Abstract
Funding for ecological restoration efforts sometimes ends prematurely and exacerbates problems that originally were the rationale for the project. In our test of methods to manage exotic species, we mimicked this real world situation and compared management after one year with no ecological restoration with exotic species management continued yearly for five years and followed by ecological restoration (transplanting adult plants of four native species) in year five. Our study site in Ontario, Canada consisted of eight fragmented woodlots dominated by sugar maple (Acer saccharum) and American beech (Fagus grandifolia) that supported dense populations of the exotic species garlic mustard (Alliaria petiolata), dame’s rocket (Hesperis matronalis), and celandine (Chelidonium majus). In 1998, we quantified the impact and duration of one-time use of glyphosate, hand-pulling, inflorescence clipping, and mulch on the seedbank and shoots of three exotic species, native herbaceous species, and (for shoots, non-adult) native species of shrubs and trees. By 2006, above- and belowground densities of exotic species significantly increased and native species significantly decreased with one-time treatments of glyphosate and hand-pulling (ANOVA). The exotic species recovered quickly from one-time application of glyphosate, and hand-pulling disturbed the soil and increased relative emergence of exotic species from seed. As expected, inflorescence clipping and mulching were ineffective as one-time treatments but did not worsen the exotic species problem or decrease native species’ densities. The repeated management plus ecological restoration was more successful in all cases, with similar results by 2006, while one-time application of glyphosate and hand-pulling worsened problems. We caution that initiating exotic species management can be risky if funding is not secure enough to support longer term efforts.
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