Depth of water uptake in woody plants relates to groundwater level and vegetation structure along a topographic gradient in a neotropical savanna

Davi Rodrigo Rossatto, Lucas de Carvalho Ramos Silva, Randoll Villalobos-Vega, Leonel da Silveira Lobo Sternberg, Augusto César Franco

Research output: Contribution to journalArticle

82 Scopus citations

Abstract

Vegetation structure of the savannas is variable across the landscape, ranging from open grassland to savanna woodland within topographic gradients of a few hundred meters in length. Here we investigated whether patterns of soil water extraction by the woody layer and vegetation structure changed in response to groundwater depth. We determined depth of plant water uptake, groundwater level and vegetation structure on five different locations along a topographic gradient in the highlands of Central Brazil. The elevation gradient of about 110. m covered all vegetation physiognomies generally associated with topographic gradients in savannas of Central Brazil. To estimate the depth of plant water uptake in the different slope positions we relied on comparisons of hydrogen and oxygen isotope ratios of plant stem water, water from different soil depths, from groundwater and from rainfall. We subsequently used a stable isotope mixing model to estimate vertical partitioning of soil water by woody plants along the elevation gradient. We were able to show that groundwater level affected plant water uptake patterns and soil water partitioning among savanna woody species. Vegetation at higher elevation extracted water from deeper unsaturated soils and had greater variability in water uptake strategies, which was coupled to a denser and more complex woody layer. Plants on these soils used stored water from both shallow (<0.6. m) and deep (0.6-2.00. m) soil layers. At lower elevation sites, however, the presence of a water table near the soil surface restricted water uptake to the shallower wet season unsaturated zone of the soil profile. The sparser woody vegetation is probably composed of species that only rely in superficial water uptake, or are plastic in relation to root characteristics.

Original languageEnglish (US)
Pages (from-to)259-266
Number of pages8
JournalEnvironmental and Experimental Botany
Volume77
DOIs
StatePublished - Apr 1 2012

Keywords

  • Savanna
  • Stable isotopes
  • Topographic gradient
  • Vegetation structure
  • Water uptake

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Plant Science
  • Agronomy and Crop Science

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