Analysing Amazonian forest productivity using a new individual and trait-based model (TFS v.1)

Summary Plant phenotypic diversity is shaped by the interplay of trade‐offs and constraints in evolution. Closely integrated groups of traits (i.e. trait dimensions) are used to classify plant phenotypic diversity into plant strategies, but we do not know the degree of interdependence among trait dimensions. To assess how selection has shaped the phenotypic space, we examine whether trait dimensions are independent. We gathered data on saplings of 24 locally coexisting tree species in a temperate forest, and examined the correlation structure of 20 leaf, branch, stem and root traits. These traits fall into three well‐established trait dimensions (the leaf economic spectrum, the wood spectrum and Corner's Rules) that characterize vital plant functions: resource acquisition, sap transport, mechanical support and canopy architecture. Using ordinations, network analyses and Mantel tests, we tested whether the sapling phenotype of these tree species is organized along independent trait dimensions. Across species, the sapling phenotype is not structured into clear trait dimensions. The trait relationships defining trait dimensions are either weak or absent and do not dominate the correlation structure of the sapling phenotype as a whole. Instead traits from the three commonly recognized trait dimensions are organized into an integrated trait network. The effect of phylogeny on trait correlations is minimal. Our results indicate that trait dimensions apparent in broad‐based interspecific surveys do not hold up among locally coexisting species. Furthermore, architectural traits appear central to the phenotypic network, suggesting a pivotal role for branching architecture in linking resource acquisition, mechanical support and hydraulic functions. Synthesis. Our study indicates that local and global patterns of phenotypic integration differ and calls into question the use of trait dimensions at local scales. We propose that a network approach to assessing plant function more effectively reflects the multiple trade‐offs and constraints shaping the phenotype in locally co‐occurring species.

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“…FTS, Fyllas et al . and aDGVM2, Scheiter, Langan & Higgins ) or globally (e.g. LPJmL‐FIT, Sakschewski et al .…”

Section: Discussionmentioning

confidence: 99%

Interspecific integration of trait dimensions at local scales: the plant phenotype as an integrated network

et al. 2017

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“…Scheiter et al, 2013;Fyllas et al, 2014;van Bodegom et al, 2014;Ali et al, 2015;Fisher et al, 2015;Meng et al, 2015;Sakschewski et al, 2015). Some trait-based modelling approaches have relied on empirical information on trait-trait and trait-environment covariation, but others (e.g.…”

Section: Implications For Modellingmentioning

confidence: 99%

Leaf nitrogen from first principles: field evidence for adaptive variation with climate

et al. 2017

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Abstract. Nitrogen content per unit leaf area (N area ) is a key variable in plant functional ecology and biogeochemistry. N area 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 c i : c a 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 δ 13 C, 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 c i : c a (from δ 13 C) on N area were all significant and their directions and magnitudes were in line with predictions. Over 80 % of the variance in community-mean (ln) N area was accounted for by these predictors plus LMA. Moreover, N area 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 c i : c a to be perfectly plastic, while species turnover contributed about half the variation in LMA and N area .Interest has surged in methods to predict continuous leaftrait variation from environmental factors, in order to improve ecosystem models. Coupled carbon-nitrogen models require a method to predict N area that is more realistic than the widespread assumptions that N area is proportional to photosynthetic capacity, and/or that N area (and photosynthetic capacity) are determined by N supply from the soil. Our results indicate that N area has a useful degree of predictability, from a combination of LMA and c i : c a -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 Published by Copernicus Publications on behalf of the European Geosciences Union. and/or genotypic differentiation within species vs. progressive species replacement, along environmental gradients. Our analysis suggests that variation in N area is about evenly split between these two modes.

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“…This new generation of models is partly inspired by individual plant-based and forest stand models (e.g., [Fyllas et al, 2014;Fischer et al, 2016;Maréchaux and Chave, 2017]), and they explicitly represent forest dynamics via tree demography Biogeosciences Discuss., https://doi.org /10.5194/bg-2018-308 Manuscript under review for journal Biogeosciences Discussion started: 18 July 2018 c Author(s) 2018. CC BY 4.0 License.…”

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The importance of tree demography and root water uptake for modelling the carbon and water cycles of Amazonia

Joetzjer

Maignan

Chave

et al. 2018

Preprint

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Abstract. Amazonian forest plays a crucial role in regulating the carbon and water cycles in the global climate system. 20However, the representation of biogeochemical fluxes and forest structure in dynamic global vegetation models (DGVMs) remains challenging. This situation has considerable implications for modelling the state and dynamics of Amazonian forest.To address these limitations, we present an adaptation of the ORCHIDEE-CAN DGVM, a second-generation DGVM that explicitly models tree demography and canopy structure with an allometry-based carbon allocation scheme and accounts for hydraulic architecture in the soil-stem-leaf continuum. We use two versions of this DGVM: the first one (CAN) includes a 25 new parameterization for Amazonian forest; the second one (CAN-RS) additionally includes a mechanistic root water uptake module, which models the hydraulic resistance of the water transfer from soil pores to roots. We compared the results with the simulation output of the "big-leaf" standard version of the ORCHIDEE DGVM (TRUNK) and with observations of turbulent energy and CO 2 fluxes at flux tower locations, of carbon stocks and stand density at inventory plots and observation-based models of photosynthesis (GPP) and evapotranspiration (LE) across the Amazon basin. CAN-RS 30 reproduced observed carbon and water fluxes and carbon stocks as well as TRUNK across Amazonia, both at local and at regional scales. In CAN-RS, water uptake by tree roots in the deepest soil layers during the dry season significantly improved the modelling of GPP and LE seasonal cycles, especially over the Guianan and Brazilian Shields. These results imply that explicit coupling of the water and carbon cycles improves the representation of biogeochemical cycles in Amazonia and their spatial variability. Representing the variation in the ecological functioning of Amazonia should be the 35 next step to improve the performance and predictive ability of new generation DGVMs.

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Analysing Amazonian forest productivity using a new individual and trait-based model (TFS v.1)

Cited by 50 publications

References 109 publications

Interspecific integration of trait dimensions at local scales: the plant phenotype as an integrated network

Interspecific integration of trait dimensions at local scales: the plant phenotype as an integrated network

Leaf nitrogen from first principles: field evidence for adaptive variation with climate

The importance of tree demography and root water uptake for modelling the carbon and water cycles of Amazonia

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