For many of us, winter in the Northeast means cold temperatures and piles of snow, drifting through forests and across fields. It’s hard to imagine that winter here could be different, but the prospect of climate change has scientists asking just what our winters might look like in the future – and how those changes might influence forest ecology.
At the U.S. Forest Service’s Hubbard Brook Experimental Forest in the White Mountains of New Hampshire, scientists are thinking about the year 2100. How much warming will occur isn’t certain, but some projections suggest that average air temperatures in our region may increase 5.5 to 9 degrees over the course of this century. The effects are likely to be complex and are difficult to predict, with benefits and costs for different organisms. Some tree species, for example, may benefit from longer and warmer growing seasons, but they may also sustain root damage from more frequent soil freezing.
It may seem counter-intuitive that soils would freeze more often during warm winters. The reason is a projected lack of snow. The blanket of snow that usually accumulates during winter insulates the soil below, preventing it from experiencing the full, sub-freezing temperatures of the air. When warmer temperatures leave a thinner blanket of snow, or none at all, the soil is more likely to freeze when cold-snaps strike.
To tease apart the opposing effects of a warmer growing season and more soil freezing in winter, Hubbard Brook researchers have started the “Climate Change Across Seasons Experiment” (CCASE), to investigate cross-season effects on maple trees. Geoff Wilson, a research technician at Hubbard Brook, explained that there is a long history behind this project.
Since 1955, the U.S. Forest Service has maintained a long-term watershed monitoring project, taking daily or weekly measurements of environmental and meteorological conditions such as temperature, precipitation, snowpack, streamflow, and biogeochemistry. These data supported pioneering work on acid rain research, and also revealed, in the 1990s, another surprising change. There was something weird in the watershed records: unexplained spikes of high nutrient runoff in some years. Because they occurred after winters with less snow, researchers suspected the nutrient spikes were linked to the weather.
To investigate this phenomenon, in 1999, a research team led by Peter Groffman of the Cary Institute of Ecosystem Studies conducted a series of soil freezing experiments at Hubbard Brook. The researchers used shoveling to mimic reduced snowpack on 10 x 10 meter plots of mixed tree species at different elevations. This was not easy work – imagine drawing the short straw and trudging out to the study plots after every snowfall – but it yielded some clear consequences of soil freezing.
The shoveled plots that experienced soil freezing had higher levels of nutrients in the soil water collected from them – corresponding with the elevated nutrient runoff that researchers had first noticed following warm winters. These plots also exhibited more root damage than control plots that were insulated with snow. The team found that the trees most affected were sugar maples.
Like all good science, these studies led to yet more questions, which is why Hubbard Brook started the CCASE project.
This project, led by Dr. Pamela Templer of Boston University, tracks six 11 x 14-meter plots dominated by red maple. To prepare, in 2012, Templer’s team buried 2.5 miles of electrical cable to warm the soil. “The electricity bill must be substantial!” Wilson commented.
In some plots, the soil is warmed an additional nine degrees during the April – November growing season, and an insulating blanket of snow is left for the winter. In other plots, the soil is warmed for the growing season, but the snow is shoveled off for the first several weeks of winter to let the soil freeze.
The CCASE experimenters measure nutrient and water uptake by trees, root growth and death, and competition for nutrients between plants and microbes. They also investigate the effect on soil arthropods, as Templer and her students have seen soil arthropod diversity drop after soil freezing events.
This is a multi-year study that’s still in progress, but Wilson shared some early observations. They’re seeing that the extra warming in summer plots does increase tree growth. Unfortunately, even if trees benefit from more growth in the summer, this benefit may be limited since the trees also experience root damage due to soil freezing in the winter. Studies like this one are early steps in exploring how climate change may impact forests, but there are still many questions to be answered.
Rachel Sargent is an editor for a pharmacology journal, as well as a freelance nature writer and illustrator. The illustration for this column was drawn by Adelaide Tyrol. The Outside Story is assigned and edited by Northern Woodlands magazine, and sponsored by the Wellborn Ecology Fund of New Hampshire Charitable Foundation.
But our Ostrich-in-Chief says it isn’t so.
Just marginalize the naysayers and do what we can without them. Each of us makes choices every day that can add or detract from the problem. All we can do is try to make as many right decisions as possible.
Your words are a comfort to me this morning, Boreas. Thank you.
“All we can do is try to make as many right decisions as possible.”
Yes Boreas but we are limited. Those who have the power to make changes for the better are the very ones who are going against change for the better. I like your optimism though…we need more of that.
I guess what I am saying is that politicians make a few big decisions occasionally, whereas as individuals we make many decisions daily that can affect the environment. There are seven billion individuals and counting on this earth that have more power than some retrograde decisions by politicians whose pockets are being lined by Big Energy and Big Corporations.
Many of us are now connected via the internet throughout the world and have the ability to make politicians and corporations accountable despite Citizen’s United and other intrusions by corporations into government. It certainly isn’t easy, but if the Tea Party can make a big noise, so can people who want to help preserve and perhaps even improve our environment.
Once again Boreas…I like your optimism!
This is impressive research done by USFS. Large-scale field studies are time consuming and tedious, but provide critical real life data. With a $787 million proposed reduction in the Forest Service budget, let’s hope this project is not cut short.
One limitation (through no fault of the researchers) is the consideration of warming soil under present conditions. Climate change will likely affect many other factors besides temperature, such as increased drought or more frequent heat waves. Both of these events will stress forests making them even more susceptible to root damage from lack of snow insulation. When we observe a combination of events, the impact will likely become exponential and drive systems to a tipping point that much faster.
I agree Jesse. Temperature is only ONE consideration. Water supply is another. How will this effect rains? We argue a lot about global warming but we cannot really predict weather much beyond 2-3 days. In many areas of the ADK’s, it is even less. Atmospheric make up is being effected now. How will it change in the future and what will the impact be, to temperature, to plants and animals, to climates, and to large scale ecosystems? There is no history of this event we can point to and say this will happen. As a scientist, I am amazed that, with our lack of knowledge about the very planet we live on is so limited, let alone what we do no is a politicized topic, we have made some progress in this area. This study is a good one and typically focuses on a commercial crop. The figures released to date about temperature increases are mostly best case, incorrectly calculated (in my opinion) from what data we do have.
I wouldn’t call it optimism as much as a plan of attack. As long as Big Energy and Big Chemical are running our government via Citizens United, they control the dialog and direction of politicians. Corporations can only influence government – they can’t vote. Only citizens can vote. Until everyone votes and we vote for representatives willing to overturn Citizens United by intelligent justice appointments, it will be an uphill battle.
But in the meantime, make every seemingly small decision count! We all can help leave a smaller carbon footprint on an individual basis. Nothing new here!