Forest ThreatNet

Volume 9, Issue 2 - May/June 2016

ForWarn Map Details Evergreen Forest Decline in the Southern Appalachians

ForWarn evergreen decline mapIn western North Carolina and eastern Tennessee, one doesn’t have to look too hard to see dead and dying hemlock trees resulting from invasions of the non-native hemlock woolly adelgid (HWA). With a new map, the Eastern Threat Center research team behind the satellite-based ForWarn monitoring and assessment tool has shown a landscape-scale perspective of the extent and westward movement of evergreen forest decline, including hemlock forests, in the Southern Appalachians. Using an approach that removes the occasional snowpack and winter weather factors, researchers mapped the change in vegetation greenness in winter (when deciduous trees are dormant and evergreen species are most visible) between 2000 and 2014. The declines in winter greenness revealed are due to impacts from HWA, logging, or fire, but most of the areas of decline correspond to known epicenters of HWA-caused tree mortality. “Many think of eastern hemlock as primarily a riparian species in the Southern Appalachians, but it is also common on high elevation north slopes where the decline has been profound,” says Center research ecologist Steve Norman. Norman and Center research ecologist and lead ForWarn researcher Bill Hargrove recently presented the map as a potential planning tool at a meeting of state and private forestry professionals and landowners at the North Carolina Hemlock Woolly Adelgid Bio-Control Forum. The meeting was sponsored by the Hemlock Restoration Initiative, whose Coordinator, Margot Wallston, previously worked on a ForWarn hemlock decline mapping project while studying at the University of North Carolina Asheville.

Pictured: A ForWarn map shows evergreen forest decline across western North Carolina and eastern Tennessee. Red and purple colors on the map indicate areas of greatest decline. Click to enlarge.

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