A team of researchers led by the University of Sheffield and the Smithsonian Tropical Research Institute have found that legume trees play a key role in unlocking vital minerals in ancient tropical soils.
These nitrogen-fixing trees can enhance mineral weathering in their surrounding soils, increasing their own access to important growth supporting minerals. These benefits are also passed on to nearby plants, showing that leguminous trees play an important role for forest health and recovery.
Ancient tropical soils are often highly weathered and nutrient-poor, making it a challenge for trees to take up vital minerals needed for growth, such as phosphorus and molybdenum. These minerals are often locked up in inaccessible forms such as in insoluble iron and aluminium minerals.
However, the researchers have found leguminous trees to be capable of changing their soil microbiomes though acidifying the surrounding soil and altering the ratio of carbon to nitrogen within it. This has the effect of improving plant access to minerals and supporting an iron-breaking type of bacteria, which breaks down iron-bound minerals to make them available for plant uptake.
Dr Dimitar Epihov said: “Our research shows that legume trees not only provide valuable nitrogen through their symbioses with bacteria that live in their roots, but interact with free-living soil bacteria allowing nutrients to be chemically released.”
Overall, these trees effectively speed up the mineral weathering process to support not only their own growth, but also the continued growth of other trees in their vicinity. This is vital as it demonstrates the significance of legume trees for safeguarding tropical forest function within the biosphere.
The results of this study will be important for informing policy makers on how best to approach tropical reforestation, especially on degraded land, to ensure the most success and help meet climate change mitigation targets.
Professor David Beerling said that the findings of this study have “addressed a long standing puzzle of how fast growing trees access sufficient nutrients to support their growth from nutrient poor soils.”
