The partitioning of water uptake between growth forms in a Neotropical savanna: Do herbs exploit a third water source niche?

D. R. Rossatto, Leonel Sternberg, A. C. Franco

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

In addition to trees and grasses, the savannas of central Brazil are characterised by a diverse herbaceous dicot flora. Here we tested whether the coexistence of a highly diversified assemblage of species resulted in stratification or strong overlap in the use of soil water resources. We measured oxygen and hydrogen isotope ratios of stem water from herbs, grasses and trees growing side by side, as well as the isotopic composition of water in soil profile, groundwater and rainfall, and predawn (Ψpd) and midday (Ψmd) leaf water potentials. We used a stable isotope mixing model to estimate vertical partitioning of soil water by the three growth forms. Grasses relied on shallow soil water (5-50cm) and were strongly anisohydric. Ψpd and Ψmd decreased significantly from the wet to the dry season. Trees extracted water from deeper regions of the soil profile (60-120cm) and were isohydric. Ψpd and Ψmd did not change from the wet to the dry season. Herbs overlapped with grasses in patterns of water extraction in the dry season (between 10 and 40cm), but they took up water at soil depths intermediate (70-100cm) to those of trees and grasses during the wet season. They showed seasonal changes in Ψpd but not in Ψmd. We conclude that vertical partitioning of soil water may have contributed to coexistence of these three growth forms and resulted in a more complex pattern of soil water extraction than the two-compartment model of soil water uptake currently used to explain the structure and function of tropical savanna ecosystems.

Original languageEnglish
Pages (from-to)84-92
Number of pages9
JournalPlant Biology
Volume15
Issue number1
DOIs
StatePublished - Jan 1 2013

Fingerprint

growth form
water uptake
savanna
herb
savannas
herbs
niche
niches
partitioning
soil water
grass
grasses
dry season
water
coexistence
soil profiles
soil profile
shallow soil
hydrogen isotope
hydrochemistry

Keywords

  • Niche partitioning
  • Plant diversity
  • Savanna
  • Two-layer soil water model
  • Water potential
  • Water uptake

ASJC Scopus subject areas

  • Plant Science
  • Ecology, Evolution, Behavior and Systematics

Cite this

The partitioning of water uptake between growth forms in a Neotropical savanna : Do herbs exploit a third water source niche? / Rossatto, D. R.; Sternberg, Leonel; Franco, A. C.

In: Plant Biology, Vol. 15, No. 1, 01.01.2013, p. 84-92.

Research output: Contribution to journalArticle

Rossatto, D. R. ; Sternberg, Leonel ; Franco, A. C. / The partitioning of water uptake between growth forms in a Neotropical savanna : Do herbs exploit a third water source niche?. In: Plant Biology. 2013 ; Vol. 15, No. 1. pp. 84-92.
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