Forests may be more resilient to climate change than previously thought — new research finds that increased inputs from plant roots can keep carbon levels in soil stable, even as temperatures and nitrogen deposits in the atmosphere rise.
A collaborative research project conducted in the Harvard Forest in Massachusetts looked at the effects of increased temperatures due to climate change, and increased nitrogen in the atmosphere released by burning fossil fuels.
These two environmental threats have been studied separately, however this is the first experiment that allowed researchers to consider both of these factors simultaneously over time.
“There is a lot of uncertainty when these two antagonistic stressors are combined,” says Myrna Simpson, professor in the Department of Physical and Environmental Sciences at U of T Scarborough who collaborated on the research. “Which is why this study is so significant.”
Past warming studies done in the Harvard Forest suggested that increased temperatures caused forests to lose carbon, while increases in nitrogen can result in carbon buildup. Warming alone makes soil lose carbon because heat speeds up decomposition, and decomposition converts the carbon into CO2. But researchers found when rising temperatures were coupled with higher nitrogen levels, the plants added more carbon to soil by increasing their growth, activity and root turnover (the rate that their roots grow, die and decompose).
This study, led by researcher Melissa Knorr and Professor Serita Frey, both in the Department of Natural Resources and the Environment at the University of New Hampshire and published in Nature Ecology and Evolution, found that both the soil warming and nitrogen maintained soil carbon levels.
Simpson says the research “is unique because it includes both individual and combined treatments that represent combined impacts to temperate forests.” Simpson, who is the Tier 1 Canada Research Chair in Integrative Molecular Biogeochemistry and associate director of the Environmental NMR Centre, has been collaborating with Frey for many years on the effects of soil warming and nitrogen on the biogeochemistry of soil carbon in the Harvard Forest.
“Because of the advanced analytical capabilities in my laboratory and the Environmental NMR Centre at U of T Scarborough, we can uniquely decipher how multiple stressors alter the chemistry and potential long-term stability of soil organic matter at the molecular-level.”
Despite the research being conducted in Harvard Forest, Simpson says that soil warming has been shown to cause carbon loss worldwide. Excess nitrogen has also been found to suppress the microorganisms that keep forests healthy, even in forests that are rich in nutrients, notes Simpson.
“We found that the way in which carbon flows within the soil biogeochemical cycle cannot be predicted from one stressor alone,” says Simpson. “It is likely that these observations may occur in other forests too.”
When it comes to future climate change research, Simpson says that there is more work to be done.
“We need more observational data because climate change’s impacts on ecosystems are complex and difficult to predict due to the diversity of ecosystem properties,” she says. “These ecosystems are influenced by more than one stressor, but we lack data to adequately predict the impacts,” she says.
Simpson adds there is not a single solution to the issue of climate change, especially given that there is not yet a completely clear understanding of all of its impacts. For now, she says that collaboration between researchers is necessary.
“Each expert can contribute data that can then be integrated into a more comprehensive assessment of how ecosystems are responding to stressors,” she says.
Reprinted with permission from UTSC News. The original story is here.