Which type of wetland is constantly submerged in water and contains trees ?

A wetland refers to a different ecosystem, which is flooded by water, either seasonally or permanently, where the oxygen-free procedures exist. The main element, which separates wetlands from the other water bodies or landforms is the characteristic vegetation of aquatic plants, amended with the specific hydric soil.  

Swamp refers to a wetland ecosystem featured by mineral soils with poor drainage and by plant species dominated by trees. The swamps are found all through the world, most usually in low-lying regions with poor drainage adjacent to rivers that supply the swamp with water. Some of the swamps develop from marshes, which gradually fill in, permitting woody shrubs and trees to develop.  

... Swamp ... (Apex)

all matter is made up of atoms

in any element all atoms are the same

elements in a compound are always in a constant ratio: apex