Lessons 8 · 1 lessons · Sh. M. Sharipov, V. N. Fedorko, N. I. Safarova, V. A. Rafiqov. Geography (Applied geography), Grade 10, 1st edition. “O‘zbekiston milliy ensiklopediyasi” State Scientific Publishing House, Tashkent, 2017
8
The law of altitudinal zonation
Textbook: pp. 33–35
GoalKnow the law of altitudinal zonation, the effect of the snow line and slope exposure, and the belts of Uzbekistan's mountains.
Altitudinal zonation is the regular change of nature from the foot of a mountain to its watershed. With height air temperature and pressure fall, and precipitation increases up to a certain height and then decreases; soils, plants and animals change accordingly. Altitudinal belts resemble the natural zones of the plains but are not identical: for example the plains have no zone of subalpine and alpine meadows. The number of belts is greater the higher the mountain and the closer to the equator, and the first belt begins in the natural zone where the foot of the mountain lies. The snow line is the boundary above which snow lies all year; it is low in polar latitudes, very high in the tropics, and lower in wet areas near the ocean than in continental interiors. Slope exposure matters too: a south-facing slope is sunny and dry, a north-facing one cooler and wetter. In Uzbekistan's mountains four belts are usually distinguished: desert, adir, mountain (tog‘) and pasture (yaylov), with a snow-and-glacier (glacial-nival) belt above.
Worked examples
Air temperature falls on average 6 °C for every 1000 m of height. If it is 28 °C at the foot of a mountain at 500 m, then at 2500 m it is 28 − 6 × (2500 − 500) ÷ 1000 = 16 °C.
At the same height (for example 1200 m) a south-facing slope may carry dry adir vegetation while the north-facing slope has shrubland or forest-steppe needing more moisture, because the south slope gets more sunlight and less moisture.
Class activity
“Mountain section”: draw a mountain profile in a notebook, colour the belts with pencils according to height limits given by the teacher, and write a typical plant for each.
Practice
1
How do altitudinal belts differ from the natural zones of the plains?
They change faster and some do not occur on plains (for example subalpine and alpine meadows) because temperature and pressure change quickly with height.
2
At the foot of a mountain the temperature is 30 °C. If it falls 6 °C per 1000 m, what is the temperature 3000 m above the foot? (Number only.)
12
3
List the belts of Uzbekistan's mountains from bottom to top.
Desert, adir, mountain, pasture, then the snow-and-glacier belt.
4
Why does the snow line lie much higher in the tropics than near the poles?
In the tropics it is warm, so one must go much higher for snow to persist, while near the poles it is so cold that the snow line lies near sea level.