Coastal wetland forest ecosystems rely on the intimate interactions of hydrology, salinity, and coastal forest vegetation. The boundary between marsh and forest is often where hummock-swale terrain exists. It remains unknown as to the degree to which trees may experience varied salinity level within hummocks provided with freshwater flux. This study examined the hydrological regime of the hummock-swale terrain that resulted in salinity variation and whether freshwater source exists for baldcypress. Natural tracers of stable isotopes of water and salinity were applied to understand the sources of water. To better examine the tracers used, we conducted several experiments to gain a clearer understanding of the variability in isotopic compositions in throughfall and by extracting water from wood and soil. The studies indicated that baldcypress are able to avoid saline flooding from hummocks. We found that the throughfall process does correspond with the canopy structure enough to strongly influence throughfall amount but only weakly influence isotopic composition. Also at microtopographic scale, salinity of the groundwater in hummocks remained chronically high and vertical solute exchange was little. The shallow subsurface of hummocks was a zone characterized by slow dilution and episodic salinization rather than slow salinization and episodic flushing. Rainfall and frequent inundation by generally low-salinity water flushed salts and maintained lower salinity in upper layers. Thus the baldcypress forest overall occupies a nonsaline site, but the episodic influxes followed by slow leaching occurs superimposed on a layer of salinity that lies presumably beneath the root zone for most of the growing season. In addition, the systematic errors were little considering the isotopic fractionation during water extraction from wood.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-04022015-142902 |
| Date | 21 April 2015 |
| Creators | Hsueh, Yu-Hsin |
| Contributors | Krauss, Ken W., Keim, Richard F., Chambers, Jim L. |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-04022015-142902/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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