| Summary: | Since the first vascular plants appeared on land at least 430 million years ago, plant-soil feedback has started through the root-soil interface. Plant species have inherently specific and diverse root traits, but root functional and morphological plasticity is important to respond to soil changes or diversity in terms of nutrient forms and availabilities, especially in ecosystems with low plant species diversity. This paper synthesized how tree plasticity facilitates soil nutrient acquisition from the tropics to the Arctic. The fine roots of dipterocarp (Shore laevis) and rhizosphere microbes increase malate release in acidic soils for phosphorus solubilization, aluminum detoxification, and lignin degradation. The development of finer roots is a well-known strategy for the acquisition of limited nutrients, but the allocation of roots foraging “nutrient hotspots” in deeper soil is an alternative strategy. Scots pine increases the allocation of finer roots into the subsoil to solubilize P bonded to Al/Fe oxides in fine-textured podzol, but not in the coarse-textured podzol with deeper nutrient hotspots. The black spruce trees increase the biomass allocation to the belowground to acquire soil nitrogen, especially when black spruce roots absorb urea in the shallow soil on permafrost. Even in northern ecosystems with limited species diversity, a combination of functional plasticity and vertical plasticity of root system architecture facilitates soil phosphorus or nitrogen limitation.
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