Do woody and herbaceous species compete for soil water across topographic gradients? Evidence for niche partitioning in a Neotropical savanna

D. R. Rossatto, L. C.R. Silva, L. S.L. Sternberg, A. C. Franco

Research output: Contribution to journalArticle

27 Scopus citations

Abstract

Savannas are characterized by sparsely distributed woody species within a continuous herbaceous cover, composed mainly by grasses and small eudicot herbs. This vegetation structure is variable across the landscape, with shifts from open grassland to savanna woodland determined by factors that control tree density. These shifts often appear coupled with environmental variations, such as topographic gradients. Here we investigated whether herbaceous and woody savanna species differ in their use of soil water along a topographic gradient of about 110m, spanning several vegetation physiognomies generally associated with Neotropical savannas. We measured the δ2H and δ18O signatures of plants, soils, groundwater and rainfall, determining the depth of plant water uptake and examining variations in water uptake patterns along the gradient. We found that woody species use water from deeper soil layers compared to herbaceous species, regardless of their position in the topographic gradient. However, the presence of a shallow water table restricted plant water uptake to the superficial soil layers at lower portions of the gradient. We confirmed that woody and herbaceous species are plastic with respect to their water use strategy, which determines niche partitioning across topographic gradients. Abiotic factors such as groundwater level, affect water uptake patterns independently of plant growth form, reinforcing vegetation gradients by exerting divergent selective pressures across topographic gradients.

Original languageEnglish (US)
Pages (from-to)14-18
Number of pages5
JournalSouth African Journal of Botany
Volume91
DOIs
StatePublished - Mar 1 2014

Keywords

  • Cerrado
  • Growth forms
  • Herbaceous layer
  • Niche partitioning
  • Resource use
  • Water uptake
  • Woody layer

ASJC Scopus subject areas

  • Plant Science

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