Climate Change Does Not Contribute to the Migration of Sugar Maples

Climate is said to be a significant factor when it comes to establishing the growing zone of plant species. Toward the end of the next century, climate change is estimated to cause certain species to spread several dozens of kilometers north of their existing distribution regions, suggest several studies.

Changes like that can have a considerable impact on the function of land-based ecosystems.

But according to Alexis Carteron, who recently reported his doctoral research findings in the Journal of Ecology, a northern migration is not a viable solution for sugar maples. Carteron’s work was monitored by Professor Etienne Laliberté from the Université de Montréal and jointly supervised by Mark Vellend from the Université de Sherbrooke.

Before reaching this conclusion, Carteron and his collaborators from the Department of Biological Sciences of Université de Montréal as well as from the Institut de recherche en biologie végétale performed experiments in greenhouses located at the Jardin botanique de Montréal by making use of soil samples collected from Mont-Mégantic National Park.

The Importance of Soil Composition

Although climate and the increasing temperatures captured in recent years play a major role in the migration of trees, so does the composition of the soil. But not much is known about the impacts of soil as opposed to climate.

That was the reason why Carteron and his collaborators decided to analyze the effects of soil chemistry and microorganisms on the performance (that is, biomass and survival) of sugar maple (Acer saccharum) seedlings.

Initially, the scientists gathered soil samples from the eastern slope of Mont Saint-Joseph located in Mont-Mégantic National Park in June 2016. These soil samples were collected at different altitudes to reflect the two kinds of forest growing at the location.

Mont Saint-Joseph has a substantial variation in altitude with a temperate forest of mostly sugar maple trees growing next to a boreal forest populated with conifers. When you look at the mountain from a distance, it's easy to see where one forest starts and the other one ends.

Alexis Carteron, Department of Biological Sciences, University of Montreal

Different Soil Experiments

In the next step, maple seeds, also called samaras, were grown. These seeds were planted in greenhouses located at the Jardin botanique and were allowed to grow over the summers of 2016 and 2017 and interrupted only by a dormant phase in winter.

The scientists then used numerous inoculation and sterilization treatments on the soil samples to better figure out and distinguish between the impacts of abiotic (nutrients and acidity) and biotic (fungi and microorganisms) factors on growth and survival of sugar maples.

Lower Survival Rates and Biomass in Boreal Forests

By the end of summer 2017, Carteron and his collaborators assessed the young sugar maples and how well it had grown (based on biomass and survival rates) in different types of soil.

The researchers discovered that sugar maples grown in boreal forest soil showed considerably poorer performance when compared to the ones grown in the transition zone between boreal and temperate forests.

Similarly, sugar maple trees grown in inoculated boreal forest soil and boreal forest soil performed 44% and 37% worse, respectively, when compared to the trees grown in temperate forest soil.

Additionally, the researchers observed that the pH of boreal forest soil could have adversely affected the survival rates of the sugar maples. In the meantime, soil obtained from temperate forests, where sugar maples usually grow, enabled better colonization of arbuscular mycorrhizal fungi in the trees’ roots, which can support the growth and survival of the trees.

Due to the interaction of biotic and abiotic factors, boreal forest soil seems to offer a less hospitable environment for sugar maple trees than other soil types. While global warming might have made it physiologically possible for sugar maple trees to grow in more northern areas, the soil conditions in these areas make a northern migration less likely.

Alexis Carteron, Department of Biological Sciences, University of Montreal

But should not the composition of soil also change as the climate heats up?

It’s certainly possible that the soil's biotic and abiotic properties could change and allow for the sugar maple's growing zone to expand, but that type of change would take a very long time to occur.

Alexis Carteron, Department of Biological Sciences, University of Montreal

Carteron has received several research awards in recent years.

The study titled “Soil biotic and abiotic properties constrain the establishment of a dominant temperate tree into boreal forests” was written by Alexis Carteron et al. It was recently reported on January 13^th, 2020 in the Journal of Ecology.

The study was supported by the Université de Montréal, the Fonds de Recherche du Québec–Nature et Technologies, the Institut de recherche en biologie végétale de l'Université de Montréal, the Centre de la science de la biodiversité du Québec, and the Natural Sciences and Engineering Research Council of Canada.

Source: https://www.umontreal.ca/en/