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This article in SSSAJ

  1. Vol. 56 No. 5, p. 1492-1499
     
    Received: July 23, 1991


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doi:10.2136/sssaj1992.03615995005600050026x

Distribution of Soil and Plant Nutrients along a Trophic Gradient in the Florida Everglades

  1. M. S. Koch  and
  2. K. R. Reddy
  1. South Florida Water Management District, Division of Everglades Systems Research, P.O. Box 24680, West Palm Beach, FL 33416
    Soil and Water Science Dep., Institute of Food and Agricultural Sciences, Univ. of Florida, Gainesville, FL 32611

Abstract

Abstract

Historically, atmospheric precipitation has been the primary source of N and P to the Florida Everglades. Alterations to the natural hydrology, surface water runoff from agricultural lands, and controlled releases from Lake Okeechobee have increased nutrient loading to the Everglades. A nutrient front encompassing approximately 8000 ha has developed in a northern Everglades marsh, Water Conservation Area 2A (WCA-2A; 44 684 ha), during the last three decades from surface water P and N loading, in addition to atmospheric inputs. Soil cores (0–60 cm) and plant tissue were collected from sawgrass, Cladium jamaicense Crantz, and cattail, Typha domingensis Pers., stands at a distance of 1.6, 5.6, and 9.3 km south of major surface water inflows in WCA-2A; Site N (northern), Site C (central), and Site S (southern), respectively. Although N loading was approximately 10-fold greater at Site N compared with Sites C and S, no significant difference in total N was found between sites at any soil depth. In contrast, P accumulated threefold in soils at Site N compared with Site S (P < 0.05). Organic P accounted for approximately 75% of the total P. Acid-extractable inorganic P (HCl-Pl), as an indicator of Ca-bound P, accounted for 80% of the inorganic P and was significantly correlated to dissolved P concentrations of the soil pore water (r = 0.89). Alkali-extractable inorganic P (NaOH-Pl), as an indicator of the Fe- and Al-bound P, comprised 20% of the total inorganic P. High pH values (> 8.0) were measured from pore water associated with benthic algal mats. Interstitial P concentrations were 2 to 3 orders of magnitude higher at Site N (> 1000 µg L−1) than at Site S (<4 µg L−1) and plant tissue N/P ratios at Site N and C were lower, 11:1 compared with 40:1 at Site S. These data suggest P may be an important nutrient limiting primary productivity in the Everglades and that Ca-P precipitation, catalyzed by algal photosynthesis, may be an important mechanism for soil P assimilation.

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