PARENT SESSION
Contributed Oral Session 135: Invasive Species: Plant - Soil Feedbacks; Invasion Success
Thursday, August 11, 1:30 PM - 5:00 PM, Meeting Room 518 A, Level 5, Palais des congrès de Montréal
The fate of alien conifers in long-term plantings in the U.S.
Mortenson, Susan*,1, Mack, Richard1, 1 Washington State University, Pullman, Washington, USA
ABSTRACT- Early in the 20th century many species of non-native conifers were introduced into habitats in the U.S. that already supported native conifers. These introductions have yielded few naturalizations and even less evidence of invasions. We investigated the specific fates of these non-native conifers in an array of introduction sites across the U.S. (Priest River, ID, Wind River, WA, Cedar Creek, MN, and Nantucket Is. and Martha's Vineyard, MA) through tree ring analyses, comparisons of growth with adjacent native conifer populations, surveys for regeneration and spread, and reviews of 20th century meteorological data. Most of the original non-native tree plantings have died; a few have survived but display low vigor and are not regenerating. More specifically, Abies veitchii, Pinus densiflora, and Pinus halepensis all died less than 20 years after introduction at Wind River, WA, while we detected no regeneration in Larix decidua, Pinus mugo, or Picea abies stands at Priest River, ID. Pinus thunbergii appears to be invasive on Nantucket Is., although Bursaphelenchus xylophilus (pine wood nematode) causes high mortality in mature trees. Plantations of introduced conifers in the southeastern U.S. had died en masse (e.g. Harrison Experimental Forest, MS) or were abandoned by the U.S. Forest Service due to the trees' low growth and survival (Olustee Arboretum, FL). These outcomes are in sharp contrast to the fate of native conifers in adjacent stands as well as the multiple cases of large-scale conifer invasions in the Southern Hemisphere. Given the onslaught of alien plant species that have invaded the U.S. and their diversity in taxonomy, life forms and ecology, the circumstances surrounding the wholesale failure of introduced conifers to persist becomes an important line of inquiry in developing our understanding of biological invasions.
Key words: invasive species, conifers, Pinus, naturalization