Air humidity on the clear-cut and the gap

The aim of the study was to determine the spatial variation of vapour pressure (c), relative humidity (f) and vapour pressure deficit (Delta) on the clear-cut and gap as well as to compare the spatial distribution of air humidity conditions on both areas. The research was carried out in Rogow Forest Experimental Station (51.827023 degrees N, 19.922315 degrees E) on a clear-cut with a width of 60 m and on a gap of an ellipsoid shape (40x70 m). The measurements were carried out in two series: spring-summer, i.e. in the period when the height of the sun during the day conditioned inflow of direct solar radiation to any surface (May-August 2006), and autumn, i.e. when direct radiation was limited by neighbouring stands (October-November 2006). We found the modest spatial diversification of vapour pressure that, on average, amounted to 0.4 and 0.2 hPa in the clear-cut and gap, respectively, in spring-summer period as well as 0.3 and 0.7 hPa, respectively, in the autumn. The major impact of the clear-cut and gap location was marked in relative humidity and humidity deficit. Differences in relative humidity on the clear-cut amounted averagely to 3.7 and on the gap 12.7%, whereas the humidity deficit equalled 0.3 and 5.4 hPa, respectively. Particularly large diversification of relativity humidity and vapour pressure deficit was in spring-summer period in the situation of heat waves. In that weather conditions in sun-filled clear-cut and gap parts, the relativity humidity fall to about 17%, whereas vapour pressure deficit increased to about 60 hPa. In the same clear-cut and gap parts the occurrence of dry days was more frequent that in other places. It was noticed that in the positions located in sun-filled clear-cut and gap parts (z4, g3), the diurnal vapour pressure course was very similar to the one observed in the forest, whereas the course of the relativity humidity and vapour pressure deficit was significantly different. That is mainly involved with the extreme thermal conditions in this parts of the studied areas. The least beneficial humidity conditions for plants growth occurred in the north-east parts of clear-cut and gap, that's why it necessary to take particular note of these locations when undertaking the silvicultural treatments.