Plants are far more adventurous underground than scientists once believed. A new study reports that many species extend a second, hidden network of roots more than a meter below the surface.
This discovery could ultimately reshape how researchers model nutrient cycling, water use, and the planet’s carbon budget.
Mingzhen Lu, an assistant professor in New York University’s Department of Environmental Studies, led this multi-institutional project.
“Understanding where plants grow roots is vital, as deeper roots could mean safer and longer-term carbon storage,” she said. “Harsher conditions at depth may prevent detritus-feeding microbes from releasing carbon back to the atmosphere.”
The findings suggest that plant roots may already be storing climate-warming carbon well below areas tracked by most ecological surveys.
Data goes deeper
Traditional root research stops at roughly 30 centimeters, the depth that shovels and corers reach most easily.
Lu and her colleagues pushed past that limit by tapping into the National Ecological Observatory Network (NEON), which collects samples down to two meters at dozens of U.S. sites.
From Alaskan tundra to Puerto Rican rainforest, the database provided thousands of soil cores reaching 6.5 feet – deep enough to chart root presence in realms seldom studied.
With those records in hand, the team set out to answer three intertwined questions: How does root density shift as soil gets deeper? Which environmental factors govern that distribution? And are subterranean nutrients being tapped as thoroughly as surface nutrients?
Roots defy expectations
The most eye-opening pattern was “bimodality.” Nearly one-fifth of the ecosystems examined showed two separate peaks in root abundance with depth: one in familiar shallow layers and another much farther down, often aligning with deposits of nitrogen, phosphorus, or moisture.
In other words, plants were quietly plumbing secondary resource pockets, countering the long-held assumption that root activity simply dwindles the deeper one goes.
“The current understanding of roots is literally too shallow. Aboveground, we have eagle vision – thanks to satellites and remote sensing. But belowground, we have mole vision,” Lu said.
That “mole vision,” she argues, has left major gaps in Earth system models that guide climate policy and land-management decisions.
Carbon storage – or carbon release?
The presence of deep roots raises a crucial follow-up: What happens to the carbon that plants ferry into those depths? Avni Malhotra, a co-author and lead investigator on a companion paper, notes that outcomes could diverge.
“Deep plant roots may cause increased soil carbon storage in one condition or lead to losses in other conditions due to a stimulation of soil microbes,” she said.
Cool, compacted subsoil tends to slow microbial digestion, potentially locking carbon away for centuries.
Yet in some settings, added root exudates might energize buried microbes, accelerating decomposition. Deciding which scenario dominates will require the kind of stratified sampling that NEON has only begun to provide.
Deep roots defy models
Global climate models often assume that most biologically relevant actions – plant root growth, microbial decay, nutrient turnover – occur in the topsoil.
Lu’s study indicates that a significant share of plant activity, including carbon allocation, happens far below that zone.
If roots can chase nutrients downward during droughts or warming events, they may confer more resilience than current simulations capture. Conversely, land-use changes that compact or strip deep horizons could hamper an unseen but vital layer of carbon storage.
Putting root data to work
These subterranean discoveries matter for forestry, agriculture, and conservation. Crop breeders might select varieties with deeper, bimodal rooting patterns to better capture water in arid regions.
Restoration ecologists could prioritize species that drive carbon into stable subsoil pools.
Policymakers aiming to offset emissions through reforestation or soil-carbon credits will need estimates grounded in full-profile measurements rather than the customary shallow cores.
Plant roots store climate secrets
“Scientists and policymakers need to look deeper beneath the Earth’s surface as these overlooked deep soil layers may hold critical keys for understanding and managing ecosystems in a rapidly changing climate,” Lu said. The team envisions denser networks of deep cores, advanced imaging, and sensor arrays able to watch roots grow in real time.
While many unknowns remain – How universal is bimodality? Which soil chemistries foster it? How stable is deep-buried carbon? – the message is cautiously optimistic.
“The good news is plants may already be naturally mitigating climate change more actively than we’ve realized – we just need to dig deeper to fully understand their potential,” Lu concluded.
By illuminating a hidden architecture beneath our feet, the study invites scientists and citizens alike to rethink what lies between the surface and bedrock – and to recognize that the battle against rising CO2 might have powerful, unseen allies in the dark below.
The study is published in the journal Nature Communications.
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English (US) ·