Structure Condition Services Stressors
Trees can become damaged for a variety of reasons ranging from lightning strikes, neighboring treefall, logging damage, poor growing conditions, insects, or genetics, to name a few. Physical damage to trees can reduce their life span by allowing diseases and fungi to infiltrate the wood, leading to rot and decay. While damaged and decaying trees have a vital role in the forest ecosystem through providing habitat and food for a variety of organisms from fungi to insects, an increase in the proportion of our trees that are classified as damaged or decaying can impact the value of our forests and suggest that trees are being negatively impacted by stressors. Here, damage and decay is a measure of the proportion of Vermont’s trees that are considered “non-growing stock". Non-growing stock trees are classified from a timber perspective and are trees with deformities, damage, or rot. We computed the ratio of these non-growing stock trees to all live trees on Forest Inventory and Analysis plots1. The current year is scored as the difference from the long-term mean (scaled 1-5).
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 the minimum and maximum (scaled between 1 and 5)
|Directionality of scores||
No change from the long-term mean is better
|Minimum value used in scoring||
Data minimum - 10% of the range
|Maximum value used in scoring||
Data maximum + 10% of the range
Data on the proportion of trees in Vermont’s forest considered non-growing stock were extracted from the USFS Forest Inventory and Analysis Program EVALIDator1. We used a FIA-established queries (“T005_Number of growing-stock trees on forestland” and “T004_Number of all live trees on forestland”) to compute the ratio. We took the inverse of this ratio to obtain the percentage of live trees not classified as growing stock. FIA defines a “growing stock tree” as a live tree ≥5.0 inches (12.7 cm) DBH that meet (now or prospectively) regional merchantability requirements in terms of saw-log length, grade, and cull deductions, and excludes rough and rotten cull trees2. Annual data began in 1997. We relied on FIA's statistical models for computing this value over time. We set the target for this dataset as the long-term mean. Here, damage and decay is measured as a ratio of damaged living trees to all living trees on forestland. Damages to trees can be caused by insects, diseases, wind, fire, other vegetation, animals, and human activity. Trees were recorded at 5 inches or greater on Forest Inventory and Analysis Plots3. We set the data target as the long-term mean. The current year is scored for where it falls between the target and the upper scoring bounds (maximum value in the dataset plus 10% of range) or the lower scoring bounds (minimum value in the dataset plus 10% of range), scaled to be between 1 and 5.
The average crown dieback of trees in Vermont's forest provides us information on overall forest health.
Damages to forests occur from insects, diseases, weather events, animals, and human impacts.
Forest growth provides information on how much biomass Vermont's trees add annually.
Higher values of canopy density indicate a more lush, green, and productive forest.
Mapped forest mortality is an assessment of the total area of current-year tree mortality across the landscape.
The proportion of trees with damage and decay provides information on the condition and the potential timber quality of Vermont's trees.
Individual tree mortality is a natural and common event, but changes to the baseline rate can signify worsening environmental conditions for trees.