Tree age estimation across the U.S. using forest inventory and analysis database

Abstract

Tree age information is crucial for a range of environmental, scientific, and conservation-related purposes. It helps in understanding and managing forest resources effectively and sustainably. This study presents an approach to estimate tree age across diverse U.S. forested ecosystems using field inventory and climate datasets. The age-size relationship modeling framework incorporates species-specific and environmental variables, enabling its application across various regions. Model R² values range from 0.51 to 0.87 and relative RMSEs (using the mean as the denominator) ranging from 0.14 to 0.49. These models have higher accuracies and are applicable over larger areas than existing studies. The developed tree age dataset reveals marked differences in tree age distribution between Eastern and Western U.S. forests, attributed to historical land use, disturbance, climatic variations, and forest management practices. In the East, forests exhibit a younger age structure due to historical deforestation and subsequent reforestation, while Western forests show an older age structure, influenced by diverse environmental conditions and less human disturbance. By deriving individual tree ages for all the trees surveyed in the United States Forest Inventory and Analysis Program, the approach increases by more than 20 times the number of tally trees in the FIA database that have age data over what is currently. The curated dataset emerges as a crucial resource for forest management and conservation, enhancing our ability to estimate forest carbon sequestration accurately. The tree age dataset is available at https://zenodo.org/records/14775738.