Sci-Comm: Holt Research Forest Timber Inventory

Since 1986, we have conducted a timber inventory at the Holt Research Forest (HRF) every few years. During these surveys, we mark trees and measure their diameter and growth stage. By monitoring individual trees' growth, health, and eventual death over long periods, we can learn how tree species respond to significant disturbances such as harvests and changing climatic conditions. Extensive long-term ecological monitoring data, such as the timber inventory, allows for a broader examination of these organisms and provides a more comprehensive understanding of their life cycles.

Holt Research Forest Technician measures tree DBH.

Timber inventories require teams of three - two observers and one recorder. The team of three goes block by block in the forest, moving through each one in a sweeping motion to ensure no previously marked trees are skipped. The observers are in charge of measuring the DBH (diameter at breast height), species, and condition of the tree. The tree's condition can be marked as one of the following: live, dead, cull (deformed/damaged or of no commercial value), dead top, almost dead, still standing (previously marked dead but still upright), or dead and down. The recorder's job is to write down everything the observer is saying and keep count of how many trees have been observed to ensure that none are missed. This is a slow process, and over time, some variables have been removed from the procedure due to time constraints, such as tree height. 

Beyond the Holt Research Forest, timber inventories are a key part of forestry, providing essential data for managing forests sustainably while balancing economic and ecological goals. Inventories help landowners, loggers, and foresters evaluate timber value, plan harvests, and maintain long-term forest productivity by tracking tree species, DBH, height, and volume. They also play a role in wood supply forecasting, carbon sequestration estimates, and biodiversity conservation. On the regulatory side, timber inventories help forest managers and other professionals align harvesting with best practices and sustainability guidelines. A well-structured timber inventory relies on accurate, long-term datasets to track forest conditions and inform management decisions. At the Holt Research Forest, our datasets provide a detailed record of tree growth, species composition, and structural changes over time.

Holt Research Forest Technician marks tree number #22 with a tree tag for the timber inventory.

There are seven Timber Inventory datasets available for download as CSV files at the HRF data archive on the Forest Ecosystem Monitoring Cooperative (FEMC) website (https://www.uvm.edu/femc/data/archive/project/hrftimberinv). Each dataset corresponds to a year in which a timber inventory was conducted. Complete timber inventories are typically performed before and after a planned disturbance, such as our timber harvests. Partial timber inventories are historically conducted between Complete Timber Inventories every few years to facilitate ongoing monitoring. Please refer to the table below for more information about each Timber Inventory dataset, and, visit the Holt Research Forest data archive to learn more about our other publicly available datasets and their metadata!

Table 1. Downloadable Timber inventory datasets.

Name	Description
TimberInv1984	Complete 1984 (pre-harvest) inventory of the entire HRF study area; over 32k stems, located at quad level, no tree ID numbers.
TimberInv1986	Partial 1986 (pre-harvest) inventory of E and I quadrats in HRF study area; 10k stems, located at subquad level, includes tree ID numbers.
TimberInv1988	Complete 1988 (post-harvest) inventory of HRF study area; 30k stems, located at subquad level, includes tree ID numbers.
TimberInv1996	Complete 1996 inventory of HRF study area; 32k stems, located at subquad level, includes tree ID numbers.
TimberInv2007	Partial 2007 inventory of HRF study area; 14k stems, located at subquad level, includes tree ID numbers.
TimberInv2019	Partial 2019 inventory of HRF study area; 7k stems, located at subquad level, includes tree ID numbers.
TimberInv2020	Complete 2020 inventory of HRF study area; 17k stems, located at subquad level, includes tree ID numbers.