Approach to water cycle in forest ecosystems

Energy and water are essential in the functionalism of ecosystems, because solar energy, total radiation, drives the hydrological cycle through the movement of water from soil to atmosphere by means of evapotranspiration. This is the sum of evaporation from surfaces (soil and canopies) and direct water loss from plants, called transpiration. Ecosystems affect total radiation buy means of shortwave reflectance (albedo), which depends of rugosity of leaves and canopies. The great amount of absorbed energy is released as latent heat of vaporization (evapotranspiration) and sensible heat flux. The first one cools the surfaces and release water vapor to the atmosphere and the second one heats the air in the surfaces. The relationship between them is called Bowen’s ratio and characterized the relationship among water and energy in the different ecosystems. Rainfall is the more important source of water for the ecosystems and runoff and evapotranspiration cause the water losses in these.Water moves along a gradients from high to low potential energy, according to gradients of water potential, which determines the water’s continuum soil –plant– atmosphere. The water balance is affected by biotic and abiotic environmental stresses.