Natural durability of Douglas fir (Pseudotsuga menziesii [Mirb.] Franco) heartwood grown in southern Germany

Abstract

The natural durability of timber is an important property in order to assess its performance in service. For numerous species grown in primary forests, this property has already been determined. As plantation-grown timber becomes more and more important, detailed information on its properties is needed, because increasing amounts of this material are coming to the market. The majority of planted Douglas fir (Pseudotsuga menziesii [Mirb.] Franco) in Germany is around 40 years old. In the present study, representative material of totally ten trees from two different sites in the south of Germany was investigated with regard to natural durability. In laboratory tests based on European standard DIN EN 350-1, inner and outer heartwood zones were exposed to basidiomycetes. Density measurements were additionally used for further characterisation of this material. Results showed a lower durability of the plantation-grown Douglas fir wood as compared with wood from natural sites. Significant differences for both durability and density were found between inner and outer heartwood, even though no correlation between the parameters was recognised. Data illustrate that for a better understanding of durability variations, chemical, topochemical and electron microscopic studies are needed.     

Fertilisation with biosolids in a silvopastoral system established with Pseudotsuga menziesii (Mirb.) Franco in Galicia (NW Spain)

Agroforestry Systems - In Europe, sewage sludge has to be stabilised before its use as fertiliser in agricultural land. Stabilisation processes can cause differences in the concentration of heavy...     

Response of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) to some different fertilizers applied at planting

Four fertilization at planting experiments were conducted with Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) on eastern Vancouver Island. In experiment 1 Agriform (20-10-5, AGR) and Osmocote (17-7-12, OSM) supplied N at 0, 4.2, 8.4, 16.8 or 33.6 g/tree either broadcast, within 15 cm of the tree, or in a hole 15 cm from the tree (adjacent). In experiment 2 AGR, diammonium phosphate (21-55-0, DAP), ammonium sulphate (21-0-0, AMS), sulphur coated urea (35-0-0, SCU) supplied N at 0, 8.4, 16.8 and 25.2 g/tree. Triple superphosphate (0-45-0, TSP) supplied P at the same levels as DAP: 0, 9.6, 19.2 and 28.8 g/tree. In experiment 3 AGR and SCU (32-0-0) supplied N at 0, 8.4 and 16.8 g/tree. In experiment 4 DAP was used to fertilize trees on five different dates, between March and October, and each treatment supplied 16 g N/tree. Two-year old, bare root, planting stock was used except in experiment 3, where container stock was compared with bare root stock.Little growth response was obtained after one year, but height growth responses of 12 to 31% were measured after 3 to 6 years with fertilizers supply 8.4 to 16.8 g N per tree. Growth responses were little affected by the type of fertilizer and were primarily due to N, with release rate having no marked effect. The exception to this was TSP which did not increase growth but did increase survival. Survival was reduced by AMS and to a lesser extent by AGR. Container seedlings responded more to fertilization at planting than bare root seedlings.Seedling N, P and K concentrations and contents declined following planting for 6 months and only started to recover after July. Application of fertilizer caused a small increase in seedling nutrient concentration regardless of date, but this had no detectable effect on dry weight measured six weeks later.     

Effect of wide spacing on tree growth, branch and sapwood properties of young Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] in south-western Germany

The influence of stand density on Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] is conceptually understood, but for wide spacings not well quantified, particularly in Europe. This study used 41 trees from 7 different locations in south-western Germany to compare important tree- and branch-level attributes across three different densities, namely 100, 200, and 1,200 stems ha⁻¹. In general, there were only a few tree and branch attributes that were significantly different between the 100 and 200 ha⁻¹ densities. Crown projection area and diameter of the thickest branches were the most important differences between the 100 and 200 ha⁻¹ densities. The most obvious and significant differences in this study were between 100 and 1,200 ha⁻¹ densities, where nearly every examined tree and branch attributes were statistically significant. However, relative sapwood area, the number of branches, branch angle, and the occurrence of spike knots were insensitive to stand density. Although the two lowest stand densities in this study represent rather extremely wide spacings, these results still have important implications for the development of effective thinning regimes for Douglas-fir in south-western Germany. Important management recommendations from this study include thinned stands should be maintained to at least 200 stems ha⁻¹ to maintain high log quality and stand stability. Furthermore, even at stand densities exceeding more than 1,200 trees ha⁻¹ planted trees, artificial pruning may even be necessary to produce high quality logs.     

Root growth and water use efficiency of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and lodgepole pine (Pinus contorta Dougl.) seedlings

One-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and lodgepole pine (Pinus contorta Dougl.) seedlings were grown for 17 weeks in 100-cm deep, 7.8-liter containers. Two Douglas-fir provenances, one from a wet and one from a dry site in coastal British Columbia, and two lodgepole pine provenances, one from a wet and one from a dry site in interior British Columbia, were grown in wet (522% water content) or dry (318% water content) peat/vermiculite soil in a factorial design. Each container was sealed so that water loss occurred only through the seedling. Five harvests were made at three to five week intervals and water use, dry matter increment, root length and root weight were determined at each harvest. Stomatal conductance and shoot water potentials were measured during the last 12 weeks of the experiment. Lodgepole pine seedlings had greater dry matter production, water use, stomatal conductance and new root length than Douglas-fir seedlings. New root weight of lodgepole pine seedlings exceeded that of Douglas-fir seedlings during the last five weeks of the experiment, and specific root length (root length per unit root weight) of new roots was higher for lodgepole pine seedlings throughout the experiment. Douglas-fir seedlings showed higher water use efficiency (WUE) than lodgepole pine seedlings, and both species showed higher WUE in the dry soil treatment. Douglas-fir seedlings had lower water potentials and higher water uptake rates per unit of new root length than lodgepole pine seedlings, although water uptake rates per unit of root dry weight showed little difference between species. Soil water treatment influenced specific root length of new roots, water uptake per unit of new root length, and WUE in Douglas-fir seedlings more than in lodgepole pine seedlings.     

Forest inventory-based assessments of the invasion risk of Pseudotsuga menziesii (Mirb.) Franco and Quercus rubra L. in Germany

European Journal of Forest Research - In Europe, some non-native tree species (NNT) are classified as invasive because they have spread into semi-natural habitats. Yet, available risk assessment...     

Genetic control of the tree-ring response of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) to the 2003 drought and heat-wave in France

The genetic control of tree ring growth in Douglas-fir in response to the drought and heat-wave that occurred in 2003 in Europe was studied with microdensity profiles in three clonal experiments located in three different French regions. The drought and heat-wave significantly affected Douglas-fir wood formation. The Chassenoix site (Northeast of Massif-Central) was more severely affected that the other two: the 2003 year-ring was narrower and less dense than in the other sites and than the previous (2002) and following (2004) year-rings in the same site: ring growth stopped earlier and latewood did not develop completely. The year-rings 2004 and 2002 were very similar in this site. There was a significant genetic control for all ring parameters in the three sites and during the three years. The heritability was highly variable between years and among sites, without any clear pattern in this variability, except in Chassenoix where it was slightly lower in the 2003 year-ring. Variables measuring the response of trees to the 2003 event, i.e., the difference in ring width between 2002 and 2003, or between 2003 and 2004, showed a very variable degree of genetic control, from very low to relatively high. Douglas-fir seemed plastic enough to acclimate to the drought and heat-wave and then to recover during 2004. Furthermore the level of heritability estimated demonstrates that Douglas-fir has an adaptive potential that could be useful for multi-generation long-term response.     

Effect of site preparation on survival and growth of Douglas-fir (Pseudotsuga menziessi Mirb. Franco.) seedlings

The performance (survival and growth) of Douglas-fir (Pseudotsuga menziesii Mirb. Franco.) seedlings planted in minimally disturbed, scalped, and bedded soils, both with and without herbicidal control of weeds, were compared. Douglas-fir growing for 3 years in bedded soils treated with herbicide were heavier, taller, and had deeper root systems than trees growing in other preparations. Scalping did not improve seedling performance when compared to minimally disturbed soils. Soils rich in organic matter benefited tree growth. Competing vegetation in raised beds was detrimental to seedling performance.     

华北落叶松人工林差分地位指数模型构建

以阴山山地苏木山林场华北落叶松人工林为研究对象,利用43株解析木数据,基于Richards方程构建差分地位指数模型。结果表明:差分模型拟合结果明显优于基础模型,R²均在0.96以上,RMSE在0.86~0.96之间,MAE在0.42以下。ADA法推导的模型,以b或c为自由参数拟合结果要好于以a为自由参数;GADA法推导的模型,假设自由参数c与变量X₀成线性关系更合理。通过统计分析、残差分析和地位指数曲线簇比较,采用GADA法,假设自由参数a=e^X₀,c=c₁+c₂X₀所推导的差分模型为最佳模型,满足生物学和统计学两方面的要求。地位指数越大,优势木树高及其连年生长量的极值也越大,到达拐点的时间也越早。研究结果可为华北落叶松人工林立地质量科学评价提供依据。     

Growth rate and shoot: Root allometry in Pseudotsuga menziesii (Mirb.) Franco and Pinus contorta Dougl. Seedlings raised under two photoperiodic regimes

Six provenances of both Pseudotsuga menziesii (Mirb.) Franco and Pinus contorta Dougl. from a range of locations in the interior of British Columbia between latitudes 49° and 58° were grown for 80 days in controlled environment chambers programmed to provide daylengths comparable with those at either latitude 48°, or latitude 58°, during the period from mid‐June to early September. Neither shoot : root ratio nor whole plant dry weight of P. menziesii were affected by photoperiod. However, P. contorta seedlings, which unlike P. menziesii set bud during the experiment, had a greater dry weight and a higher shoot:root ratio (p<0.05) under longer daylengths. The results appear relevant to the interpretation of effects of cross‐latitudinal provenance transfer on plantation productivity.     

Growth reaction patterns of tree height,diameter, and volume of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) under acute drought stress in Southern Germany

Climate change in Central Europe may come along with acute drought stress, which can severely reduce growth and vitality of forest trees and whole stands. For a tree species such as Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) which is cultivated far beyond its natural range in Europe, knowledge of its behaviour under stress is crucial for the cultivation of Douglas-fir in view of a changing climate. Because of its easy accessibility, growth response to stress was mainly studied based on diameter growth at breast height. In long-term experiments on one dry and one moist site in Southern Germany, stem analyses of 133 mature and even-aged Douglas-firs were performed. The short-term growth reaction pattern under acute drought stress of 2003 had not only consequences on diameter but more pronounced effects can be observed when studying tree height: Respecting the different age trends by previous detrending, height increment only reacted more sensitive on the dry site. We also showed that extrapolating a particular decline in basal area increment to the whole stem can result in misunderstandings. However, results were less biased, when original data were smoothed or short-term assessment of volume growth was based on basal area measurements. By means of a linear mixed model approach, the influence of site, tree, and stand characteristics on Lloret’s indices of resistance and resilience (Lloret et al. in Oikos 120:1909–1920. doi:10.1111/j.1600-0706.2011.19372.x, 2011) were analysed. For Douglas-fir, site played a crucial role and became more important considering the age trend. On the contrary, the positive influence of site quality on drought tolerance decreased with data processing. However, more growing space by thinning can advance tree resistance and resilience regarding height, diameter, and volume growth. Large individual crown volume improved the growth pattern under drought, and large stand density impaired it. Douglas-fir is obviously equipped with a morphological variability, which fosters lateral rather than vertical growth allocation under severe stress. Silviculture can mitigate stress through the choice of the site and through lower stand densities by thinning. Our refined stress response analysis confirmed a favourable growth and resilience of Douglas-fir even under extreme drought events.     

Applying the IDS method to remove seeds infested with the seed chalcid,Megastigmus spermotrophus Wachtl,in Douglas-fir,Pseudotsuga menziesii (Mirb.) Franco

Douglas-fir seedlots were treated with the Incubation Drying Separation (IDS) method to test whether seeds infested with the seed chalcid, Megastigmus spermotrophus Wachtl, could be separated from non-infested seeds. Seeds were soaked in distilled water for 24 h, drained, placed in plastic bags and incubated at 15 °C for 3 days. The seeds were dried for either 0.5, 1, or 2 h at 25 °C, and then separated into floaters and sinkers in a water column. An average of 97% of the infested seed floated. The drying period did not affect the separation of infested seeds but significantly fewer sound seeds floated in the seedlots dried for 0.5 h than those dried for 1 h. Germination capacity of IDS-treated seeds did not differ from that of untreated seeds but the germination rate was significantly faster for IDS-treated seeds when all lots were stratified.     

A reduced growth model based on stand basal area. A case for hybrid poplar plantations in northeast Spain

Whole-stand models normally require data on initial stand basal area and dominant height. Dominant height measurements are time-consuming and often imprecise, compromising subsequent predictions. Poplar plantations provide a special case where basal area correlates with site index; a whole-stand model could thus be based on stand basal area. We report a static model constructed by the generalized algebraic difference approach (GADA) for poplar plantations for three different hybrid poplars (Populus × euramericana (Dode) Guinier “I-214”, “MC”, and “Luisa Avanzo”) in northeast Spain. The transition function was based on current stand basal area and was fitted with data from 158 permanent plots ranging from 1- to 17-year-old plantations. Merchantable stand volume was estimated by a volume equation where height was predicted by a height–basal area relationship based on 458 temporary plots. The model differences between clones were compared using the nonlinear extra sum of squares method. Significant differences were detected, while Luisa Avanzo presented the highest merchantable volume at the end of the rotation. Errors in basal area predictions were below 20% within 6 years in the case of Luisa Avanzo and MC clones, and within 3 years in the case of I-214. Our research showed that satisfactory predictions can be obtained using GADA with a single transition function based on an easily measurable variable such as stand basal area.     

Dendroclimatological regions of Douglas fir (<Emphasis Type="Italic">Pseudotsuga menziesii</Emphasis> Franco) in western Poland

Abstract Six Douglas fir (Pseudotsuga menziesii Franco) stands were selected in both the Sudety Mountains and the Great Poland Lowland. These two regions are distinctly different with regard to thermal and pluvial conditions. In each stand, two increment cores per tree were extracted from 20 approximately 100-year-old trees and the tree-ring widths measured. It is clear from the different growth reactions of the study trees to the climatic conditions that the Sudety Mountains and the Great Poland Lowland are two dendrochronologically separate regions. The tree-ring width chronologies form homogeneous groups for each region. The tree ring–climate models for Douglas fir in both regions indicate similarities and differences. The similarities among chronologies are attributed to winter temperature. The differences are attributed to rainfall (which changes with longitude and altitude of sites) during the vegetation season.     

Modelling mortality of Scots pine (Pinus sylvestris L.) plantations in the northwest of Spain

Mortality is an important element of growth and yield models, especially if only low intensity silvicultural treatments are carried out. The objective of the present study was to develop a model for predicting tree number decline in planted even-aged stands of Scots pine (Pinus sylvestris L.) in Galicia (northwestern Spain). The model was constructed using data from two inventories of a trial network involving 68 permanent plots located in unthinned stands, or stands thinned lightly from below. Two alternatives were tested. In one alternative, a two-step modelling strategy was applied. First, a binary response function predicting the survival probability of all the trees in the stand was constructed, and an equation for reduction in tree number was developed, using only data where death had occurred over the period analyzed. Three different approaches were then used to compare the application of the above-mentioned functions together. In the other alternative, a mortality function for directly predicting the reduction in tree number was fitted, including all plots (with and without occurrence of mortality). Both alternatives provided similar results, showed logical behavior, and performed satisfactorily in evaluation tests. However, in choosing the best strategy for inclusion in a stand-level simulator, the use of the second alternative is recommended because it possesses the path invariance property required in a mortality model.     

Site quality of pedunculate oak (<Emphasis Type="Italic">Quercus robur</Emphasis> L.) stands in Galicia (northwest Spain)

Accurate estimates of forest productivity are required for sustainable forest management. Height of dominant and codominant trees at a reference age is often used as a measure of site productivity. Eight algebraic difference equations based on the models proposed by Sloboda, Bertalanffy-Richards, Korf, Hossfeld, and McDill-Amateis were tested on the transformed, longitudinal data structure that considers all possible growth intervals. Autocorrelation was modelled by expanding the error term as an autoregressive process according to this data structure. Generalized nonlinear least squares methods were used for model fitting. Several numerical and graphic analyses were used to compare the different candidate models. The relative error in dominant height prediction was used to select 60 years as the best reference age. An algebraic difference equation based on the model proposed by Korf provided the best compromise between biological and statistical aspects and produced the most adequate site index curves. This model is therefore recommended for height growth prediction and site classification of pedunculate oak stands in Galicia. The model is polymorphic and base-age invariant, having only one asymptote. Predictions of height for age intervals between t₁ and t₂ of more than 15 years should be considered with caution because of the associated critical error.