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Fig. 5.2
Mean duration (days) of the period with sustainable temperature above 10
◦
C(from
The natural and economic potential of the mountains in Bulgaria,
1989
). > 200 - most favor-
able; 150-200 - favorable; 100-150 - medium favorable; 50-100 - unfavorable; < 50 - extremely
unfavorable; 0 - lack of conditions for vegetation
The duration of the period with a sustainable temperature of the air exceed-
ing 10
◦
C represents a very indicative thermal characteristic for the conditions of
vegetation of natural and cultural plants (Fig.
5.2
).
A basic climatic characteristic is also moistening in the most general sense, with
precipitation being the most important factor for life and human economic activities;
it provides a basic contribution to the river basins in the formation of the vitally
necessary water resources. It is also ensures soil moisture, especially important for
agricultural crops during the vegetation period. The circumstance that all of the
larger rivers derive almost entirely their runoff in the mountain territories and are
dominated to a great extent by only transit flow through the plains, emphasizes
the extremely important role of the higher amount of precipitation in their spring
areas, where the annual precipitation sums exceed 1,000 mm, this figure gradually
decreasing to 500-550 mm towards the neighboring plain lands (Fig.
5.3
).
Of course, all the other characteristics of climate (atmospheric pressure, air
humidity, cloudiness, mists, icing, etc.) are also rather important, especially from
the viewpoint of habitation environment, transport and production, but in the context
of the present evaluative analysis they are not considered.
Climate in the mountains is of great importance - both as a resource and as
a condition - for the versatile human activity and as a factor for this activity -
respectively for improving the parameters of its sustainable development.
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