Date of Award

11-2024

Degree Type

Thesis

Degree Name

Master of Science

Department

Biology

Program

Biology (MS)

First Advisor/Chairperson

Dr. Alan Rebertus

Abstract

Ram’s head lady slipper (Cypripedium arietinum) is rare across its range, but the Grand Sable Dunes (GSD) on the southern shore of Lake Superior harbors the largest known population in North America. It thrives in jack pine (Pinus banksiana) islands throughout the dunes. In this study, I updated the population status of ram’s head lady’s slipper at GSD and tracked changes in its distribution and reproductive health after a 14- year period since Bozic (2015) first surveyed GSD. I counted orchids, flowers, and fruit set in 741 1-m radius plots using stratified random sampling across 44 islands. I also resurveyed three 4 x 4-m permanent plots established by Bozic. The estimated C . ari e t i n u mpopulation declined by 65% in the random plot survey (from 3,596,000  951,000 (95% CI) in 2009, to 1,1777,000  257,000 in 2023). Orchids in three permanent plots declined by 42% (n=366). I mapped forest cover expansion at GSD using historical aerial photography (1939-2022) to analyze the effects of forest age on ram’s head densities and distribution. Orchid densities declined the most in the oldest and largest forest islands that established pre-1964 and pre-1939. In contrast, orchid densities remained stable in younger stands. Additionally, ram’s head spread from 26 islands in 2009 to 42 islands in 2023. Changes in the orchid population are tied to forest succession and Lake Superior dune formation and stabilization cycles. These findings will contribute to the conservation of rare orchids in this diversity hotspot.

Access Type

Open Access

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