Calcium and pH preferences and establishment responses of a common biocrust moss from Brazilian rocky outcrops

Brazilian rocky outcrops are home to prominent biological soil crusts (biocrusts), with mosses standing out due to their specific adaptations, such as desiccation tolerance and the ability to regulate toxic element concentrations. These outcrops-quartzite, ironstone (Cangas), and limestone-represent a gradient of calcium and pH levels in the soil: quartzite < ironstone < limestone. This study explores the calcium and pH preferences of Bryum atenense R.S. Williams (Bryaceae), a common moss in biocrusts from Brazilian outcrops, to assess potential ecotypic variation in response to these edaphic conditions. Our findings show that higher calcium concentrations (≥156.35 mmol/L) and elevated pH levels (≥ 7.0) can reduce or inhibit establishment and asexual reproduction in B. atenense plants collected from the ironstone outcrop. We further hypothesize that B. atenense populations from distinct outcrop types may exhibit varying levels of calcium adaptability. These insights contribute to understanding how calcium influences bryophyte ecology and their adaptability to different rocky outcrop ecosystems in Brazil.