- Metric Name:  Seral Stage

- Data Vintage:  2021

- Unit Of Measure: Integer, 1 to 3

The seral stages are categories that represent the developmental progression of forest ecosystems from initial establishment or following a stand replacing event (e.g., high severity fire) to a forest dominated by trees in the upper age classes for a given forest type. Late seral forests are also often characterized by multiple ages of forest trees and dead and dying trees in some form of equilibrium. Seral conditions across landscapes were highly variable prior to major European settlement in the western US. These patterns were highly attuned to dominant disturbance regimes and the multi-scaled variability in environmental conditions across topographic and climatic gradients. These patterns helped to reinforce fire regimes dominated by low- to moderate-severity fire across much of the region and provided for multiple habitat requirements for a wide variety of species.- Creation Method:  The limitations imposed by FVS allow for the CWHR classification to be used by the F3 model, however the seral stages for forested lands had to be binned into one of three categories (Early, Mid, Late) and those are defined by tree diameter, per the CWHR system. 

Size Class 

Size (inches DBH) 

Seral Stage 

1  Seedling 

less than 1 

Early (1)

2  Sapling 

1 – 6 

Early (1)

3  Pole 

6 – 11 

Mid (2)

4  Small 

11 – 24 

Mid (2)

5  Medium to Large

24+ 

Late (3)

6  Multi-storied 

36 – 48 

Late (3)

Late Seral conditions have been lumped into a single classification (24” and up). Early and late seral stage conditions were evaluated (separately) at the HUC12-scale (10,000-30,000 ac) as these patterns can be highly variable at finer-scales. For each HUC12, the proportion of the watershed covered by the evaluated seral stage has been calculated.

- Credits:  F3 data outputs, Region 5, MARS Team
USDA Forest Service - Region 5 - Pacific Southwest Region