Where are tropical desert climates mainly distributed?

Tropical desert climate is distributed in the interior of the continent or the west coast of the continent between the Tropic of Cancer and 30° north and south latitude, and extends to the inland areas, such as northern Africa, the Arabian Peninsula in Asia and the desert areas of Australia are typical representatives.

The tropical desert climate is mainly distributed in the interior of the continent or the west coast of the continent near the Tropic of Cancer. The main geographical locations are in northern Africa, western Asia, central and western Australia and the narrow area on the west side of South America, roughly on the Tropic of Cancer. Nearby mainland interior and west coast. Typical examples include northern Africa, the Arabian Peninsula in Asia, and the desert areas of Australia.

It is characterized by high annual average temperature, large annual temperature difference, larger daily temperature difference, and scarce precipitation. The annual precipitation is generally less than 250 mm. In many areas, it is only tens of millimeters or even several millimeters. The precipitation varies. The rate is very high, and it often doesn't rain for several consecutive years.

Under the control of subtropical high pressure belts or trade wind belts, and controlled by tropical continental air masses throughout the year, there is drought and little rain. The annual precipitation is about 100 mm. In some places, it is only tens of millimeters or less. The evapotranspiration may be less than Precipitation is more than 20 times greater.

The annual average temperature is higher than 18°C, and the summer is very hot. The average temperature in the hottest month is mostly between 30°C and 35°C. The absolute highest temperature in some locations is as high as 58°C, and the highest ground temperature can reach over 80°C. The average temperature in the coldest month is no less than 10℃. The daily temperature range can reach 35℃-40℃, and the lowest temperature at night can drop to about 0℃. There are few clouds, strong sunshine, and abundant solar energy resources.

The contradiction between heat and moisture is prominent. The distribution and formation of the world's great deserts are closely related to the dry tropical climate.

The Sahara Desert and Kalahari Desert in Africa, the Arabian Desert in Southwest Asia, the western and central Australian deserts, the lower Colorado and California deserts in North America, and the Atacama Desert in South America all have typical characteristics. Tropical desert climate. The tropical desert climate zone is located on the north and south sides of the savannah climate zone.

The air pressure in these places is high and the weather is stable. The wind always blows from the land to the ocean, but the moist air from the sea cannot enter the land. Therefore, there is very little rainfall and it is very dry. The rocks on the ground have been weathered. Fine sand grains are formed, and the sand grains are blown by the wind. When they are accumulated, they form sand dunes. When the sand dunes spread widely, they become a vast desert.

In some places, the weathering rate of rocks is slower, forming large expanses of gravel. This is a desert. The area of ​​deserts on the earth is very large, and there is a trend of further expansion.

Main vegetation in tropical desert climate

The climate in tropical desert areas is dry, high temperature, windy and sandy, and the soil has high salt content. Plants must have the unique ability to adapt to the natural environment of the desert in order to survive and grow. Therefore, compared with plants in general areas, plants in the desert are very different in terms of appearance, internal structure, and physiological functions.

1. Most perennial sand plants have strong root systems to increase the absorption of water from the sandy soil. Generally, root depth and root width are many times greater than plant height and plant width. Horizontal roots (lateral roots) can expand far in all directions and are not hierarchical, but spread and grow evenly to avoid concentrating in one place and consuming too much. Sand layer moisture.

For example, the plant height of the shrub yellow willow is generally only about 2 meters, and its main root can drill into the sandy soil to a depth of 3 and a half meters, and its horizontal roots can extend to 20 to 30 meters away, even if it is exposed by wind erosion. Even though the roots are horizontal, the whole plant will not die. The lateral roots of yellow willows that have only been planted for one year can reach 11 meters.

However, the roots of some annual plants are very shallow. If there is some rain occasionally in spring, even if it is very little, as long as the surface is moist, they will make full use of it and grow vigorously, bloom, and bear fruit. It completes its life cycle in a short period of time to avoid the drought and high temperature in summer. People call them "ephemeral plants."

2. In order to reduce water consumption and reduce the transpiration area, the leaves of many plants shrink very small, or become rod-shaped or thorn-shaped, or even have no leaves, and use twigs for photosynthesis. Haloxylon ammodendron is leafless and is assimilated by green branches, so it is called "leafless tree".

Some plants not only have small leaves, but also small flowers, such as tamarisk. In order to inhibit transpiration, the epidermal cell walls of some plants become lignified and the cuticle is thickened, or the surface of the leaves is covered with a waxy layer and a large number of hairs, and the stomata of the leaf tissue are sunken and partially blocked.

3. The surface of the branches of many sand-growing plants turns white or off-white in order to resist the strong sunlight in summer and avoid being burned by the high temperature of the sand surface, such as Shaguai Zao.

4. There are many plants with strong sprouting ability and strong side branches, which can withstand the attack and burial of sand.

This is the case with Tamarix (tamarisk). It can still grow adventitious roots when buried in the sand, and its sprouting branches will grow more vigorously. In deserts and Gobi areas, wind and sand activities are strong. Tamarix growing in low wetlands is often attacked by quicksand, causing the shrubs to continuously accumulate sand. However, after being buried in the sand, tamarisk can still continue to grow due to the action of adventitious roots, so "a rising tide lifts all boats", forming tall shrub sand piles (sandbags).

5. Many plants are succulent plants that contain high concentrations of salt, and can absorb water from soil with high salinity to maintain life, such as Suaeda salsa, Salt Claw, etc.

The method of plant propagation in the desert is also very strange.

Many annual or perennial plant seeds have wings or hairs on them. When the seeds mature, they fly and carry far away with the wind. When they encounter a suitable place, they sprout and grow.