Douglas-fir Needles Research Articles

Effects of needle cast diseases on the growth of a 33-year-old Douglas-fir provenance plantation in northwestern Bulgaria

Abstract In this study, the effects of defoliation caused by fungal pathogens on the tree vitality and growth of a 33-year old Douglas-fir (Pseudotsuga menziesii) provenance plantation in northwestern Bulgaria was presented. The results of the conducted surveys in 2011 and 2020 showed that there were significant differences between the individual provenances of Douglas-fir concerning their susceptibility to the needle cast diseases, caused by the fungal pathogens Rhabdocline pseudotsugae and Phaeucryptopus gaeumannii. The extent of damage, expressed as the amount of Douglas-fir needles cast, varied among provenance groups in individual years. A serious degree of defoliation was assessed among all continental provenances. In 2011, all examined trees from the group of continental provenances had severe symptoms of the needle cast disease. In 71.5% of them, the defoliation of the crowns was over 25% – moderately to severely affected. The average degree of defoliation varied from 18.3% (32 Wаrm Springs) to 89.3% (55 Alamogordo). In 2020, severe defoliation was found among all continental provenances. Both fungal pathogens were found as causes of the defoliation of 64.3% of the trees. The growth indicators: average height, average diameter at breast height, average height- and diameter increment for survived provenances in 2011 (at age 24) and 2020 (at age 33) were evaluated. The loss of needles and the reduced physiological function of the trees affected their vitality in the following years. Relationships between the average current annual height and diameter increment by provenance groups for 2003–2011 and 2011–2020 were calculated. It was found that with an increase in the degree of defoliation, the height and diameter increment of the provenances decreases.

The effectiveness of filter material for respiratory protection worn by wildland firefighters

During a wildland fire event, firefighters often receive significant exposure to smoke consisting of particulate matter (PM) and gaseous emissions. Major respiratory and cardiovascular health concerns are related to inhalation of smoke and respiratory protection (RP), such as masks, are one of the most important pieces of personal protective equipment (PPE) that can be used to mitigate this exposure. One barrier to RP implementation is that the effectiveness of different PPE worn by firefighters is not well studied in the literature. In this study, six different filtering materials were tested against simulated wildland fire smoke produced by smoldering Douglas fir needles in a custom-made lab-scale apparatus. Both PM and gases were measured with and without the filter material and their effectiveness is reported in this study. As expected, cloth bandanas, currently the most worn RP material, provided little benefit in terms of both PM and gaseous emissions reduction, while all other filter materials provided significant benefits. N95, P95 and P100 filters were very effective at removing PM and somewhat effective at filtering some gaseous species, especially those with nuisance VOC capabilities, although this effect may not be sustained for longer durations.

Quantifying Forest Litter Fuel Moisture Content with Terrestrial Laser Scanning

Electromagnetic radiation at 1550 nm is highly absorbed by water and offers a novel way to collect fuel moisture data, along with 3D structures of wildland fuels/vegetation, using lidar. Two terrestrial laser scanning (TLS) units (FARO s350 (phase shift, PS) and RIEGL vz-2000 (time of flight, TOF)) were assessed in a series of laboratory experiments to determine if lidar can be used to estimate the moisture content of dead forest litter. Samples consisted of two control materials, the angle and position of which could be manipulated (pine boards and cheesecloth), and four single-species forest litter types (Douglas-fir needles, ponderosa pine needles, longleaf pine needles, and southern red oak leaves). Sixteen sample trays of each material were soaked overnight, then allowed to air dry with scanning taking place at 1 h, 2 h, 4 h, 8 h, 12 h, and then in 12 h increments until the samples reached equilibrium moisture content with the ambient relative humidity. The samples were then oven-dried for a final scanning and weighing. The spectral reflectance values of each material were also recorded over the same drying intervals using a field spectrometer. There was a strong correlation between the intensity and standard deviation of intensity per sample tray and the moisture content of the dead leaf litter. A multiple linear regression model with a break at 100% gravimetric moisture content produced the best model with R2 values as high as 0.97. This strong relationship was observed with both the TOF and PS lidar units. At fuel moisture contents greater than 100% gravimetric water content, the correlation between the pulse intensity values recorded by both scanners and the fuel moisture content was the strongest. The relationship deteriorated with distance, with the TOF scanner maintaining a stronger relationship at distance than the PS scanner. Our results demonstrate that lidar can be used to detect and quantify fuel moisture across a range of forest litter types. Based on our findings, lidar may be used to quantify fuel moisture levels in near real-time and could be used to create spatial maps of wildland fuel moisture content.

First detection of invasive Douglas fir needle midges from the genus Contarinia Rondani (Diptera: Cecidomyiidae) in Switzerland

First detection of invasive Douglas fir needle midges from the genus Contarinia Rondani (Diptera: Cecidomyiidae) in Switzerland

A long-read and short-read transcriptomics approach provides the first high-quality reference transcriptome and genome annotation for Pseudotsuga menziesii (Douglas-fir).

Douglas-fir (Pseudotsuga menziesii) is native to western North America. It grows in a wide range of environmental conditions and is an important timber tree. Although there are several studies on the gene expression responses of Douglas-fir to abiotic cues, the absence of high-quality transcriptome and genome data is a barrier to further investigation. Like for most conifers, the available transcriptome and genome reference dataset for Douglas-fir remains fragmented and requires refinement. We aimed to generate a highly accurate, and complete reference transcriptome and genome annotation. We deep-sequenced the transcriptome of Douglas-fir needles from seedlings that were grown under nonstress control conditions or a combination of heat and drought stress conditions using long-read (LR) and short-read (SR) sequencing platforms. We used 2 computational approaches, namely de novo and genome-guided LR transcriptome assembly. Using the LR de novo assembly, we identified 1.3X more high-quality transcripts, 1.85X more "complete" genes, and 2.7X more functionally annotated genes compared to the genome-guided assembly approach. We predicted 666 long noncoding RNAs and 12,778 unique protein-coding transcripts including 2,016 putative transcription factors. We leveraged the LR de novo assembled transcriptome with paired-end SR and a published single-end SR transcriptome to generate an improved genome annotation. This was conducted with BRAKER2 and refined based on functional annotation, repetitive content, and transcriptome alignment. This high-quality genome annotation has 51,419 unique gene models derived from 322,631 initial predictions. Overall, our informatics approach provides a new reference Douglas-fir transcriptome assembly and genome annotation with considerably improved completeness and functional annotation.

Fungal Community Composition as Affected by Litter Chemistry and Weather during Four Years of Litter Decomposition in Rainshadow Coastal Douglas-Fir Forests.

Climate and litter chemistry are major factors influencing litter decay, a process mediated by microbes, such as fungi, nitrogen-fixing bacteria and ammonia-oxidizing bacteria. Increasing atmospheric CO2 concentrations can decrease nitrogen (N) and increase condensed tannin (CT) content in foliar litter, reducing litter quality and slowing decomposition. We hypothesized that reduced litter quality inhibits microbes and is the mechanism causing decomposition to slow. Litterbags of Douglas-fir needles and poplar leaves with a range of N (0.61–1.57%) and CT (2.1–29.1%) treatment and natural acid unhydrolyzable residue (35.3–41.5%) concentrations were placed along climatic gradients in mature Douglas-fir stands of coastal British Columbia rainshadow forests. The structure (diversity, richness and evenness) and composition of microbial communities were analyzed using DGGE profiles of 18S, NifH-universal and AmoA PCR amplicons in foliar litter after 7, 12, 24 and 43 months of decay. High CT and low N concentrations in leaf litter were associated with changes in microbial community composition, especially fungi. Contrary to our hypothesis, high CT and low N treatments did not inhibit microbial colonization or diversity. The joint effects of air temperature and soil moisture on microbial community composition at our sites were more important than the effects of initial litter chemistry.

Simulated Wildfire Smoke Significantly Alters Sperm DNA Methylation Patterns in a Murine Model.

Wildfires are now a common feature of the western US, increasing in both intensity and number of acres burned over the last three decades. The effects of this changing wildfire and smoke landscape are a critical public and occupational health issue. While respiratory morbidity due to smoke exposure is a priority, evaluating the molecular underpinnings that explain recent extrapulmonary observations is necessary. Here, we use an Apoe−/− mouse model to investigate the epigenetic impact of paternal exposure to simulated wildfire smoke. We demonstrate that 40 days of exposure to smoke from Douglas fir needles induces sperm DNA methylation changes in adult mice. DNA methylation was measured by reduced representation bisulfite sequencing and varied significantly in 3353 differentially methylated regions, which were subsequently annotated to 2117 genes. The differentially methylated regions were broadly distributed across the mouse genome, but the vast majority (nearly 80%) were hypermethylated. Pathway analyses, using gene-derived and differentially methylated region-derived gene ontology terms, point to a number of developmental processes that may warrant future investigation. Overall, this study of simulated wildfire smoke exposure suggests paternal reproductive risks are possible with prolonged exposure.

Varijabilnost sadržaja kalijuma u četinama kanadskih provenijencija duglazije

The provenance test model is based on the analysis of growth, anatomical, physiological, chemical, mechanical, and other properties of an allochthonous species to justify its transfer from the place of origin to new ecosystems. Douglas-fir is one of the most common allochthonous conifer species in the forest plantations of Europe. Given that the analysis of different physiological properties of trees is important for the introduction of specified provenances into new habitats, this paper presents the results of an investigation of the variability of potassium content in young Douglas-fir needles of 14 Canadian provenances raised on two experimental sites in Belgrade. Potassium is an essential element involved in a number of biochemical and physiological processes and plays a significant role in the adaptation of plants on biotic and abiotic stress factors. Determination of the deviation of potassium content in the needles of each Douglas-fir provenance studied was performed using the Z-test.

Effect of site and provenance on the length of transfusion parenchyma of Douglas-fir needles

Douglas-fir has been the most common introduced conifer species in European plantations since 1825. The analysis of the characteristics of the introduced tree species by conducting genetic tests may predict the success of transfer of Douglas-fir seed of different provenances. The projection of the model of provenance test aims at providing information on adaptation to habitat and climate conditions in new ecosystems in Serbia. The original seed of Douglas-fir from North America was used for setting the experiment of different provenances at two sites in Serbia. The first experiment was set in a beech forest (Fagetum moesiacae montanum Jov. 1976) on district cambisol in the area of Juhor mountain in central Serbia, while the second one was set in Tanda near the town of Bor in eastern Serbia on the habitat of Hungarian and Turkey oak (Quercetum frainetto-cerris Rud. 1949) on eutric cambisol. Through the analysis of the anatomical structure of Douglas-fir needles this paper tends to determine whether there are statistically significant differences in the length of transfusion parenchyma of provenances located in different habitats. The important function of parenchyma in needles is the physiological process of water, organic and mineral matter flow. The effects of the sites where the experiments were set on the transfusion parenchyma of needles were determined by statistical analysis.

Variability of potassium concentration in the needles of Douglas-fir provenances

Douglas-fir is one of the most common conifer species in the forest plantations of Europe. The provenance test model is based on the analysis of the properties (growth, anatomical, physiological, chemical, mechanical and other properties) of Douglas-fir in order to justify the transfer of seeds from North America to the ecosystems of Serbia. This type of program has been implemented in Serbia on several locations using different Douglas-fir provenances. Given that the analysis of different physiological properties of trees is important for the introduction of specified provenances into habitats in Serbia, in this paper the variability of potassium concentration in young Douglas-fir needles of different provenances was examined in an experimental field in Serbia. Potassium is very important in the physiological processes of plants. It is an essential element involved in a number of biochemical and physiological processes and plays a significant role in the adaptation of plants on biotic and abiotic stress factors. The highest potassium concentration was found in the ?Oregon 205-14? provenance - the only provenance in which the potassium concentration was significantly higher than the average value, so it can be characterized as a superior provenance for the uptake and accumulation of this element. It was found that, at this stage of development, the differences in the potassium concentration in trees in the provenance test have no significant effect on growth parameters. Further studies should show whether the concentration of this biogenic element in any way affects other properties important for the selection of provenances during the introduction process, such as resistance to stress factors.

Effect of site and provenance on the thickness of transfusion parenchyma of Douglas-fir needles

Variability of introduced tree species can be assessed through provenance tests. Their genetic and ecological adaptability can be confirmed by investigating the variability of anatomical traits, analyzed in this research study. The aim of the paper was to determine whether there are differences in the width of transfusion parenchyma of Douglas-fir needles in different provenance in different habitats in Serbia. In Serbia, 2 provenance tests of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), whose seed originated from North America, were established with the aim of testing the species. A 2-factor analysis of variance of the thickness of needle transfusion parenchyma was carried out in order to study the effects of the interactions between site-specific conditions of the locations where the provenance tests were set. The role of this parenchyma is to support conductivity of water and mineral matters from xylem bundles and organic matters from chlorenchyma to phloem bundles. The analysis of variance shows that there are statistically significant differences in the values obtained for the studied anatomical traits between the provenances. LSD test shows that the provenances are homogeneous, i.e. there are no statistically significant differences in the mean values between them. The smaller range of variation in the properties of these provenances in comparison to other provenances can be partially explained with their genetic similarity which led to similar phenotypic expressions in the interaction with the external factors of the experimental sites.

Transcription through the eye of a needle: daily and annual cyclic gene expression variation in Douglas-fir needles

BackgroundPerennial growth in plants is the product of interdependent cycles of daily and annual stimuli that induce cycles of growth and dormancy. In conifers, needles are the key perennial organ that integrates daily and seasonal signals from light, temperature, and water availability. To understand the relationship between seasonal cycles and seasonal gene expression responses in conifers, we examined diurnal and circannual needle mRNA accumulation in Douglas-fir (Pseudotsuga menziesii) needles at diurnal and circannual scales. Using mRNA sequencing, we sampled 6.1 × 109 reads from 19 trees and constructed a de novo pan-transcriptome reference that includes 173,882 tree-derived transcripts. Using this reference, we mapped RNA-Seq reads from 179 samples that capture daily and annual variation.ResultsWe identified 12,042 diurnally-cyclic transcripts, 9299 of which showed homology to annotated genes from other plant genomes, including angiosperm core clock genes. Annual analysis revealed 21,225 circannual transcripts, 17,335 of which showed homology to annotated genes from other plant genomes. The timing of maximum gene expression is associated with light intensity at diurnal scales and photoperiod at annual scales, with approximately half of transcripts reaching maximum expression +/− 2 h from sunrise and sunset, and +/− 20 days from winter and summer solstices. Comparisons with published studies from other conifers shows congruent behavior in clock genes with Japanese cedar (Cryptomeria), and a significant preservation of gene expression patterns for 2278 putative orthologs from Douglas-fir during the summer growing season, and 760 putative orthologs from spruce (Picea) during the transition from fall to winter.ConclusionsOur study highlight the extensive diurnal and circannual transcriptome variability demonstrated in conifer needles. At these temporal scales, 29% of expressed transcripts show a significant diurnal cycle, and 58.7% show a significant circannual cycle. Remarkably, thousands of genes reach their annual peak activity during winter dormancy. Our study establishes the fine-scale timing of daily and annual maximum gene expression for diverse needle genes in Douglas-fir, and it highlights the potential for using this information for evaluating hypotheses concerning the daily or seasonal timing of gene activity in temperate-zone conifers, and for identifying cyclic transcriptome components in other conifer species.

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

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.

Varijabilnost broja epitelnih ćelija u smolnom kanalu četina duglazije

The research on the interactions between the genetic potential of introduced provenances and the environmental features of the locations in which the plantations were established was carried out in Douglas-fir plantations in Serbia. The twoway ANOVA was conducted in order to study the effects of the site conditions in the localities of Douglas-fir provenance tests in Serbia on the anatomical properties of needles. These analyses look into the effects of two factors (locality and provenance) on the number of epithelial cells in the resin duct of Douglas-fir needles.

Homogenization of detrital leachate in an old-growth coniferous forest, OR: DOC fluorescence signatures in soils undergoing long-term litter manipulations

Characterizing the relationship between plant detrital inputs and the resulting dissolved organic carbon (DOC) leachate is vital to understanding the ultimate fate of root carbon, fallen wood and needles in forested watersheds. Similarly, elucidating chemical differences in the soil DOC pool may help to explain which DOC fractions are sorbed to mineral surfaces and contribute to accumulation of soil organic carbon, are respired as CO2, or are exported to nearby catchments. In order to test the hypothesis that soils with different detrital inputs impart a detectable signal on DOC in mineral soil, soil solution DOC was sampled from the Detrital Input and Removal Treatment (DIRT) plots located in the H.J. Andrews Experimental Forest, OR. Multiple types of fresh litter extracts, along with lysimeter and soil extracts from DIRT treatment plots were characterized using UV-Vis and fluorescence spectroscopy coupled with the Cory and McKnight (Environ Sci Technol 39:8142–8149, 2005) parallel factor analysis (PARAFAC) model. Principal component analysis of 13 unique fluorophores distinguished using PARAFAC show that litter and soil extracts (Douglas-fir needles, wood of decomposition Class 2, Class 3 and Class 5, O-horizon, and 0–5 cm A-horizon) each have distinct fluorescence signatures. However, while litter-leached DOC chemistry varies by litter type, neither lysimeter-collected DOC or soil extracts in the DIRT plots show statistically significant differences in fluorescence signatures among treatments, even after 17 years of litter manipulations. The lack of observed differences among DIRT treatments suggests that both abiotic interactions and microbial activity effectively homogenize organic carbon constituents within the dissolved pool. Minor but observable changes in PARAFAC components and optical indices during a 1-month biodegradation incubation of litter and soil extracts indicate that while biodegradation significantly alters DOC chemistry, abiotic mechanisms are also critical to DOC transformation in these soils with high sorption capacity. Although leachates from different plant detrital sources have distinct carbon chemical signatures, these DOC signatures are effectively homogenized after passage through mineral soil. These results highlight the dominant role of both biotic and abiotic interactions in controlling the chemistry of DOC in shallow soils.

Relationships between Swiss needle cast and ectomycorrhizal fungus diversity

Swiss needle cast (SNC) is a disease specific to Douglas-fir (Pseudotsuga menziesii) caused by the ascomycete Phaeocryptopus gaeumannii. Here we examine characteristics of the EM fungus community that are potentially useful in predictive models that would monitor forest health. We found that mean EM density (number of colonized root tips/soil core) varied nearly 10-fold among sites of varying levels of SNC, while mean EM fungus species richness (number of species/soil core) varied by about 2.5 times. Strong relationships were found between EM and SNC parameters: EM species richness was positively correlated with both Douglas-fir needle retention (R2 = 0.93) and EM density (R2 = 0.65); EM density also was significantly correlated with Douglas-fir needle retention (R2 = 0.70). These simple characteristics of the EM fungus community could be used to monitor forest health and generate predictive models of site suitability for Douglas-fir. Based on previous findings that normally common EM types were reduced in frequency on sites with severe SNC, we also hypothesized that some EM fungi would be stress tolerant-dominant species. Instead, we found that various fungi were able to form EM with the stressed trees, but none were consistently dominant across samples in the severely diseased areas.

Soil Microbe Active Community Composition and Capability of Responding to Litter Addition after 12 Years of No Inputs

One explanation given for the high microbial diversity found in soils is that they contain a large inactive biomass that is able to persist in soils for long periods of time. This persistent microbial fraction may help to buffer the functionality of the soil community during times of low nutrients by providing a reservoir of specialized functions that can be reactivated when conditions improve. A study was designed to test the hypothesis: in soils lacking fresh root or detrital inputs, microbial community composition may persist relatively unchanged. Upon addition of new inputs, this community will be stimulated to grow and break down litter similarly to control soils. Soils from two of the Detrital Input and Removal Treatments (DIRT) at the H. J. Andrews Experimental Forest, the no-input and control treatment plots, were used in a microcosm experiment where Douglas-fir needles were added to soils. After 3 and 151 days of incubation, soil microbial DNA and RNA was extracted and characterized using quantitative PCR (qPCR) and 454 pyrosequencing. The abundance of 16S and 28S gene copies and RNA copies did not vary with soil type or amendment; however, treatment differences were observed in the abundance of archaeal ammonia-oxidizing amoA gene abundance. Analysis of ∼110,000 bacterial sequences showed a significant change in the active (RNA-based) community between day 3 and day 151, but microbial composition was similar between soil types. These results show that even after 12 years of plant litter exclusion, the legacy of community composition was well buffered against a dramatic disturbance.

Long-Term Site Preparation Effects on Volcanic Ash Forest Soils and Douglas-Fir

Long-term site preparation effects on soil characteristics and Douglas-fir (Pseudotsuga menziesii var. glauca) growth and foliar nutrition were measured over a 24-year period following a ground-based harvest in Northern Idaho, USA. Harvest unit soils were classified as Andisols overlaying metasedimentary parent material within a udic-frigid moisture and temperature regime. Douglas-fir site index at base age 50 was 29 m. Site preparation treatments included undisturbed control, broadcast burn, pile and burn, and mechanical scarification. Periodic soil-site measurements were collected on each treatment at regeneration stand ages 6, 14, and 24 years. Six- and 14-year soil bulk density on scarified treatments were significantly higher at 0-15 and 15-30 cm than all other treatments. At 24 years, scarified soil bulk density at 0-15 and 15-30 cm showed recovery to bulk densities observed in non-scarified soils. Scarified soil organic matter (SOM) and N were significantly reduced by 32% and 42% over control levels 6 years post-harvest. After 24 years, scarified SOM and N were significantly lower than that found in broadcast burn (44% and 54%) and pile and burn (33% and 49%). Douglas-fir needle mass and foliar N and P content on scarified soils were significantly lower than on broadcast burn or pile and burn treatments after 24 years (p<0.1). After 24 years, soil and foliar N content was significantly higher on microsites that received a burn treatment (p<0.1). Tree growth on either burn treatment showed significantly greater diameter (35%), height (14%), and volume (92%) when compared to trees growing on scarified soils after 24 years (p<0.1). These results indicate that tree growth on frigid, ash-mantled forest soils of Northern Idaho, USA, can be significantly reduced following soil compaction and displacement of organic matter and nutrient-rich topsoil. Where soil disturbance was minimized and organic matter retention was coupled with a burn treatment, soil and tree productivity was maintained or enhanced.

Piloted ignition of live forest fuels

The most unpredictable and uncontrollable wildfires are those that burn in the crowns of live vegetation. The fuels that feed these crown fires are mostly live, green foliage. Unfortunately, little is known about how live fuels combust. To understand how live fuels burn, piloted ignition experiments were performed with lodgepole pine and Douglas-fir. The thermal behavior (thick versus thin) of both live and dead needles was explored. Both live and dry needles were shown to behave as thermally intermediate solids in this apparatus. Additionally, samples were collected throughout the growing season to take advantage of the natural variation in moisture content and chemical composition. This data set was then compared to several correlations found in the literature to determine whether live fuel ignition can be predicted by moisture content alone and to test the applicability of these models to the wildland fire problem. Many of the correlations from the literature for ignition time with moisture content fail to capture the trends with live fuels. A linear regression of the ignition time with moisture content only predicts 74–80% of the variability suggesting that there is another mechanism controlling ignition time of live fuels. Based on the hypothesized difference in water storage between live and wet dead fuels, the chemical composition of the live needles was included in an empirical model for ignition time. Including chemical composition improved the prediction accuracy for Douglas-fir needles only. Because the thermal properties of live foliage are largely unknown, it is possible that the predictions from more physically-based models would show improvement with more accurate values of density, thermal conductivity, and specific heat.

Climatic influences on needle cohort survival mediated by Swiss needle cast in coastal Douglas-fir

Swiss needle cast (SNC) severity in Douglas-fir (Pseudotsuga menziesii) has been shown to vary spatially and temporally in response to climatic factors both within its native range and in regions where it has been planted as an exotic species. Survival models were developed for different Douglas-fir needle cohorts to enhance our understanding of how climatic influences on needle longevity are mediated by SNC in the Oregon Coast Range. The climate-based models were based on repeated measurement of 100 plots between 1998 and 2005 coupled with downscaled PRISM climate data. Potential predictors of needle survival by annual cohort were selected from numerous climatic variables at annual, seasonal, and monthly scales. Needle survival probability was positively associated with maximum summer temperature, and negatively associated with minimum winter temperature and spring precipitation. Seasonal climate variables associated with needle longevity are consistent with current epidemiological understanding of Phaeocyrptopus gaeumannii, as well as with previous analyses of climatic influences on SNC severity as measured by average years of foliage retention and frequency of fungal fruiting bodies, or pseudothecia, in stomates.