The Ecology of Hydric Hammocks - USGS National Wetlands ...

Sandy surface layers and sandy loamsubsoils arc com~on (Table 2). Theweakly cemented Bh horizon (hardpan)typical of pine flatwoods is absent.Clayey soi 1 s support hydric-hammockvegetation in some areas. Near theSilver Springs run in north-centralFlorida, hydric hammocks grow on phosphaticclayey soils (loamy fine sands)that contain 1 imestone nodules andshells. Known locally as "gumbo," thesoils belong to the Eureka and Paisleyseries and are poorly drained (U.S.Soil Conservation Service 1979).Shallow limestone bedrock in the gulfcoastal hammocks of Levy County, centralFlorida, is capped by severalinches to several feet of sandy loamor sandy clay loam (J. D. Slabaugh,U.S. Department of Agriculture SoilConservation Service, Bronson, Fl a. ;pers. comm.). In Waccasassa finesandy loam (Table 2), permeabil ity ismoderately slow t.o slow. The loamycap is, in turn, covered by a mantleof sand that gradually thickens withincreasing distance from the tidalmarshes. Due to the irregular configurationof the bedrock, the sandy mantlealso varies in thickness overshort distances. Slash pine, Pinuse]]iottii, grows On soils with thesandy mantle; conversely, hydric-hammockveyeial iurr w;~:I ve1-y ;CW VT ftOslash pines occupies the soils lackingthe mantle.In contrast to the highly acid soilsof pine flatwoods and bayheads, hydric-hammocksoils generally areslightly acid to mildly alkaline(Tables 2 and 3). Five hydric hammockstands at the northern reach of thegulf coastal hammocks had soil pH valuesbetween 5.7 dtid 5.3, end 5 ixthhad a value of 5.1 (Thompson 1980).The clayey soi 1 s that support hydrichammocks near Silver Springs are moderatelyacid (U.S. Soil ConservationService 1979). Organic matter contentof hydric-hammock soils is variablebut often low (Table 2), particularlyin relation to the amounts in bayheadsoils. More aptly termed "peat," bayheadsoil in northwestern and centralFlorida contains l5%-98% organic matter(Wharton et al. 1977; Clewell eta 1 . 1982). Thompson (1980) reportedorganic matter concentrations of 18%-54% in surficial samples of hydrichammocksoils, but the results probablywere biased by the inclusion ofTable 2. Characteristics of some sol1 series associated with hydric-hammock vegetation (from U.S. SoilConservation Service 1974; 1977; 1980; data for the Waccasassa series are from J. D. Slabaugh, pers.comrn.).Depth Texture pH Organic Cations (Meq./100 g)(cm) matter (%)Soil series % sand % silt % clay Ca Mg K NaAripeka 0-8 91 7 2 6.2 1.6 3.1 1.6 0.1 0.033-38 70 6 24 7.7 1 .O 7.7 1.5 0.2 0.8Pa rkwood 0-18 87 7 6 7.6 5.0 15.8 2.0 0.4 0.7fine sand 28-43 69 7 24 8.3 1.3Tuscawi 11 a 0-8 88 11 1 6.0 3.1 9.2 1.0 0.2 0.525-33 82 2 14 6.9 0.9 12.2 0.6 0.1 0.2