ИСТИНА

Changes in the boundaries of high-altitude mountain belts can be treated as a proof of climate change. These changes were caused by termination of human activities. The presentation shows the role of climatic factors in changes of the boundaries and state of sub-alpine landscapes in the North Caucasus, where the transformation of land use system was observed. These are mainly mountain meadows, which were being shaped for centuries of grazing and are semi-natural formations. The system of mountain land use has been changing for the last decades: nowadays more than 60% of sub-alpine meadows are abandoned. Heat and moisture are the limiting factors of vegetation existence. The estimate of changes in heat and humidity was made for the territory of 42–44N 42–44.5E using vegetation index (NDVI), the index of vegetation conditions (VCI), Satellite Climatic Extremes Index (SCEI) and the sum of active temperatures (air temperature above + 10 °C). Analysis of index changes shows normal humidification on the slopes of the main Caucasian ridge throughout the more humid period (2000–2006). In the second – dry period (2007–2013) for most part of the southern European Russia, the situation is changing. In the foothills moisture decreases, whereas in the middle mountains the increase in moisture is seen. The estimate of the amount of active temperatures and precipitation for the period of modern warming (1981–2010) compared with the previous period (1951–1980) shows the increase of these parameters in the early twenty-first century in the foothills of the North Caucasus. These changes cause the increase in vegetation in the middle mountains of the North Caucasus. It is evidenced by the growth of vegetation index (NDVI) at the beginning of the twenty-first century in this area. And in the areas with low altitudes (500–1000 m) vegetation index decreased after 2006, reflecting degradation of vegetation state. In the middle mountains the increase of vegetation index is observed, showing the improvement on conditions of vegetation. In the middle mountains of the North Caucasus regeneration of natural boundaries of altitude zones is observed: the expansion of mountain-forest belt and restoration of pine forests on the southern slopes; restoration of mountain meadow steppe and steppe sub-alpine meadows on former agricultural terraces; northern slopes overgrown with crooked birch. These processes occur in the context of climate change (rising temperatures, increasing moisture) and reduce of human impact. Thus, climate change and weakening economic activity on the territory lead to restoration of vegetation in the area of middle mountains.