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This study investigates competing vegetation effects on foliar and total plant-derived nutrient ratios, nutrient use efficiency (NUE), and foliar nutrient content and concentration of ecosystem components using vector analysis for 19-year-old Douglas-fir (Pseudotsuga menzeisii (Mirb.) Franco), western hemlock (Tsuga hereophylla (Raf.) Sarg.), western redcedar (Thuja plicata Donn ex D. Don), and grand fir (Abies grandis (Dougl.) Lindl.) stands in Oregon's Coast Range and for Douglas-fir and western redcedar in Oregon's Cascade foothills. Treatments included the Control, which received no spring release herbicide applications, and vegetation management (VM), which received 5 years of spring release herbicide applications, reducing competing vegetation abundance. VM increased the NUE of N, P, Mg, S, and Cu across all species when calculated with total plant-derived carbon and of all nutrients when calculated with stemwood carbon. VM often produced more harvestable and plant-derived carbon per unit nutrient fixed, improving the NUE of stands managed for carbon sequestration and timber. Species showed different stand nutrient requirements, evident through foliar and plant-derived nutrient ratios and their relationship with biomass production. Grand fir may obtain larger biomass increments for a given P:N ratio in plant-derived tissue and may be efficient in P-limited Coast Range sites. [ABSTRACT FROM AUTHOR]

AbstractSeedlings of 95 greenhouse-grown interior Douglas-fir half-sibling families originating from four breeding zones were subject to overwatering and periodic underwatering and compared to an optimally watered control (15 per family = 1425 seedlings total). Averaged over all trees, annual height was reduced by 4% and 11% compared to controls for overwatering and periodic underwatering, respectively. Family overwatered seedling height was 135–75%, and underwatered height was 100–75% of their respective control heights. Shorter families under stress grew like their control compared to taller families, but this was reversed in taller families when the watering conditions were ideal. A survival analysis indicated that after 30–50 days without water, family survival varied from 25% to 90%, and most trees died after 60 days. The breeding zone had little effect on the tolerance to suboptimal water or survival during complete water withdrawal and did not interact with watering treatments. Family traits for tolerance to overwatering favoured root biomass, traits for underwatering favoured reduced stem biomass, especially in ratio to roots, and traits for survival favoured belowground biomass over aboveground biomass. No tradeoffs between tolerance to over- and underwatering were found. Some families did well in all three conditions and some in one or the other. The study results suggest that variation in family growth and survival to suboptimal watering partly relate to root and stem biomass partitioning in the interior Douglas-fir population of British Columbia. [ABSTRACT FROM AUTHOR]

Summary: Understanding the genetic basis of how plants defend against pathogens is important to monitor and maintain resilient tree populations. Swiss needle cast (SNC) and Rhabdocline needle cast (RNC) epidemics are responsible for major damage of forest ecosystems in North America.Here we investigate the genetic architecture of tolerance and resistance to needle cast diseases in Douglas‐fir (Pseudotsuga menziesii) caused by two fungal pathogens: SNC caused by Nothophaeocryptopus gaeumannii, and RNC caused by Rhabdocline pseudotsugae.We performed case–control genome‐wide association analyses and found disease resistance and tolerance in Douglas‐fir to be polygenic and under strong selection. We show that stomatal regulation as well as ethylene and jasmonic acid pathways are important for resisting SNC infection, and secondary metabolite pathways play a role in tolerating SNC once the plant is infected. We identify a major transcriptional regulator of plant defense, ERF1, as the top candidate for RNC resistance.Our findings shed light on the highly polygenic architectures underlying fungal disease resistance and tolerance and have important implications for forestry and conservation as the climate changes. [ABSTRACT FROM AUTHOR]

Summary: Tree growth performance can be partly explained by genetics, while a large proportion of growth variation is thought to be controlled by environmental factors. However, to what extent DNA methylation, a stable epigenetic modification, contributes to phenotypic plasticity in the growth performance of long‐lived trees remains unclear. In this study, a comparative analysis of targeted DNA genotyping, DNA methylation and mRNAseq profiling for needles of 44‐year‐old Douglas‐fir trees (Pseudotsuga menziesii (Mirb.) Franco) having contrasting growth characteristics was performed. In total, we identified 195 differentially expressed genes (DEGs) and 115 differentially methylated loci (DML) that are associated with genes involved in fitness‐related processes such as growth, stress management, plant development and energy resources. Interestingly, all four intronic DML were identified in mega‐sized (between 100 and 180 kbp in length) and highly expressed genes, suggesting specialized regulation mechanisms of these long intron genes in gymnosperms. DNA repetitive sequences mainly comprising long‐terminal repeats of retroelements are involved in growth‐associated DNA methylation regulation (both hyper‐ and hypomethylation) of 99 DML (86.1% of total DML). Furthermore, nearly 14% of the DML was not tagged by single nucleotide polymorphisms, suggesting a unique contribution of the epigenetic variation in tree growth. [ABSTRACT FROM AUTHOR]

Summary: Tree seedlings from populations native to drier regions are often assumed to be more drought tolerant than those from wetter provenances. However, intraspecific variation in drought tolerance has not been well‐characterized despite being critical for developing climate change mitigation and adaptation strategies, and for predicting the effects of drought on forests.We used a large‐scale common garden drought‐to‐death experiment to assess range‐wide variation in drought tolerance, measured by decline of photosynthetic efficiency, growth, and plastic responses to extreme summer drought in seedlings of 73 natural populations of the two main varieties of Douglas‐fir (Pseudotsuga menziesii var. menziesii and var. glauca).Local adaptation to drought was weak in var. glauca and nearly absent in menziesii. Var. glauca showed higher tolerance to drought but slower growth than var. menziesii. Clinal variation in drought tolerance and growth species‐wide was mainly associated with temperature rather than precipitation. A higher degree of plasticity for growth was observed in var. menziesii in response to extreme drought.Genetic variation for drought tolerance in seedlings within varieties is maintained primarily within populations. Selective breeding within populations may facilitate adaptation to drought more than assisted gene flow. [ABSTRACT FROM AUTHOR]

Fire injury stresses Douglas-fir trees (Pseudotsuga menziesii) that survive a wildfire event, allowing subsequent Douglas-fir beetle (Dendroctonus pseudotsugae) infection to kill trees that may have otherwise survived. This study aimed to determine how fire injury, stand, and tree characteristics drive Douglas-fir beetle host tree selection five years post-fire. We paired 28 adjacent beetle-infected and uninfected stands (infected N = 14) and 140 Douglas-fir trees (infected N = 70) within the 416 Fire burn area in Southwest Colorado. We found no statistically significant differences between infected and uninfected stand characteristics. Individual tree height, DBH, and bark char severity index were significantly higher in infected versus uninfected trees. We created a regression decision tree model to determine the influence of fire injury and tree characteristics on the probability of infection. Trees with a height ≥ 27 m, bark char height < 2.3 m, and DBH < 80 cm had the greatest probability of attack (100%). Trees with a height < 27 m, bark char severity index < 5.5, and DBH < 49 cm had the lowest probability of attack (3.7%). Understanding the influence of fire on Douglas-fir beetle host selection allows land managers to model potential epidemic outbreaks and guide proactive management actions that may reduce beetle outbreak severity or preserve high-value trees not killed by fire. [ABSTRACT FROM AUTHOR]

Tree-ring δ15N may depict site-specific, long-term patterns in nitrogen (N) dynamics under N2-fixing species, but field trials with N2-fixing tree species are lacking and the relationship of temporal patterns in tree-ring δ15N to soil N dynamics is controversial. We examined whether the tree-ring δ15N of N2-fixing red alder (Alnus rubra Bong.) would mirror N accretion rates and δ15N of soils and whether the influence of alder-fixed N could be observed in the wood of a neighboring conifer. We sampled a 27-year-old replacement series trial on south-eastern Vancouver Island, with red alder and coastal Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) planted in five proportions (0/100, 11/89, 25/75, 50/50 and 100/0) at a uniform stem density. An escalation in forest floor N content was evident with an increasing proportion of red alder, equivalent to a difference of ~750 kg N ha−1 between 100% Douglas-fir versus 100% alder. The forest floor horizon also had high δ15N values in treatments with more red alder. Red alder had a consistent quadratic fit in tree-ring δ15N over time, with a net increase of |$\sim$| 1.5‰, on average, from initial values, followed by a plateau or slight decline. Douglas-fir tree-ring δ15N, in contrast, was largely unchanged over time (in three of four plots) but was significantly higher in the 50/50 mix. The minor differences in current leaf litter N content and δ15N between alder and Douglas-fir, coupled with declining growth in red alder, suggests the plateau or declining trend in alder tree-ring δ15N could coincide with lower N2-fixation rates, potentially by loss in alder vigor at canopy closure, or down-regulation via nitrate availability. [ABSTRACT FROM AUTHOR]

Climate projections predict more frequent and severe drought in coastal Pseudotsuga menziesii forests of western North America, raising concerns over how to promote drought adaptation. Thinning often increases drought resistance (the ability to maintain growth during a drought) and resilience (the ability to recover growth after a drought), but these effects vary with thinning intensity, shift over time, and may have tradeoffs with fiber production. We collected tree cores from a long-term thinning study with four residual density levels replicated across both uniform thinning and thinning with gaps, and used annual growth data to investigate responses to droughts occurring 8 and 21 years after thinning. For the first drought, resistance and resilience were higher in treatments with lower residual densities. For the second drought, there were no differences in drought response between the lowest and highest residual density treatments, and all treatments had lower drought resistance and resilience than for the first drought. Spatial arrangement had little impact on drought resistance or resilience and residual density level had a significant effect on the periodic annual volume increment—drought resistance tradeoff. Our results suggest that thinning can promote drought adaptation in Pseudotsuga menziesii forests, but these effects dissipate over time. [ABSTRACT FROM AUTHOR]

A series of ISO 5658-2 flame spread experiments on Douglas-fir specimens were carried out to investigate the relationship between flame spread characteristics and thermal thickness of solid combustibles, which is greatly influenced by char formation during combustion. Computations using the fire dynamics simulator (FDS) were performed to recreate these experiments. The measured and calculated flame spread characteristics were then compared and analyzed based on thermal thickness and char residue ratio. The results clearly show that the effects of char formation on the surface of wood during combustion are more noticeable in thermally thick regimes than in thermally thin regimes. The findings provide an important foundational understanding of the influence of char formation on solid combustibles on flame retardant properties, which has not previously been studied. [ABSTRACT FROM AUTHOR]

In forest resource inventory, tree height is often estimated by easily measurable diameter from height-diameter model. In this study, we tried to use random forest (RF), an important machine learning method, to model individual-tree height. Results showed that the optimized RF model had better fitting and prediction accuracy (R2 = 0.8146 and RMSE = 2.2527 m). In terms of relative importance, diameter at breast height (DBH) was the most important factor, followed by neighborhood-related variables and other variables related to environmental conditions. Further, tree height was generally positively affected by DBH, mean diameter of neighbors, DBH dominance, number of neighbors, and mean annual precipitation, but negatively affected by elevation. The results indicated that the RF-based height model was statistically reliable and highly accurate, and it had strong interpretability with ecological significance. Our study will provide a new perspective for the application of machine learning algorithms to forest dynamic modeling. [ABSTRACT FROM AUTHOR]

Adult individuals and seeds of two mixed stands of coastal and interior Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) were analysed for genetic differentiation between the two varieties and evidence of intervarietal pollination. Clear genetic discrimination between the two varieties was observed based on multilocus evaluation of nine microsatellite markers using other Douglas-fir stands of known variety composition for comparison. Analysis of pollination distances showed that 80% of pollinations took place within a distance of about 44–55 m. Analysis of stand structure showed clearly separated areas of mainly coastal or interior Douglas-fir within both stands. Together with short pollination distances this led to an apparent dominance of intravarietal pollinations. However, analysis of pollination partners of trees growing near the border of the variety specific areas, does not indicate the existence of reproductive barriers between trees of the two varieties growing in mixed stands. Therefore, commercial seed harvesting in mixed stands should be avoided if the production of seed lots of pure coastal or interior Douglas-fir is intended. [ABSTRACT FROM AUTHOR]

Shear fracture frequently occurs in timber beams and panels subjected to transverse loads. At elevated temperatures, wood will undergo complex physical and chemical processes which significantly affect the shear properties. In this paper, the v-notched Douglas-fir specimens with three different shear planes: (a) Radial-Tangential (RT); (b) Radial-Longitudinal (RL), and (c) Longitudinal-Radial (LR), were fabricated and tested under the elevated temperatures from 20 °C to 180 °C. The digital image correlation (DIC) technique was used to measure the shear strain. It was found that the shear plane had a significant effect on the failure modes, shear strength, and shear modulus. The shear strength and shear modulus generally decreased with the increase of temperature. However, the shear strength was significantly improved when the hardening of the dry lignin occurred between 100 °C and 140 °C. Moreover, the design curve for the shear strength in Eurocode 5 is conservative for all the specimens with different shear planes. [ABSTRACT FROM AUTHOR]

Purpose: Douglas-fir occupies a growing role in the European timber industries but its effects on soils and the environment are still not well understood. We monitored the biogeochemical cycle of major elements in 11 representative mature stands throughout France over the 2013 to 2020 period to better understand repercussions on soil processes. Methods: The present study is focused on throughfall and soil solution chemistry: concentrations were measured monthly at 15 cm and 60 cm depth and fluxes of major anions and cations were computed. Results: Our results show that nitrate strongly dominated the soil solution chemistry: concentrations were elevated (>20 mg L−1) for 8 out of 11 sites with mean annual NO3− values ranging from 2 to 253 mg L−1. Fluxes of nitrate at 60 cm of depth, ranging from 23 to 309 kg ha−1 yr−1, were much higher than those in throughfall for nine studied sites. Nitrate, which was the dominant anion in soil solution, associated either to Ca2+, Mg2+ and K+, or to Al3+ was lost out of the soil-plant system through leaching. Conclusions: These results suggest a production of NO3− in the soil exceeding tree uptake and microbial immobilization resulting in strong ongoing soil acidification at many sites and potential degradation of water quality. Significant negative correlations were found between nitrate concentration in soil solution and sandy texture, soil C and N, site elevation and, annual rainfall, but further research is necessary to clarify the role of these factors in reducing the negative impacts on terrestrial and aquatic ecosystems. [ABSTRACT FROM AUTHOR]

The contribution of Douglas-fir (Df) to European forests is likely to increase as the species is a potential adaptation option to climate change. In this study, we investigated growth and survival of Df seed sources to fill a knowledge gap regarding recommendations for the future use of Df provenances in Poland. Our experimental test site represents the most continental climate among all Df trials installed in the IUFRO 1966–67 test series in Europe. At this unique single site, we evaluated the performance of 46 Df provenances from North America, and nine local landraces of unknown origin. Repeated measurements of tree diameter, height, and volume were analysed, to age 48, representing integrated responses to geographic and climatic conditions. Significant variation in survival and productivity-related traits were found, with the interior Df provenances performing best, in contrast to previous European reports. The higher survivability and volume of the interior provenances resulted from their superior frost resistance. The low precipitation seasonality at the location of seed origin provided an additional advantage to the trees at the test site. Geographic and climatic factors of seed origin explained most of the variation in productivity (77 and 64%, respectively). The tested landraces exhibited diverse performance, implying that naturalized local seed sources in Poland need improvement and perhaps enrichment with new genetic material from North America, while considering geography and climate. Assisted migration programs should consider the limitations imposed by both frost and drought events in guiding future Df selections for continental climates. Further field testing, early greenhouse screening and DNA testing are also recommended. [ABSTRACT FROM AUTHOR]

The forest stands of Douglas-fir [Pseudotsuga menziesii (Mirbel) Franco] and Norway spruce [Picea abies (L.) Karst.] in the South Bohemian uplands (Czech Republic) represent an artificial community of a neophyte (native to North America) and indigenous species (with natural distribution in mountain forests). Ecological characteristics of these two tree species and their response to climatic factors were studied using tree ring analyses and correlation of growth indices for tree-to-tree and between trees and historical parameters of climate (average air temperatures, sum of precipitations and relative air humidity). The two datasets were analysed using multidimensional methods. The ordination analysis shows a considerable difference between both tree species. Growth of both species differed significantly by districts and plots. The effect of climate was studied using correlations as floating time-window. Our results showed that average air temperature had a stronger effect on Douglas-fir growth, for which an increment decrease was found at higher temperatures between May 25th and June 24th. Also, the average maximum air temperature affected the growth of Douglas-fir more strongly than that of Norway spruce. More precipitation was associated with a similar positive effect on the growth of both tree species. Air humidity had a significant effect on growth of both studied tree species and the effect of air humidity was more significant than of distinct precipitation. The combined effects of lack of precipitation and high temperature in vegetation period was the major limiting factor for radial growth. Douglas-fir showed higher productivity (+17.2%) and resistance to climate extremes compared to Norway spruce. Our results suggest that a mixed stand could be more resistant in terms of growth stability than mono-specific stands, as the two studied species exhibited different reaction to climate extremes. Our study further showed that mixed stands with high species diversity had a higher production potential (+13.1%). [ABSTRACT FROM AUTHOR]

Conifers often occur along steep gradients of diverse climates throughout their natural ranges, which is expected to result in spatially varying selection to local climate conditions. However, signals of climatic adaptation can often be confounded, because unraveled clines covary with signals caused by neutral evolutionary processes such as gene flow and genetic drift. Consequently, our understanding of how selection and gene flow have shaped phenotypic and genotypic differentiation in trees is still limited.A 40‐year‐old common garden experiment comprising 16 Douglas‐fir (Pseudotsuga menziesii) provenances from a north‐to‐south gradient of approx. 1,000 km was analyzed, and genomic information was obtained from exome capture, which resulted in an initial genomic dataset of >90,000 single nucleotide polymorphisms. We used a restrictive and conservative filtering approach, which permitted us to include only SNPs and individuals in environmental association analysis (EAA) that were free of potentially confounding effects (LD, relatedness among trees, heterozygosity deficiency, and deviations from Hardy–Weinberg proportions). We used four conceptually different genome scan methods based on FST outlier detection and gene–environment association in order to disentangle truly adaptive SNPs from neutral SNPs.We found that a relatively small proportion of the exome showed a truly adaptive signal (0.01%–0.17%) when population substructuring and multiple testing was accounted for. Nevertheless, the unraveled SNP candidates showed significant relationships with climate at provenance origins, which strongly suggests that they have featured adaptation in Douglas‐fir along a climatic gradient. Two SNPs were independently found by three of the employed algorithms, and one of them is in close proximity to an annotated gene involved in circadian clock control and photoperiodism as was similarly found in Populus balsamifera. Synthesis. We conclude that despite neutral evolutionary processes, phenotypic and genomic signals of adaptation to climate are responsible for differentiation, which in particular explain disparity between the well‐known coastal and interior varieties of Douglas‐fir. [ABSTRACT FROM AUTHOR]

Phytophthora pluvialis is an oomycete that was first isolated from soil, water, and tree foliage in mixed Douglas-fir-tanoak forests of the U.S. Pacific Northwest (PNW). It was then identified as the causal agent of red needle cast mdiata pine (Pinus mdiata) in New Zealand (NZ). Genotyping-by-sequencing was used to obtain 1-543 single nucleotide polymorphisms across 145 2 ph, vialis isolates to characterize the population structure in the PNW and NZ. We tested the hypothesis that P pluvialis was introduced to NZ from PNW using genetic distance measurements and population structure analyses among locations between countries. The low genetic distance, population heterozygosity, and lack of geographic structure in NZ suggest a single colonization event from the United States followed by clonal microbeexpansion in NZ The PNW Coast Range was proposed as a presuinptive center of origin of the curTently known distribution of P pluvirdis based on its geographic range and position as the central cluster in a minimum spanning network. The Coastal cluster of isolates were located at the root of every U.S. cluster and emerged earlier than all NZ clusters. The Coastal cluster had the highest degree of heterozygosity (Hs = 0.254) and median pairwise genetic distance (0.()93) relative to any other cluster. Finally, the rapid host diversification between closely related isolates of P phivia/is in NZ indicate that this pathogen has the potential to infect a broader range of hosts than is currently recognized. [ABSTRACT FROM AUTHOR]

A central challenge in global change research is the projection of the future behavior of a system based upon past observations. Tree‐ring data have been used increasingly over the last decade to project tree growth and forest ecosystem vulnerability under future climate conditions. But how can the response of tree growth to past climate variation predict the future, when the future does not look like the past? Space‐for‐time substitution (SFTS) is one way to overcome the problem of extrapolation: the response at a given location in a warmer future is assumed to follow the response at a warmer location today. Here we evaluated an SFTS approach to projecting future growth of Douglas‐fir (Pseudotsuga menziesii), a species that occupies an exceptionally large environmental space in North America. We fit a hierarchical mixed‐effects model to capture ring‐width variability in response to spatial and temporal variation in climate. We found opposing gradients for productivity and climate sensitivity with highest growth rates and weakest response to interannual climate variation in the mesic coastal part of Douglas‐fir's range; narrower rings and stronger climate sensitivity occurred across the semi‐arid interior. Ring‐width response to spatial versus temporal temperature variation was opposite in sign, suggesting that spatial variation in productivity, caused by local adaptation and other slow processes, cannot be used to anticipate changes in productivity caused by rapid climate change. We thus substituted only climate sensitivities when projecting future tree growth. Growth declines were projected across much of Douglas‐fir's distribution, with largest relative decreases in the semiarid U.S. Interior West and smallest in the mesic Pacific Northwest. We further highlight the strengths of mixed‐effects modeling for reviving a conceptual cornerstone of dendroecology, Cook's 1987 aggregate growth model, and the great potential to use tree‐ring networks and results as a calibration target for next‐generation vegetation models. [ABSTRACT FROM AUTHOR]

Douglas-fir (Pseudotsuga menziesii) has distinctly colored heartwood as a result of extractive deposition during heartwood formation. This is known to affect natural durability and treatability with preservatives, as well as other types of wood modification involving infiltration with chemicals. The distribution of extractives in sapwood and heartwood of Douglas-fir was studied using fluorescence microscopy. Several different types of extractive including flavonoids, resin acids, and tannins were localized to heartwood cell walls, resin canals, and rays, using autofluorescence or staining of flavonoids with Naturstoff A reagent. Extractives were found to infiltrate the cell walls of heartwood tracheids and were also present to a lesser extent in sapwood tracheid cell walls, especially in regions adjacent to the resin canals. Förster resonance energy transfer measurements showed that the accessibility of lignin lining cell wall micropores to rhodamine dye was reduced by about 50%, probably as a result of cell wall-bound tannin-like materials which accumulate in heartwood relative to sapwood, and are responsible for the orange color of the heartwood. These results indicate that micro-distribution of heartwood extractives affects cell wall porosity which is reduced by the accumulation of heartwood extractives in softwood tracheid cell walls. [ABSTRACT FROM AUTHOR]

Although thermal modification is primarily used to improve wood durability, it also has a tendency to darken lighter colored hardwoods to make them more valuable. This process might also be useful for darkening softwoods, but it will be important to develop colors that customers prefer. One potential species for this application is Douglas-fir (Pseudotsuga menziesii). Consumer preferences for differing degrees of thermal modification (i.e. darkening) were assessed using a convenience sampling survey at a Home Show in Eugene, Oregon. Respondents provided demographic information then ranked five thermally modified samples with widely differing degrees of darkening based on their most to least preferred colors. The lightest colored sample was most preferred; however, the darkest sample was the second most preferred. There were no preference differences for samples in between the extremes, suggesting that there is some latitude with regard to color that could be used to differentiate modified Douglas-fir from other products. [ABSTRACT FROM AUTHOR]

Timber durability is often assessed using small wood stakes exposed in direct soil contact, and the assessment generally emphasizes effects on wood rather than organisms involved. Understanding fungal colonization patterns can help identify key decay agents under varying conditions and use these patterns to improve wood protection strategies. Fungal colonization of red alder (Alnus rubra), Douglas-fir (Pseudotsuga menziesii) heartwood/sapwood, and western redcedar (Thuja plicata) field stakes was assessed over 2 y in western Oregon. Spatiotemporal fungal community variations were identified via culturing and DNA sequencing, where 814 isolates were identified from 84 stakes. Forty-six ascomycete genera were identified, with Phialophora, Trichoderma, and Epicoccum species occurring most frequently. Twenty-three basidiomycete genera were identified, with Trametes and Phanerochaete being the most common. Douglas-fir and western redcedar stakes contained the highest and lowest diversity levels, respectively, reflecting natural durability differences of these species. Fungal species abundance was higher below ground than in the above ground and groundline zones, likely reflecting more stable moisture regimes, proximity to soil-based fungi, and potential nutrient migration into wood beneath the soil surface. Ascomycetes were proportionally more abundant early in the exposure period, but basidiomycetes were also observed early in the process, and there appeared to be no consistent colonization pattern. [ABSTRACT FROM AUTHOR]

Few studies have quantified intraspecific variation of hydraulic functional traits in conifers across elevation gradients that include range boundaries. In the Intermountain West, USA, the lower elevational limit of forests (lower treeline) is generally assumed to be caused by water limitations to growth and water relations, yet few studies directly show this. To test this assumption, we measured changes in a suite of traits that characterize drought tolerance such as drought-induced hydraulic vulnerability, hydraulic transport capacity and morphological traits in branch tips and branches of Douglas-fir (Pseudotsuga menziesii var. glauca (Mirb.) Franco) along a 400-m elevation gradient in southeastern Idaho that included lower treeline. As elevation decreased, vulnerability to hydraulic dysfunction and maximum conductivity both decreased in branches; some hydraulic safety–efficiency trade-offs were evident. In branch tips, the water potential at the turgor loss point decreased, while maximum conductance increased with decreasing elevation, highlighting that branch-tip-level responses to less moisture availability accompanied by warmer temperatures might not be coordinated with branch responses. As the range boundary was approached, we did not observe non-linear changes in parameters among sites or increased variance within sites, which current ecological hypotheses on range limits suggest. Our results indicate that there is substantial plasticity in hydraulic functional traits in branch tips and branches of Douglas-fir, although the direction of the trends along the elevation gradient sometimes differed between organs. Such plasticity may mitigate the negative impacts of future drought on Douglas-fir productivity, slowing shifts in its range that are expected to occur with climate change. [ABSTRACT FROM AUTHOR]

Maps of the growth potential for the non-native coastal Douglas-fır (Pseudotsuga menziesii var. menziesii) are presented for Austria and Germany. The regional growth potentials were derived using a site-sensitive statistical model which determines productivity as the dominant-height at age 60 (SI60). The model was calibrated using data from 28 Douglas-fır stands in Austria and Germany growing on silicate and carbonate bedrock. The model is based on non-linear relationships between SI60 and ten climatic, soil physical and soil chemical parameters. Model predictions were calculated for a 1 km x 1 km grid for Austria and Germany. The results revealed that the Northern Alpine foothills in southern Germany are an area with a particularly high growth potential under current climatic conditions (mean 1970-2000). Applying two climate change scenarios (RCP 4.5 and RCP 8.5) to assess the future productivity of Douglas-fır, we see that the changing growth conditions will have a positive impact on Douglas-fır growth at higher altitudes, whereas the productivity may decline in areas where the current growing conditions are dry and highly productive. [ABSTRACT FROM AUTHOR]

Climate change is increasing fire activity in the western United States, which has the potential to accelerate climate-induced shifts in vegetation communities. Wildfire can catalyze vegetation change by killing adult trees that could otherwise persist in climate conditions no longer suitable for seedling establishment and survival. Recently documented declines in postfire conifer recruitment in the western United States may be an example of this phenomenon. However, the role of annual climate variation and its interaction with long-term climate trends in driving these changes is poorly resolved. Here we examine the relationship between annual climate and postfire tree regeneration of two dominant, low-elevation conifers (ponderosa pine and Douglas-fir) using annually resolved establishment dates from 2,935 destructively sampled trees from 33 wildfires across four regions in the western United States. We show that regeneration had a nonlinear response to annual climate conditions, with distinct thresholds for recruitment based on vapor pressure deficit, soil moisture, and maximum surface temperature. At dry sites across our study region, seasonal to annual climate conditions over the past 20 years have crossed these thresholds, such that conditions have become increasingly unsuitable for regeneration. High fire severity and low seed availability further reduced the probability of postfire regeneration. Together, our results demonstrate that climate change combined with high severity fire is leading to increasingly fewer opportunities for seedlings to establish after wildfires and may lead to ecosystem transitions in low-elevation ponderosa pine and Douglas-fir forests across the western United States. [ABSTRACT FROM AUTHOR]

Abstract Statistically downscaled climate change scenarios from four General Circulation Models for two Representative Concentration Pathways (RCP) were applied as inputs to a biogeochemical model, PnET-BGC, to examine potential future dynamics of water, carbon, and nitrogen in an old-growth Douglas-fir forest in the western Cascade Range. Projections show 56% to 77% increases in stomatal conductance throughout the year from 1986–2010 to 2076–2100, and 65% to 104% increases in leaf carbon assimilation between October and June over the same period. However, future dynamics of water and carbon under the RCP scenarios are affected by a 49% to 86% reduction in foliar biomass resulting from severe air temperature and humidity stress to the forest in summer. Important implications of future decreases in foliar biomass include 1) 20% to 71% decreases in annual transpiration which increase soil moisture by 7% to 15% in summer and fall; 2) decreases in photosynthesis by 77% and soil organic matter by 62% under the high radiative forcing scenario; and 3) altered foliar and soil carbon to nitrogen stoichiometry. Potential carbon dioxide fertilization effects on vegetation are projected to 1) amplify decreases in transpiration by 4% to 9% and increases in soil moisture in summer and fall by 1% to 2%; and 2) alleviate decreases in photosynthesis by 4%; while 3) having negligible effects on the dynamics of nitrogen. Our projections suggest that future decrease in transpiration and moderate water holding capacity may mitigate soil moisture stress to the old-growth Douglas-fir forest. Future increases in nitrogen concentration in soil organic matter are projected to alleviate the decrease in net nitrogen mineralization despite a reduction in decomposition of soil organic matter by the end of the century. Graphical abstract Unlabelled Image Highlights • Element dynamics projected in an old-growth Douglas-fir forest under RCP scenarios • Future increasing temperature causes severe physiological stress on the vegetation • Decreasing photosynthesis, plant biomass, and soil organic matter are projected • Projected mortality decreases transpiration and slightly increases soil moisture • Future climate change alters foliar and soil carbon to nitrogen stoichiometry [ABSTRACT FROM AUTHOR]

Forest birds are sensitive to habitat change and may be suitable for measuring responses to retention forestry. I present the short-term effects of 6 treatments in a 6 block randomized design experiment on 15 breeding small bird species in mature Douglas-fir (Pseudotsuga menziesii) forests in western Washington and Oregon, 1994-2001. The 13-ha treatment stands contained aggregated (A) green-tree retentions of 100, 75, 40 and 15%, and a dispersed tree distribution pattern (D) of 40 and 15% retention. I compared numbers of entire singing bird territories (abundances) mapped inside sampling plots in post- (2-y ... ) and pre-treatments (1 y). Species richness significantly declined in both 15% treatments. In the 15%D treatment, significantly lower richness and lower species similarity were less than A treatments with ≥40% retention, and significantly lower species diversity was less than the other treatments. The size of decline of abundances of canopy-associated species (summed members) increased with successively lower tree retention; the cavity-nesting species declined with lower snag retention in treatments ≤40% retention; and there was no response for species associated with understory vegetation, but medians of the percentage change in abundance of understory species were negative in cut treatments. There was no detectable difference in treatment effects between tree distribution cut patterns. Greater amounts of tree retention helped maintain composition and abundance better than less retention, and overall the variety of treatments maintained all species. For maintaining richness, similarity, and diversity, the 15%A and 40%D treatments were transitional between the A treatments ≥40% retention, where these community parameters were maintained, and 15%D, which did not maintain natural diversity or species persistence. [ABSTRACT FROM AUTHOR]

The potential for polyurea coatings to improve wood crossarm performance was assessed on untreated and treated Douglas-fir exposed to termite/fungal attack in Hawaii. Treated materials performed similarly regardless of coating, although coating reduced UV damage. Untreated non-coated timbers were decayed within 2-years of exposure and were unserviceable after 7 years. Upper surfaces of coated, untreated samples experienced pronounced coating loss and contained advanced decay on the undersides of the timbers, but no decay occurred on coated, treated samples. Decay fungi were isolated from treated and non-treated coated arms, but isolation frequency was greater for non-treated materials. Coating thickness declined on both treated and non-treated materials, but the effects were greater on non-treated samples. Termites did not attack treated samples with or without coating, but destroyed untreated, non-coated samples and penetrated the polyurea coating to destroy untreated and borate dipped Douglas-fir. Polyurea coatings provided limited protection for non-treated wood. [ABSTRACT FROM AUTHOR]

Abstract Wood is among the most decay-resistant cellulosic materials; however, all organics eventually succumb to decay. Understanding the degradation process is important when considering how products perform, but this knowledge can also be useful when determining how climates affect the organisms involved and the rates at which degradation occurs. Above ground wood decay tends to occur more slowly than decay in direct soil contact and is more dependent on climatic differences and wood species chemistries. While above ground wood deterioration is a subject of interest, most research has concentrated on the effects of the organisms on the wood. There are surprisingly few comprehensive studies of the fungi involved in the process and most have been performed under aggressive tropical conditions. Fungal colonization of red alder and Douglas-fir samples exposed above ground was evaluated over a 24-month period. Red alder is highly susceptible to fungal attack while Douglas-fir is moderately resistant. As such, they presented two differing selective media for fungal colonization. Red alder was more heavily colonized than Douglas-fir, reflecting the differing susceptibility of the two wood species to degradation. A similar number of Ascomycete and Basidiomycete species were isolated (11 vs 8 species, respectively), but Basidiomycetes were more frequently isolated. These results were similar to those found under more tropical conditions. The results illustrate the wide range of species that colonize wood exposed above ground. Highlights • Ascomycotina were more abundant than Basidiomycotina • White rot fungi were the predominant. • Alder was more heavily colonized than Douglas-fir. • Plant pathogens were among fungi in decaying wood. [ABSTRACT FROM AUTHOR]

Abstract Photosynthesis is a critical component to understanding how CO 2 uptake and vegetation productivity drives the terrestrial carbon cycle. Light use efficiency (LUE) is a key indicator of photosynthesis, which is determined by the most limiting/co-limiting environmental stresses such as nutrition, water, and temperature, restraining the photochemical reaction process across both space and time due to remote sensing offers a capability to relate changes in LUE with changes in the spectral characteristics of leaves through the photochemical reflectance index (PRI). The PRI is a narrow waveband index that responds with changes in xanthophyll-induced absorption feature at 531 nm. It remains challenging, however, to upscale PRI from leaf to canopy and ultimately to the landscape level due to physiological and structural factors such as leaf angle distribution, leaf area, canopy structure and pigment pool size as well as observational considerations such as sun-view geometry and background reflectance. As a result, understanding patterns of PRI and LUE across different climate-induced stress conditions and within age-induced vertical stand structures is helpful for improving our understanding how these relationships change over forested landscapes in anticipation of future airborne and ultimately satellite-based observations. In this study, we report on the use of the automated multi-angular spectro-radiometer (AMSPEC) and eddy-covariance techniques to examine how PRI and LUE varies at young (HDF88) and older (DF49) Douglas-fir sites. Results indicate that a strong relationship between bidirectional reflectance distribution function (BRDF) corrected PRI and LUE exists (DF49: R2 = 0.73; HDF88: R2 = 0.79). The overall LUE at the older, more structurally complex site was higher than at the younger, structurally simpler stand under a range of air temperature and light conditions. We used the standard deviation (SD) of light detection and ranging (LiDAR) return pulses to characterize canopy vertical structure of the site, and found that complex vertical structures (i.e., high SD) may contribute to a higher long-term averaged LUE (R2 = 0.87). While interesting we conclude the mechanism of the relationship between LUE and vertical forest structures needs to be further explored because of the key role internal and external shadowing has on light regimes with stands and thus vertical patterns of LUE varying across forest stands of different age. Highlights • Patterns of LUE across Douglas-fir forest stands of different age were analyzed. • AMSPEC-observed PRI accurately estimated LUE across stands. • LUE was higher in older Douglas-fir forest stands. • Long-term LUE showed a direct relationship with the complexity of canopy structure. [ABSTRACT FROM AUTHOR]

Highlights • Extrusion process imparted physical and structural changes to the wood particles. • Specific mechanical energy had a strong positive correction with sugar yield. • The lowest moisture content and temperature led to the highest sugar yield. • Recrystallization and agglomeration occurred after the extrusion process. Abstract The impact of independent variables of extrusion on dependent variables of pre-milled Douglas-fir forest residuals was studied to enhance the enzymatic hydrolysis for production of fermentable sugar without catalysts. Co-rotating twin screw extruder was operated with three different feedstock moisture contents (30, 40, and 50%) at four different barrel temperatures (25, 50, 100, and 150 °C) as a pretreatment. The specific mechanical energy input ranged from 0.07 and 0.30 kWh/kg and had a very strong positive correlation with torque (r = 0.96, p < 0.01), glucose (r = 0.92, p < 0.01) and xylose/mannose yields with (r = 0.84, p < 0.01). Douglas-fir residuals extruded at lowest moisture content (30%) and temperature (25 °C) had the highest sugar yield, requiring the highest SME. Higher barrel temperature increased the median particle size and had lower glucose and xylose/mannose yields. Recrystallization and agglomeration were observed under higher temperature conditions. [ABSTRACT FROM AUTHOR]

ABSTRACT: Snags are important habitat features for many forest‐dwelling species, so reductions in the number of snags can lead to the loss of biodiversity in forest ecosystems. Intentional snag creation is often used in managed forests to mitigate the long‐term declines of naturally created snags, yet information regarding the use of snags by wildlife across long timescales (>20 yr) is lacking and prevents a complete understanding of how the value of created snags change through time. We used a long‐term experiment to assess how harvest treatment (i.e., small‐patch group selection, 2‐story, and clearcut) and snag configuration (i.e., scattered and clustered) influenced nesting in and foraging on 25–27‐year‐old Douglas‐fir (Pseudotsuga menziesii) snags by cavity‐nesting birds. In addition, we compared our contemporary measures of bird use to estimates obtained from historical surveys conducted on the same group of snags to quantify how bird use changed over time. Despite observing created snags for >750 hours across 2 consecutive breeding seasons, we found limited evidence of nesting activity. Only 11% of created snags were used for breeding, with nesting attempts by 4 bird species (n = 36 nests); however, we detected 12 cavity‐nesting species present on our study sites. Furthermore, nearly all nests (94%) belonged to the chestnut‐backed chickadee (Poecile rufescens), a weak cavity‐excavating species that requires well‐decayed wood for creating nest cavities. Our surveys also recorded few observations of birds using created snags as foraging substrates, with only 1 foraging event recorded for every 20 hours of observation. We detected 82% fewer nests and recorded 7% fewer foraging observations during contemporary field work despite spending >7.5 times more effort observing created snags relative to historical surveys. We conclude that 25–27‐year‐old created Douglas‐fir snags provided limited opportunities for nesting and foraging by most cavity‐nesting birds, and that the period of greatest use by this group occurred within 5–15 years of creation. © 2018 The Wildlife Society. [ABSTRACT FROM AUTHOR]

Black bears ( Ursus americanus Pallas, 1780) peel conifers in early spring to forage on energy-rich vascular tissues, resulting in damage to timber stands. The objective of our study was to develop and demonstrate a conceptual framework and methods for estimating stand-level volume and economic losses from black bear damage. We created tree lists from surveys of healthy and bear-damaged trees in timber stands of western Washington and Oregon. The forest growth model Forest Vegetation Simulator (FVS) was used to project stand volume under two damage scenarios and an undamaged scenario. One damage scenario (salvage) accounted for mortality and volume losses of fully and partially girdled trees; a second scenario (total loss) assumed complete loss of all trees peeled by black bears, regardless of peeling severity. The Fuel Reduction Cost Simulator (FRCS) was applied to estimate the value of logs delivered to the mill after accounting for logging and hauling costs associated with harvest. Present value of stands was calculated to translate volume losses into economic losses associated with bear damage. Economic losses ranged from 4% to 16% (salvage) and from 17% to 46% (total loss) of net present value. Our approach can be adapted for other forest settings and for forest management plans that assess wildlife damage. [ABSTRACT FROM AUTHOR]

The western spruce budworm (WSB; Choristoneura freemani Razowski) shapes Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) forests throughout western North America with periodic, severe landscape-level defoliation events. The largest and most continuous recorded defoliation occurred in the 2000s, largely centered in the Williams Lake and 100 Mile House WSB outbreak regions, peaking in 2007 at 847 000 ha defoliated in British Columbia (B.C.). Unique WSB outbreak regions in south-central B.C. are described using biogeoclimatic ecosystem classification, geography, 106 years of documented defoliation, and 46 stand-level Douglas-fir host tree-ring chronologies. Since the 1980s, recorded defoliation in B.C. has shifted from coastal ecosystems and become a dominant disturbance in drier, colder, interior Douglas-fir ecosystems. Defoliation records demarcate four outbreaks from 1950-2012 and up to three growth suppression events from 1937-2012. Outbreak duration was shorter in the north and far south of B.C., with recovery periods (no trees showing growth suppression) shorter over all WSB outbreak regions in the 2000s, suggesting that trees may be increasingly susceptible to each successive defoliation event. Knowing the regional outbreak periodicity may facilitate early detection of incipient WSB populations, which is critical for management as many of our low-elevation Douglas-fir forests become more stressed with changing and unpredictable climate regimes. [ABSTRACT FROM AUTHOR]

Douglas-fir forests of the coastal Pacific Northwest experience yearly summer droughts; however, the variation in shallow soil available water supply throughout the region is not well understood nor is the effect of future climate change. Soil moisture sensors were installed in 60 Douglas-fir plantation forests over 6 years. Stands were grouped by physiographic regions to describe differences in climate and available water supply. Monthly available water supply (MAWS) (0-50 cm) was calculated as the average daily available moisture content. MAWS was modeled using monthly climate variables, and the equation was then used to predict the change in MAWS due to mild, moderate, and severe climate change predictions. Regional monthly air temperature and precipitation were strongly predictive of MAWS. Mild to severe climate change are predicted to decrease yearly available water supply by 8% to 19%, while summer available water supply will decrease from 25% to 72%. The greatest decreases due to climate change will be found in the coastal regions of Washington and Oregon due to greater negative effects of temperature on available water supply. Climate change, especially the most severe predictions, was shown to have a sizeable effect on shallow soil available water supply in coastal Douglas-fir forests. [ABSTRACT FROM AUTHOR]

Warmer temperatures associated with climate change have the potential to accelerate litter decay and subsequently release large amounts of carbon stored in soils. Condensed tannins are widespread secondary metabolites, which accumulate to high concentrations in many woody plants and play key roles in forest soil nutrient cycles. Future elevated atmospheric CO concentrations are predicted to reduce nitrogen content and increase tannin concentrations in plant tissues, thus reducing litter quality for microbial communities and slowing decomposition rates. How the distinct condensed tannin fractions (water-soluble, acetone:MeOH-soluble and solvent-insoluble) impact soil processes, has not been investigated. We tested the impact of condensed tannin and nitrogen concentrations on decay rates of poplar and Douglas-fir litter at sites spanning temperature and moisture gradients in coastal rainshadow forests in British Columbia, Canada. The three condensed tannin fractions were quantified using recent improvements on the butanol-HCl assay. Decay was assessed based on carbon remaining, while changes in litter chemistry were primarily observed using two methods for proximate chemical analyses. After 0.6 and 1 year of decay, more carbon remained in poplar litter with high, compared to low, condensed tannin concentrations. By contrast, more carbon remained in Douglas fir litter than poplar litter during this period, despite lower condensed tannin concentrations. Rapid early decay was especially attributed to loss of soluble compounds, including water-soluble condensed tannins. Water-insoluble condensed tannin fractions, which were transformed to acid-unhydrolyzable residues over time, were associated with reduced carbon loss in high condensed tannin litter. [ABSTRACT FROM AUTHOR]

The potential for migration of pentachlorophenol (PCP) and copper naphthenate (CuNaph) from Douglas-fir was assessed in a bridge over a stream located in Western Oregon in the United States. All rainfall runoff was collected from a portion of the bridge on 15 occasions over a 27 month period and analyzed for pentachlorophenol or copper. PCP and copper were detected at every time point. PCP concentrations ranged from 0.296 to 6.183 μg/mL, while those for copper ranged from 0.37 to 7.80 μg/mL. These data were then used to estimate PCP and Cu inputs in runoff from the entire bridge. Stream flow data were then used to predict the concentrations that would develop in the receiving stream. The results showed that runoff from the bridge would result in PCP and copper concentrations that were 500–1000 times lower than the reported levels of effect for each component. The results are discussed in the context of this location as well as other sites with lower stream flow conditions. [ABSTRACT FROM AUTHOR]

Broadcast weeding of naturally regenerating paper birch (Betula papyrifera) to improve performance of conifer crop trees is common in forest plantations in British Columbia, Canada, but such treatments are costly, reduce biodiversity and may increase disease. To investigate whether alternative treatments can enhance conifer performance with minimal loss of other ecosystem services, we examined effects of selective removal of paper birch in two interior Douglas-fir (Pseudotsuga menziesiivar.glauca) plantations on Douglas-fir growth and survival, and cover and height of residual birch and the understorey plant community. Douglas-fir-centred birch-free patches of varying radius (0–2.5 m) were created by single and repeated manual cutting and Triclopyr® application. The “threshold brushing radius,” defined as the birch removal radius at which Douglas-fir performance was optimized was 2.0 m at the more productive site and 1.5 m at the less productive one. Armillaria root disease, the major Douglas-fir mortality agent, spiked in the 1.0 m radius manual cutting treatment at one location. The greatest reductions in birch and understory plant abundance occurred following the most intensive treatments. Selective brushing treatments are an effective alternative to broadcast removal of paper birch for increasing conifer performance, and have less impact on the plant community. [ABSTRACT FROM PUBLISHER]

Background: Genomic selection (GS) can offer unprecedented gains, in terms of cost efficiency and generation turnover, to forest tree selective breeding; especially for late expressing and low heritability traits. Here, we used: 1) exome capture as a genotyping platform for 1372 Douglas-fir trees representing 37 full-sib families growing on three sites in British Columbia, Canada and 2) height growth and wood density (EBVs), and deregressed estimated breeding values (DEBVs) as phenotypes. Representing models with (EBVs) and without (DEBVs) pedigree structure. Ridge regression best linear unbiased predictor (RR-BLUP) and generalized ridge regression (GRR) were used to assess their predictive accuracies over space (within site, cross-sites, multi-site, and multi-site to single site) and time (age-age/trait-trait). Results: The RR-BLUP and GRR models produced similar predictive accuracies across the studied traits. Within-site GS prediction accuracies with models trained on EBVs were high (RR-BLUP: 0.79-0.91 and GRR: 0.80-0.91), and were generally similar to the multi-site (RR-BLUP: 0.83-0.91, GRR: 0.83-0.91) and multi-site to single-site predictive accuracies (RR-BLUP: 0. 79-0.92, GRR: 0.79-0.92). Cross-site predictions were surprisingly high, with predictive accuracies within a similar range (RR-BLUP: 0.79-0.92, GRR: 0.78-0.91). Height at 12 years was deemed the earliest acceptable age at which accurate predictions can be made concerning future height (age-age) and wood density (trait-trait). Using DEBVs reduced the accuracies of all cross-validation procedures dramatically, indicating that the models were tracking pedigree (family means), rather than marker-QTL LD. Conclusions: While GS models' prediction accuracies were high, the main driving force was the pedigree tracking rather than LD. It is likely that many more markers are needed to increase the chance of capturing the LD between causal genes and markers. [ABSTRACT FROM AUTHOR]

Due to its productivity and potential to adapt to the expected climate change, the Douglas-fir is one of the most important commercial non-native forest tree species in Europe. Currently, seeds from both non-native European and native American seed stands are used for plantations. In this study, we investigate European seed lots for their native origin (variety and potential geographic origin in America) and assess the adaptability, growth and survival potential of European versus American Douglas-fir seed lots. We compare the genetic diversity, morphological characteristics such as height ( h), root collar diameter (rcd) and the ratio of h/rcd, and the timing of bud burst. We investigate 852 1-year-old seedlings from 10 different US and European seed lots representing 5 provenance regions which are sold in Germany and Austria. Seedlings are genotyped for 13 nuclear SSRs and analysed together with reference data set and standard genetic structuring and assignment methods. Adaptive traits of morphological characteristics and timing of bud burst of the seedlings are recorded and statistically analysed. The results show that the investigated European seedlings originate from recommended American native seed sources and represent both varieties and inter-varietal admixed individuals. European seedlings have a lower genetic diversity versus the American seedlings and native populations. They show significant differences in the adaptive traits such as morphological characteristics and timing of bud burst. According to the genetic diversity indices, certified North American Douglas-fir seed sources should be preferred for planting in Central Europe. [ABSTRACT FROM AUTHOR]

In the context of ongoing climatic warming, certain landscapes could be near a tipping point where relatively small changes to their fire regimes or their postfire forest recovery dynamics could bring about extensive forest loss, with associated effects on biodiversity and carbon-cycle feedbacks to climate change. Such concerns are particularly valid in the Klamath Region of northern California and southwestern Oregon, where severe fire initially converts montane conifer forests to systems dominated by broadleaf trees and shrubs. Conifers eventually overtop the competing vegetation, but until they do, these systems could be perpetuated by a cycle of reburning. To assess the vulnerability of conifer forests to increased fire activity and altered forest recovery dynamics in a warmer, drier climate, we characterized vegetation dynamics following severe fire in nine fire years over the last three decades across the climatic aridity gradient of montane conifer forests. Postfire conifer recruitment was limited to a narrow window, with 89% of recruitment in the first 4 years, and height growth tended to decrease as the lag between the fire year and the recruitment year increased. Growth reductions at longer lags were more pronounced at drier sites, where conifers comprised a smaller portion of live woody biomass. An interaction between seed-source availability and climatic aridity drove substantial variation in the density of regenerating conifers. With increasing climatic water deficit, higher propagule pressure (i.e., smaller patch sizes for high-severity fire) was needed to support a given conifer seedling density, which implies that projected future increases in aridity could limit postfire regeneration across a growing portion of the landscape. Under a more severe prospective warming scenario, by the end of the century more than half of the area currently capable of supporting montane conifer forest could become subject to minimal conifer regeneration in even moderate-sized (10s of ha) high-severity patches. [ABSTRACT FROM AUTHOR]

Background: Perennial 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. Results: We 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. Conclusions: Our 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. [ABSTRACT FROM AUTHOR]

Background: Condensed tannins (CT) are the most abundant secondary metabolite of land plants and can vary in abundance and structure according to tissue type, species, genotype, age, and environmental conditions. Recent improvements to the butanol-HCl assay have separately helped quantification of soluble and insoluble CTs, but have not yet been applied jointly. Our objectives were to combine previous assay improvements to allow for quantitative comparisons of different condensed tannin forms and to test protocols for analyses of condensed tannins in vegetative plant tissues. We also tested if the improved butanol-HCl assay can be used to quantify water-soluble forms of condensed tannins. Results: Including ~50% acetone in both extraction solvents and final assay reagents greatly improved the extraction and quantification of soluble, insoluble and total condensed tannins. The acetone-based method also extended the linear portion of standard integration curves allowing for more accurate quantification of samples with a broader range of condensed tannin concentrations. Estimates of tannin concentrations determined using the protocol without acetone were lower, but correlated with values from acetone-based methods. With the improved assay, quantification of condensed tannins in water-soluble forms was highly replicable. The relative abundance of condensed tannins in soluble and insoluble forms differed substantially between tissue types. Conclusions: The quantification of condensed tannins using the butanol-HCl assay was improved by adding acetone to both extraction and reagent solutions. These improvements will facilitate the quantification of total condensed tannin in tissues containing a range of concentrations, as well as to determine the amount in water-soluble, acetone:MeOH-soluble and insoluble forms. Accurate determination of these three condensed tannin forms is essential for careful investigations of their potentially different physiological and ecological functions. [ABSTRACT FROM AUTHOR]

To quantify the impact of forest management practices and tree growth rate on the potential uses of Douglas-fir wood, nine physico-mechanical properties were studied on more than 1250 standardized clear specimens. These were collected from trees cut in 11 even-aged stands (six trees per stand) located in Wallonia (southern Belgium). Stands were 40 to 69 years old, and mean tree girth was ca. 150 cm. Mean ring width of the 66 trees ranged from 3 to more than 7 mm. Statistical analysis showed significant but weak effects of ring width on the studied properties. Considered jointly, mean ring width and cambial age of the test specimens only explained 28% to 40% of the variability of their properties. Also, when ring width increases, these properties display higher decreases in juvenile wood than in mature wood. From a technological standpoint, maintaining mean ring width under 4 mm in juvenile wood and 6 mm in mature wood should accommodate all potential uses of Douglas-fir wood. However, considering that density appeared to be the main driver of wood properties, our results and the literature corroborate the importance of genetic selection as a complement to silvicultural measures to improve or guarantee the technological properties of Douglas-fir wood. [ABSTRACT FROM AUTHOR]

Douglas-fir ( Pseudotsuga menziesii) is one of the best timber conifers providing long sawnwood components. Original from North America, it has been planted in Europe on approximately 550 thousand ha. Twenty Douglas-fir trees growing in two sites in Portugal were studied regarding ring analysis, heartwood, sapwood and bark development, and taper. The radial growth rate was 7.1 and 6.6 mm year at stem base for 45- and 50-year-old trees, respectively, in the two sites. Initial growth rate was slower, increasing until about 20 years and decreasing afterwards. Heartwood proportion represented on average 49% of the cross section in the lower part of the stem and decreased upwards. Heartwood formation was estimated to start at a cambial age of 8-9 years and increasing by 0.7-0.9 rings year. Sapwood width was on average 75 mm at stem base, decreasing upwards. Bark was 26-27 mm thick at stem base, where it represented 15% of the cross-sectional area and decreased to 3-5 mm at the top. Stemwood and heartwood tapers were on average 15 mm m in the lower stem part and 21 and 18 mm m, respectively, in the upper part. Douglas-fir showed a good potential for the mountain areas of Portugal, and under the silvicultural conditions of both stands the trees presented ring homogeneity, small conicity and low taper suitable for long wood components. [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY:: Conifers have the highest rates of mortality during their first year, often attributed to water stress; yet, this tree life stage is the least studied in terms of hydraulic properties. Previous work has revealed correlations between xylem anatomy to both hydraulic transport capacity and resistance to hydraulic dysfunction. In this study, we compared xylem anatomical and plant functional traits of Pseudotsuga menziesii, Larix occidentalis, and Pinus ponderosa seedlings over the first 10 wk of growth to evaluate potential maximum hydraulic capabilities and resistance to drought‐induced embolism. We hypothesized that, based on key functional traits of the xylem, predicted xylem embolism resistance of the species will reflect their previously determined drought tolerances with L. occidentalis, P. menziesii, and P. ponderosa in order of least to most embolism‐resistant xylem. METHODS:: Xylem and pit anatomical characteristics and additional hydraulic‐related functional traits were compared at five times during the first 10 wk of growth using confocal laser scanning microscopy (CLSM). KEY RESULTS:: Based on thickness to span ratio, torus to pit aperture overlap, and torus thickness, primary xylem appeared to be not only more hydraulically conductive but also less embolism‐resistant than secondary xylem. By week 10, P. menziesii was predicted to have the most embolism‐resistant xylem followed by P. ponderosa and L. occidentalis. CONCLUSIONS:: Theoretical measurements suggest that hydraulic transport capacities and vulnerability to embolism varied for each species over the first 10 wk of growth; thus, the timing of germination and onset of limited soil moisture is critical for growth and survival of seedlings. [ABSTRACT FROM AUTHOR]

Wood poles are a critical part of the electrical transmission system in North America. Wood poles are normally selected on the basis of visual features such as knots, slope of grain or other defects, but there is currently no simple, nondestructive bending (NDB), pre-flexural testing for sorting poles prior to use. In the present paper, the potential for NDB based on bending below the proportional limit was examined to calculate modulus of elasticity (MOE) and thereby predict actual modulus of rupture as determined by destructive bending (MORDB). The investigation was performed on 92 full length 13.3-m long Douglas-fir pole sections. Pre-flexural testing was reasonably correlated with MOEDB, but less well correlated with MORDB. The testing also revealed that visual selection of the best face of a pole, which is used to select a pole oriented to line direction (the "best face"), was poorly correlated with pre-flexing. Increasing the number of NDB tests did not noticeably improve the prediction. The results suggest that pre-flexing might be useful for identifying poles' performance in service, if more data are available. [ABSTRACT FROM AUTHOR]

The genus Aureobasidium is wellknown as a wood-staining mold and as a black yeast-like fungi, which produces mainly dark spores or pigmented hyphae within the wood cell lumens. Nevertheless, few studies are dedicated to wood-colonizing Aureobasidium species and little is known about the wood degradation patterns of this genus. In the present study, four Aureobasidium species, including Aureobasidium melanogenum, Aureobasidium leucospermi, Aureobasidium pullulans, and an unknown Aureobasidium sp., were isolated and identified based on phylogenetic analysis. A. melanogenum and A. leucospermi were observed for the first time in Korea. The degradation pattern of Douglas-fir by Aureobasidium was observed for the first time by scanning electron microscopy (SEM). All tested Aureobasidium species except an unknown Aureobasidium sp. revealed soft-rot Type II (erosion) in sapwood pine. [ABSTRACT FROM AUTHOR]

Growth responses of coastal Douglas-fir (Pseudotsuga menziesii [Mirbel] Franco) were quantified 14 years following mechanical damage from commercial thinning. Damaged, adjacent, and non-adjacent trees were measured for total height, crown length, and diameter at breast height (DBH) to assess neighbor competitiveness between damaged and undamaged trees. Results indicated that mechanical damage had no significant effect between damaged and undamaged trees relative to adjacent or non-adjacent trees on total tree height, height/diameter curves, basal area growth after thinning, height to crown base, or crown length. However, there was a significant difference in crown length between the damaged and adjacent trees. Trends in height to crown base over tree diameter curves were not significantly different between damaged and undamaged trees of either the adjacent or non-adjacent group. [ABSTRACT FROM AUTHOR]

This paper documents the accuracy of a post-correction method applied to precipitation regionalized by the Weather Research and Forecasting (WRF) Regional Climate Model (RCM) for improving simulated rainfall and feeding impact studies. The WRF simulation covers Burgundy (northeastern France) at a 8-km resolution and over a 20-year long period (1989–2008). Previous results show a strong deficiency of the WRF model for simulating precipitation, especially when convective processes are involved. In order to reduce such biases, a Quantile Mapping (QM) method is applied to WRF-simulated precipitation using the mesoscale atmospheric analyses system SAFRAN («Système d'Analyse Fournissant des Renseignements Adaptés à la Nivologie») that provides precipitation data at an 8 km resolution. Raw and post-corrected model outputs are next used to compute the soil water balance of 30 Douglas-fir and 57 common Beech stands across Burgundy, for which radial growth data are available. Results show that the QM method succeeds at reducing the model's wet biases in spring and summer. Significant improvements are also noted for rainfall seasonality and interannual variability, as well as its spatial distribution. Based on both raw and post-corrected rainfall time series, a Soil Water Deficit Index (SWDI) is next computed as the sum of the daily deviations between the relative extractible water and a critical value of 40% below which the low soil water content induce stomatal regulation. Post-correcting WRF precipitation does not significantly improve the simulation of the SWDI upon the raw (uncorrected) model outputs. Two characteristic years were diagnosed to explain this unexpected lack of improvement. Although the QM method allows producing realistic precipitation amounts, it does not correct the timing errors produced by the climate model, which is yet a major issue to obtain reliable estimators of local-scale bioclimatic conditions for impact studies. A realistic temporality of simulated precipitation is thus required before using any systematic post-correction method for appropriate climate impact assessment over temperate forests. [ABSTRACT FROM AUTHOR]

Phytophthoraspecies are widespread and diverse in forest ecosystems, but little is known about their ecology. We explore ecological attributes of the closely related clade 3 species that occur sympatrically in western North American forests. We address the population structure, pathology, and epidemiology ofP. ilicis, P. nemorosa, P. pluvialis, P. pseudosyringae, andP. psychrophila. Phytophthoraspecies were isolated from plant tissues, rainwater falling through the forest canopy, streams, and soils in forests in western Oregon. Species identifications were based on morphology in culture with molecular confirmation using COX spacer and internal transcribed spacer (ITS) sequences. All five clade 3Phytophthoraspecies are present in western Oregon forests, althoughP. ilicis(only 1 forest isolate) andP. psychrophila(only 12 isolates) are apparently rare.P. ilicisis known only from holly in horticultural situations and once from a naturalized seedling in an urban forest. The known distribution ofP. nemorosain forest settings coincides with the ranges of its principle hosts, tanoak and myrtlewood, in Oregon and California. Although it is regularly identified from streams within the tanoak range, it has not been recovered from streams beyond that range.P. pluvialisis primarily associated with Douglas-fir canopies. It was identified from scattered locations throughout western Oregon in rain traps beneath Douglas-fir plantations and from diseased needles.P. pseudosyringaeis also isolated from tanoak and myrtlewood in southwest Oregon and California, but its distribution, in streams at least, extends throughout much of western Oregon.P. psychrophilain Oregon is known only from rain traps beneath tanoak trees. Little intraspecific variation was detected in the nuclear rDNA ITS of clade 3 species. Variation in the mitochondrial COX spacer region was more frequent, with 2 to 10 haplotypes identified in the clade 3 species, for which we had multiple isolates. [ABSTRACT FROM PUBLISHER]