Aplectrum hyemale and Tipularia discolor are wintergreen orchids native to the eastern and central United States. Each produces a single leaf in late fall that persists through the winter and senesces in early spring. Both species occur in scattered patches in the understory of deciduous forests, and although they overlap in range and often co-occur in the landscape, their habitat and photosynthetic potential have not been compared directly. In this study we examine the relative abundance of A. hyemale and T. discolor in western North Carolina and quantify habitat characteristics and levels of leaf chlorophyll for each species. We conducted broad-scale surveys (walkabouts) of seven sites in Pisgah National Forest during the winter and collected habitat data in 26 patches of each species in one mesic forest. Both species shared similar habitat attributes at this site (plants located ∼ 2 m from overstory trees of similar diameter in ∼ 45% sunlight). However, across all sites, T. discolor was three times more abundant than A. hyemale, more likely to occur in large patches (> 20 plants), and more consistently distributed across a range of slope aspects. In contrast, A. hyemale occurred most often on slopes facing 91–180°, and at elevations > 750 m. Whereas A. hyemale was most often associated with Liriodendron tulipifera overstory trees, T. discolor was often in close proximity to Quercus spp. as well as L. tulipifera. Leaf chlorophyll was twice as high in A. hyemale, which could support differences in photosynthetic strategies, or reflect differences in leaf size and morphology.
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