As one proceeds poleward from the equatorial rainforests, one finds a progressively longer dry season until one finally encounters truly arid climates. This latitudinal and moisture gradient is reflected in the natural vegetation. The forests poleward of the rainforest become shorter in stature and simpler in structure. The proportion of trees that are deciduous increases as the dry season becomes more pronounced.
Leaves become smaller and thorns or spines more frequent.
At the drier extremes of this gradient, succulents become common. Tropical Semi-evergreen Forests. These are broadleaf forests, some species of which are evergreen and some of which are deciduous. There are many fewer tree species than in the rainforests, but still many lianas. Epiphytes are infrequent.