Bedrock composition of the Goat Hill serpentine barrens and a proposed serpentine factor for predicting floral response

The Goat Hill Serpentine Barrens tract, largely underlain by serpentinite, hosts many rare plants that thrive only on serpentinite. Because of the sequence of minerals that crystallized from the Baltimore Mafic Complex when it was still on the ocean floor, later metamorphic events after it had been obducted onto the Laurentian continental margin, and variable leaching by recent meteoric water, bedrock in the tract has a widely variable composition. Traditionally, the bedrock components MgO and Ni are believed to be positive factors for serpentine-endemic flora, and CaO and the nutrients K₂O and P₂O₅ are believed to be negative. These variables have been combined into a quantitative serpentinite factor (SF): (MgO + 50 Ni) / (10 K₂O + 10 P₂O₅ + CaO). Using analyses of 35 bedrock composite samples, a plot has been generated to enable botanists to compare the distribution of flora of special concern and for others to use as one tool among many in managing the Goat Hill Serpentine Barrens in order to protect serpentine endemics and selected microenvironments and, by extension, other areas underlain by serpentinite bedrock.