Structure Condition Services Stressors
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.
Forest damage is assessed by a visual inspection of forest damage via fixed-wing aircraft and reported in the Insect and Disease Surveys (IDS). IDS are conducted annually by the State of Vermont and the USDA Forest Service to map forest disturbance, including damage caused by insects, diseases, fire, weather events, or a range of other causes1. These data offer a comprehensive assessment of the condition of forests and the stresses affecting them across the landscape. Here, we quantify the total area mapped as either defoliation or crown dieback (a measure of gradual crown deterioration) and does not include mortality. A high score means the acreage of forest damage is staying low over time.
Aerial detection surveys (ADS) are conducted annually by the Vermont Division of Forestry and USDA Forest Service to document the extent and severity of forest disturbance caused by insects, disease and abiotic factors throughout the state. These data offer a comprehensive assessment of the condition of forests across the landscape. Here, we quantify the total area mapped as either defoliation or crown dieback (a measure of gradual crown deterioration) and does not include mortality. The current year is scored as the difference between the minimum -10% of the range and maximum +10% of the range.
Josh Halman, Forest Health Specialist; Vermont Department of Forests, Parks and Recreation (2020)
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 (-10%) and maximum (+10%) (scaled 1-5)
|Directionality of scores||
Lower values in the data are better
|Minimum value used in scoring||
Data minimum - 10% of the range
|Maximum value used in scoring||
Data maximum + 10% of the range
Insect and Disease Surveys (IDS) are annual aerial surveys of forests conducted by the State of Vermont and the USDA Forest Service to map forest disturbance, including damage caused by insects, diseases, fire, and weather events1. While the program has been conducted for many decades in Vermont, the first year of digitally available data was 1995. This metric is computed as a sum of forest area identified with visible damage in a given year (excluding any areas identified as current-year mortality) that has occurred since the previous survey. We set the target for this dataset to be the minimum value in the dataset minus 10% of the range. The current year is scored as the difference between the target and the upper scoring bounds (maximum value in the dataset plus 10% of the range), scaled to be between 1 and 5.