Interspecific Differences in Seed Germination, Establishment, and Early Growth in Relation to Preferred Soil Type in an Alpine Community

Abstract

ABSTRACTSpecies distributions may be limited by substrate boundaries due to constraints at either the germination or seedling establishment life history stages. In a community of alpine tundra plants from the Sierra Nevada, some species are widespread, occurring across all four substrates studied: diorite, granite, hornfels, and marble. Other species are restricted to fewer soil types. We collected seeds from 12 species and performed a reciprocal transplant experiment in growth chambers using native soils. Eleven species germinated and established equally well across all soil types, indicating substrate chemistry did not alone determine species field distributions. However, two patterns emerged that may contribute to our understanding of species composition and dominance across substrates. First, species more dominant on the drier substrates reached at least half their total germination within two weeks of planting. Species more dominant on the wetter substrates required a longer period in wet soil to germinate. Second, there is a strong correlation between species relative abundance and percent germination, indicating that high percent germination may contribute to some species’ dominance. To determine the influence of soil type on plant size, a subset of species were grown for more time. All species were larger on hornfels and marble than on granite and diorite, indicating that species have the highest growth on the most nutrient-rich soils, rather than on their native soils. Taken together, these data suggest that water may be the limiting factor for species germination, and the differential nutrient availability across soil types has a strong influence on early seedling growth.