Analysis of leaf traits which can characterize pioneers and
shade-tolerants
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Our goal is to understand the variety of shade tolerance from the differences in leaf physiological and morphological traits, such as photosynthetic capacity, leaf mass per area (LMA), leaf lifespan, and biomass allocation ratio. To address it, we investigate how a whole-plant relative growth rate (RGR, biomass gain per biomass per a year) changes with leaf traits under various light availabilities by simulations and growth analysis. Plant species typically inhabit a high-light environment or a low-light environment are well known as “pioneers” or “shade-tolerants”. However, why they grow advantageously in a high- or low-light environment is not fully understood. Published data have shown that pioneers and shade-tolerants have different traits: pioneers grow faster but have a lower survival rate, while shade-tolerants grow slower but have a higher survival rate. That is “trade-off” between traits that contribute to enlarge RGR (e.g., small LMA) and to enlarge survival rate (e.g., large LMA). Such tendency is apparently constant at any light environment, so it is thought that advantageous species change depending on light availability. However, there are some exceptions: in cool temperate forests, evergreen conifers with a higher LMA have a larger RGR than deciduous trees in some cases; deciduous shrubs have low LMA but they seem to be shade tolerant. Previous studies have drawn conclusions on the basis of qualitative analysis. We think that quantitative analysis of the effect of leaf traits on RGR will show a new perception of traits that enlarge RGR at a certain light availability. In this talk, we demonstrate the results of simulations for the effect of leaf traits on RGR. From the results, we discuss the appropriate traits of pioneers or shade-tolerants. |
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