EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Optimal trait theory: testing predictions on the Northeast China Transect

Ruijie Ding1,2, Ning Dong2, Jian Ni3, and Iain Colin Prentice2
Ruijie Ding et al.
  • 1Masters Programme in Ecosystems and Environmental Change, Imperial College London, Department of Life Sciences, Silwood Park Campus, Buckhurst Road, Ascot SL5 7PY, UK
  • 2Georgina Mace Centre for the Living Planet, Department of Life Sciences, Imperial College London, Silwood Park Campus, Buckhurt Road, Ascot SL5 7PY, UK
  • 3College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua, China

Recently developed ecosystem models based on eco-evolutionary optimality hypotheses can predict many aspects of the carbon, water and nutrient economy of ecosystems. These models have focused on various key plant functional traits and their environmental controls. Gross primary production (GPP) is partly determined by the ratio of intercellular to ambient CO2 concentrations (χ), which can be inferred from leaf stable carbon isotope ratios (δ13C). The effect of nitrogen (N) supply on GPP is mediated by the allocation of carbon (C) to leaves, while leaf-level photosynthetic traits (e.g. χ and photosynthetic capacity) and morphological traits (e.g leaf size and leaf mass per area, LMA) are modified or constrained by climate. The amount of N in the leaf is related in part to the quantity of photosynthetic enzymes, indexed by carboxylation capacity at standard temperature (Vcmax,25), and in part to LMA – as all plant tissues, including cell walls, contain N. Plant N isotope ratios (δ15N) are sensitive to the partitioning of N loss from soil between the gaseous and leaching pathways (a balance that is strongly under climatic control), and also to plants’ N uptake strategy (mycorrhizal type or symbiotic N-fixation).

Plant and ecosystem data collected on the Northeast China Transect (NECT) are used here to test a series of quantitative trait predictions based on optimality principles. The NECT is characterized by a long continuous gradient in precipitation and community structure, ranging from moist forests in the east, via grasslands, to semi-desert in the west. We investigated the relationships among leaf traits, ecosystem properties and N loss pathways, including χ, LMA, leaf N per unit area (Narea), leaf area index (LAI, inferred from satellite data), above-ground biomass, and δ15N. The calculations involve testable predictions of intermediate quantities, including community-mean photosynthetic capacity and GPP. By reproducing observed patterns of trait variation along the NECT, this analysis has provided empirical support for an emerging, optimality-based theory for the coupling of C and N cycles in terrestrial ecosystems.


How to cite: Ding, R., Dong, N., Ni, J., and Prentice, I. C.: Optimal trait theory: testing predictions on the Northeast China Transect, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1752,, 2022.


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