Ecosystems are complex, evolving structures whose characteristics and properties depend on many interrelated links between climate, soil, and vegetation. The dynamics of these links are critically influenced by the scale at which the phenomena are studied, as well as by the physiological characteristics of the vegetation, the pedology of the soil, and the type of climate. The evolution of an ecosystem is crucially dependent on the need of its vegetation for light and water as external inputs that drive its productive mechanisms. These inputs are highly variable in time and space and their assimilation depends on the plant characteristics and the ecosystem structure. Thus, vegetation plays an active role in the space–time dynamics of soil water being both cause and effect of these dynamics. Similarly, plant structure and the canopy three-dimensional characteristics result from and at the same time control the use and impact of the radiative energy. Light and water exert key controls on the functioning of the leaf stomates and thus in the uptake and assimilation of carbon dioxide. Insolation and rainfall vary throughout the day and the seasons; moreover, and especially in the case of rainfall, the intermittent and unpredictable nature of the resource makes the study of its impact on ecosystem functioning an especially challenging field.

The hydrologic and ecologic mechanisms underlying the climate–soil–vegetation dynamics and thus controlling the most basic ecologic patterns and processes are one of the most exciting scientific frontiers at the start of the twenty-first century.