Tree Age Estimation Across the U.S. Using Forest Inventory and Analysis Database (FIADB)

The tree age dataset was derived for tally trees in the Forest Inventory and Analysis program (FIA) of the US Forest Service using an age-size relationship modeling framework that incorporates species-specific and environmental variables.

Associated paper: Lu, J., Huang, C., Schleeweis, K., Zou, Z., & Gong, W. (2025). Tree age estimation across the US using forest inventory and analysis database. Forest Ecology and Management, 584, 122603.

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.Keywords: Tree Age; Forests; FIA; Structural Attributes

Data Summary

The tables are stored as csv files separately for each state. Please see the table below for the column names and description. Among the columns, CN, PLT_CN, INVYR, STATE can be linked to FIA's tree and plot data to query the tree and plot records.  Users can also query other variables that were used in the modeling such as diameter and species groups using these keys.

Columns Name
Description

CN
Tree sequence number

PLT_CN
Plot sequence number

INVYR
Inventory year

Tree_Age
Predicted tree age

zoneID
ID number indicating the modeling zone where this tree is located, corresponding to the modeling zones in Figure 6 in the paper.

US_L3CODE
Code indicating the US level-3 ecoregion where this tree is located.

US_L3NAME
Name of the US level-3 ecoregion where this tree is located.

State
Two-letter abbreviation for each state.