Exposure to sunlight is often a critical determinant of vegetation composition.
Adret slope—Sun slope; slope where Sun’s rays arrive at a relatively direct angle.
Relatively hot and dry, and its vegetation is sparser and smaller than that on adjacent slopes with different exposures.
Likely to have species composition different from adjacent slopes.
Ubac slope—a slope where sunlight strikes at a low angle and hence is much less effective in heating and evaporating than on the adret slope, thus producing more luxuriant vegetation of a richer diversity.
Difference between adret and ubac decreases with increasing latitude.
Valley-bottom locations can have vegetation composition significantly different from slopes running to it.