Thermal wood modification has been intensively studied in the recent decades because of the possibility to produce wood with improved biodurability and dimensional stability without use of harmful chemicals. Beside altered physical characteristics, wood colour is changed to lighter or darker brown as a result of thermal treatment. Growth of interest in thermal wood treatment has stimulated numerous researches concerned with discoloration of thermally modified wood which is subjected to light exposure. The objective of this study was to evaluate the colour stability of thermally modified hardwood during storage in the dark where wood discolouration is not photoinduced but rather a result of oxidative ageing. Three thermally modified hardwood species – aspen (Populus tremula L.), alder (Alnus incana Moench), birch (Betula pendula Roth.), where investigated. Wood discoloration was monitored by spectrophotometrical measurements of reflectance spectra and chromaticity parameter calculations using CIELAB colour system where L* is the lightness, and a* and b* are the chromatic coordinates. The colour stability of thermally modified wood as well as of untreated wood of the same species was examined by means of assessment of the colour parameter changes (ΔL*, Δa*, Δb*, ΔEab). All wood specimens under study discoloured during the experiment, but the colour change did not exceed two units that are common and accepted for wood products. Untreated and thermally modified wood showed different trends of discoloration during storage in the dark. The final colour changes that were fixed at the end of the experiment were greater for the thermally treated wood.

In society, discussions occasionally raise whether current level of wood cutting in Latvia is not too high to maintain sustainable forest industry and biodiversity. Cutting volumes for the state owned forests are calculated based on the model whose aim is to even the timber stock of each tree species in a long term period. The wood resource extraction in the private forests takes place according to free market conditions and depending on market prices. Therefore amount of round wood delivered from private forests can shift in a large range. The research had two main tasks. First task was to survey primary wood processing companies in Latvia and gather information about their round wood processing volumes, how their processing volumes divides between softwoods and hardwoods, dimensions of round wood companies demand for production and assortment of produced materials. Second task was to evaluate round wood utilization balance in the territory of Latvia and estimate if current use of timber resources in Latvia corresponds to amounts that are sustainable. Research results showed that consumption of softwood timber in Latvia is close to maximum to perform sustainable forestry, but consumption of hardwoods is possible to increase at least by 20–25%. Survey of primary wood processing companies showed that round wood processing volumes in Latvia vary from 6 to 7 million m3 annually and that large enterprises, which count only for 4% from total number of primary wood processing entities, process two thirds from annual round wood volume in country.

Forest industry consists of two related industries forestry and wood processing. Wood processing industry, which is a direct consumer of timber resources generated by forestry sector is eager to search for an answer about kind and amount of round wood they can count on in long term period. In Latvia for every five years State Forest Service calculates cutting volumes for the state owned forests based on models which do not guarantee safe long term income maximization. Long term cutting volumes and assortments in privately owned forests have not been analyzed very deeply. The aim of the research was to estimate the hypothetic amount of different timber resources available in the territory of Latvia for wood processing industry within next hundred years and look at geographic location of timber resources and woodworking companies. Research results showed that forests in Latvia are not being depleted and current annual cutting volumes could be increased. Geographic observation of primary wood processing companies showed that most of them are located close to large cities or near main roads of Latvia. This location makes easier round wood deliveries to factory and facilitates transportation of produced goods to an end customer. To clarify where and what profile (softwood or hardwood) production volumes should be increased, model of timber resource demand indicator was implemented.

A questionnaire related to the wood drying was carried out among wood processing enterprises in Latvia to clarify the main problems and possible differences depending on production capacity and products. Deformation (twist, bow, spring, cupping etc.) during the kiln drying has been identified as the most important problem for all enterprises. Many problems are related to the product area as very often improper drying technology or incorrect drying schedule is used. Others are connected to the organization and control of drying process - optimisation of the drying schedule, energy consumption, kiln control unit, maintenance of measuring equipment, MC measurement, quality control during drying. There is a difference between softwood and hardwood drying in the product and sales area. Considerably more problems are recognized in hardwood drying (hardwood is often used in furniture production and has higher quality demands).