Terrestrial ecosystems, and forests in particular, are important components of land processes because of their key role in reducing atmospheric greenhouse gas concentrations by storing a large amount of carbon in tree biomass and soils. Increasing attention is being paid to forestland area, which accounts for 30% of the total land surface and acts as the main C store in the Earth system. In their life cycle, plants uptake, process, allocate (i.e., the distribution of net primary production among the different plant organs), and remobilize the product of photosynthesis. The relative amount of above- and below-ground biomass partitioned among leaves, branches, stems, roots, non-structural pools, and reproductive tissues is a good indicator for forest productivity and reflects the material flow, the health, the wood quality, and the plant’s survival strategies. How plants share their labile products across their compartments is not fixed, rather is influenced by plant size and likely varies over time, among species and growth environments, and is affected by natural and anthropogenic disturbances (e.g., forest management). Accordingly, the whole allocation process would be constrained under strong natural selection.