Eastern forests shaped more by Native Americans’ burning than climate change

By Jeff Mulhollem
Native Americans’ use of fire to manage vegetation in what is now the Eastern United States was more profound than previously believed, according to a Penn State researcher who determined that forest composition change in the region was caused more by land use than climate change.

“I believe Native Americans were excellent vegetation managers and we can learn a lot from them about how to best manage forests of the U.S.,” said Marc Abrams, professor of forest ecology and physiology in the College of Agricultural Sciences. “Native Americans knew that to regenerate plant species that they wanted for food, and to feed game animals they relied on, they needed to burn the forest understory regularly.”

Over the last 2,000 years at least, according to Abrams — who for three decades has been studying past and present qualities of eastern U.S. forests — frequent and widespread human-caused fire resulted in the predominance of fire-adapted tree species. And in the time since burning has been curtailed, forests are changing, with species such as oak, hickory and pine losing ground.

“The debate about whether forest composition has been largely determined by land use or climate continues, but a new study strongly suggests anthropogenic fire has been the major driver of forest change in the East,” said Abrams. “That is important to know because climate change is taking on an ever larger proportion of scientific endeavor.”

Source: Eastern forests shaped more by Native Americans’ burning than climate change – Penn State University, 2019-05-21

Researchers map symbiotic relationships between trees and microbes worldwide

by Taylor Kubota, Stanford University
In and around the tangled roots of the forest floor, fungi and bacteria grow with trees, exchanging nutrients for carbon in a vast, global marketplace. A new effort to map the most abundant of these symbiotic relationships—involving more than 1.1 million forest sites and 28,000 tree species—has revealed factors that determine where different types of symbionts will flourish. The work could help scientists understand how symbiotic partnerships structure the world’s forests and how they could be affected by a warming climate.

In and around the tangled roots of the forest floor, fungi and bacteria grow with trees, exchanging nutrients for carbon in a vast, global marketplace. A new effort to map the most abundant of these symbiotic relationships—involving more than 1.1 million forest sites and 28,000 tree species—has revealed factors that determine where different types of symbionts will flourish. The work could help scientists understand how symbiotic partnerships structure the world’s forests and how they could be affected by a warming climate.

Source: Researchers map symbiotic relationships between trees and microbes worldwide – Phys.org, 2019-05-15

Plants bounce light to forest floor


Recent research has shown that plants help themselves grow by releasing volatile organic compounds. These chemicals form a mist of aerosols above the vegetation that blocks some of the direct light but enhances diffuse light. This boosts the solar radiation reaching the forest understory and increases growth.

Alexandru Rap from the University of Leeds, UK, and colleagues assessed the impact of plant volatiles on primary productivity by using atmospheric and vegetation models along with measurements of aerosols and plant productivity. Their findings, published in Nature Geoscience, show that globally plant volatiles boost vegetation productivity by around 1.23 Pg of carbon per year — equivalent to around 10% of the world’s fossil fuel carbon emissions.

“Amazingly we found that by emitting volatile gases, forests are altering the Earth’s atmosphere in a way which benefits the forests themselves,” says Rap. “While emitting volatile gases costs a great deal of energy, we found that the forests get back more than twice as much benefit through the effect the increased diffuse light has on their photosynthesis.”

Source: Plants bounce light to forest floor – Physics World, 2019-04-01

Transparent wood can store and release heat

Wood may seem more at home in log cabins than modern architecture, but a specially treated type of timber could be tomorrow’s trendy building material. Today, scientists report a new kind of transparent wood that not only transmits light, but also absorbs and releases heat, potentially saving on energy costs. The material can bear heavy loads and is biodegradable, opening the door for its eventual use in eco-friendly homes and other buildings.

“Back in 2016, we showed that transparent wood has excellent thermal-insulating properties compared with glass, combined with high optical transmittance,” says Céline Montanari, a Ph.D. student who is presenting the research at the meeting. “In this work, we tried to reduce the building energy consumption even more by incorporating a material that can absorb, store and release heat.”

As economic development progresses worldwide, energy consumption has soared. Much of this energy is used to light, heat and cool homes, offices and other buildings. Glass windows can transmit light, helping to brighten and heat homes, but they don’t store energy for use when the sun goes down.

Three years ago, lead investigator Lars Berglund, Ph.D., and colleagues at KTH Royal Institute of Technology in Stockholm, Sweden, reported an optically transparent wood in the ACS journal Biomacromolecules. The researchers made the material by removing a light-absorbing component called lignin from the cell walls of balsa wood. To reduce light scattering, they incorporated acrylic into the porous wood scaffold. The team could see through the material, yet it was hazy enough to provide privacy if used as a major building material. The transparent wood also had favorable mechanical properties, enabling it to bear heavy loads.

Building on this work, Montanari and Berglund added a polymer called polyethylene glycol (PEG) to the de-lignified wood. “We chose PEG because of its ability to store heat, but also because of its high affinity for wood,” Montanari says. “In Stockholm, there’s a really old ship called Vasa, and the scientists used PEG to stabilize the wood. So we knew that PEG can go really deep into the wood cells.”

Known as a “phase-change material,” PEG is a solid that melts at a temperature of 80 F, storing energy in the process. The melting temperature can be adjusted by using different types of PEGs. “During a sunny day, the material will absorb heat before it reaches the indoor space, and the indoors will be cooler than outside,” Montanari explains. “And at night, the reverse occurs — the PEG becomes solid and releases heat indoors so that you can maintain a constant temperature in the house.”

Source: Transparent wood can store and release heat – ScienceDaily, 2019-04-03

Nitrogen-fixing red alder trees tap rock-derived nutrients

By Steven S. Perakis and Julie C. Pett-Ridge

Tree species that form symbioses with nitrogen-fixing bacteria can naturally fertilize forests by converting atmospheric nitrogen gas into plant-available forms. However, other mineral nutrients that plants require for growth are largely locked in bedrock, and are released only slowly into soil. We used strontium isotopes to trace nutrient sources for six common tree species in a temperate rainforest, including one species from a globally widespread genus known for high rates of biological nitrogen fixation. We found that trees capable of fixing atmospheric nitrogen gas were also best able to directly access mineral nutrients from bedrock. This gives nitrogen-fixing trees the unique ability to provide the full suite of essential nutrients required to fuel growth and carbon uptake in forest ecosystems.

Source: Nitrogen-fixing red alder trees tap rock-derived nutrients – PNAS, 2019-01-19

Is wood pellet-based electricity less carbon-intensive than coal-based electricity?

Is wood pellet-based electricity less carbon-intensive than coal-based electricity? It depends on perspectives, baselines, feedstocks, and forest management practices
P Dwivedi, M Khanna, and Madisen Fuller

Abstract
Some studies suggest that the carbon intensity of electricity generated in the United Kingdom by using imported wood pellets from the southern United States is higher than that of coal-based electricity, whereas other studies suggest that the use of wood pellet-based electricity reduces carbon emissions significantly, relative to coal-based electricity. We developed the Forest Bioenergy Carbon Accounting Model (ForBioCAM 1.0) to analyze factors that influence the carbon intensity of wood pellet-based electricity, using a common set of assumptions and the same system boundary. We show that widely differing assessments of the carbon intensity of wood pellet-based electricity depend on the choice of forest management perspectives (landscape or stand), baselines (no harvest, or harvesting for the manufacture of traditional finished wood products), feedstocks (whole trees, pulpwood, or logging residues), forest management practices (change in rotation age), and the duration of the analysis itself. Unlike with a stand perspective, we demonstrate conditions under which a landscape perspective results in carbon savings net of avoided emissions from coal-based electricity. Our results also suggest that the two perspectives of forest management converge in their assessment of the positive carbon effects of various feedstock types used to manufacture wood pellets relative to a no-harvest baseline, and that the use of whole trees for wood pellets results in net carbon savings after a break-even period of about three years relative to a no-harvest scenario. The results of this study can guide future policy deliberations on the use of wood pellets as a renewable energy source worldwide.

Source: Is wood pellet-based electricity less carbon-intensive than coal-based electricity? It depends on perspectives, baselines, feedstocks, and forest management practices – IOPscience, 2019-01-19