Climate shapes the ratio between aboveground plant biovolume and topsoil macronutrients worldwide

Soil nutrients are a major limiting factor for plant biomass, yet paradoxically, some of the most productive ecosystems thrive in nutrient-poor soils. Here, we conducted a global field survey in 421 sites across all major biomes to investigate the environmental factors controlling the ratio between plant biovolume (a proxy for aboveground plant biomass) and topsoil macronutrient content (N, P, Ca, K, Mg and S) worldwide. We found that temperature and precipitation were the most important factors associated with this ratio. Warm and wet regions exhibited higher plant biovolume to soil nutrient content ratios than cold high-latitude regions. We also identified an intriguing trade-off: a negative correlation between soil microbial biomass and the plant-nutrient ratio, suggesting that higher microbial biomass might be associated with lower plant biomass relative to soil nutrient content. These findings are instrumental for a better understanding of terrestrial carbon storage and anticipating ecosystem services under climate change.