Structure Condition Services Stressors
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.
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.
Distance between minimum and maximum (scaled 1-5)
|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.
Forest cover is the percent of the state of Vermont with tree cover.
Regeneration of sugar maple seedlings provides information about the future of Vermont's hardwood forests.
Regeneration of red spruce seedlings provides information about the future of Vermont's softwood forests.
Forests with greater stand complexity have trees in a range of sizes and as a result, may be more productive and resilient to stress.
Forest patch sizes provides information on the average size of contiguous forest blocks.
Forest connectivity is a measure of the linkages among Vermont's forests.
With greater diversity in tree species, forests can support more biodiversity, exhibit higher resilience to stress, and store more carbon.
Across the landscape, having a range of forest stand ages provides diversity, varied habitat conditions, and resilience to stressors.