The model of Pichancourt et al. (2014) (link) is primarily based on the life-history theory. According to this theory, biophysical constraints on the allocation of energy between reproduction, growth and self-maintenance are viewed as the primary explanation for why species do not possess arbitrary combinations of life-history traits (LHTs) between organs and life-stages, throughout the life cycle of the organism. These ultimately drive the population growth rate of species to adapt to their environmental conditions. To reflect this principle, the model is structured according to a multiple-tier approach to LHTs (Fig. 2 ).
The first tier of LHTs represents the specific vital rates of stage and size throughout the life cycle of a tree species (i.e., seed survival, germination, tree growth, survival and fertility). These traits are constrained by allometric traits that are assumed to be optimally defined by natural selection (the second tier of LHTs, as outlined by the scaling theory of ecology). Finally, the second tier of LHTs is itself constrained by the third tier—the metabolic LHTs—based on the different physiological processes, e.g., photosynthetic carbon assimilation, respiration, Vmax, Jmax, biomass turnover, water absorption, carbon biomass production (as outlined, e.g., by the metabolic theory of ecology).
For plant species, the theory also predicts that ~50% of the variability of most of the tree LHTs on Earth can ultimately be reduced to three ((van Bodegom, Douma & Verheijen, 2014 (link)): specific leaf area (SLA) (m2.kg−1); specific wood density (SWD) (kg.m−3); and seed size (SS) (kg)). Under this realistic assumption, species with similar values of these three LHTs share other similar 1–2- and 3-tier LHT and life-cycle strategies. Based on this organization, mathematical models can be developed to create a wide range of unique tree species life cycle strategies (see summary of models in Pichancourt et al. (2014) (link) and in van Bodegom, Douma & Verheijen (2014) (link)). In this article, computational capabilities limited our exploration to eight species, representing all the combinations between a range of extreme values of LHTs found in the literature (see Pichancourt et al., 2014 (link)): SLA (2.5–20 m2.kg−1); SWD (400–1,000 kg.m−3); and SS (10−7–10−3 kg per seed).
The first tier of LHTs represents the specific vital rates of stage and size throughout the life cycle of a tree species (i.e., seed survival, germination, tree growth, survival and fertility). These traits are constrained by allometric traits that are assumed to be optimally defined by natural selection (the second tier of LHTs, as outlined by the scaling theory of ecology). Finally, the second tier of LHTs is itself constrained by the third tier—the metabolic LHTs—based on the different physiological processes, e.g., photosynthetic carbon assimilation, respiration, Vmax, Jmax, biomass turnover, water absorption, carbon biomass production (as outlined, e.g., by the metabolic theory of ecology).
For plant species, the theory also predicts that ~50% of the variability of most of the tree LHTs on Earth can ultimately be reduced to three ((van Bodegom, Douma & Verheijen, 2014 (link)): specific leaf area (SLA) (m2.kg−1); specific wood density (SWD) (kg.m−3); and seed size (SS) (kg)). Under this realistic assumption, species with similar values of these three LHTs share other similar 1–2- and 3-tier LHT and life-cycle strategies. Based on this organization, mathematical models can be developed to create a wide range of unique tree species life cycle strategies (see summary of models in Pichancourt et al. (2014) (link) and in van Bodegom, Douma & Verheijen (2014) (link)). In this article, computational capabilities limited our exploration to eight species, representing all the combinations between a range of extreme values of LHTs found in the literature (see Pichancourt et al., 2014 (link)): SLA (2.5–20 m2.kg−1); SWD (400–1,000 kg.m−3); and SS (10−7–10−3 kg per seed).
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