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The zero inflation of standing dead tree carbon stocks

Informally Refereed

Abstract

Given the importance of standing dead trees in numerous forest ecosystem attributes/processes such as carbon (C) stocks, the USDA Forest Service’s Forest Inventory and Analysis (FIA) program began consistent nationwide sampling of standing dead trees in 1999. Modeled estimates of standing dead tree C stocks are currently used as the official C stock estimates for the National Greenhouse Gas Inventory (NGHGI). Given the enhanced rigor of empirical estimates of standing dead C stocks, it is paramount to assess the differences between empirical and modeled C stocks for standing dead trees. The goal of this study was to compare field- and model-based (Carbon Calculation Tool) estimates of plot-level (FIA plots) standing dead-tree C for the United States. The results suggest a strong divergence between the predictions of the model versus the field estimates. The model appears to have underestimated observed carbon stocks at the extremes (i.e., plots with very low and very high amounts of standing dead-tree biomass) and overestimated C stocks in between. Most notably, there was an enormous difference in the number of plots observed versus predicted to have little or no standing dead-tree mass, which field data suggest make up the bulk of the FIA plots. Some of this discrepancy may be caused by too many non-observations of dead trees at FIA plots (i.e., zero-inflated data) — a focal point for continuation of this line of research. The results of this study suggest that the current model-based estimates do not accurately reflect observations in the field.

Parent Publication

Citation

Woodall, Christopher W.; MacFarlane, David W. 2012. The zero inflation of standing dead tree carbon stocks. In: McWilliams, Will; Roesch, Francis A. eds. 2012. Monitoring Across Borders: 2010 Joint Meeting of the Forest Inventory and Analysis (FIA) Symposium and the Southern Mensurationists. e-Gen. Tech. Rep. SRS-157. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 297-299.
https://www.fs.usda.gov/research/treesearch/41017