Or … how to improve our chances of finding native American chestnut
by Christine Cadigan
It's that time of year when we pull out all stops trying to find native American chestnut trees to pollinate across the native range.
A recent suggestion by CT-TACF member and Director Bill Moorhead has led to a full-blown attempt to make locating potential Chestnut trees easier for all chapter members. Specifically focusing in Litchfield County, several criteria were identified as optimal habitat for Chestnut trees. Based on historic sightings and pollinations, the most common soil type and moisture was inferred. It appears as though the highest frequency of Chestnut sprouts were found on
Charlton – Chatfield complex soils which are very rocky and have a slope somewhere between 3 and 45 percent (classifications 73C and 73E). In addition, the sprouts appear to prefer dry-mesic sites. Based on this information, a geospatial analysis was conducted in order to determine potential hotspot of Chestnut sprout occurrences. The effectiveness of this method can only be verified by further sightings in the field. Therefore, it is the hope of this research team that this year’s tree identifiers will use this map as a guide and will report back on success rates.
[click for larger photo]Preliminary chestnut hotspot maps created using geospacial analysis.
Click here [3.2 mb download] for the downloadable and printable version. Or click on image below for expanded view.
The green sites indicate all preferential soil sites. However, many of these sites are not accessible by road. Therefore, the bright magenta sites combine soil type and road accessibility to produce a more realistic potential site, especially for drive by spotters.
The preliminary maps are a bit premature. The hope is to weight preferred soil moisture with preferred soil type as well as distance to the nearest road (important for bucket truck access and visibility from roads). Soil moisture calculations are a bit involved, however. Digital elevation models are used to estimate a variety of topographic indices. Slope, perhaps the most popular topographic index, strongly affects flow and residence time of moisture. Aspect (the Azimuth direction of the side of a hillslope) is used to estimate solar incidence, thermal conditions, and exposure between sites. Keeping that in mind, a Topographic Relative Moisture Index (TRMI) combines relative slope position, slope configuration, slope steepness, and slope aspect into a single value ranging from 0 to 60. Lower numbers indicate more xeric sites while higher numbers indicate more mesic sites (Method modified after Wilds 1996). Once the soil moisture index is properly calculated, its importance can be weighted into site determination. This will hopefully be available soon.
To start with, the following map rates Chestnut site preference based on soil type and distance to roads (<10 meters). The distance to roads was weighted with 75% importance while soil type 25% importance. This will change when moisture data is added. green sites indicate all preferential sites. However, many of these are not accessible by road. Therefore, the bright magenta combine and road accessibility produce a more realistic potential site.
Simply glancing over the map suggests that there are several hotspots to keep an eye on. On the western side of Litchfield County, areas around Skiff Mountain Road and Segar Mountain Road look promising.
[click for larger photo]Segar Mountain Road aerial photo
[click for larger photo]Segar Mountain Road aerial photo with superimposed geospacial hot spot map
[click for larger photo]Segar Mountain Road aerial photo with superimposed geospacial hot spots
Segar Mountain Road
The maps to the left [click on map for larger version] show a detailed look at Segar Mountain Road(Route 341) and the environs in an area west of the Village of Warren. The maps all cover the exact same area, and are designed to be illustrative of the process of showing hotspots overlays on a road map (thank you Google Maps). Simply driving a few mile circuit should test the hypothesis that American chestnut can be found in this area. Click here for a detailed map of the area that can be printed to follow on a driving circuit.
[click for larger photo]Skiff Mountain Road aerial photo with superimposed geospacial rendering of possible chestnut hot spots
Skiff Mountain Road
The map to the left [click on map for larger version] shows a detailed look at Skiff Mountain Road and West Woods Road in the Oak Ledge Pond area south of Sharon and west of Cornwall Bridge. Again, simply driving a few mile circuit should test the hypothesis that American chestnut can be found in this area. Click here for a detailed map of the area that can be printed to follow on a driving circuit.
On both maps, the squiggly lines without major roads means a road may have been shown on the geospatial layers – but like so many roads in rural Connecticut – you may want to think twice before driving it.
To the south, areas around Washington and just east of Elm may have significant clumps of trees. To the southeast, it appears as though some of the smaller roads surrounding Bristol may be ideal habitat. In addition, there is a large area north of Burlington Road and south of the city of Torringford. Finally, in the northeastern part of the county, the area along Hartland Road as well as some of the smaller roads around Winsted, particularly Highland Lake and West Hill Lake may be prime locations. I encourage Litchfield County CT-TACF members to find these hotspots in their area and take a look.
These are not the only places you will find chestnut, but hopefully our indicators are good, and you will have a higher probability of finding chestnut on these sites. Either way, please report back to the research team so we can better produce these mappings of potential sites. Thanks for your attention, and please contact me with any questions and comments.
Christine M. Cadigan
Candidate for Master of Environmental Management and Master of Forestry 2010
Nicholas School of the Environment
Duke University
Summer Intern – CT Chapter TACF
In every walk with nature, one receives far more than he seeks. -John Muir
