Structure Condition Services Stressors
Forest connectivity is the degree to which the distance between adjacent forest patches impedes or facilitates movement1. Forests with higher connectivity better allow for the exchange of water and nutrients, movement of wildlife, dispersal and genetic interchange between populations, and long distance range shifts of species, such as in response to climate change2,3. Maintaining connectivity becomes a higher priority as forests become more fragmented with urban expansion. Not only must the connections exist but they must be functional as well. Here, forest connectivity is measured using the “Contagion Index” calculated using FragStats software4. The current year is scored as the difference between the data minimum -10% of the range and the long-term mean.
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 target (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 range
|Maximum value used in scoring||
Data maximum + 10% of the range
From the Forest Cover images we generated (see details under that metric above). While the first available year of data was 1992, NLCD methodology changed between 1992 and 2006, so we began our analysis with 2001 data. We used FragStats1 to compute the mean size of forest patches. We used the 8 cell neighborhood rule with a ‘no sampling’ strategy. We selected ‘Contagion’ as the Landscape Aggregation metric to compute. We set the target for this dataset to be the long-term mean. The current year is scored for where it falls between target and either the lower scoring bounds (dataset minimum minus 10% of the range) or the upper scoring bounds (dataset maximum plus 10% of the range) and the target when values are above the target, scaled to be between 1 and 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.