ABSTRACT
Modeling ............................................................................................... 311 14.4 Estimating Evapotranspiration as an Indirect Valuation for Soil
Moisture Stress on Vegetation ................................................................. 312 14.5 Final Remarks/Conclusions ..................................................................... 317 Acknowledgments .............................................................................................. 319 References ............................................................................................................. 319
Surface soil moisture monitoring plays an important role not only for quantifying water content variability and calibrating/validating hydrological models but also in determining limit states for ecosystems and providing information to value different ecosystem services. The soil moisture regime is the result of the energy and water budgets, coupled with evaporative fluxes from both soil and vegetation. Moisture gradients determine the direction and intensity of water fluxes through the soil (e.g., Brutsaert 1982, 2005; Jury and Horton 2004) and, among others, on the medium-and long-term distribution of vegetation, dominant species, and rooting depth. The latter affects the local regime of wetness through the transpiration process, the shadowing of the soil surface, soil structure and composition modifications, the increase in the surface effective roughness, and a long list of aspects involved in the different terms of the energy and water balance. Nutrient, and also pollutant, adsorption/desorption and movement through the soil are also greatly influenced by soil moisture and vegetation (Sposito 1989), for both advective and diffusive transport conditions (Jury and Horton 2004). Thus, not only provisioning services, such as water-nutrient-pollutant availability for plants and animals, are influenced by the changes in soil moisture, but also regulatory and maintenance services are affected (runoff generation by rainfall, flood risk, soil maintenance, surface and groundwater quality, etc.). Cultural services of ecosystems are also involved, provided the impact of vegetation and wetlands on landscape, and their effects in man’s physical and intellectual activities in relation to ecosystems.
