Ecohydrology is a branch of hydrology that takes the ecological processes entailed in the water cycle as its focus. The primary manifestations of these processes are in foliage and soil; therefore ecohydrology focuses mostly on transpiration, or the evaporation of water vapor from leaves and other vegetation. The hydrologic cycle is viewed in terms of the plant-atmosphere-soil continuum, which is a total consideration of the interacting conditions of the soil, plants, and atmosphere within an area of study. Dominant theories of ecohydrology hold that rainfall over a period of time is a key factor in the development of an ecosystem. For instance, dry environments develop such that plants will not need much nutrition, whereas a lush, wet environment will develop plants that require plenty of nourishment.