Assessment of the Spatial Distribution of Soil Properties in a Northern Everglades Marsh R. Corstanje, S. Grunwald,* K. R. Reddy, T. Z. Osborne, and S. Newman ABSTRACT Florida Everglades restoration plans are aimed at maintaining and restoring characteristic landscape features such as soil, vegetation, and hydrologic patterns. This study presents the results from an ex- haustive spatial sampling of key soil properties in Water Conservation Area 1 (WCA 1), which is part of the northern Everglades. Three soil strata were sampled: floe, upper 0- to 10-cm soil layer, and 10- to 20-cm soil layer. A variety of properties were measured including bulk den- sity (BD), loss on ignition (LOI), total phosphorus (TP), total inor- ganic phosphorus (TIP), total nitrogen (TN), total carbon (TC), total iron (TFe), total magnesium (TMg), total aluminum (TAI), and total calcium (TCa). Interpolated maps and model prediction uncertainties of properties were generated using geostatistical methods. We found that the uncertainty associated with spatial predictions of floc, par- ticularly floc BD, was highest, whereas spatial predictions of soil chemi- cal properties such as soil Ca were more accurate. The resultant spatial patterns for these soil properties identified three predominant fea- tures in WCA 1: (i) a north to south gradient in soil properties as- sociated with the predominant hydrological gradient, (ii) areas of considerable soil nutrient enrichment along the western canal of WCA 1, and (iii) areas of considerable Fe enrichment along the eastern canal. By using geostatistical techniques we were able to describe the spatial dynamics of soil variables and express these predictions with an acceptable level of uncertainty. COLOGICAL RESTORATION of degraded lands is an emerging challenge arising from the growing rec- ognition of the value of services provided by healthy ecosystems. Restoration efforts range in intensity and complexity aiming to recover previous functions (e.g., to re-establish exogenous flows of water and sediment) and/or landscape patterns (e.g., nutrient status, vegeta- tion structure). Restoration in the Everglades, as enacted under the Everglades Forever Act (State of Florida, 1994), is concerned with maintaining and restoring a habitat mosaic that is comprised of, among others, saw- grass (Cladium jamaicense Crantz) prairies and patches, open water sloughs, tree islands, and marl-forming marshes (Noe et al., 2001). Soil nutrient enrichment has been as- sociated with significant alterations of Everglades wet- land ecosystem structure and function (DeBusk et al., 1994, 2001; Davis et al., 2003; King et al., 2004). Nutrient gradients (Davis, 1991; DeBusk et al., 1994) produce a patterned response within the Everglades. For example, R. Corstanje and S. Grunwald, GIS Research Laboratory, and K.R. Reddy and T.Z. Osborne, Wetland Biogeochemistry Laboratory, Soil and Water Science Department, University of Florida-Institute of Food and Agricultural Sciences, 2169 McCarty Hall, PO Box 110290, Gainesville, FL 32611-0510. S. Newman, Everglades Department, South Florida Water Management District, P0. Box 24680, West Palm Beach, FL 33416-4680. Received 23 June 2005. *Corresponding author (SGrunwald@ifas.ufl.edu). Published in J. Environ. Qual. 35:938-949 (2006). Technical Reports: Wetlands and Aquatic Processes doi:10.2134/jeq2005.0255 © ASA, CSSA, SSSA 677 S. Segoe Rd., Madison, WI 53711 USA cattail (Typha domingensis Pers.) dominates areas close to nutrient inflows, which were also found to contain high levels of water column and soil phosphorus (P) content. This study focuses on Water Conservation Area 1 (WCA 1), which is part of the Loxahatchee National Wildlife Refuge (LNWR) of the Greater Everglades. The area has been designated as "Outstanding Florida Waters" by the State of Florida and contains much of the distinctive habitat favored under the Greater Everglades restoration plans. The conservation area is also a unique hydrologic unit of the Everglades that is a slightly acidic, rain-fed system that sits on deep peat (South Florida Water Man- agement District, 1992). Since it was last sampled in 1991 there is little current knowledge on the movement and distribution of soil nutrients and cations in this particular water conservation area (Newman et al., 1997). Soils in wetlands often exhibit characteristic, complex spatial patterns that indicate heterogeneity in soil re- sources and affect patterns of soil process rates (Ettema et al., 1998). These patterns are often a combination of current and historical autochtonous and allochtonous functions that influence wetland systems (Stolt et al., 2001). Commonly, the spatial distribution of soil properties is not uniform. This uneven distribution of soil character- istics, such as nutrient availability, organic content, and mineral content, implicitly reflects the processes that occur within the larger ecosystem. Spatial variability of soil characteristics can strongly affect the outcomes of logical, empirical, and physical models of soil and landscape processes (Lin et al., 2005) including those available to managers and planners in the Everglades restoration efforts. As a result, an adequate understand- ing of soil variability as a function of space becomes es- sential. Geostatistics views soil properties as continuous variables and models these as the most likely outcomes of random processes (Webster, 2000). This allows the random variation in soil properties to be formulated mathematically, which minimizes the prediction error for the observed variables and provides confidence in pre- dictions for the unsampled locations. In other words, by designing, executing, and analyzing a spatial study using geostatistics we can quantitatively assess the properties and associated uncertainty of the spatial distribution of soil characteristics. This paper will analyze underlying causes of soil variability, increase our understanding of a soft water system in the Everglades, and support future research efforts aimed at protecting this portion of the Florida landscape. The specific objectives of this study were to identify spatial patterns of physical and chemical soil properties in the topsoil and floc (decaying plant Abbreviations: BD, bulk density; LNWR, Loxahatchee National Wild- life Refuge; LOI, loss on ignition; TAI, total aluminum; TC, total carbon; TCa, total calcium; TFe, total iron; TIP total inorganic phos- phorus; TMg, total magnesium; TN, total nitrogen; TP. total phos- phorus; WCA, Water Conservation Area. 938