Root foraging
Root foraging is the process by which plants explore and mine the soil for nutrients. By proliferating roots into new areas, plants explore the soil and can then stimulate denser root growth in nutrient rich patches. Plants can change the shape of their roots to increase root surface area or the number of root tips to enhance nutrient uptake. Plants also exude biochemical compounds that interact with soil minerals and micro-organisms to increase nutrient availability and thereby plant nutrient uptake. All these different plant strategies to acquire nutrients are considered under the process of root foraging.
Root foraging occurs in two of the four soil function models. It plays a crucial role in the Nutrient cycling model forming the bridge between soil nutrient cycling and aboveground plant performance. Root foraging is also considered in the Water regulation and purification model because the nutrients that are acquired by the plants cannot be leached out of the soil anymore. Indirectly, root foraging also contributes to the Climate and carbon regulation model. Root exudation which is considered as a strategy under root foraging occurs individually in the Climate and carbon regulation model because it functions as an important supply of labile carbon to soil fuelling microbial activity and growth.
Measuring root foraging isn’t easy because it would entail monitoring root growth over time. Often root biomass is measured as a proxy by taking soil cores and measuring the amount of roots within these cores. This also allows for measuring other root traits such as nutrient concentration indicative of nutrient uptake. Recently, a guide to root ecology was published which describes more specialised methods for measuring root foraging and root traits[1].
[1] Freschet GT et al. 2020. A starting guide to root ecology: strengthening ecological concepts and standardizing root classification, sampling, processing and trait measurements. https://hal.archives-ouvertes.fr/hal-02918834