Community characteristics and vegetation management of Karner blue butterfly (Lycaeides melissa samuelis) habitats on rights-of-way in east-central New York, USA
Published source details
Smallidge P.J., Leopold D.J. & Allen C.M. (1996) Community characteristics and vegetation management of Karner blue butterfly (Lycaeides melissa samuelis) habitats on rights-of-way in east-central New York, USA. Journal of Applied Ecology, 33, 1405-1419.
Published source details Smallidge P.J., Leopold D.J. & Allen C.M. (1996) Community characteristics and vegetation management of Karner blue butterfly (Lycaeides melissa samuelis) habitats on rights-of-way in east-central New York, USA. Journal of Applied Ecology, 33, 1405-1419.
Blue lupine Lupinus perennis and associated nectar-providing plants are critical habitat components for the endangered Karner blue butterfly Lycaeides melissa samuelis. The Karner blue depends on early successional plant communities that include blue lupine (the sole larvae food plant), as well as being one of several nectar species for adult butterflies. Such plant communities exist on transmission line rights-of-way in New York State, where 'traditional' management results in maintenance of early successional shrub-dominated communities where these flowers can also persist. Rights-of-way vegetation management reduces the prevalence of woody species that represent a hazard to high-tension lines, and these rights-of-way are now frequent habitats of extant Karner blue populations
This study investigated rights-of-way in east-central New York to: i) characterize blue lupine populations and associated plant communities; ii) quantify the relationship between the lupine and environmental characteristics and management; and iii) assess the relationship between butterfly population size and habitat characteristics.
Study areas: Sixteen blue lupine populations on rights-of-way in counties of the Hudson Valley Sand Belt, New York State (northeastern USA) with extant or recently extirpated Karner blue populations were selected.
Lupine sampling: Sampling was undertaken to evaluate percentage cover and density of lupine clumps, and the abundance of associated herbs and woody vegetation. Sampling occurred during the flowering period in May to early July 1992. Lupine population sizes ranged in area from 50-1,500 m². At each rights-of-way location that included a lupine population, in those that contained fewer than 30 clumps, all clumps were sampled for micro-scale features (vegetative and environmental attributes). Otherwise, at least 30 clumps, but not more than 10% of the clumps, were sampled. Clumps were randomly selected and were compared to an equal number of similarly sampled random points without lupine in adjacent areas.
Light intensity was measured as photosynthetically active radiation with a LI-COR light meter during several days in August 1992 at all locations.
Management history: Data was available for the first and second most recent management cycles for all locations. In some cases older records were available, the oldest dated back to 1977. Management generally occurred on a 7- or 8-year cycle, although on sometimes as little as 3-5 years. Management included: i) herbicide stump treatments, ii) foliar herbicides, iii) basal herbicides, (iv) mechanical trimming of trees, v) brush-hogging, vi) broadcast herbicides, vii) hand-cutting followed by foliar herbicide and viii) hand-cutting.
Because of management variation relative to the limited number of study sites available, it was necessary to group management schemes by mode and method of application.
Karner blue census data: Population data associated with the 16 locations were obtained for the 1990 census from various sources. Census data were based on the maximum count of Karner blues seen during a visit at the peak of the second brood, and thus providing an index of population size. Census data were divided into three levels: zero; at least 1 but less than 20; and >20 individuals. These levels reflected observed clusters of population-size distribution and a balance of the number of right-of-way locations for each group.
Blue lupines were robust in open communities with sweet fern Comptonia peregrine, various grasses (Poaceae) and wild carrot Daucus carota. Lupine and Karner blue abundance were correlated positively with high light intensity and large patch areas, and inversely correlated with the number of years since the last management activity (as succession advanced and woody regrowth developed).
There was no clear relationship between vegetation patterns and the different types of recent vegetation management. However, in the longer term, vegetation management based on infrequent mechanical removal of woody stems (e.g. hand-cutting, mowing, brush-hogging) was associated with increased woody plant density.
Other conditions associated with a larger Karner blue population size included more frequent vegetation management that reduced the cover and density of woody species.
Conclusions: Results suggest that to enhance both blue lupine and Karner blue populations, vegetation management on rights-of-way should reduce trees and shrubs, and increase light intensity to a level of photosynthetically active radiation that exceeds 65% of the maximum possible light intensity. A more frequent mechanical treatment or a seasonally timed application of an appropriate herbicide would be more effective at controlling woody vegetation regrowth that competes with and shades out blue lupine.
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