With the help of satellites, NASA has studied Earth's place in the solar system, learning about everything from stars to comets. Satellites also reveal secrets about Earth itself, from the clouds to the ocean depths. Now, satellites are going closer still, uncovering underground forest fungi and what they can tell us about the health of the forests.
A NASA-led team of researchers has created a method for detecting the presence of different types of woodland fungi from space. The information may help predict how climate change impacts forest habitats.
There's a miles-long network of mycorrhizal fungi that live in a "mutually beneficial relationship" with the surrounding trees, according to NASA. It's a barter system of sorts: The fungi find nutrients, and they trade those nutrients with trees for the sugars the trees make during photosynthesis.
There are two types of mycorrhizal fungi associated with nearly all tree species, according to Richard Phillips of Indiana University, Bloomington, coauthor of the new study, which was published in the journal Global Change Biology.
Each type of fungi is expected to respond in a different way to climate change, so knowing where the fungi are located now may help scientists predict where forests will thrive in the future — and where they won't.
The first step is creating maps of forests and their fungi. In the past, when researchers have done this, they had to count individual tree species, a method that can't be implemented on a large scale. For this new study, researchers detected the fungus network using satellite imagery.
Each tree species has what's called a "spectral signature." That means it reflects or absorbs light in a certain pattern across all wavelengths in the light spectrum. The team — led by Joshua Fisher of NASA's Jet Propulsion Laboratory — used satellite images of forest canopies to identify patterns in the spectral signatures of trees linked with one type of mycorrhizal fungus but not associated with another.
"Individual tree species have unique spectral fingerprints, but we thought the underlying fungi could be controlling them as groups,” Fisher said.
The researchers analyzed images of four forests, including 130,000 trees across 77 species, and all taken by NASA/U.S. Geological Survey Landsat-5 satellite from 2008 to 2011. They were able to predict the fungus association — based on changes in the tree canopies — correctly in 77 percent of the images. They uncovered "intriguing patterns in forests" that they will continue to study.
"That these below-ground agents manifest themselves in changes in the forest canopies is significant," said Fisher. "This allows, for the first time, some light to be shed on their hidden processes."