The feature of the deserts
The soil in the dry regions has many mineral substance and a little organic manure. The accumulation of the water change some soil into the salty soil layer. The calcium carbonate precipitated in the salt solution can be used to dip the sand and stones into a 50-meter-thick “cement”.
The saltpeter layer is a common reddish brown to white layer of desert soil. The saltpeter layer is generally agglomerated or wrapped around mineral particles and is formed by a complex interaction between water and carbon dioxide. Carbon dioxide comes from the roots of plants, or rotten by-products of organic products. The climate is hot and the temperature difference is large in the morning and evening.
Most desert plants are drought-resistant or salt-tolerant plants. Some have water in the roots, stems and leaves; some have a large rhizome system that can reach the groundwater layer, stop the soil and prevent soil erosion; some have larger stems and leaves, which can reduce the wind speed and preserve the sand.
The distribution of plants in the desert is fewer, but there are many varieties. The saguaro in the desert of the southwestern United States can live for 200 years, grow to 15 meters, 10 tons, and become a tree in the desert. Saguaro grows very slowly, only 15 centimeters after 9 years, and the first branch is only 75 years old. Because of the size of the body, it looks like there are many cacti in the desert.