FIG. 39--This view is representative of the open steppeland of Ukraine in southwestern Russia.] Changes in the aspect of the land resulting from human activity provide an easily observable boundary between the territory inhabited by Poles and that occupied by Ruthenians. The former, proceeding from the Vistulian lowland, are now scattered over a territory in which deforestation and large areas of tilled soil bespeak prolonged occupancy. The latter, coming from the Pontic steppes, reached the Carpathian slopes much later than their western neighbors. Consequently only 20 per cent of the surface of the western Carpathians is now available as prairie and pasture land, whereas the percentage of grazing land in the eastern section of the mountain chain is twice as much.[102] The area of plowed land in the western region covers between 40 and 50 per cent of the surface. In the east it barely varies between 5 and 10 per cent. Again the Polish section is practically clear of the forests, which cover, in contrast, from 50 to 60 per cent of the eastern Carpathians. Similar differences can be noted in the valleys up to an altitude of about 2,300 feet. Within them the proportion of plowed land constitutes 88 per cent of the surface in the Polish section while in the Ruthenian valleys the proportion of plowed land does not exceed 15 per cent. On the southwestern border a number of localities in the Teschen country are claimed alike by Czechs and Poles. The increasing use of Polish and German, however, tends to invalidate the claims of Bohemians.[103] A transition zone between Czech and Polish exists here and is characterized by a local dialect of mixed language. In the western Beskid mountains Polish and Moravian are divided at the Jablunka pass. The ancient duchies of Teschen, Auschwitz and Zator were situated in this region and at the southern end of the long Slavo-Germanic borderland. The two last-named duchies were incorporated with Poland in the fifteenth century. German language and customs disappeared from their territory soon after this fusion. This important district is in every aspect a zone of transition. Its climate becomes alternately continental or oceanic according to the prevalence of winds from east or west. The change occurs sometimes in a few weeks. Occasionally it is sudden and atmospheric conditions have been known to have changed completely from one stage to the other in the course of a single day.[104] During periods of oceanic climate, the temperature often rises above 0° C. Snows melt and spring temperature prevails during January and February. Again sometimes the east wind brings all the signs of winter in April. In summer western breezes bring rain and dryness prevails when eastern winds blow. As a result of this semi-continental climate wheat crops on the Polish side are from three to six weeks later than on the Moravian side.