Nitrogen (N) and phosphorus (P) are co-limiting nutrients of net primary productivity in most terrestrial ecosystems (Fay et al., 2015;Harpole et al., 2011). To satisfy N and P demand for shoots, plants take up nutrients from the soil but also recycle nutrients internally through resorption and reallocation from storage organs (e.g. roots), which allows the reuse of nutrients for new growth (Freschet & Roumet, 2017;Klimešová et al., 2018). Reallocation of N and P from roots is an important nutrient-use strategy for plant growth when