Vegetation and flora of marble outcrops and their nearby matrices in mountains of central Argentina. Rock chemistry also matters

We present a comparative study of the flora and vegetation of marble outcrops and their nearby migmatite matrix from mountains in central Argentina. In all, we sampled 50 sites and recorded the cover-abundance of all vascular plants present according to the Braun-Blanquet cover-abundance scale. In addition, rock fragments were collected for chemical analysis (Ca2+ , Mg2+ , K and Na). Three plant communities were classified using ISOPAM, one occurring in the migmatite matrix and two others associated with calcic (richer in Ca2+) and dolomitic (richer in Mg2+) marble, respectively. The marble outcrops and nearby matrix vegetation differed in plant species and life form composition, as well as in diagnostic species. Rocky outcrops also exhibited differences in floristic composition between dolomitic and calcic marble. The overall number of species in the matrix vegetation was higher than in the outcrop communities, but dolomitic outcrops revealed a higher average species richness per releve. We found a higher proportion of endemics in the marble vegetation with respect to the surrounding matrix communities, with herbs, grasses and subshrubs dominating in the marble outcrops, while trees and shrubs dominated the matrix vegetation. Taxa of the Southern-Brazilian and Chaquenian chorotypes were the most abundant in the three communities. Our results suggest that the marble outcrops harbor a flora including several highly restricted endemics, which is clearly distinct from that of the surrounding habitats, indicating that outcrop diversity should be taken into account in conservation policies.

Automated summary

A comparative study of flora and vegetation from marble outcrops and their nearby migmatite matrix in central Argentina revealed differences in plant species, life form composition, and diagnostic species. Marble outcrops have a higher proportion of endemic species, dominated by herbs, grasses, and subshrubs, while the matrix vegetation is dominated by trees and shrubs. The results suggest that outcrop diversity should be considered in conservation policies.