Acorn review: How do trees cope with ancient soils?

Growth of forests depends on access to nutrients from soils, with each nutrient element exhibiting different rates of inputs, cycling, and losses. Supplies of some nutrients are too low in most forest soils to support maximum growth rates, on soils of any age. The supplies of several elements depend on recycling of atoms contained in minerals of the geological parent material. Even very slow annual rates of loss can lead to substantial depletion over millennia, raising an expectation that ancient soils ought to have very low nutrient supplies and low rates of growth. This expectation does not match the reality of most ancient soils because several features combine to sustain growth. Ancient soils in humid regions are deep, with opportunities for roots to exploit very large volumes and masses of soil materials and supplies of stored water. Some elements that are depleted from geologic parent material are replenished via air-borne dust; very low rates of input can be substantial over very long periods. Plants and associated microbes have evolved abilities to access nutrients from pools at very low concentrations, and from relatively insoluble forms. Local biogeochemistry of soils always influences growth rates, and simple expectations of poor growth on ancient soils are unwarranted.