Forests in New England may store more carbon than previously estimated

Forests in New England may store more carbon than previously estimated
by Clarence Oxford
Los Angeles CA (SPX) Sep 26, 2024

New England's forests are grappling with the dual impacts of rising temperatures due to climate change and increased nitrogen deposits from fossil fuel emissions. Until now, these effects have often been studied separately, but researchers at the University of New Hampshire (UNH) have taken a closer look at how these two factors interact. Their findings reveal that carbon storage in the soil remains stable, thanks to increased carbon inputs from plant roots below the surface, challenging previous predictions. This new research suggests that the soil carbon loss from climate change in Northeastern forests may be lower than earlier studies indicated.

"What is most exciting about this study is that it's one of the longest-running experiments to look at two global change pressures instead of just focusing on one," said Melissa Knorr, a lab research supervisor in UNH's College of Life Sciences and Agriculture. "This is particularly important to study in the Northeast, where the region has experienced greater nitrogen deposition historically, and now faster warming than in other parts of the country."

The research, published in 'Nature Ecology and Evolution', was led by Knorr and Serita Frey, a professor in the UNH department of natural resources and the environment. They used data from a 16-year study at the Harvard Forest Long-Term Ecological Research site in Massachusetts. The researchers exposed soil to continuous warming of 5 C and nitrogen fertilization of five grams per square meter annually. Previous research at the site showed that soil warming leads to significant carbon loss, while nitrogen enrichment results in carbon accumulation.

"Plants, particularly through root turnover - the natural process where plant roots grow, die, and decompose - and increased plant growth and activity, add new carbon to the soil," explained Frey, who is also a scientist with the New Hampshire Agricultural Experiment Station. "And while microbial activity breaks down organic matter, releasing CO2, we observed that enhanced plant carbon inputs belowground - caused by warmer temperatures and increased nitrogen - help maintain soil carbon levels, counteracting what would otherwise have been a significant net loss of carbon from the soil."

In the past century, the average temperature in New England has risen by 1.7 F. While nitrogen deposition rates are declining, they are still five to six times higher than pre-industrial levels. Excess nitrogen, which enters ecosystems through rain and snow, can harm forests by affecting plant health and acidifying water bodies.

The study emphasizes the critical role of plant-soil interactions in forest ecosystems and how these processes could be vital in managing forests to ensure they continue to absorb CO2, thereby helping mitigate climate change.

"By challenging previous predictions from studies that looked at only one factor alone, this research offers a fuller picture of how ecosystems respond to multiple stressors and forests' role in combating climate change," Knorr said. "The study offers insights that could inform conservation strategies to enhance carbon sequestration and preserve forest health across the Northeast."

The research team also included Alexandra Contosta, Eric Morrison, and Thomas Muratore from UNH; Mark Anthony from the University of Vienna; Kevin Geyer from Allegheny College; and Luliana Stoica and Myrna Simpson from the University of Toronto Scarborough.

Research Report:Unexpected sustained soil carbon flux in response to simultaneous warming and nitrogen enrichment compared with single factors alone