Challenges in humid land ecohydrology: Interactions of water table and unsaturated zone with climate, soil, and vegetation

Soil water content is a key determinant of the health of terrestrial ecosystems. It plays a fundamental role in the feedbacks between the Earth and the atmosphere, as well as in all aspects of vegetation growth and composition. The dynamics of soil water in humid areas, and especially in wetlands, presents particularly challenging features for its quantitative description, since it needs to be linked to the intertwined stochastic fluctuations of the water table and the soil moisture of the unsaturated zone. These fluctuations are themselves dependent on the climate, soil, and vegetation of the region. The paper describes some of the most important problems that need to be considered in attempting to develop a quantitative framework for the ecohydrology of humid areas. The avenues of research suggested here will play a keystone role in the understanding of the complex dynamics of humid lands as well as in their scientifically based management in the face of a changing climate.