Latest Score:

4.4/5

in 2019

score trend is down over time
Weight: 10%

The age of the trees in a forest provides us a sense of the amount of time since a stand-replacing disturbance event has occurred, which can result from hurricane or logging, for example. Across our forests, we want a diversity of stand ages, with some stands being newly initiated and others having been in place for a long time. Many wildlife species thrive in areas of recent disturbance where there are young saplings and lots of understory plants. Other important ecosystem services come from those forest stands that are the oldest. Here, we use stand ages (in 40 year grouping) extracted from Forest Inventory and Analysis data1 to quantify the proportion of our forest in three age groups: very young (0-40 years), young (41-80 years), and mature (81+ years) The current year is scored as the distance between the deviation from the long-term mean, scaled to be between 1 and 5.

1USDA Forest Service. 2017. Forest Inventory and Analysis National Core Field Guide, Volume 1: Field Data Collection Procedures for Phase 2 plots. Version 7.2. Available at: https://www.fia.fs.fed.us/library/field-guides-methods-proc/docs/2017/core_ver7-2_10_2017_final.pdf

-- Expert interpretation for Stand Age Diversity is not available--

The score is calculated using a target value and the historical range of the the entire long-term dataset. The higher the score, the closer this year's value is to the target.

Once the score is computed for each year, the trend in scores over time is calculated. If the trend is significantly positive or negative, the long-term trend is marked as increasing or decreasing respectively.

Component Description
Scored as

Distance between minimum and maximum (scaled 1-5)

Target value

Long-term mean

Directionality of scores

No change from the long-term mean is better

Minimum value used in scoring

Data minimum -10% of the rang

Maximum value used in scoring

Data maximum + 10% of the range

Data on the annual acreage occupied by forests divided into 20 year age classes were extracted from the Forest Inventory and Analysis EVALIDator1. The first year of available data was 2011. We re-categorized stand ages into 40 year buckets (0-40, 40-80, and 80+ years) and created a ratio per each age class per year based on the estimated forestland. Per FIA protocol, plots are reassessed every 5 years until 2014, and every 7 years after that. The target for this dataset was set to the long-term mean, and the score was then computed as the deviation from this target, scaled to be between 1-5.

1 USDA Forest Service. 2018. FIA EVALIDator. Available at: https://apps.fs.usda.gov/Evalidator/evalidator.jsp

STRUCTURE INDICATORS