THE STATE AND DYNAMICS OF THE BORDERS OF CEDAR FORESTS AT THE WESTERN TANNU-OLA RANGE IN THE TYVA REPUBLIC

Abstract

The paper presents the recent response of dark coniferous forest and cedar undergrowth in the forests of the Western Tannu-Ola Range to the observed climate change in the region. According to the nearby Chadan meteorological station, the anomaly of the average annual air temperature was 1,6 ± 0,8°С, the anomaly of the growing season was 1,0 ± 0,7°С. Key study areas are located in the Tyva Republic within 50°55′-51°15′N and 91°30’-92°20’E, which corresponds to three altitudinal levels: the lower belt of the middle mountains (1100-1300 m a.s.l.) bordering the steppe and covered with larch forests with birch; the middle belt of the middle mountains (1300-1800 m a.s.l.) covered with larch and cedar forests; larch and cedar forests of the upper belt of the middle mountains (1800-2120 m a.s.l.). In the course of field work, the increment of the top shoot of cedar sapling (Pinus sibirica Du Tour) was measured, as well as its height, age and total number. Correlations between the increment, air temperature and relative humidity were quantitatively determined using data from the Chadan weather station for a number of years. The results indicate a positive correlation with humidity in the lower zone of the middle mountains and with air temperature in the upper zone of the middle mountains. Higher amounts of cedar sapling in the lower zone of the middle mountains and in the upper zone of the middle mountains confirm the shift of dark coniferous forests down and up the ridge under the regional climate warming. Space images of Landsat TM/ETM+/OLI show the increasing values of NDVI and NDWI vegetation indices. According to satellite images, an increase in the area of dark coniferous forests over the past decades was calculated for the territory of key areas; however, the reliability of these data was not evaluated statistically. The work needs to be continued in the field.