A new individual-based forest model for the species beech (Fagus sylvatica L.) was developed and implemented. The model called BEEch Plasticity (BEEP) describes tree crown plasticity phenomenologically and is able to model aboveground competition for PAR on a process basis. The current debate about the tree interactions in near-natural beech forests and their role in emergent forest structures and dynamics led to the research questions if (1) observed patterns can be modeled and reproduced by only describing the aboveground tree interactions, (2) what effects tree crown plasticity has on the structure and dynamics of near-natural beech forests, and (3) what effects selective thinning has on the structure and dynamics of near-natural beech forests. The BEEP model was developed, parameterized, calibrated, and validated according to data from the unmanaged forest `Schattiner Zuschlag' near Lübeck, North-Germany, while additional data from the sites Langula (Thuringia) and Fabrikschleichach (Bavaria) was used for model parameterization and calibration. Three simulation experiments were conducted. In the first experiment, the BEEP model was run 10 times for 2000 time steps with plastic tree crowns and the emergent forest structure was analyzed using structural indices. In the second experiment, the BEEP model was run again 10 times for 2000 time steps but with a modified crown model that only uses rotation-symmetric tree crowns. In the third experiment, the BEEP model was enhanced with a selective thinning procedure that uses target trees with specific diameter and heights as thinning objects. Forest structure was analyzed through the application of structural indices that capture different aspects of forest structure and by means of characterization of forest development phases. Analysis was accomplished only for the time steps 1000-2000 in order to allow transient oscillation in forest dynamics to develop. The results showed that the focus on aboveground competition and tree interactions sufficed to model beech forests and reproduced a wide range of patterns observed in near-natural and old-growth beech forest. In particular, the BEEP model was able to simulate a multi-layered forest structure with a mosaic structure of several developmental stages on a relatively small area of 0.5 ha. The simulated forest had wide diameter and age distributions. The diameter distribution was reversed-J-shaped. The age range of canopy trees exceeded 200 years. The comparison between simulations with plastic and rotation-symmetric tree crowns revealed that crown plasticity reduced tree competition for crown space and PAR and enhanced the forest structure and heterogeneity in the long term by allowing more tree cohorts of dfferent developmental stages to coexist. This supports the notion that crown plasticity drives beech forest dynamics in near-natural forests. The comparison between simulations with plastic tree crowns and with additional selective thinning showed that thinning does not affect the forest structural heterogeneity and reduces tree crown competition, while spatial patterns of tree positions remained unaltered. However, crown centroids were more regularly distributed. Model assumptions in the submodel routines, especially in the radiation and mortality submodel, question the reliability of the model results, because of the high sensitivity that these routines evoke on model outcomes. Therefore, revised versions of the submodels and a thoroughly validated crown growth model, may produce different results. Thus, the results presented in this study should be treated with care and cannot be used for generalizations about tree interactions in near-natural beech forests.

No description available.

A compact laminated board can be obtained by pressing layers of veneers with no other material or substance placed between them. The process does not require the use of steam pretreatment, surface activation methods, a gastight press, friction or adhesives. It strictly involves the heat and the pressure induced by the press in the veneers. The levels of temperature, pressure and time leading to the highest bending-strength values when material factors are held constant are investigated. The objective of optimizing the process is reached using response surface methodology for modelling and analysis. The parameter interactions are found to be significant.Photography, scanning, X-ray densitometry, light microscopy and scanning electron microscopy (SEM) are the methods used to visually analyse the final product. Densification and darkening are two of the effects observed. / <p>Godkänd; 2008; 20081113 (ysko)</p>

No description available.

No description available.

No description available.

Repeated partial cutting in the Appalachian hardwood region has often favored the development of tolerant species like American beech (Fagus grandifolia Ehrh.) and stands with a high proportion of cull trees. Crop tree release is a widely recommended practice to improve species composition and growth rates in these unevenaged structured stands. Chemical control offers some distinct advantages from the standpoint of safety and residual stand damage, over mechanical methods. Control of American beech was the primary focus of this study. Beech is a low value timber tree, normally considered difficult to control. It is a major competitor to more valuable trees, especially on better sites in the Appalachians. Research plots were established in hardwood stands at three sites in central West Virginia to evaluate the effectiveness of glyphosate (Accord), imazapyr (Arsenal AC and Chopper), and triclopyr (Garlon 3A and Garlon 4) using the hack-and-squirt application method and low volume basal spray treatments. In the injection treatments .051 fl oz (1.5 ml) of solution was used per inch of diameter (dbh). The basal spray treatments used 0.101 fl oz (3 ml) of solution per inch of diameter. The following concentrations were used: Accord (65.2%), Arsenal AC (7.5%), Garlon 3A (50%), Garlon 4 (26.25%), and Chopper (6.25% ). These concentrations were determined by using the highest costing injection and basal treatment at the lowest recommended labeled rate as standards, Garlon 3A and Chopper respectively. Eighteen 0.1 acre plots were systematically located at each study site where crop trees were present and to maximize the number of American beech on each plot. Crop trees, mostly black cherry (Prunus serotina Ehrh.) were chosen on a 0.025 acre subplot established at each plot center. All beech two inches and larger on the 0.1 acre plots and competing trees touching crop trees were treated in June 1998. The treatments were evaluated in September of 1998 and again in June of 1999. A numerical rating system ranging from 1-7, (0-100% crown affected), which utilized visual symptoms, was used to evaluate the efficacy of each treatment. Trees receiving a rating of 5 (75 % crown control) or greater were considered controlled. The relationship between the kinds of herbicide, application method, and numerical rating were analyzed by means of one-way analysis of variance with an incomplete random factorial design. The most effective treatments for the three month evaluations were the Accord and Garlon 3A injection treatments. Average beech crown control ranged from 95-99% for Accord to 96-99% for Garlon 3A across all study sites. The basal spray treatments were not effective. Average crown control ranged from 1-22%, across all study sites. Accord, Garlon 3A, and Arsenal AC were the most effective treatments for the 12 month evaluations, with average beech crown control ranging from 99-100% across all study sites. The imazapyr treatments (Arsenal Ac and Chopper) had adverse effects on the crop trees and are not recommended for hardwood crop tree release. The cost effectiveness based on treatment costs and the amount of basal area (BA) controlled were averaged for all study sites. The average treatment costs based on the 12 month evaluations expressed in dollars/ft2 BA controlled were as follows: Accord ($0.91), Garlon 3A ($1.04), Arsenal AC ($0.84), Garlon 4 ($15.09), and Chopper ($7.74). NE-TWIGS was used to predict future composition and value of the projected stands. The stem injection treatments decreased the amount of beech and increased the amount of black cherry sawtimber thereby dramatically increasing the future value of the stands. Real rates of return were calculated for the stem injection (8.81%) and low-volume basal spray (-0.81%). / Master of Science

Context and objectives: The impacts of climate change on forests and the increasing demand for ecosystem services emphasize how important it is to adapt forests to changing and partially uncertain climatic and societal conditions. A challenge for active forest adaptation is to safeguard and manage regeneration under increasingly extreme environmental conditions while minimizing risks to the remaining forest stand. Options for such targeted regeneration management arise from fine adjusting gap-based silvicultural interventions. The overarching aim of this study was to analyze the establishment of beech regeneration (Fagus sylvatica L.) in gaps under the influence of climate change in order to derive recommendations for targeted regeneration management. Gap experiment: Methodologically, this study focused on the investigation of fenced gaps ranging from 28 to 550 m2 in size (n=24), felled during the winter of 2016/17, within four beech and oak (mixed) forest stands located in the Rostocker Heide in Northeast Germany. A detailed assessment of the environmental conditions within these gaps was conducted, along with an annual (2017/18/19) inventory of artificial and natural beech regeneration. Since this period included the extreme hotter drought events of 2018 and 2019, a connection between climate change, forest structure, and thus silvicultural interventions, and the resulting regeneration dynamics was established. Vitality, stature, and growth, as well as the precise position of each individual, were recorded as regeneration characteristics. In order to capture the environmental conditions to which each individual was exposed as differentiated as possible, the following data were collected: (1) Direct, diffuse, and total radiation (DIRSF, DIFFSF, and PHAR) were determined using hemispherical photography. (2) Water availability (BGR) was estimated based on inverted, modeled fine root biomass distributions of the remaining beech (BGRB) and oak (BGRO) trees. (3) Nutrient availability (SF) and groundwater influence (GW) were derived from forest site maps, and small-scale variations in terrain elevation were recorded. (4) Annual vegetation surveys were conducted. Substudy 1 - Survival probability: Survival is a crucial factor for the success of regeneration and can be substantially affected by extreme weather conditions during theestablishment phase. Hence, the goal of the first substudy was to better understand the survival of beech regeneration under the influence of severe hotter drought events within the context of the gap experiment and to derive silvicultural interventions to safeguard and manage the survival of beech. For this purpose, the potentially interactive effects of resource availabilities and (a-)biotic factors on the survival probability of artificially regenerated beech seedlings were systematically analyzed using logistic generalized linear mixed-effects models (GLMM). DIFFSF, BGRB, and SF exhibited positive individual as well as interactive effects on the probability of survival, indicating complementary resource use of beech seedlings. On the other hand, increased DIRSF led to a significantly reduced survival probability. This effect, attributed to water stress, was enhanced when BGRB was reduced and when DIRSF interacted with stronger GW influence and exposed micro-sites. The model predictions indicated that the survival probability of beech seedlings was substantially reduced in closed forests, small gaps, and northern compartments of larger gaps under drought conditions. Conversely, increased resource availabilities in larger gaps under limited exposure to direct radiation resulted in improved survival probability. Thus, creating gaps larger than 200 m2 and focusing regeneration efforts on suitable, e.g., southern, gap partitions, present options for adapting silvicultural interventions in the context of hotter drought periods. Substudy 2 – Relative height growth: Height growth, alongside survival, is another central factor determining the overall success of regeneration, and is significantly influenced by resource availabilities. The objective of the second substudy was to establish a sound relationship between silvicultural interventions and the height growth of beech seedlings under the influence of hotter drought within the context of the gap experiment. This allows for the identification of potential establishment bottlenecks and opportunities for managing beech regeneration. To achieve this, the potentially interactive effects of PHAR, BGR, and SF on the relative height growth of artificial and natural beech regeneration were analyzed using multiplicative non-linear mixed-effects models (NLME). By means of these interactive models, both the positive effects of PHAR, BGR and SF on height growth could be specified and complementary resource use patterns of beech regeneration could be confirmed. It was also found that a larger initial root collar diameter was associated with a significant increase in height growth. Natural regeneration outperformed the height growth of artificial regeneration under all conditions except for optimal resource availabilities. These findings highlight the importance of root development in relation to height growth and the advantage of natural regeneration under waterand nutrient limitations. Furthermore, BRGB had a stronger effect on the growth of regeneration compared to BRGO. Under the given site and weather conditions, both in closed forests and small gaps, relatively low height growth was observed. A recommendation for adapting silvicultural interventions to hotter drought periods is to create gaps larger than 200 m2. In these, and especially in central gap compartments, significantly increased height development was observed. Negative effects on height growth above a certain gap size were not found but should be considered. Conclusions: The presented results indicate an analogous decrease in shade tolerance of beech regeneration with the given water limitation. A high susceptibility of beech regeneration to drought stress was confirmed. The average environmental conditions in small gaps (below 100 m2) and closed forests did not allow for successful establishment of beech in the context of hotter drought periods. This calls into question both the regeneration potential in natural beech forests, given the small-scale disturbances prevalent here, and the suitability of corresponding close-to-nature regeneration methods. The optimal gap size for beech regeneration depends on site, climate, and weather conditions. Under the conditions covered by this study, it varied between 200 and 400 m2. The negative effect of poor site conditions and stronger GW influence on regeneration success could be partially compensated for in larger gaps, where, on average, light and water availability was increased. However, above a gap size of approx. 400 m2, increased DIRSF can lead to a decrease in establishment success. The models further allow for the spatial explicit prediction of beech regeneration establishment success within the studied gaps. While this method requires extensive input data, it substantially improves prediction accuracy, especially in the case of larger gaps. Based on these predictions, there is considerable optimization potential for the planning and implementation of regeneration methods. In the context of adapting forests to climate change, the methodological approach presented in this study is particularly relevant. It enables the precise analysis of regeneration processes of further tree species, the identification of potential establishment bottlenecks, and the derivation of silvicultural strategies. Prospectively, this allows for more precise fine-tuning of regeneration dynamics in species- and structurally-rich mixed forests under climate change conditions.

No description available.

Colour and appearance of hardwood are of great importance for the interiorand furniture industry. The widespread use of transparent surface treatmentand a fashion that prescribe light colour on many species, means that deviationfrom the ideal have considerable impact on the industrial operations. Kilndrying is generally regarded as the process that has the greatest impact on thecolour of Nordic hardwood species. The lack of satisfactory explanation modelsfor many types of discoloration, however, complicates the control of the dryingprocess.This thesis is an attempt to increase the knowledge of which factors thatcontrol the appearance of some commonly found discolorations associated withdrying of beech, birch and oak. The main focus is on convection drying but alsothe influence of timber storage, pre-steaming and press drying has beeninvestigated for individual species. The studies have been conducted ascomparative studies based on design of experiments in which the colour wasdetermined using a colorimeter.Results show that reddish and dark discoloration of beech and birch duringconvective drying is mainly dependent on the temperature and time of exposurewhen the local moisture content exceeds the fibre saturation point. Theconversion of naturally occurring substances in birch into coloured compoundsis not due to active precursors created at high moisture content levels duringthe subsequent drying at low moisture content levels. Interior grey stain inbeech is caused by slow initial drying at low temperatures. Log storage in coldwinter and spring climate does not cause discoloration in beech. Birch becomeslighter when press-dried at high temperatures, resulting in a colour comparableto that of traditionally kiln dried wood. Steaming of oak before kiln dryingreduce the presence of brown discoloration, a general darkening of the woodoccurs at temperatures above 50°C.