Germination responses of northern red maple (Acer rubrum) populations

Abstract

Samaras of red maple (Acerrubrum L.) were collected at six locations at the northern edge of its distribution. Two populations from southern Quebec, in the deciduous forest, and four populations at its northern limit in the boreal forest were selected. Germination responses of these populations were evaluated in growth chambers and in the field. The effects of cold moist stratification, temperature (20/10°C, 10/1°C) and light intensity (750 μmol · m-2 · s-1, 160 μmol · m-2 · s-1) were evaluated in growth chambers. Seeds collected at the two most southern sites had 46% to 90% germination without stratification, while germination without stratification varied between 0% to 41% for the four most northern populations. In the six populations tested, the highest germination percentages were obtained at 10/1°C under low light conditions. Cold moist stratification enhanced germination of the four most northern populations. We observed in the field experiment that germination occurred during the summer months for sites located in the deciduous forest, while germination was delayed until the next spring for the sites located in the boreal forest. The percentages of seedling emergence in the field were similar under shade and nonshade conditions. Overall, our results indicate a marked degree of dormancy in the most northern populations. The heterogeneous germination response of northern red maple populations could be associated with the temperature regime at the collection site.