title: Heterogeneity of elemental composition and natural abundance of stables isotopes of C and N in soils and leaves of mangroves at their southernmost West Atlantic range.
abstract: Mangrove communities were selected in the state of Santa Catarina, Brazil, near their southernmost limit of distribution, to study mineral nutrient relation in soils and plants. Communities included three true mangrove species, Rhizophora mangle, Laguncularia racemosa and Avicennia germinans, and two associated species, the fern Acrostichum danaeifolium, and the grass Spartina densiflora. The sites included communities in the lower Río Tavares near Florianopolis city, Sonho beach near Palhoça city, and the Santo Antonio lagoon. These sites included a full range of mangroves under humid climate where winter temperatures, instead of salinity, may be the main factor regulating their productive capacity and species composition. Soil salinity was determined by the concentration of soluble Na, and soil C and N were linearly correlated indicating their association in organic matter. Tavares site showed higher specific conductivity, and concentrations of Na and Mg in the soil layer below 40 cm depth, indicating larger influence of marine water. Isotopic signature of C increased with soil depth suggesting that microorganisms decomposing organic matter are releasing 13C depleted CO2. Nitrogen isotopic signature decreased with soil depth, indicating enrichment in 15N possibly as a result of denitrification in the upper soil layers. Mineral elements in leaf tissues showed A. schaueriana with higher concentrations of N, P, Na, K, Cu, Zn, and Na/Ca ratio. Spartina densiflora was characterized by the lowest N and K concentrations, and the highest concentrations of Al and Fe. Rhizophora mangle and L. racemosa had the highest Ca concentrations. Carbon isotopic signatures identified S. densiflora as a C4 plant, and A. schaueriana as the mangrove species occupying comparatively more water stressed microsites than the rest. Leaf nitrogen isotopic signatures were positive, in correspondence with the soil values. The results support the hypothesis that sites sampled were comparatively fertile, because sediment transport through fresh water run-off is predominant in humid coasts, and therefore plants were not limited by nutrient supply, nor particularly stressed by soil salinity.
authors.affiliation: Laboratório de Gestão em Manguezal - GEMA, Departamento de Ciências Agrárias e Biológicas, Centro Universitário Norte do Espírito Santo - CEUNES, Universidade Federal do Espírito Santo - UFES, Rod. BR 101 Norte, Km 60, Bairro Litorâneo, CEP 29934-430, São Mateus, ES, Brazil.
authors.forename: M M P
authors.initials: MM
authors.lastname: Tognella
authors.affiliation: Núcleo de Estudos em Manguezais - NEMA, Departamento de Oceanografia Biológica, Faculdade de Oceanografia - FAOC, Universidade do Estado do Rio de Janeiro - UERJ, Rua São Francisco Xavier, 524, sala 4023-E, Maracanã, CEP 22420-020, Rio de Janeiro, RJ, Brazil.
authors.forename: M L G
authors.initials: ML
authors.lastname: Soares
authors.affiliation: Department of Biology, Faculty of Natural Sciences, Center for Applied Tropical Ecology and Conservation, University of Puerto Rico - UPR-Rio Piedras, Facundo Bueso Building, 301-A, PO Box 23360, 00931-3360, San Juan, Puerto Rico.
authors.forename: E
authors.initials: E
authors.lastname: Cuevas
authors.affiliation: Centro de Ecología, Instituto Venezolano de Investigaciones Científicas - IVIC, Carretera Panamericana, Km 11, Edo Miranda, Aptdo 20632, Caracas 1020-A, Venezuela.|USDA Forest Service, International Institute of Tropical Forestry, 1201, Calle Ceiba, Jardín Botánico Sur, 00926-1119, San Juan, Puerto Rico.
authors.forename: E
authors.initials: E
authors.lastname: Medina
mesh_terms: D001938:Brazil; D002247:Carbon Isotopes / Q000032:analysis*; D019684:Magnoliopsida / Q000737:chemistry*; D009587:Nitrogen Isotopes / Q000032:analysis*; D018515:Plant Leaves / Q000737:chemistry*; D054712:Salinity; D012987:Soil / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D012987:Soil