University of Birmingham researchers have uncovered key findings about mature English oak trees, which could shape future tree planting and care. These trees reshape their nutrient acquisition strategies under conditions of increased atmospheric carbon dioxide (CO₂). Scientists from the University of Birmingham collaborated with the Birmingham Institute of Forest Research (BIFoR) near the Forest of Dean. They set out to better understand how trees would cope with global climate change through an atmosphere that resembles one with more than a third more CO₂ than found today. This research provides an important look at what these developments could mean for climate policy and forest management.
The scientists tracked the circadian rhythms of 4 giant English oak trees, each about 180 years old. For this experiment specifically, they used Perspex-sided root boxes that were buried inside the forest. These open root boxes offered a clear look at the soil and root structures beneath the trees. For five years, researchers subjected the forest to elevated CO₂ levels. They wanted to reproduce the atmospheric conditions expected by the mid-21st century.
Enhancements in Root Systems and Nutrient Acquisition
The results indicated that oak trees grew exceptionally well with higher levels of CO₂. As a result, they saw an astounding 73% proliferation in their extensive fine root branching systems. This adaptation helps the trees tap into more soil over the course of the entire year. Consequently, they are better able to look for those critical nutrients.
Professor Sami Ullah, who led the research at the University of Birmingham, stresses the importance of these adaptations. He stated, “These mechanistic insights into how trees growing in future atmospheres acquire soil nutrients will have significant policy implications with direct relevance for climate mitigation initiatives such as the Paris Climate Agreement, the EU Green Deal, and the UK and EU net zero ambitions by 2050.”
As the oak trees changed their root systems to spread out and access more of the patchy soil, they increased their release of small organic molecules by 63%. This release typically occurs in early spring and early fall. It’s an important driver behind activating soil microbes, which release nutrients that would otherwise be trapped in the soil. These findings demonstrate that trees are able to adopt a “DIY approach” to obtaining nutrients. This capacity is essential to their continued expansion.
The Role of Soil Microbes and Symbiosis
In addition to improving rooting structures, the research revealed a 17% boost in beneficial symbiotic root-associated fungi in the fall. Trees are sensitive trees in a vital symbiotic relationship with fungi. This interactive process facilitates nutrient exchange and promotes healthy tree development. Dr. Michaela Reay, a researcher involved in the study, noted, “Roots do not simply take up nutrients and water from soils but rather exhibit smart and dynamic choreography, which involves highly specialized tradeoffs with soil microbes via varied nutrient exploration strategies throughout the year.”
The study’s results further highlight the increasing role forests must play as a carbon sink to continue offsetting the unavoidable CO₂ emissions we need to. Professor Ullah elaborated on this point: “There is growing importance of forests to act as carbon sinks to contribute to offset essential CO2 emissions. Forest growth not only relies on CO2 but requires an ample supply of soil nutrients to keep capturing and sequestering atmospheric CO₂.”
Implications for Climate Change Mitigation
Their research suggests that mature temperate forests could be critical in the fight against climate change. Professor Iain Hartley from Exeter University remarked on the implications of these findings: “Trees in this forest increasing their growth under elevated CO2 was slightly unexpected, and suggests mature temperate forests could play a key role in the fight against climate change. Understanding oak trees’ adaptation It is important to study how oak trees are adapting. We’ve got to figure out whether their tactics will continue leading to improved access to soil nutrients.
As climate conditions shift further, it’s vital to understand how trees will be forced to adapt their growth strategies. This new research advances our understanding of just how resilient our forests will be to these changing atmospheric conditions in the future. Finally, it illustrates the deep interconnectedness between tree and soil systems.