Vascular flora and geoecology of Mont de la Table, Gaspésie, Québec

The influence of substrate lithology on the distribution of many vascular and nonvascular plants has long been recognized, especially in alpine, subalpine, and other rocky habitats. In particular, plants have been classified as dependent on high-calcium substrates (i.e., calcicoles) based on common restriction to habitats developed in calcareous rocks, such as limestone and marble. In a classic 1907 paper on the influence of substrate on plants, M. L. Fernald singled out a particular meadow on Mont de la Table in the Chic-Choc Mountains of Québec for its unusual co-occurrence of strict calcicole and calcifuge (i.e., acidophile) plant taxa. We re-located this site, investigated substrate factors responsible for its unusual plant diversity, and documented current plant distributions. No calcareous rocks were found on site. However, inclusions of calcareous rocks were found farther up the mountain. The highest pH and dissolved calcium concentrations in surface waters were found in a series of springs that deliver groundwater, presumably influenced by calcareous rocks up the slope. Within the habitat delineated by common occurrences of calcicole species, available soil calcium varied by a factor of five and soil pH varied by almost 1.5 units, depending on microtopography and relative connection with groundwater. Variation in hydrologic delivery of weathering products leads to large variation in chemical composition of soils and waters within calcareous-influenced habitats. Here, the fine-scale variability of habitat, rather than plasticity in the plants' tolerances, appeared to be responsible for co-occurrence of taxa considered to be strict calcicoles or calcifuges. The flora in 2005–2008 was very similar to what it was in 1906, although in-filling of woody vegetation and strong chemical gradients driven by climatically controlled hydrologic processes suggest the possibility of future vegetation changes with continued climate change.