Wood structure explained by complex spatial source-sink interactions

Wood is a remarkable material with great cultural, economic, and biogeochemical importance. However, our understanding of its formation is poor. Key properties that have not been explained include the anatomy of growth rings (with consistent transitions from low-density earlywood to high density latewood), strong temperature-dependence of latewood density (used for historical temperature reconstructions), the regulation of cell size, and overall growth-temperature relationships in conifer and ring-porous tree species. We have developed a theoretical framework based on observations on Pinus sylvestris L. in northern Sweden. The observed anatomical properties emerge from our framework as a consequence of interactions in time and space between the production of new cells, the dynamics of developmental zone widths, and the distribution of carbohydrates across the developing wood. Here we find that the diffusion of carbohydrates is critical to determining final ring anatomy, potentially overturning current understanding of how wood formation responds to environmental variability and transforming our interpretation of tree rings as proxies of past climates.

Automated summary

Wood is a valuable material that holds great cultural, economic, and biogeochemical significance. However, the process of wood formation is not well understood. This study presents a theoretical framework based on observations of Pinus sylvestris L. in northern Sweden, explaining the anatomical properties of wood as a result of interactions between new cell production, developmental zone dynamics, and carbohydrate distribution over time and space. The diffusion of carbohydrates is found to be crucial in determining the final ring anatomy, challenging current understanding of wood formation in response to environmental variability and redefining the interpretation of tree rings as climate proxies.