Transpiration in the water-limited regime: soil-plant-atmosphere interactions

Abstract

The use of vegetation to improve stability of natural and engineered slopes is an engineering Nature Based Solution. One effect of vegetation is to reinforce slopes ‘hydrologically’, i.e., by generatingsuction by the removal of soil water via transpiration. In turn, the depletion of soil water content reduces the hydraulic conductivity of the shallow layers of the soil, and this hinders rainwater infiltration during the wet period, possibly preserving suction in the deeper layers susceptible to failure. To improve upon thisstabilising technique, it is key to develop transpiration models that account for the hydraulic characteristics of the soil and plant (below- and above-ground). In this way, modelling can guide the choice of the plant functional traits. This paper first discusses the conceptual and experimental limitations of common empirical evapotranspiration reduction functions (e.g. Feddes function) and then revisits the physically-based ‘bottlenecks’ generating the decline in evapotranspiration in the water-limited regime within the framework of the Soil-Plant-Atmosphere Continuum.