Article

Ecosystems

, Volume 11, Issue 8, pp 1234-1246

First online:

Understanding the Influences of Spatial Patterns on N Availability Within the Brazilian Amazon Forest

  • Gabriela Bielefeld NardotoAffiliated withCentro de Energia Nuclear na Agricultura, Universidade de São Paulo Email author 
  • , Jean Pierre Henry Balbaud OmettoAffiliated withCentro de Energia Nuclear na Agricultura, Universidade de São Paulo
  • , James R. EhleringerAffiliated withSIRFER, Biology Department, University of Utah
  • , Niro HiguchiAffiliated withInstituto Nacional de Pesquisas da Amazônia
  • , Mercedes Maria da Cunha BustamanteAffiliated withDepartamento de Ecologia, Universidade de Brasília
  • , Luiz Antonio MartinelliAffiliated withCentro de Energia Nuclear na Agricultura, Universidade de São Paulo

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Abstract

Nitrogen variations at different spatial scales and integrated across functional groups were addressed for lowland tropical forests in the Brazilian Amazon as follows: (1) how does N availability vary across the region over different spatial scales (regional × landscape scale); (2) how are these variations in N availability integrated across plant functional groups (legume × non-legume trees). Leaf N, P, and Ca concentrations as well the leaf N isotope ratios (δ15N) from a large set of legume and non-legume tree species were measured. Legumes had higher foliar N/Ca ratios than non-legumes, consistent with the high energetic costs in plant growth associated with higher foliar P/Ca ratios found in legumes than in non-legumes. At the regional level, foliar δ15N decreased with increasing rainfall. At the landscape level, N availability was higher in the forests on clayey soils on the plateau than in forests on sandier soils. The isotope as well as the non-isotope data relationships here documented, explain to a large extent the variation in δ15N signatures across gradients of rainfall and soil. Although at the regional level, the precipitation regime is a major determinant of differences in N availability, at the landscape level, under the same precipitation regime, soil type seems to be a major factor influencing the availability of N in the Brazilian Amazon forest.

Keywords

nitrogen lowland tropical forest nitrogen stable isotopes Amazonia foliar phosphorus terra-firme forest campinarana forest