<p> Terrestrial litterfall is a well-documented subsidy of nutrients and organic matter to adjacent aquatic ecosystems. Nitrogen-fixing plants increase nutrient dynamics via nitrogen (N) - rich litterfall in both terrestrial and aquatic ecosystems, and the effects are often more pronounced when areas lacking native N<sub>2</sub>-fixers are invaded. This study examined differences in organic matter and nutrient inputs from the invasive, N<sub>2</sub>-fixing tree, <i>Prosopis pallida</i>, and the native, non N<sub>2</sub>-fixing tree, <i>Thespesia populnea</i>, to determine effects on anchialine ponds on Hawai`i Island's leeward coast. My objectives were to quantify: 1) tree basal area and density surrounding the ponds, 2) quality and quantity of <i>P. pallida</i> and <i>T. populnea</i> litter inputs, 3) inorganic N content of soil surrounding the ponds, 4) leached nutrients from <i>P. pallida</i> and <i>T. populnea</i> leaf litter. These response variables were then compared to water nutrient concentrations (i.e., phosphate, nitrate, ammonium, dissolved organic carbon (C), and total dissolved N and phosphorus (P)) in the ponds of interest. Basal area, density, litterfall mass, total N and C inputs, and leachate values were similar between pond types categorized as <i>P. pallida</i> – or <i> T. populnea</i> – dominated. Foliar N concentrations were 28 percent higher in <i>P. pallida</i> – dominated ponds compared to <i>T. populnea</i> – dominated ponds, but foliar P concentrations were three times greater in <i>T. populnea</i> ponds than <i>P. pallida</i> ponds. Total P inputs were greater beneath <i>T. populnea</i> ponds and there was a positive correlation between <i>T. populnea</i> size and abundance and pond water phosphate concentrations. These results suggest that the N if influencing water quality in Hawaiian anchialine ponds more than the invasive N<sub>2</sub>-fixing species, although high background water nutrient levels may be inhibiting our ability to detect any significant impacts. The transfer of <i>T. populnea</i>'s P-rich litter to pond water appears to have a strong influence on ecosystem functioning.</p>
| Identifer | oai:union.ndltd.org:PROQUEST/oai:pqdtoai.proquest.com:1550185 |
| Date | 12 February 2014 |
| Creators | Nelson-Kaula, Kehauwealani K. |
| Publisher | University of Hawai'i at Hilo |
| Source Sets | ProQuest.com |
| Language | English |
| Detected Language | English |
| Type | thesis |
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