or economically beneficial in some situations while tree improvement programs must continue to breed for tolerance to SNC. Research shows that regional scale foliage disease outbreaks can result in trophic cascades and hydrologic changes that affects more than just the trees. The environmental controls on the SNC epidemic imply that climate change could strongly influence future directions of the outbreak, with the greatest threats to trees at higher elevations.

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