Implications of alternative biomass and carbon estimation methods for standing dead trees in the United States

New models quantifying tree volume, biomass, and carbon have recently been implemented across the USA, termed the National-Scale Volume and Biomass (NSVB) framework. Little research has been done to quantify the implications of these new models on the standing dead tree (SDT) carbon pool, which occupies a substantial portion of the nation’s total forest ecosystem carbon stocks. This project compared predictions of carbon stocks in SDTs using the previous estimation approach (the Component Ratio Method) and NSVB using the most recent FIA data collected across the conterminous USA. Equivalence tests were conducted to compare predictions using the two modeling systems. Results show similar findings to what has been recently observed for live trees, namely that NSVB produces predictions of carbon in SDTs larger than those produced from CRM. However, predictions produced from NSVB and CRM for SDTs in advanced stages of decay (i.e., decay classes 4 and 5) are similar, likely due to the lack of tops and limbs in these SDTs, which has been suggested as a reason for the increased carbon stock predictions produced in live trees using the NSVB framework. Individual SDT predictions have important implications when scaled to the population (e.g., condition and state levels), where we similarly observed NSVB predictions to be larger compared to CRM predictions. These results highlight the role that biometrical methods play in determining carbon in SDTs, such as decay class and structural loss reduction factors and species-specific carbon fractions that are implemented in the NSVB framework.