From Science Now;
Hemlock forests are in a world of hurt. Across the eastern United States, an aphid-like pest is ravaging the trees, while booming populations of deer devour other native plants. Now, researchers have shown that the combination of these two threats adds up to even more trouble for the native ecosystem by favoring the invasion of weeds.
Researchers first noticed the hemlock woolly adelgid (Adelges tsugae), a 1.5-millimeter-long insect from Asia, in an arboretum near Richmond, Virginia, in 1951. The bugs feed on starch in new twigs and can kill trees in just 3 years. As the hemlocks die, exotic plants such as garlic mustard (Alliaria petiolata) have been spreading and altering the habitat that native species rely on. Anne Eschtruth, then a graduate student in ESPM and now a postdoctoral researcher at the Center for Forestry, wondered how the two phenomena were linked.
According to a study co-authored by Eschtruth and John Battles, associate professor of ecosystem sciences, which appeared in Conservation Biology in December. Two factors appear to be involved... ,
Read the full article at http://sciencenow.sciencemag.org/cgi/content/full/2008/1219/3