From Phys.org
January 4, 2019 by Emily Pontecorvo, American Geophysical Union
Tropical forests store about a third of Earth’s carbon and about two-thirds of its above-ground biomass. Most climate change models predict that as the world warms, all of that biomass will decompose more quickly, which would send a lot more carbon dioxide into the atmosphere. But new research presented at the American Geophysical Union’s 2018 Fall Meeting contradicts that theory.
Stephanie Roe, an ecology Ph.D. student at the University of Virginia, measured the rate of decomposition in artificially warmed plots of forest in Puerto Rico. She found biomass in the warmed plots broke down more slowly than samples from a control site that wasn’t warmed.
Her results indicate that as the climate warms, forest litter could pile up on the ground, instead of breaking down into the soil. Less decomposition means less carbon dioxide released back into the atmosphere. But it also means less carbon taken up by the soil, where it’s needed to fuel microbial processes that help plants grow.
“These results could have significant implications on the carbon cycle in a warmer future,” Roe said.
Roe said there are few empirical studies of how tropical forests will respond to climate change. She set out to address this gap in June of 2017, when she and her research team travelled to El Yunque National Forest in Puerto Rico. They landed at a site called TRACE—the Tropical Responses to Altered Climate Experiment.
TRACE is the first-ever long-term warming experiment conducted in a tropical forest. It was established by the US Forest Service in 2016 for research like Roe’s. The site consists of three hexagonal plots of land enclosed by a ring of infrared heaters raised four meters above the ground, and three more plots enclosed by fake heaters that are used as the “control” forest.
Roe collected leaves from the plots, dried them out in the lab, and then returned them to the plots randomly. In addition to the native plants, she also included black and green tea, and popsicle sticks to represent woody biomass, to see how different materials would respond to the warming.
The heaters were programmed to continuously heat the plots to four degrees higher than the ambient temperature of the forest. The experiment was supposed to run for a full year, but at the beginning of October, Hurricane Maria swept across the island, destroying the TRACE sites.
Roe was back in Virginia when the storm struck. She had collected samples from the first few months of the experiment, and they were already showing signs of significant decomposition, so she decided to go ahead with the analysis based on what she had. And the results were not what she thought they would be.
“We would expect that microbes tend to work faster, like their metabolisms increase, with warmer temperatures,” Roe said. “So we would expect to see an increase of activity of microbes and other decomposers to decompose the litter.”
But instead of seeing faster rates of decomposition, Roe observed the warming produced a drying effect in the plots, which slowed decomposition. “What we found is actually it went the other way because moisture was impacted so much,” Roe said. Moisture in the litter from the treatment sites was reduced by an average of 38 percent.
Read more at: https://phys.org/news/2019-01-climate-unexpected-results.html#jCp
The microbes might not be working faster, but insect life might be doing more work with greater depth of cover. It sounds like a limited and disrupted experiment anyway–not exactly replicated.
The concept of confounding variables seems to have escaped this PhD level student. Would that be as a result of decades of drumming it into people’s minds that the world’s climate is allegedly a univariate system whose state is supposedly determined by a trace gas?
So many variables, so little time.
“Moisture in the litter from the treatment sites was reduced by an average of 38 percent.” Never occurred to them that increased heat may dry out things rather than increase decomposition and release of more CO2. These advocates are pre-conditioned to interpret any of their studies as replicating natural conditions of global warming. Even to the point that they are continually surprised when their assumptions don’t pan out. They are trying their best to force nature to abide by their rules. They never stop to think that their basic premise is wrong, hence all the wrong assumptions.
Why on Earth are the control areas surrounded by fake heaters? Does this fool the forest into thinking it’s a double blind study?
If you cut off a frog’s legs one at a time, it loses its hearing with each limb lost, as measured by how far it can jump. And when you cut off its last leg, it also loses its sense of touch. You can scream at it and poke it with a stick and it still won’t jump.
Once again we find that it is more difficult to get a passing grade on a middle school science fair project than it is to pass through the peer review process in the field of climate change. The scientific standards for 11-year-olds are far higher than for Phd students.
Then again, I haven’t judged a middle school science fair in about 15-20 years. Back then, teaching the scientific method was still the focus of the science fair. Today, it may be 50% on presentation, 50% on promoting social justice, and a 20% bonus for demonstrating high self-esteem!
“Roe collected leaves from the plots, dried them out in the lab, and then returned them to the plots randomly. In addition to the native plants, she also included black and green tea, and popsicle sticks to represent woody biomass, to see how different materials would respond to the warming.”
paraphrase … “Roe collected leaves, sterilized them somewhat in the lab, returned them to the plots, reduced the humidity of the plots relative to natural conditions, and was surprised that the leaves did not break down as fast as untouched (natural condition) forest debris.”
When my doorbell rings, my dog runs to the front door (even though the chime is in the hallway above the bathroom door). If Roe lived in a house like mine, it is likely that she would be repeatedly surprised when, answering at the bathroom door, and nobody was there.
The site consists of three hexagonal plots of land enclosed by a ring of infrared heaters raised four meters above the ground, and three more plots enclosed by fake heaters that are used as the “control” forest
Enclosed by fake heaters? Placebo?
This is in the UK where moisture is usually not a soil problem.
When I was a kid living in Ecuador, we visited Panamá for several weeks for a vacation. I was struck by how the closets all had incandescent bulbs inside – that stayed on all the time. It was explained to me that the heat helped reduce moisture, keeping thing drier so mold wouldn’t grow and things would not decompose which they otherwise would in the dark in the damp warm climate.
And I didn’t even get a grant or a PhD for that wisdom which I have retained to this day.
“The secret to mold control is moisture control” – Abraham Lincoln, via the internets