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ABSTRACT
The numerous cases of the upper headwaters drying are observed in the plains of the Middle Volga region. The reasons of the streamflow change pertain to the reduction of forest vegetation and the change of its species composition. More than 1000 cartographic materials for more than 200 years, as well as aerial and satellite imagery were used during the research of forest vegetation breadth. Currently, the forest and the forest-field landscapes prevail in the north of Tatarstan, where coniferous-deciduous forests are widespread. The forest-fields, as well as the field landscapes are common in the west and south of Tatarstan, where deciduous forests and forest-steppe are prevalent. In the field landscapes the water runoff in the flood time increases to 65% of the total annual runoff, while the monthly summer runoff of low water reduces by 2.5 times compared to forest landscapes. The studies have shown that over the past about140 years the quantity of the first-order watercourses has reduced by 1.5 times in the area of mixed forests, whilst in the forest-steppe zone the quantity of the first-order watercourses has decreased by nearly 2.7 times. At the same time woodland in different regions of Tatarstan has decreased by 1.6-2.8 times for the same period of time. Low of the forest cover (17.9%), as well as the species composition of forests, in which the coniferous species as the most valuable for the infiltration does not exceed 24% from the forest area, are characterized for of Tatarstan territory. Coniferous plantations by more than half are presented the unstable monocultures of pine.
Keywords: the small rivers and their order, degradation of rivers, anthropogenic development of the territory, species and age composition of forests, infiltration.
INTRODUCTION
Anthropomorphic transformation of landscapes in Middle Volga regions lead to the changes in river order, particularly, data on drying out of small rivers, its shallowing and river bad slitting was received [1]. In some rivers in Republic of Tatarstan from the period of intensive development of the territories (XVII - XVIII centuries) most significantly changed the correlation of ground water and land runoff. Extermination of natural vegetation and plowing invoke significant increase of surface water runoff that leads to the intensification of erosion processes. Forests in comparison with other types of...