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https://hdl.handle.net/2440/105175
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Type: | Journal article |
Title: | Leaf nitrogen from first principles: field evidence for adaptive variation with climate |
Author: | Dong, N. Colin Prentice, I. Evans, B. Caddy-Retalic, S. Lowe, A. Wright, I. |
Citation: | Biogeosciences, 2017; 14(2):481-495 |
Publisher: | Copernicus Publications |
Issue Date: | 2017 |
ISSN: | 1726-4170 1726-4189 |
Statement of Responsibility: | Ning Dong, Iain Colin Prentice, Bradley J. Evans, Stefan Caddy-Retalic, Andrew J. Lowe and Ian J. Wright |
Abstract: | Nitrogen content per unit leaf area (Narea) is a key variable in plant functional ecology and biogeochemistry. Narea comprises a structural component, which scales with leaf mass per area (LMA), and a metabolic component, which scales with Rubisco capacity. The co-ordination hypothesis, as implemented in LPJ and related global vegetation models, predicts that Rubisco capacity should be directly proportional to irradiance but should decrease with increases in ci : ca and temperature because the amount of Rubisco required to achieve a given assimilation rate declines with increases in both. We tested these predictions using LMA, leaf δ13C, and leaf N measurements on complete species assemblages sampled at sites on a north–south transect from tropical to temperate Australia. Partial effects of mean canopy irradiance, mean annual temperature, and ci : ca (from δ13C) on Narea were all significant and their directions and magnitudes were in line with predictions. Over 80 % of the variance in community-mean (ln) Narea was accounted for by these predictors plus LMA. Moreover, Narea could be decomposed into two components, one proportional to LMA (slightly steeper in N-fixers), and the other to Rubisco capacity as predicted by the co-ordination hypothesis. Trait gradient analysis revealed ci : ca to be perfectly plastic, while species turnover contributed about half the variation in LMA and Narea. Interest has surged in methods to predict continuous leaf-trait variation from environmental factors, in order to improve ecosystem models. Coupled carbon–nitrogen models require a method to predict Narea that is more realistic than the widespread assumptions that Narea is proportional to photosynthetic capacity, and/or that Narea (and photosynthetic capacity) are determined by N supply from the soil. Our results indicate that Narea has a useful degree of predictability, from a combination of LMA and ci : ca – themselves in part environmentally determined – with Rubisco activity, as predicted from local growing conditions. This finding is consistent with a "plant-centred" approach to modelling, emphasizing the adaptive regulation of traits. Models that account for biodiversity will also need to partition community-level trait variation into components due to phenotypic plasticity and/or genotypic differentiation within species vs. progressive species replacement, along environmental gradients. Our analysis suggests that variation in Narea is about evenly split between these two modes. |
Rights: | © Author(s) 2017. This work is distributed under the Creative Commons Attribution 3.0 License. |
DOI: | 10.5194/bg-14-481-2017 |
Grant ID: | http://purl.org/au-research/grants/arc/FT100100910 |
Published version: | http://dx.doi.org/10.5194/bg-14-481-2017 |
Appears in Collections: | Aurora harvest 8 Environment Institute publications |
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hdl_105175.pdf | Published version | 803.51 kB | Adobe PDF | View/Open |
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