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Globally, forests cover 4 billion hectares or 30% of the Earth's land surface, and 20%–40% of the forest biomass is made up of roots. Roots play a key role for trees: they take up water and nutrients from the soil, store carbon (C) compounds, and provide physical stabilization. Estimations from temperate forests of Central Europe reveal that C storage in trees accounts for about 110 tCha⁻¹, of which 26 tCha⁻¹ is in coarse roots and 1.2 tCha⁻¹ is in fine roots. Compared with soil C, which is about 65 tCha⁻¹ (without roots), the contribution of the root C to the total belowground C pool is about 42%. Flux of C into soils by plant litter (stemwood excluded) compared with the total soil C pool, however, is relatively small (4.4 tCha⁻¹year⁻¹) with the coarse and fine roots each contributing about 20%. Elevated CO₂ concentrations and N depositions lead to increased plant biomass, including that of roots. Recent analysis in …