A thorn forest is a dense, scrublike vegetation characteristic of dry subtropical and warm temperate

Temperate

In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...

 areas with a seasonal rainfall averaging 250 to 500 mm (9.8 to 19.7 in). This vegetation covers a large part of southwestern North America and southwestern Africa and smaller areas in Africa, South America, and Australia. In South America, thorn forest is sometimes called Caatinga

Caatinga

Caatinga is a type of vegetation, and an ecoregion characterized by this vegetation in the northeastern part of Brazil. The name "Caatinga" is a Tupi word meaning "white forest" or "white vegetation"...

, and consists primarily of small, thorny trees that shed their leaves seasonally. Treese typically do not exceed 10 metres (32.8 ft) in height, usually averaging between 7 and 8 m (23 and 26.2 ft) tall. Thorn forest grades into savanna

Savanna

A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...

woodland as the rainfall increases and into desert as the climate becomes drier.