The density of wood is a key indicator of the carbon investment strategies of trees, impacting productivity and carbon storage. Despite its importance, the global variation in wood density and its environmental controls remain poorly understood, preventing accurate predictions of global forest carbon stocks. Here we analyse information from 1.1 million forest inventory plots alongside wood density data from 10,703 tree species to create a spatially explicit understanding of the global wood density distribution and its drivers. Our findings reveal a pronounced latitudinal gradient, with wood in tropical forests being up to 30% denser than that in boreal forests. In both angiosperms and gymnosperms, hydrothermal conditions represented by annual mean temperature and soil moisture emerged as the primary factors influencing the variation in wood density globally. This indicates similar environmental filters and evolutionary adaptations among distinct plant groups, underscoring the essential role of abiotic factors in determining wood density in forest ecosystems. Additionally, our study highlights the prominent role of disturbance, such as human modification and fire risk, in influencing wood density at more local scales. Factoring in the spatial variation of wood density notably changes the estimates of forest carbon stocks, leading to differences of up to 21% within biomes. Therefore, our research contributes to a deeper understanding of terrestrial biomass distribution and how environmental changes and disturbances impact forest ecosystems.

木材密度是树木碳投资策略的关键指标，影响生产力和碳储存。尽管木材密度及其环境控制的全球变化仍然知之甚少，因此无法准确预测全球森林碳储量。在这里，我们分析了来自 110 万个森林清查点的信息以及来自 10,703 个树种的木材密度数据，以在空间上明确了解全球木材密度分布及其驱动因素。我们的研究结果揭示了明显的纬度梯度，热带森林中的木材密度比北方森林中的木材密度高 30%。在被子植物和裸子植物中，以年平均温度和土壤湿度为代表的热液条件成为影响全球木材密度变化的主要因素。这表明不同植物群之间存在相似的环境过滤器和进化适应，强调了非生物因素在决定森林生态系统中木材密度的重要作用。此外，我们的研究强调了干扰（例如人类改造和火灾风险）在影响更多局部尺度的木材密度中的突出作用。考虑木材密度的空间变化会显著改变森林碳储量的估计，导致生物群落内的差异高达 21%。因此，我们的研究有助于更深入地了解陆地生物量分布以及环境变化和干扰如何影响森林生态系统。