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We assessed the influence of sample pretreatment on the amounts and forms of P extracted in NaOH-EDTA (cthylenediamine tetraacetic acid) from a series of contrasting wetland soils from the Florida Everglades. Samples of unconsolidated benthic floc and underlying soil (0-10 cm) were extracted either fresh (overnight refrigeration only), air dried (10 d at ~30[degrees]C), or frozen at -80[degrees]C and lyophilized (~48 h), before extraction and solution [.sup.31]p nuclear magnetic resonance (NMR) spectroscopy. Significant differences in total P extraction following pretreatment were detected for one out of four benthic floc samples and three out of four soil samples, although the changes were inconsistent: in two cases the total P extraction increased, while in two others it decreased. Assessment of the P composition by solution [sup.31] P NMR spectroscopy revealed differences among treatments, although these were mostly within the range of error associated with replicate analyses; however, DNA was not detected in a fresh sample of calcareous benthic floe, despite representing an important component of the organic P extracted front dried samples. The apparent sample-specific nature of the changes confirms the importance of carefully assessing pretreatment effects in studies of soil organic P in wetlands. Abbreviations: EDTA, ethvlenediamine tetraacctic acid; NMR, nuclear magnetic resonance.

The need to integrate environmental responses at the landscape scale is a reoccurring theme in biogeochemistry and ecology. This linkage can be addressed by using geostatistics to examine spatial patterns and then assessing the relationships of these patterns to known ecosystem drivers. In this study, we used a stratified random sampling design to collect soil cores from 388 sites to quantify the spatial distribution of soil properties in a 233000 ha subtropical wetland, Water Conservation Area 3 (WCA-3). To reflect hydrologic boundaries within the system, WCA-3 was divided into three zones: 3AN, 3AS, and 3B. Interpolated maps indicated that the highest levels of bulk density were located in western 3AN, whereas the highest total phosphorus (TP) values were located in northern 3AN and in areas adjacent to a canal bisecting the area. Twenty-five percent of 3AN had TP concentrations in the 0- to 10-cm layer > 500 mg [kg.sup.-1], indicating enrichment beyond historic levels. Only 5% of 3AS and 6% of 3B showed TP > 500 mg [kg.sup-1]. Total nitrogen (TN) and carbon (TC) were lowest in western 3AN, whereas the rest of WCA-3 had higher and more homogenous TN and TC distributions. Overall, distributions of soil properties were more homogeneous in 3AS than they were in 3AN or 3B. The approach used in this study provides a model for assessing current impacts to WCA-3, supplies baseline conditions against which future restoration efforts can be evaluated, and could be used in other landscape-scale wetland restoration projects.

Biogeochemical controls of N2O production and reduction during denitrification in cultivated and intermittently flooded peatland soils are poorly understood. Soils from sugarcane (Saccharum spp.), vegetable, turfgrass, and uncultivated subtropical peatlands in the Everglades Agricultural Area (EAA) were studied to elucidate influence of land use on N2O production and reduction. Under ambient soil conditions, intensively managed, tilled soils (sugarcane and vegetable) had 1.5 to 4 times lower N2O production and reduction than turfgrass soils. Uncultivated soils had 130 to 270% higher N2O production than tilled soils but had similar N2O reduction compared with tilled soils. A lower ratio of N2O reduction to production was observed for uncultivated soils compared to other land uses. Net N2O production was highest for uncultivated soils and decreased in the order of turfgrass, vegetable and sugarcane soils. For all land uses, N2O production was limited by electron donors (labile organic C) but not by electron acceptors (NO3-). Depletion of labile organic C through long-term soil oxidation after drainage resulted in limited availability of this energy source for denitrifying microorganisms. In addition, high residual NO3 - resulting from organic N mineralization and inorganic fertilizer additions inhibited N2O reduction. Our results suggest that sugarcane production is likely to reduce N2O emissions from the EAA compared with other current land uses. Management practices with addition of labile organic C to the EAA soils may possibly result in N2O emission pulses because of the greater stimulation of labile organic C on N2O production than on N2O reduction. [ABSTRACT FROM AUTHOR]