Evaluating the reliability of tree-ring-based estimates of aboveground biomass and biomass increment in managed forests

Forest biomass, as the major terrestrial reservoir of stored carbon, plays a key role in the global carbon cycle. Permanent plots are commonly used to estimate carbon stocks and net primary productivity (NPP). Because permanent plots are labor intensive, require prolonged field observations, and provide low temporal resolution, alternative methods have been developed. Dendroecological methods are commonly used to estimate forest growth, but most studies are often limited to the individual tree level rather than integrating growth estimates at the plot or stand level, which limits their use to understand forest-level biomass growth and productivity. Here, we evaluated the accuracy in estimating stand aboveground biomass (AGB) and annual AGB increments (AGBi) with two different approaches (dendroecological plots and repeated plot inventories) on a network of 40 permanent plots from managed forests representing four pine species across a wide environmental gradient in the Iberian Peninsula. Dendroecological AGB showed higher agreement with permanent plots than AGBi. For periods longer than 30 years, AGB and AGBi estimates significantly differed between methodologies. Low-productivity stands composed of drought-tolerant species showed better agreement than more productive and faster-growing forests. Recent disturbances or silvicultural treatments within the 20–30 years prior to sampling increased the deviations of dendroecological estimations compared to permanent plots. Carefully selecting sites with little past disturbance or management interventions increases the temporal range for which dendroecological estimates of forest biomass stocks and biomass growth are reliable. Our results show how dendroecological plots can complement the spatial distribution of permanent plots and provide high temporal resolution to assess the effects of climate variability on biomass dynamics in managed forests. • Dendroecological plots accurately track variability in forest total biomass and biomass increments. • Dendroecological estimates of biomass increments are less reliable than estimates of total forest biomass. • Biases in dendroecological estimates increase with longer inventory-to-sampling intervals. • Agreement between dendroecological and inventory estimates increases with decreasing stand productivity. • Recent disturbances and management increase biases in dendroecological biomass reconstructions.