“In acidic forest soils, availability of inorganic nutrients is a tree-growth-limiting factor. A hypothesis to explain
sustainable forest development proposes that tree roots select soil microbes involved in central biogeochemical processes,
such as mineral weathering, that may contribute to nutrient mobilization and tree nutrition,” says Stéphane Uroz, an author on the study.
Certain microbes are efficient at breaking down inorganic minerals into nutrients. This process, called mineral weathering,
is especially important in acidic forest soils where tree growth can be limited by access to these nutrients. Mineral-
weathering bacteria can release necessary nutrients such as iron from soil minerals. This gives trees with increased
concentrations of mineral-weathering microbes an advantage over other trees.
The researchers took soil samples from the root areas of beech, oak and Norway spruce trees and cultured them to determine the bacterial populations. They observed heightened levels of mineral-weathering bacteria in the samples near the roots of oak and beech trees compared to surrounding soil samples. This difference was not seen in the Norway spruce samples.
“Our results suggest that certain tree species have developed indirect strategies for mineral weathering in nutrient-poor
soils, which lie in the selection of bacterial communities with efficient mineral weathering potentials,” says Uroz.