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Groundwater Thresholds For Root Decomposition And The Relation To Barrier Island Ecological State Changes, Matthew Lee Smith
Groundwater Thresholds For Root Decomposition And The Relation To Barrier Island Ecological State Changes, Matthew Lee Smith
Biological Sciences Theses & Dissertations
Barrier islands off the eastern shore of Virginia exhibit distinct habitats that abruptly transition between periodically brackish/freshwater marshes, wooded swales, and sparsely vegetated dunes. There is strong evidence that the plant communities and ecosystem processes occurring in each habitat are primarily influenced by nutrient availability and the distance between two of the three free surfaces: land and freshwater. At the Virginia Coast Reserve-Long Term Ecological Research Site in Virginia, USA, thresholds to belowground decomposition rates were identified by measuring decay of native roots and rhizomes at 32 elevations in relation to mean annual groundwater levels (-0.356 – 1.937 m). Negative …
Molecular Phylogeny Of The Genus Houstonia And Allies In Rubiaceae, Hunter Lee Shanks
Molecular Phylogeny Of The Genus Houstonia And Allies In Rubiaceae, Hunter Lee Shanks
Biological Sciences Theses & Dissertations
Houstonia (Rubiaceae) is a strictly North American genus of 24 species distributed from Mexico, throughout the United States, up to Canada. Houstonia has proven to be a taxonomically difficult genus since the Linnaean description of Houstonia and the related genera: Hedyotis and Oldenlandia in 1753. For over 250 years botanists have lumped and separated Houstonia from Hedyotis and Oldenlandia based on various morphological characters. The most recent circumscription of Houstonia (Terrell 1996) separated the genus into two subgenera with each subgenus containing two sections. Nuclear (ITS) and plastid (trnL-F, rps16) DNA sequences were used to build a molecular phylogeny depicting …