Abstract
Abstract. We analysed 1040 individual trees, located in 62 plots across the Amazon Basin for leaf mass per unit area (MA), foliar carbon isotopic composition (δ13C) and leaf level concentrations of C, N, P, Ca, Mg, K and Al. All trees were identified to the species level with the dataset containing 58 families, 236 genera and 508 species, distributed across a wide range of soil types and precipitation regimes. Some foliar characteristics such as MA, [C], [N] and [Mg] emerge as highly constrained by the taxonomic affiliation of tree species, but with others such as [P], [K], [Ca] and δ13C also strongly influenced by site growing conditions. By removing the environmental contribution to trait variation, we find that intrinsic values of most trait pairs coordinate, although different species (characterised by different trait suites) are found at discrete locations along a common axis of coordination. Species that tend to occupy higher fertility soils are characterised by a lower MA and have a higher intrinsic [N], [P], [K], [Mg] and δ13C than their lower fertility counterparts. Despite this consistency, different scaling patterns were observed between low and high fertility sites. Inter-relationships are thus substantially modified by growth environment. Analysing the environmental component of trait variation, we found soil fertility to be the most important predictor, influencing all leaf nutrient concentrations and δ13C and reducing MA. Mean annual temperature was negatively associated with leaf level [N], [P] and [K] concentrations. Total annual precipitation positively influences MA, [C] and δ13C, but with a negative impact on [Mg]. These results provide a first basis for understanding the relationship between the physiological functioning and distribution of tree species across Amazonia.
Highlights
Plants are the central link in the soil-plant-atmosphere continuum, utilising and cycling a range of atmospherically (C, H, O, and N) or geologically (P, Ca, K) derived elements (Jobbagy and Jackson, 2004)
[C] and δ13C, but with a negative impact on [Mg]. These results provide a first basis for understanding the relationship between the physiological functioning and distribution of tree species across Amazonia
Taken together our results highlight three important points regarding the biogeochemistry of the Amazon basin, as expressed through a set of key tree foliar properties
Summary
Plants are the central link in the soil-plant-atmosphere continuum, utilising and cycling a range of atmospherically (C, H, O, and N) or geologically (P, Ca, K) derived elements (Jobbagy and Jackson, 2004). Different hypotheses have been proposed regarding the factors controlling the metabolic tissue concentration of the main nutrients related to plant growth (Reich and Oleksyn, 2004), especially N and P (Niklas, 2006) These hypotheses summarize a physiological, temperature or geochemical driven background of N and P cycling and have gained particular interest recently, as foliar C:N:P stoichiometry may be an important factor controlling the growth rate of a wide range of plants (Elser et al, 2000; Kerkhoff et al, 2005; Niklas, 2006). Examining a range of potential edaphic and environmental predictors, Quesada et al (2009a) found total soil phosphorus to be the best predictor of above ground woody biomass growth rates for a wide range of Amazon forest types growing on a wide range of different soil types
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