Some Lichens are veery salt tolerant- you see the best examples on coastal rocks. Other Lichens such as the Tree Lichen on thev otherhand are not Salt tolerant.Lichens have certain genes that have evolved to allow this to occur but the studies so far have proven elusive in identifying the major genes and their products involved in this.
We do not know as yet. There must be a physiological basics of the salt tolerance, so that is what we need to explore. We can look at other plants to have an idea but we will not know what makes Danish scurvygrass salt-tolerant until we design experiments and start to study it further.