Effects of experimental removal of coexisting sugar maple and trout lily on the overall plant growth and survival Ontario, Canada

The ecotone between deciduous and boreal forests, such as in Lake Superior Provincial Park, Ontario, Canada provides an excellent site for an early assessment of species' ability to migrate and adapt to climate change. Vegetation dynamics models suggest expansion of hardwood deciduous species northward into the current boreal forest, but fail to account for understory species. Since all species coexist and are interconnected through the web of relationships with one another, it is important to consider species coexistence and interactions among co-occurring species in all plants distribution and dynamics studies; as well as, in conservation and ecosystem management practices. This project evaluated the ecological significance of nutrient transfer between coexisting sugar maple seedlings (< 30 cm) and the spring ephemeral trout lily, mediated through arbuscular mycorrhizal (AM) fungi. Specifically, assessed were the effects of experimental removal of one of the two coexisting species, Acer saccharum and Erythronium americanum, from their natural habitats on plant growth, survival and carbon assimilation. Randomly selected plots within the deciduous forest portion of Lake Superior Provincial Park were divided into three sub-plots (control, sugar maple removed and trout lily removed). In order to assess the growth of individuals of each species, leaf area, leaf-level carbon gain, plant height, and mortality rates among both species were measured throughout two growing seasons (2010 and 2011) and were compared to determine any effects of experimental manipulation.;The results of the experiment indicate that removal of co-occurring A. saccharum seedlings or E. americanum has no effect on the growth, abundance, and carbon assimilation of these species. This suggests that removing one of the species from the plant-plant association mediated by AM fungi is not physiologically or ecologically significant or that the amount of transferred carbon is not sufficient to exhibit significant effects on species' physiological functions. Instead, this study being the first evaluating the specific transfer of C between E. americanum and A. saccharum, pointed out several issues that should be considered in the future experiments. The lack of convincing data underlines the need for further experimental manipulations with longer study periods, improved methodology, and experimental design and inclusion of additional variables that would help to better measure and assess plant survival, growth and reproductive success.