Salinization refers to a build up of salts in soil, eventually to toxic levels for plants. (3,000 - 6,000 ppm salt results in trouble for most cultivated plants.) Salt in soils decreases the osmotic potential of the soil so that plants can't take up water from it.
Because of different processes we get more and more salt in our environment. Water disturbences on the coast like higher sealevels, Not enough rain in the summer and a lot of other processes higher up the concentrations of salt. Some plants grow well in these sercumstances. Salt used on the highway's in winter gives a special vegetation along the roads.