Noble Fir Research Articles

Insecticide efficacy and emergence timing of the Douglas-fir twig weevil.

The Douglas-fir twig weevil (Cylindrocopturus furnissi Buchanan) (Coleoptera: Curculionidae) has recently emerged as a significant pest of Christmas trees grown in the Pacific Northwest United States. The larvae girdle and disfigure twigs, which adversely affects tree marketability. Trees produced for export are also routinely destroyed for phytosanitary reasons when C. furnissi is discovered at border crossings. Due to historically being a sporadic and benign pest on planted and natural Douglas-fir (Psuedotsuga menziesii), there is a lack of chemical management options. In laboratory experiments, we assessed the knockdown effects (ability to kill or incapacitate) of 4 insecticides commonly used on Christmas trees: one assay tested knockdown after direct contact for 24 h, and the other assay tested knockdown after being allowed to feed on treated twigs with 2 days, 7 days, and 14 days residuals. Concurrently, we monitored temperature and adult C. furnissi emergence at a noble fir bough farm for 2 years to estimate the ideal degree-day window for applying insecticides. Bifenthrin and esfenvalerate knocked down all weevils on contact within just 4 h, whereas chlorpyrifos and acephate failed to achieve 100% knockdown within 24 h. Only acephate failed to knock down more weevils than the control (water) after feeding on treated twigs, regardless of the insecticide residue age. Degree-day modeling revealed a variable emergence window between the 2 years but 50% of adult emergence occurred between approximately 1,000-1,100 degree days (1st January, 50 °F (10 °C), single sine). Future work should assess the resulting management recommendation: apply bifenthrin or esfenvalerate once annually just after 1,000 growing degree days for 2 or more years prior to harvest.

Models to predict the radial variation of stiffness, strength, and density in planted noble fir, Norway spruce, western hemlock, and western red cedar in Great Britain

Key messageThis study compares the measured radial variation in wood stiffness, strength, and density of noble fir, Norway spruce, western hemlock, and western red cedar by developing mixed-effects models for each property using age as the explanatory variable. These models could be used to simulate the effect of rotation length and species choice on sawn wood properties.ContextTimber production in Great Britain relies primarily on Sitka spruce. The use of multiple species is desirable to mitigate against biotic and abiotic risks posed to a single species. When considering alternative species, quantifying and modeling radial variation in wood properties is important to determine the potential for sawn timber production at a given rotation length.AimsTo build empirical models for the radial variation in wood properties that can account for species.MethodsClear-wood samples were produced along radial transects in trees from four conifer species: Abies procera Rehder, Picea abies (L.) Karst, Tsuga heterophylla (Raf.) Sarg., Thuja plicata Donn. ex D.Don. Modulus of Elasticity, Modulus of Rupture, and density were measured on each species according to established standards. Mixed-effects models were built using ring numbers from the pith and species as explanatory variables.ResultsThe same model forms could be used across the four species. Nonlinear models were developed for the Modulus of Elasticity and density. For the Modulus of Rupture, a linear model was most appropriate. The effect of species in the models was significant.ConclusionAt similar rotation lengths, noble fir, Norway spruce, and western hemlock can produce timber with comparable properties to Sitka spruce. Overall, western red cedar would have worse properties for structural use.

Time series DNA barcoding provides insight into factors influencing wood-boring and bark-feeding insect communities in Scots pine, Sitka spruce, and Noble fir stands.

Bark-feeding and wood-boring insect pests can have significant negative impacts on conifers and wood production. The damage they cause is expected to increase in the future due to climate change and the growth of international trade. This study employed DNA barcoding of beetle juveniles (Coleoptera) sampled from standing trap trees and cut log piles at regular intervals over a 2-yr period to monitor the beetle community dynamics and associated environmental factors. Tree species was found to have a major influence on beetle communities, most strikingly at the start of early decay stages. Lower species diversity was reported from standing trap tree samples compared to log pile samples, likely due to higher residual defences in dying and recently dead trees. While the species identified from standing trap trees are more likely to be a threat to the forestry sector, the species found in the log piles are more likely to be beneficial due to their high abundance and their ability to compete with pests for breeding substrate. The analysis of beetles collected inside trees revealed additional information on ontogenetic niches and host preferences beyond that acquired solely from flight interception trap data. Our results offer insights on community composition and dynamics of bark-feeding and wood-boring insect species in Welsh conifer forests and provide resources for monitoring and management of potential pest species.

Spatial Bayesian models project shifts in suitable habitat for Pacific Northwest tree species under climate change

AbstractWe developed spatial Bayesian hierarchical models to assess potential climate change impacts on suitable habitat for five important tree species in the Pacific northwestern United States (California, Oregon, and Washington). Individual‐species models were fit with presence–absence data from forest inventory field plots and spatial relationships were specified through a conditional autoregressive model. This modeling approach allowed us to visualize uncertainty in response curves, map current and future prediction uncertainty, and provide interval estimates for change. Upward elevational or northward latitudinal shifts in climatically suitable habitat were projected for all species. Climate change impacts were the most damaging for noble fir (Abies procera), for which 79%–100% of the current range was projected to become climatically unsuitable by the 2080s. Although coastal Douglas‐fir (Pseudotsuga menziesii var. menziesii) has been projected by others to gain habitat in Canada, within our study area we projected a net loss of climatically suitable habitat (ca. 8000–31,400 km2) under three of four future climate scenarios. A net loss in habitat was also projected for Oregon white oak (Quercus garryana) under three of four scenarios, with 40%–60% of the current range becoming unsuitable. Although there was no net loss of habitat for forest land blue oak under any scenario, other factors like competition may inhibit blue oak (Quercus douglasii) and white oak from occupying areas projected to increase in climatic suitability. Additionally, between 13% and 32% of blue oak's current range was projected to become unsuitable; some of these areas aligned with dieback following the 2012–2015 California drought, which our data set predates. Unlike the other four species, we projected a 17%–25% increase in climatically suitable habitat for California black oak (Quercus kelloggii), although 1%–20% of the current range was still projected to become unsuitable. Our findings indicate that, although some species will face more pressure in tracking climatically suitable habitat than others, climate change will impact the location of suitable habitat for many species.

Combining fluoride with either phenolic compounds or plant extracts offers potential mitigation strategy for ammonia and methane emissions from livestock manure

Emissions of ammonia and methane from agriculture caused by microbes in manure are an increasing challenge to sustainable agriculture. We screened several commercially available polyphenols, phenolic compounds, and polyphenol-rich extracts for their ability to inhibit the production of ammonia and mitigate methane emissions in pig manure in the absence and presence of sodium fluoride (NaF) using a short-term high-throughput set-up. Tested compounds were chlorogenic acid, lignosulfonic acid, lignin, chitosan, green tea extract, and chestnut tannins. Green tea extract, at a concentration of 8.5 mg/ml with 1 mM NaF, reduced total ammonia nitrogen (TAN) in pig manure by 72%, while methane emissions were lowered by 95% at an extract concentration of 2.5 mg/ml. The ability of four extracts of plant waste (spent coffee grounds, noble fir needles, shea meal, and rapeseed press cakes) to mitigate ammonia production and methanogenesis in pig manure was also investigated. Adding 7.0 ± 0.7 mg/ml of extract from shea meal, noble fir, or rapeseed press cake, or 3.2 mg/ml of coffee ground extract reduced TAN production in manure by approximately 50%. Shea meal and noble fir had the largest effect on methane emissions, with reductions of approximately 60%. Gallocatechin- and epigallocatechin-rich extracts appeared to be especially potent for the inhibition of methane emissions, while ammonia production could be inhibited by a variety of tannins. Based on the current work, we conclude that extracts from certain plants have the potential for use in sustainable manure management to reduce ammonia and methane emissions. • Sustainable mitigation of ammonia and methane emissions by the STAF technology. • Green tea and shea meal extracts exhibit synergy with fluoride against ammonia. • Polyphenols can be an effective way to reduce greenhouse gasses from manure.

An analysis of conifer experiments in Britain to identify productive alternatives to Sitka spruce

Abstract As the climate changes there is a need to reduce the reliance on Sitka spruce (Picea sitchensis (Bong) Carr.) in upland British forestry and increase species diversity to lower the risk of damage or loss of production due to biotic or abiotic events. An analysis of relevant species trials was carried out to assess the productivity of potential alternative conifer species on upland site types in Britain. Data from 87 forest experiments planted between 1929 and 1995 were analysed to compare long-term performance of 52 species with that of Sitka spruce under the same conditions and site type. Sites were broadly categorized using soil and climatic factors, which were used as primary factors in models predicting General Yield Class (GYC, the maximum mean annual increment in m3 ha−1 year−1) of the potential alternative species and of Sitka spruce. No species had significantly higher GYC estimates than Sitka spruce, but grand fir (Abies grandis (Douglas ex D. Don) Lindl.), noble fir (Abies procera (Rehder)), western hemlock (Tsuga heterophylla (Raf.) Sarg.), Lutz’s spruce (Picea x lutzii (Little)), maritime pine (Pinus pinaster (Aiton)), Lawson cypress (Chamaecyparis lawsoniana (A. Murray bis) Parl.), Scots pine (Pinus sylvestris (L.)), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western red cedar (Thuja plicata (Donn ex D.Don)) all had GYC estimates which were not significantly lower than that of Sitka spruce under certain soil and climate conditions. A further 26 species, particularly Abies species, had GYC within 3 m3 ha−1 year−1 of Sitka spruce but were present on too few sites for inclusion in statistical models. The results of the analysis provide objective evidence for the planting of a wider range of species where Sitka spruce may currently be first choice. In the absence of any major pest or disease affecting Sitka spruce, it is still a good choice for many upland sites, however, a wider range of options with equivalent productivity exist, allowing forest managers to diversify and reduce the risk of damage or loss of production due to biotic or abiotic events.

Controlling Leader Growth on Noble and Turkish Fir with S-ABA

Control of leader growth in Christmas tree production is a critical and expensive component in developing quality trees. Producers typically hand trim leaders to a desired length. With noble and Turkish fir this practice frequently results in poor top development in the subsequent year. This study investigated the use of S-abscisic acid (S-ABA) at various rates up to 6% active ingredient (a.i.) to determine if the plant growth regulator provides predictable leader control with minimal phytotoxicity. S-ABA was effective in controlling leader extension of both noble fir and Turkish fir. Shoot growth of Turkish fir was slightly more sensitive to S-ABA than noble fir, and effective growth control was achieved at 2% a.i., versus 3% a.i. for noble fir. With Turkish fir, we achieved an 80–90% reduction in growth across all sites, depending on rate. For noble fir, we achieved a 67–88% growth reduction. The addition of a surfactant did not increase the effectiveness of S-ABA for growth control and is not recommended. Repeating S-ABA applications 2 weeks after initial application resulted in a slight increase in growth control and phytotoxicity compared to a single application at the same rate. The results suggest that S-ABA can be an effective tool in Christmas tree production to control leader growth on fir species that often produce crooked or multiple leaders in response to conventional leader pruning.

Abies procera (noble fir)

Abies procera (noble fir)

Landscape scale environmental DNA sampling for a rare fungal species: Implications for forest management

Surveys for conks on noble fir trees (Abies procera) have suggested that the fungus Bridgeoporus nobilissimus is rare in the Pacific Northwest. As a result, the fungus has been managed for several decades as a rare old-growth forest species on federal lands. We undertook a randomized landscape sampling approach to determine the distribution of B. nobilissimus in an 88,200 ha study area in the northern Oregon Cascade mountains. We used molecular tools to test for the presence of fungal DNA in wood cores from living and dead trees. We sampled 58 plots from a system of permanent forest plots. Of these, 25 (43%) produced positive detections though no plots had visible B. nobilissimus conks. We estimate that B. nobilissimus occurs throughout 41% (±11%) of the northern Oregon Cascade mountains. Bridgeoporus nobilissimus presence was not related with land use status (reserve vs. non-reserve) or stand age. The use of molecular DNA technology with environmental samples changed our perception from a rare species present at a few sites, to a widely distributed species that produces few fruit bodies.

Characterisation of Bioactive Ingredients in Extracts of Fresh and Dried Coniferous Trees for the Development of Sustainable Packaging Materials

Background: Coniferous woods (Abies nordmanniana (Stev.) Spach, Abies procera Rehd, Picea abies (L.) H.Karst, and Picea pungens Engelm.) could contain useful secondary metabolites to produce sustainable packaging materials, e.g., by substitution of harmful petrol-based additives in plastic packaging. This study aims to characterise the antioxidant and light-absorbing properties and ingredients of different coniferous wood extracts with regard to different plant fragments and drying conditions. Furthermore, the valorisation of used Christmas trees is evaluated. Methods: Different drying and extraction techniques were applied with the extracts being characterised by determining the total phenolic content (TPC), total antioxidant capacity (TAC), and absorbance in the ultraviolet range (UV). Gas chromatography coupled with mass spectrometry (GC-MS) and an acid–butanol assay (ABA) were used to characterise the extract constituents. Results: All the extracts show a considerably high UV absorbance while interspecies differences did occur. All the fresh and some of the dried biomass extracts reached utilisable TAC and TPC values. A simplified extraction setup for industrial application is evaluated; comparable TAC results could be reached with modifications. Conclusion: Coniferous woods are a promising renewable resource for preparation of sustainable antioxidants and photostabilisers. This particularly applies to Christmas trees used for up to 12 days. After extraction, the biomass can be fully valorised by incorporation in paper packaging.

Ad hoc breeding of a genetically depauperate landrace of noble fir (Abies procera Rehder) using SNP genotyping via high-throughput targeted sequencing

Pedigree reconstruction via DNA markers and subsequent quantitative genetic analyses in production stands of trees is an alternative to traditional forest tree breeding. The method requires variable DNA markers; preferably cost-efficient to genotype. We tested the approach in breeding for Christmas tree traits in a Danish landrace of Abies procera. Initial analysis with simple sequence repeats (SSRs) revealed a substantial reduction in genetic diversity of Danish A. procera compared with direct imports from the USA, indicating a genetic bottleneck. Due to the reduced genetic variation, the SSRs were not variable enough for pedigree reconstruction, and 145 single nucleotide polymorphisms (SNPs) were therefore identified and genotyped via high-throughput targeted sequencing. In the field, we phenotypically selected 674 superior trees, based on criteria for good Christmas trees, among 21,000 trees in three Christmas tree plantations originating from an A. procera clonal seed orchard. By SNP-genotyping and parentage analysis, pedigree was reconstructed for the selected individuals, and genetic predictions for the Christmas tree traits were estimated. A final selection of 45 trees out of the 674 genotyped, based on an index of predicted values for different traits, foresees a gain in the Christmas tree score and branch angle score of 16% and 10%, respectively. The study clearly demonstrated the benefits of pedigree reconstruction, even though mass selection seemed to give similar gain. Primarily, the possibilities to control the level of inbreeding, and to check whether the production stands, from where we select trees, actually originate from the declared and desired parent pool.

Contributions to the knowledge on biology and phenology of Cryphalus piceae (Coleoptera: Curculionidae: Scolytinae)

ABSTRACT The small fir bark beetle (Cryphalus piceae) was discovered in Denmark in 2012. Since then, several local outbreaks in greenery plantations have occurred, with numerous dead Noble firs (Abies procera) reported. The aim of this study was to investigate the life cycle and behavioral patterns of C. piceae in Denmark, compared with a literature review of the general life cycle. Currently, C. piceae has been recorded from 24 plantations spread across Denmark. Experimental results confirm the possibility of two complete generations a year plus pertaining sister generation. Cryphalus piceae is generally considered a secondary bark beetle, and in Denmark it was mainly associated with Heterobasidion infected trees. However, its ability to overwinter in living healthy trees makes it a potential vector of unwanted diseases and therefore preventive control methods could be desired. Based on the life cycle, a yearly sanitary cutting in either mid-May or mid-June is recommended, as a control method against C. piceae in monocultures. In Danish greenery plantations, preventive measures against Heterobasidion were evaluated as the most important factor to avoid dead A. procera and the pertaining high populations of C. piceae.

Underplanting is a practical silvicultural method for regenerating and diversifying conifer stands in Britain

Abstract There is a strong policy move in Britain to improve forest resilience to climate change by increasing stand structural and species diversity. Although currently little used in Britain, the technique of underplanting allows regeneration and diversification of stands while avoiding some of the disadvantages of clearfelling. Two experiments were examined: (1) the growth and survival of five underplanted conifer species of differing shade tolerance in a shelterwood and (2) compared performance of underplanted and open-grown Douglas-fir seedlings on restocking sites. Underplanted Sitka spruce, Norway spruce, noble fir, European silver fir and Douglas-fir were all able to survive and grow. However increased exposure following overstorey removal resulted in some damage and ‘socketing’, especially to taller seedlings, particularly Douglas-fir. This may be linked to poor root development when growing under an overstorey. Microclimate conditions on some underplanted sites were more sheltered from extreme climatic conditions, and in some cases this improved survival of Douglas-fir seedlings. However, seedling growth rates were reduced compared with those on open sites probably due to lower light levels. Underplanting may help to improve establishment success of some species, particularly in exposed areas. However, the shelter benefits of underplanting must be carefully balanced against the trade-off with lower light, and underplanting is likely to be more successful where low canopy density is maintained.

Thermal infrared imaging of conifer leaf temperatures: Comparison to thermocouple measurements and assessment of environmental influences

Thermal infrared (TIR) imaging provides a potentially powerful tool for ecological and biometeorological research, but the accuracy of TIR imaging of plant surface temperature in a variable outdoor environment has been poorly characterized. This study evaluated the accuracy of TIR measurements of a conifer tree that were made using the thermal camera’s factory default settings, and developed a post-collection data processing method to correct measurements for ambient conditions that depart from the factory default settings. We conducted a 42-day measurement campaign in Corvallis, Oregon during spring 2014 that focused on the canopy temperature of a noble fir (Abies procera) and included the simultaneous collection of meteorological data and leaf temperature measurements with an array of thermocouples. We then developed empirical functions for temperature corrections that better accounted for emissivity, and atmospheric and reflected temperature. The original TIR temperatures using the factory settings averaged 8.6±5.6°C (−4.2 to 25.4°C in range), and the original TIR temperatures differed from the thermocouple temperatures by 1.4–1.6K. The TIR temperatures were generally accurate, except for a low temperature bias at leaf temperatures below 5°C. TIR temperature corrections reduced this bias to a <1.0K mean error relative to the thermocouples. Our results show that TIR measurements can be corrected to more accurately quantify canopy temperature, and that the importance of this correction increases under more extreme ambient conditions, such as colder periods.

Variation in the incidence and severity of drought crack in three conifer species in North East Scotland

ABSTRACTThe incidence of longitudinal drought cracks in coniferous trees may increase as a consequence of climate change. While larger diameter trees are more prone to splitting, it is unclear why only some of the larger trees within the same stand typically suffer damage. Matched pairs of trees of the same size with and without cracks were studied in two adjacent pole-stage mixed stands of Sitka spruce/grand fir (Picea sitchensis/Abies grandis) and Sitka spruce/noble fir (Picea sitchensis/Abies procera) located in North-East Scotland. A range of attributes were measured on 15 damaged and undamaged trees of each species. Length and position of cracks on stems were also recorded, and annual ring width and latewood percentage measured on cores. Noble fir had significantly longer cracks and these were located higher in the stem than the other species. Fewer cracks formed on east-facing side of stems in all species suggesting that prevailing westerly winds may place greater tensile forces on the damaged sides of stems. A higher proportion of latewood (associated with higher tangential shrinkage) was found in the firs and may explain the greater incidence of cracking on grand and noble fir stems (13% and 16%, respectively) in comparison with Sitka spruce (3%).

Biomass production dynamics for common forest tree species in Denmark – Evaluation of a common garden experiment after 50 yrs of measurements

Common gardens are suited for analysing the behaviour of different species in a common environment. We used a common garden experiment including 12 different tree species (Fagus sylvatica, Pseudotsuga menziesii, Abies grandis, Larix kaempferi, Chamaecyparis lawsoniana, Pinus contorta, Pinus mugo, Abies procera, Picea abies, Quercus robur, Abies alba, and Picea sitchensis) grown at 13 different sites, and representing almost 50yrs of measurements, for answering the following questions: (i) how do the species differ in their average biomass production?, (ii) how does their performance vary in space, and (iii) how does their performance vary over time. The analyses showed that the North American conifers including A. grandis, and P. sitchensis had a significantly higher potential for biomass production than the other species. However, while P. sitchensis was relatively invariant to site conditions, the analysis indicated that, compared to the other species, A. grandis benefited more than the other species from a general improvement in growing conditions. The effectiveness of substituting fossil fuels and carbon intensive materials with woody bioenergy is highly dependent on plant growth rates. Our results may suggest a selection of species with superior biomass production and carbon sequestration.

Comparison of noble fir progeny from US Pacific Northwest collection regions and Denmark for Christmas tree traits

ABSTRACTNoble fir is the leading Christmas tree produced in the US Pacific Northwest (PNW). This study is based on evaluations of 24,721 trees collected from five native collection regions in Oregon and Washington plus imported seed from Denmark. The major collection areas were further subdivided into provenances utilizing 16 in the PNW and 6 from Denmark. A total of 22 test sites were evaluated from progeny trials planted between 1996 and 2007. Traits important for commercial Christmas tree production were evaluated and include commercial height, tree grade, value and colour. Tree height and quality were positively correlated while colour showed little correlation with either trait. Provenances from the Oregon Coast and Willapa Hills, Washington provided the highest potential gain for Christmas tree market value. Provenances from Denmark exhibited superior colour and slow growth. For breeding purposes, the gain from backwards selection estimated a range of improvement in marketable value from 0.91 to 1.22 Euros per tree.

Quantifying density-independent mortality of temperate tree species

Forest resilience to climate change is a topic of national concern as our standing assets and future forests are important to our livelihood. Many tree species are predicted to decline or disappear while others may be able to adapt or migrate. Efforts to quantify and disseminate the current condition of forests are urgently needed to guide management and policy. Here, we develop a new indicator to summarize raw density-independent mortality of forested stands by species from the last decade of the 20th century to the first decade of the 21st century using forest inventory data. We define density-independent mortality to be stand mortality by species due to processes unrelated to natural mortality from succession or stand maturation, which is marked by overall increase in tree girth at the expense of density of individuals. We assess trends for 22 species on national forests in two U.S. states, Washington and Oregon. Populations of some species including timber species have no or low overall levels of density-independent mortality (Juniperus occidentalis, Abies procera, Thuja plicata, Tsuga heterophylla, Pinus ponderosa, and Pseudotsuga menziesii). In contrast, other species demonstrate unsustainable levels of density-independent mortality (Pinus monticola, Arbutus menziesii, Pinus albicaulis, Abies lasiocarpa, Taxus brevifolia, Pinus contorta, Abies grandis, Picea englemanii, and Larix occidentalis). Additionally, the net potential for unsustainable levels of density-independent mortality in standing populations does not necessarily warrant concern when examined across species for our study area and time period; however, when examined by species, the number of species in decline exceeds the number of species where mortality can be generally attributed to endogenous self-thinning. We argue that this work can aid management and policy decisions and our understanding of complex vegetation dynamics in a changing climate. Application of the indicator at larger spatial scales and in conjunction with data on migration and establishment may be used to address questions such as, how can we make cost-effective management decisions to ensure long-term sustainability of tree species and forests? Tree species distributions across the landscape are complex systems, and raw characterization of current trends occurring in forest inventories is important especially given the uncertainty associated with the modeling and prediction of complex systems such as tree species.

Precommercial Thinning in Mixed-Species Conifer Plantations Affected by Armillaria and Heterobasidion Root Diseases in West-Central Oregon and Washington: 30-Year Results

Four 10- to 20-year-old plantations were precommercially thinned to determine the effects on tree growth and mortality caused by armillaria and heterobasidion root diseases. The plantations represented different species compositions with one each of (1) coastal Douglas-fir and noble fir, (2) Douglas-fir and western hemlock, (3) pure Douglas-fir, and (4) Shasta red fir and mountain hemlock. After 30 years, the probabilities of leave-tree survival and actual leave-tree survival (trees/ha [TPH]) were significantly (P ≤ 0.05) higher in thinned versus unthinned plots in one of the four plantations with no significant differences in the other three plantations. Most tree mortality was caused by armillaria root disease. Despite the high frequency of Heterobasidion occidentale in overstory stumps, only two leave trees in one plantation were killed by this fungus after 30 years. Quadratic mean diameter (QMD) growth and basal area (BA) (per ha) growth of leave trees were significantly (P ≤ 0.05) greater in thinned than in unthinned plots in one plantation for QMD and in three plantations for BA. Precommercial thinning does not appear to exacerbate the incidence of leave-tree mortality from armillaria or heterobasidion root diseases after 30 years, and leave-tree QMD and BA growth increased significantly in most but not all plantations for the tree species sampled. Armillaria and heterobasidion root diseases are not an impediment to precommercial thinning in plantations or stands similar to those we studied.

Testing species of genus Abies for Christmas tree production in Norway

Ten exotic Abies species were tested in two field trials, where the aim was to find suitable species and provenances for Christmas tree production in coastal and fjord areas in Norway. The material included 14 provenances of Abies nordmanniana, 3 provenances of Abies bornmuelleriana, 3 provenances of Abies koreana, 2 provenances of Abies amabilis, and 1 provenance each of Abies equi-trojani, Abies alba, Abies procera, Abies homolepis, Abies nephrolepis, and Abies forrestii. Field trials were established at Gulen in Sogn og Fjordane County and at Verdal in Nord-Trøndelag County. Christmas tree classification was done seven and eight growing seasons after establishment. The Christmas tree yield was higher in Gulen (64%) than in Verdal (45%), which is situated further north. Also, the survival and the height growth were higher in Gulen than in Verdal. A more humid climate and a longer growth season in Gulen may explain some of the differences. Of the 10 species, A. nordmanniana, A. homolepis, and A. bornmuelleriana produced the highest Christmas tree yield at Gulen, while A. homolepis and A. koreana had the highest yield at Verdal. Due to early bud burst, A. equi-trojani and A. bornmuelleriana are only suited for Christmas tree growing in the best climatic areas.