| The Pine Rockland forest originating from limestone substrates is listed as one of the most endangered ecosystems in the United States, and has harbored the South Florida slash pine. Changes of fire regime and landscape fragmentation have caused a declination of Pine Rockland forest ecosystem. The objectives of this research were to (1) determine nutrient limitation and effects of prescribed fire on nutrient availability; (2) determine impacts of fire intensity and soil moisture on soil nutrient pools; and (3) predict availability of P after a fire.;Results of analysis of foliar nutrient contents and DRIS indices indicated that P is the most limiting factor and potassium is the second limiting nutrient in the Pine Rockland forest; whereas, nitrogen is in marginal to limitation. Prescribed fire significantly increased soil pH, EC, and extractable P, Mg, K, Mn after 14 days, and extractable Fe and Ca in 270 and 360 days after the fire respectively, but not for extractable Cu and Zn. Soil NH4 + pool significantly increased immediately after the fire, whereas the soil NO3- pool was increased in post-fire 180 days.;Fire intensity significantly decreased total contents of C, N, and K in residual ash, but not for total content of P, Ca, Mg, Fe, Mn, and Zn. The fire intensity significantly impacted soil pH, EC, and soil extractable contents of PO4-P, NO3-N, NH4-N, Mg, K, Fe, Mn, Cu, and Zn. However, soil moisture after a fire significantly changed soil pH, EC, and soil extractable NH4-N, NO3-N, PO4-P, Fe, and time after a fire only significantly changed extractable content of Mn.;HPO42-, H2PO4 -, FeHPO4 (aq), MgHPO4 (aq), CaHPO4 (aq), MnHPO4 (aq), FeH2PO4+, CaH2PO4+, and CaPO4 - were major compounds of P in the soil solution in the Pine Rockland. Prescribed fire significantly increased extractable concentrations of these P compounds after 14 days, except for FeH2PO4 +. Within a relatively low P availability, solubility of P in the soil solution was controlled by vivianite and MnHPO4, and undersaturated with Ca/Mg-P minerals. Changes of ionic activities in the soil solution following the fire shifted equilibrium of P between vivianite and MnHPO4. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html )... |
