Plant root-shoot biomass allocation over diverse biomes: A global synthesis

Globally, the allocation of root-shoot biomass is a key plant-adaptive strategy for terrestrial ecosystems to enhance carbon-sequestration capacity. However, the deep mechanisms of above-/below-ground biomass distribution remain unclear, partly due to the multiple influencing factors. We thus aim to clarify the role of various factors in biomass allocation across diverse terrestrial biomes in the paper. A key indicator named root/shoot ratio (RSR) was established, and 7763 observational data-sets were collected from literature, including root biomass, shoot biomass, plant height, climate information and the geographical coordinates. Results highlighted the differences in RSR across terrestrial plants in biomes with a mean value of approximately 0.90. Grasses and boreal forest captured the highest and lowest mean RSR, respectively, while tree had a lower mean RSR than shrub and grass. Angiosperms and deciduous plants, on the other hand, have a higher mean RSR than gymnosperms and evergreen plants, respectively. Moreover, RSR is negatively correlated with mean annual temperature, precipitation, plant height and shoot biomass, but positively correlated with elevation and latitude. Redundancy analysis reflected that biotic and abiotic factors explained RSR variability similarly with a residual of 0.883. These findings support the optimal partitioning hypothesis that plants adjust their growth strategy according to different environments, and in particular, tend to partition more biomass to root systems under more stressful, low-nutrient and poor climatic conditions.