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 relevé. 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.

我们对来自阿根廷中部山区的大理石露头及其附近的辉锰矿基质的植物和植被进行了比较研究。我们总共采样了50个位点，并根据Braun-Blanquet覆盖度量表记录了所有维管束植物的覆盖度。另外，收集岩石碎片用于化学分析（Ca 2 ⁺，Mg 2 ⁺，K和Na）。使用ISOPAM对三个植物群落进行了分类，其中一个发生在辉锰矿基质中，另外两个与钙^离子（Ca ^2+含量较高）和白云岩（Mg ^2+含量较高）相关。）大理石。大理石露头和附近的基质植被在植物种类和生命形态组成以及诊断种类上都不同。白云岩和钙质大理石之间的岩石露头在植物组成上也表现出差异。基质植被中的物种总数高于露头群落，但白云质露头显示每个相关物种的平均物种丰富度更高。我们发现，相对于周围的基质群落，大理石植被中的特有种比例较高，其中草本，草和亚灌木在大理石露头中占主导，而树木和灌木则在基质植被中占主导地位。在三个社区中，巴西南部和巴西quechian型的分类单元最为丰富。