The homogeneous and light wood of birch is suitable for different types of treatment processes and is highly valued for products where visual aspect is important, however, birch assortments are highly susceptible to damages caused by fungi during the storage. Such fungal damages cause discoloration of birch roundwood intended for further woodworking. Sapwood discoloration development and its influencing factors for birch roundwood were analyzed in the summer - autumn period of the year 2016 (August, September and October). Control cut for assessment of sapwood discoloration development was made in four birch roundwood stacks in the districts of Auce and Daugavpils. In order to evaluate the influence of harvesting type, side surface damages, placement in pile, storage duration, diameter, distance from the end plane, daily average temperatures, precipitation amount and relative humidity on development of sapwood discoloration, 616 discs from birch log end planes were prepared. After conducting multiple factor linear regression, it was concluded that a significant development of discoloration and its changes for birch roundwood are promoted by harvesting type, placement in pile, distance from the end plane, daily average temperatures and relative humidity (R2 = 0.450). For birch logs that are prepared by harvester with the daily average air temperature + 6 °C, the first signs of discoloration appear after 17 – 18 days, but on all logs stacked in pile they appear after 68 – 69 days. Whereas, with the daily average temperature of + 18 °C, the first signs of discoloration can occur after only six days, but on all logs stacked in pile they appear after 23 days.

In order to get maximum economic effect, when setting a solar collector in a peasant yard, it is important to choose the correct place. The yield of obtained heat energy will be at its maximum, if the temperature of surrounding air and solar radiation are higher by the relative humidity of the air - lower. To define these parameters, a special device 'Meteorological Device' (MD-4) was developed. The device was supplied with a mechanism which tracks the sun all day round. So the direct solar radiation on the surface perpendicular to the sun beams was measured. The second measuring of the solar radiation was made in relation to the surface, which was perpendicular to the sun beams only at the middle of a day time. For the measuring of the air temperature and relative humidity, corresponding sensors were used. In every 15 minutes the data of these four meteorological parameters were automatically measured and the results were saved into a logger - the device for data accumulation. After a certain period of time the information was brought into the memory of a computer and analysed.