While boreal forest habitats have historically been relatively free from invasive plants, there have been recent increases in the diversity and range of invasive plants in Alaska. It is critical that we understand how disturbances influence invasibility in northern boreal forests, to avoid the economic damage other regions have experienced from invasive plants. Black spruce (Picea mariana) is the dominant forest type in interior Alaska, and wildfire is the dominant disturbance in these forests. Furthermore, disturbances in the form of management for fire suppression are common in forests close to urban areas. I surveyed recently burned, managed, and undisturbed black spruce forests for invasive plants to determine if fire and management facilitate invasive plant colonization. I also conducted an experimental seeding trial with three invasive plants common to Alaska (bird vetch (Vicia cracca), common dandelion (Taraxacum officinale), and white sweetclover (Melilotus officinalis) in burned and mature black spruce forest to determine if fire facilitates invasive plant germination. To determine the effect of substrate type on invasive plant germination, I planted seeds on a variety of substrates in the burned forest. Results indicate that fire and fire suppression treatments promote invasive plant colonization, as invasive plants were observed in burned and managed areas, but not in mature stands. Analysis of environmental data taken at survey sites indicate that fire mediates invasibility through its effects on substrate quality. In burned stands, invasive plants are most likely to colonize areas of shallow post-fire organic depth. Results from the seeding trials were consistent with results from invasive plant surveys, with reduced germination in mature compared to burned forest, and no germination on the residual organic layer in the burned forest. The highest germination occurred on mineral soil in burned forest, indicating that severe fires that combust the organic layer are likely to increase invasibility. The results of this study suggest that invasive species control efforts should be prioritized to disturbed forests, particularly areas where the disturbance has exposed mineral soil.

In 1957 Vroom presented an article that dealt with the kinetics of the sulphate cook. He showed that the lignin dissolution exhibited a temperature/time dependency that could be explained by the Arrhenius equation and that the reaction was of first order with respect to lignin. However, even before Vroom introduced the H-factor all wood components were assumed to react according to a first order reaction. In recent years progresses in this area have been made. Lignin for example is nowadays considered to dissolve during three parallel first order reactions, all with differences in activation energies. When the kinetics are evaluated, several cooking series at different temperatures and concentrations of active cooking chemicals are needed. The data points obtained are then fitted into some equation. If the concentration of the active cooking chemicals is constant, the activation energies and the chemical dependency for the dissolution of wood components can easily be found. In order to simplify the evaluations of the kinetics, very high liquor-to-wood ratios are sometimes used, often as high as 50:1 or even 75:1. In this manner, the chemical concentrations are almost constant during the cook. The problem is that in the normal industrial cook where the liquor-to-wood ratio is about 4:1, the chemical concentration is not constant. This is due mostly to the alkali consumption that takes place in the cook for example when neutralising the acidic groups in the hemicelluloses. A disadvantage with high liquor-to-wood ratios is the high dilution of the dissolved organic matter. A high concentration of dissolved lignin boosts the dissolution of the remaining lignin in the wood residue and xylan can redeposit on the fibres when its concentration in the cooking liquor is high. The aim of this project was to describe how different liquor-to-wood ratios influence the kinetics during sulphate cooking of spruce.

In this thesis, the moisture characteristics of spruce plywood are studied experimentally and numerically with special attention given to moisture storage and release as the indoor humidity changes diurnally. This is referred to as the moisture buffering capacity. Two test facilities (a glass jar facility and a transient moisture transfer facility) are used to measure the moisture accumulation and temperature and relative humidity profiles within spruce plywood. These measured data are used to determine the moisture buffering capacity of spruce plywood and validate a one-dimensional transient numerical model that can be used to calculate the transient heat and moisture transfer in spruce plywood. There is good agreement between the measured and simulated results over the range of test variables investigated. </p><p>This validated numerical model is used to investigate the effect of initial conditions, boundary conditions, thickness and humidity step change on the moisture buffering capacity. In addition, sensitivity studies are performed to investigate the effect of variations in material properties used in the numerical model. The properties that are considered in these sensitivity studies are the sorption isotherm, effective thermal conductivity, heat of sorption and effective diffusion coefficient. These studies show that the sorption isotherm has the greatest effect on the moisture buffering capacity, as well as the temperature and relative humidity profiles within spruce plywood. For example, a ± 10% change in sorption isotherm has a ± 7%, ± 6% and ± 10% effect on the moisture buffering capacity, and the relative temperature and relative humidity change, respectively. </p><p>This thesis also verifies the moisture diffusivity property for spruce plywood, which was developed by Olutimayin and Simonson (2005) to account for moisture storage in cellulose insulation for a single step change in humidity. It was found that for spruce plywood, the moisture penetration depth may be over predicted by an order of magnitude when moisture storage is neglected using a transient analytic solution which does not include moisture storage.

Climate change is predicted to increase rates of fire activity in boreal forests. A shortened fire return interval may result in different outcomes of community structure in the northern boreal forest, since the age of a forest influences seed production and potential post-fire regeneration. With two closely timed fires, dominant boreal conifers such as black spruce (Picea mariana) may be vulnerable to regeneration failures after fire because of the long time required to reach reproductive maturity. I report on the relationship between stand age and seed productivity of black spruce in northern Yukon Territory and central Alaska. I used fire history maps to select sites of various stand ages, including stand ages that would occur in a short fire return interval (less than 80 years) versus longer fire intervals (up to 200 years). At each site, I measured stand density and basal area using the point-center-quarter method. Ten black spruce trees were randomly selected for cone surveys and age analysis. I also selected a subset of five trees for detailed analyses of cone and seed production within yearly cohorts. The results of this study illustrate the strong relationships between stand age and stand basal area with cone and seed production of northern black spruce. The resulting equations can be used to predict the seed capacity and regeneration potential of black spruce stands with known stand basal area or stand age. I estimate, along with the number of seeds required to produce a two year old black spruce seedling on high quality seedbeds, stands burned at an age less than 50 years will likely have reduced black spruce post-fire density. On low quality seedbeds, black spruce forests are more vulnerable to regeneration failures and fire cycles less than 150 years are likely to result in reduced recruitment. Under a shortened fire return interval these northern black spruce forests are likely to have reduced post-fire density.

The aim of this PhD project was to transfer the remarkable mechanical properties of compression wood to technical applications. Compression wood can be strongly deformed because of its high cellulose microfibril angle and allows permanent plastic deformation without significant damage. These special features of compression wood make this material particularly suitable for the three-dimensional processing of veneers. By applying advanced technologies high deformation levels were achieved. / Das Anliegen dieses Promotionsprojektes bestand in der Überführung der beachtenswerten mechanischen Eigenschaften von Druckholz in eine technische Anwendung. Druckholz kann aufgrund seines großen Cellulose-Mikrofibrillenwinkels stark verformt werden und erlaubt eine permanente plastische Verformung ohne signifikante Materialschädigung. Insbesondere diese Eigenschaften lassen Furniere aus Druckholz für eine dreidimensionale Verarbeitung geeignet erscheinen und führen unter Verwendung neuartiger Verformungstechnologien zu hohen Verformungsgraden.

<p>After decades of investigation, we still have to deal withthe problem of environmental effects of the use of de-icingsalt on roads. Lacking useful indicators of the system, westill do not know the environmental utility of ameliorativemeasures taken. The thesis aims at</p><p>i) describing the system of de-icing practices and theirenvironmental effects with special reference to the exposure ofthe roadside environment to air-borne salt and damage to Norwayspruce seedlings and ii) at proposing indicators for afollow-up system. By collecting bulk deposition and relatingthe deposition pattern to factors concerning wind androad-maintenance characteristics, the influence of thesefactors on air-borne exposure is investigated. By exposingNorway spruce (<i>Picea abies</i>(L.) Karst.) seedlings to roadsideconditions the influence ofsalt exposure on the degree ofdamage is investigated. Based on a comparison of severalsystems of monitoring, improvements are suggested by proposingnew indicators for salt use and its environmental effects.</p><p>A large part of the salt that is applied on the road surfacewill be transported by air and deposited on the ground in theroadside. While the vast majority of the salt will be depositedwithin some tens of metres of the road, some may still be windtransported several hundred metres away. The wind directionplays an important role for the deposition already at adistance of some ten metres from the road. Wind speedinfluences the distance to which the salt is transported.Chloride concentration in unwashed needles collected after thesalting season is positively related to the bulk deposition ofCl during the exposure. The degree of damage can be describedby a sigmoid curve of response to the Cl concentration inneedles. Improvements to the follow-up system are suggested byproposing indicators of the driving forces, pressures, states,impacts and possible responses as regards the undesired impactson water resources, vegetation and the roadside scenery as asocietal asset.</p><p><b>Keywords:</b>road, de-icing salt, air-borne, environmentalimpact, vegetation damage, Norway spruce, seedling, follow-up,monitoring, indicator</p>

Den produktiva skogsarealen i Sverige som är grandominerad utgörs av 9,5 miljoner ha(Skogsstyrelsen 2011). Varav knappt 0,2 miljoner ha står på torr mark (personlig kommunikation Göran Kämpe, 2015). Problematiken i södra Sverige är att gran planteras på allt för torra marker, eftersom att tall anses för osäkert pga av betestrycket av vilt.  I undersökningen utreds om och när tillväxten avtar för granen på torrare marker i sydöstra Sverige med hjälp av bestämning av ståndortsindex (SI).  Höjdtillväxten har, med hjälp av borrning/kapning på olika trädhöjder, rekonstruerats i granbestånd för en hel omloppstid. Detta har utförts på två olika lokaler där tall hade varit det naturliga valet och där granen bedöms lida av vattenbrist. Fokusområdet är ifall höjdtillväxten och SI avtar för granen på tall/torra marker under omloppstiden, som kan ses som en indikation på granknytning. Resultatet visar att granbestånden har ett betydligt högre ståndortindex i ungskogsfasen jämfört med när beståndet är äldre.  Under omloppstiden visar det sig att ståndortindexen ändrar sig vid två tillfällen under granbeståndets livslängd, eventuell vattenbrist uppstår. Bestämning av SI visade att bestånden motsvarade en G30 i ungskogsfasen men vid slutavverkning hade det sjunkit till en G24. / Today we know that 9,5 million hectares of productive forest land in Sweden consists of Norway spruce (Skogsstyrelsen 2011), of which almost 0.2 million hectares are standing on dry land with low moisture content (personal, communication Göran Kämpe, 2015). The problem today in southern Sweden is that Norway spruce is planted on arid lands, because that pine is considered unsafe due to damage on young plants done by wild animals. The study investigates if and when growth slows down for spruce on arid lands in south-eastern of Sweden, based on determination of a site index (SI) for a whole rotation. In order to determine SI, increment cores/cutting at different tree height has been conducted. It compares the height growth of spruce stands during the rotation period, on land where the pine had been the natural choice and where the spruce likely suffers from a water deficit. The focus area of this study is if height growth and SI declines with age as an indication of water deficit in older stands. The boundaries are the economic part. The result shows that the spruce stands had a considerably higher site index at an early age, compared when it reaches older ages. During the rotation period, it turns out that site index drops twice during the rotation period, when a possible water deficit occurs. Calculations of the site index show that SI of G30 in the young stand but at time for clear-felling, it drops to a G24.

Interactions among site conditions, disturbance events, and climate determine the patterns of forest species recruitment and mortality across landscapes. Forests of the American Southwest have undergone significant changes over a century of altered disturbance regimes, human land uses, and changing environmental conditions. This study reconstructs the interactions between fire, spruce beetle outbreaks, climate, and anthropogenic factors and their influence on the species composition, spatial extent, and structure of four upper elevation forest types. We found that fire-climate associations changed following fire exclusion and recent high-severity fires occurred during less severe conditions than in several larger, lower severity fires in the historical record. Contemporary fires are burning with higher severity than similarly-sized historical fires, suggesting a shift toward higher-severity fire as a result of changes to forest structure and fuels over much of the upper elevation forest. In high elevation forests, the area occupied by Engelmann spruce and corkbark fir doubled in size over the four decades following fire exclusion. The increase in spruce beetle outbreak size and severity in the 20th century appears to be linked to significant expansion of host extent, accelerated growth of spruce in mixed-conifer forest, and incidence of anomalously warm summer temperatures followed by up to a decade of low precipitation. Trends toward warming, drying conditions are expected to increase the risk of future high-severity outbreaks, especially in locations of recent spruce population expansion. Forest conversion from disturbance-adapted to competition-adapted species following fire exclusion was a function of site productivity. Species assemblages in the lowest and highest productivity sites were the most stable over the century following fire exclusion. Frequent low severity fires maintained the stocking of forests in moderate productivity sites below their biological potential, conferring a degree of resistance to drought, insect outbreaks, and high-severity fire prior to fire exclusion. Current forests located on moderate productivity sites are now the most vulnerable to drought and future disturbance. Aggressive action to restore historical species composition, stocking and fire component of these forests may return resilience to this system in the face of projected changes to fire and climate dynamics.

This full report presents a classification of mid-seral black spruce ecosystems in the Boreal White and Black Spruce (BWBS) and Sub-boreal Spruce (SBS) zones of British Columbia. The classification is based on a total of 122 plots sampled during the summers of 1997 and 1998. We used multivariate and tabular methods to synthesize and classify ecosystems according to the Braun-Blanquet approach and the methods of biogeoclimatic ecosystem classification. The black spruce ecosystems were classified into 8 vegetation units (associations or subassociations) and the same number of site associations. We describe vegetation and environmental features of these vegetation and site units. Vegetation and environmental tables for individual plots are given in Appendices. In addition, we also present the relationships between site index of black spruce and direct and indirect measures of site quality.

This pamphlet provides a summary of a fuller report issued under the title: Classification of mid-seral black spruce ecosystems of northern British Columbia