A tree-ring perspective on terrestrial carbon dynamics
Tree-ring records can provide a powerful tool to advance our understanding of contemporary terrestrial carbon cycling and to reconstruct key metrics in the decades preceding observational data. The growing use of tree rings in carbon-cycle research is facilitated by increasing recognition of reciprocal benefits among research communities. Yet, basic questions persist regarding what tree rings represent at the ecosystem level, how to optimally integrate them with other data streams, and what the main uncertainties are that need to be taken into account. In addition to this, the unexplored but vast potential for tree rings to refine assessments of terrestrial carbon cycling across a range of temporal and spatial domains, is emerging. Here, we summarize recent advances and highlight promising paths of investigation with respect to (1) growth phenology, (2) forest productivity trends and variability, (3) CO2 fertilization and water-use efficiency, (4) forest disturbances, and (5) comparisons between observational and computational forest productivity estimates.
Our study encourages the integration of tree-ring data: with eddy-covariance measurements to investigate carbon allocation patterns and water-use efficiency; with remotely sensed observations to distinguish the timing of cambial growth and leaf phenology; and with forest inventories to develop continuous, annually resolved and long-term carbon budgets. In addition, we note the potential of tree-ring records and derivatives thereof to benchmark the performance of earth system models regarding the simulated magnitude and dynamics of forest carbon uptake, and inform these models about growth responses to climatic drivers and disturbances. Such efforts are expected to improve our understanding of forest carbon cycling and place current developments into a long-term perspective.