How Mangroves Salinize the Soil How Mangroves Salinize the Soil

A transient one-dimensional model of the vertical movement of water and salt in the mangrove root zone is investigated. This is an extension of a previous steady state model which assumed that the ability of the mangrove roots to take up water is uniformly distributed throughout the soil and that the root water uptake is reduced if there is nonzero salt concentration around the roots. We show how both the time dependent and steady state salinity prooles in the soil depend on the strength of the root water uptake, the depth of the root zone and the porosity of the soil. The withdrawal of fresh water by the mangrove roots leads to salinization of the soil in the root zone, and signiicant reduction of the transpiration of the mangroves. When a steady state is reached, the salt that is excluded by the mangrove roots must diiuse back to the surface against the ow of soil water towards the roots. For a root zone of nite depth, a nite diierence numerical scheme is used to investigate the rate of salinization of the root zone, and the diiusion of salt into the region below the root zone. Note: Work partially carried out under project MAS 1.3 "Partial Diierential Equations in Porous Media Research".