Casey R. Williams
Chris Doffitt
Darren Johnson
Beth A. Middleton
2022
<p><span>Rare plant species that are constrained by shading may be threatened by a lack of natural disturbance that removes overhanging vegetation. The original distribution of the study species </span><i>Physostegia correllii</i><span> (Lundell) Shinners included freshwater floodplains of large rivers in the southcentral U.S. (Colorado, Rio Grande, and Mississippi rivers). A second species, </span><i>Trillium texanum</i><span> Buckley was found in seep spring baygalls in east-central Texas and extreme northwestern Louisiana. Experiments to determine the effects of shading on </span><i>P. correllii</i><span> and </span><i>T. texanum</i><span> were conducted using short-term shade cloth treatments (full sunlight vs. 30% shading for 2–3 weeks), and a dryness treatment for </span><i>T. texanum</i><span> (moist vs. less moist). Mean height and cover responses of individuals for both species were determined in conservation gardens located in Lafayette, Louisiana. </span><i>Physostegia correllii</i><span> grown in shaded environments for 2.5 weeks had shorter mean height than if grown in full sunlight. Half of the shaded plants in shaded plots had died by the mid-summer. For </span><i>T. texanum,</i><span> shading reduced the mean height and cover of plants. Therefore, management to remove overhanging ground vegetation to mimic natural disturbance might revive </span><i>P. correlli</i><span>i and/or </span><i>T. texanum</i><span> populations where overhanging vegetation is increasing due to lack of natural disturbance (e.g., flood pulsing, grazing, burning).</span></p>
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10.17348/jbrit.v16.i2.1270
en
Botanical Research Institute of Texas
Effects of shading on the rare plant species, Physostegia correllii (Lamiaceae) and Trillium texanum (Melanthiaceae)
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