Park-like savannah-woodlands are often found where the dry season is longer and the rainfall less heavy than in true closed forest. They separate the earth’s belts of tropical forest from its desert regions, forming a wide range of transitional zones where moist and dry climates grade into one another and rainfall is often erratic. The trees tend to be widely scattered, except in favourable situations such as water courses. They show drought resistance and are often leafless during the dry season. In some regions they are replaced entirely by grasses.