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Abstract Detail

Ecological Section

Johnson, Sarah E. [1], Mead, Jordan [1].

Dieback in Juniperus communis as a possible indicator of climate change impacts to Lake Superior sandscapes.

Sandscape habitats are relatively rare and are a valuable resource within the Apostle Islands National Lakeshore on the south shore of Lake Superior. These coastal habitats are inhabited by specialized vegetation adapted to stressful and highly disturbed conditions. While these species naturally evolved in a dynamic system, their responses to rapid shifts in climate and other human-induced changes are a concern. Prompted by alarming levels of dieback in Juniperus communis L. var. depressa Pursh, a dioecious evergreen shrub, we investigated the patterns and possible causes for these observations. We conducted extensive surveys of J. communis on Michigan (n = 524), Outer (n = 266), and Stockton Islands (n = 366) at Apostle Islands National Lakeshore. We quantified pattern and degree of dieback, shrub size, sex, relative elevation, distance from Lake Superior, and distance to nearest conspecific. Dieback on shrubs consisted of tip death, branch death, and seemingly natural defoliation at plant centers. Across all islands, dieback was greatest on large shrubs, and was the most extensive on south-facing Michigan Island (>50% of shrubs with dead branches). The most highly stressed shrubs were positioned at relatively high elevations above Lake Superior and at farther distances from the lake. The healthiest shrubs were more likely to occur at relatively low elevations regardless of distance to the lake. Large male shrubs were more likely to exhibit die-back than females and female-biased sex ratios occurred on Michigan and Stockton Islands. Succession and age-related senescence are apparent in these populations of J. communis, but patterns of dieback reflect additional and impetuous forces at work. These sandscape habitats have experienced protracted drought conditions due to lake level declines, precipitation declines, and increased evaporative demand associated with rising temperatures. Further, the proliferation of juniper webworm cocoons suggests possible multi-trophic scale interactions with climate change. Dieback in this important dune stabilizing shrub may serve as an early indicator for community-wide changes in Great Lakes sandscape habitats.

Broader Impacts:

1 - Northland College, Natural Resources, 1411 Ellis Avenue, Ashland, WI, 54806, USA

Keywords:
Juniperus
sandscape
Climate Change
dioecious
Great Lakes
dunes
drought.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Grand Salon A - D/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 5:45 PM
Number: PEC028
Abstract ID:793
Candidate for Awards:None