Effects of Cryptogamic Soil Crust on the Population Dynamics of Arabis fecunda (Brassicaceae)

At three sites in southwest Montana, Arab is fecunda (Brassicaceae) , a rare regional endemic, occurred more often than expected in cryptogamic soil crust than in bare soil.In two of four transects, small, young plants were underrepresented, and older, reproductive plants were overrepresented in crusts.In the other two transects, the distribution of life stage classes was independent of substrate.Measures of fecundity were independent of substrate in all four transects.These results demonstrate that the presence of soil crust is beneficial to populations of A^fecunda at some sites and suggest that this relationship is more likely due to increased survival of older plants rather than enhanced recruitment.