A nation that destroys its soils destroys itself." President Franklin D. Roosevelt
We walk on soils, but often give little thought to what’s right under our feet. In fact, soils are the nation’s – and the world’s – breadbasket, providing food and a host of other necessities, including new medicines and materials.
No soils, no life.
Soils form over hundreds of years but can be destroyedbya single event, such as a hurricane.They’re vulnerable to wind and water erosion; pollutants, including runoff from highways; and nutrient loss.
Despite a humble exterior, soilsare complex ecosystems composed of organic matter, minerals, water, air – and billions upon billions of organisms.These ecosystems orchestrate the processes essential for plant growth, as well asfood and fiber production.
The U.S. National Science Foundation isfundingresearchers who study soils and their importance in our lives."As the planet’s population grows, scientists need a better understanding of the soil ecosystems that play a critical role in supporting societies around the world,"says Enriqueta Barrera, a program director in NSF’s Division of Earth Sciences.
During Earth Science Week2020, with its theme"Earth materials in our lives,"NSFcelebratesthe soils beneath us.
Ordering in for dinner? Plantslong agoperfected the process.
Next time you’re thinking about whether to cook dinner or orderin, plantshave been way ahead of youfor eons.
NSF-funded scientists at Rice and Cornelluniversitiesdiscovered that plants "call"for nutrients, using soil bacteria as a delivery service.Plants read the local environment and, when necessary, make and release molecules called flavonoids. These molecules attract microbes that infect the plants and form nitrogen nodulesin the plants’ roots,generatingfood.
When nitrogen isalreadyavailable, plants don’t need to order in, saysRice biogeochemist CarolineMasiello.Their ability to sense the presence of a nearby, slow-release nitrogen source –such asorganic carbon – satisfies plants' "hunger,"andstillstheirflavonoid signals.
Understanding howsoilcarbonaffects these signals offersscientists new ways of engineering beneficial interactions between plants and microbes and designing additivestobalance deficiencies in soil.
Leaf'tattoo'monitorshealth ofgrapevines and apple trees
Farmers and fruit growershave foundthat climate change is leading to increased ozone concentrations on the soil surface in their fields and orchards. Thatozonecan cause irreversible plant damage, reduce cropyieldsand threaten the food supply.
Now, NSF-funded researchers led by Trisha Andrew at the University of Massachusetts Amherst have developed a way of placing "tattoos" on plant leaves. These polymer tattoos allow growers to detect and measure ozone damage, even at low levels. The tattoos also enable frequent and long-term monitoring of ozone damage to economically important crops such as grapes and apples.
Thescientistsselected grapes (Vitis vinifera L.) astheirmodel plant because the fruit yield and quality of grapevines decrease significantlywhen grapes are exposed toground-level ozone, leading to economic losses.
Ground-level ozone can be produced bytheinteraction between nitrates in fertilizer and the sun, for example, and is mitigated by early detection andsoil treatments.
Theresearchershope theirplant tattoowillbe used nationwide by farmers and fruit growers,whocouldplace a few "reporter plants"among crops to periodically monitor soil ozone levels.
Soil-plant communication: A two-way street
If soil is"communicating"with plants, so, too, are plants with soil.
Soilserves as the foundation formuchof Earth’s biodiversity.There organisms interact with each other and with plants, serving important functionsinecosystems.
Trees, for example, are important drivers of microbial communities in the soil beneath them. Scientist Stephen Hart of the University of California, Merced, and colleagues discovered that giant sequoias influence the microbiota of the soil where they grow.
"Most people look toward the sky when they approach California’s giant sequoias, in awe of the size of a single tree," says Hart. "A mature sequoia’s main trunk can weigh more than 130 Volkswagen Beetles. But I look down and ask questions about the hidden half that’s belowground: the soil."
Because of the trees’ long lives and height, Hart believedsequoiaswould have big impacts on the soil beneath them.He was right.
Histeamexamined soils in the Merced and Mariposa sequoia groves in Yosemite National Park and found that communities ofmicrobes under giant sequoia trees were twice asspecies-richasthosebeneathneighboring sugar pines.
The soil in each groveultimatelycomesfrom its geologic substrate:rocks and sediments below. That substrate contributesto the diversity and composition of the microbial communities beneath trees, Hart says.
"We now know a lot more about how organisms like bacteria influence human health, the so-called human microbiome. It’s likely that interactions among microorganisms are also critical for the health of other species, like the giant sequoia, the largest living thing on Earth."
Next time you visit a giant sequoia tree"look up,"Hart says,"andbe amazednot onlybyits size and presence aboveground, but look down at the soil and ponder how these magnificent trees are weaving an imprint on the unseen world below."
With NSF support,Hartis expandinghisresearchto other giant sequoia grovesina range of geologic substrates.
Earth’s'criticalzone': Where soil forms, allowing life to flourish
Earth’s critical zone—thelayerbetweenthe forest canopyandthe base of weathered bedrock– is crucialto the planet’s functions.Here, soil forms from the breakdown of rocks, allowing life to flourish.
To better understand and protect this narrow zone,NSF’sCritical Zone Collaborative Networkfunds grantees who are investigating key questions: How does urbanization affect critical zone processes; how do critical zones function in semi-arid landscapes, and what role does dust play in sustaining these ecosystems; how can the health of the critical zone be restored after disturbances such as wildfires and floods; and how is sea level rise changing the coastal critical zone?
"There’s still so much to be learned about the planet we call home," says Richard Yuretich, director of the Critical Zone Collaborative Network program. "Scientists are developing systems-level models to predict how the critical zone is responding to natural and human-altered processes. The research is important for future decisions about how humans and the environment should interact."
To find the best path forward, scientists say, we need to listen to – and heed – signals in the soils.
No soils, indeed no life.
