Tropical forest trees often exhibit strong growth variation among individuals within a species. Some trees are persistent fast growers while others grow slowly for long periods of time. In moist closed canopy forests, this persistent growth variation is probably due to differences in light availability. Persistent growth variation has important implications for modeling tree growth and demography. Fast-growing individuals have a higher chance of reaching reproductive size and do so at a much younger age than slow growers. They may therefore have a higher contribution to population growth (λ).

Here we illustrate the demographic importance of fast growers, using the example of the tropical rainforest tree Cedrela odorata in South America. We constructed an age-size matrix model that realistically reproduced observed growth differences among juveniles. As we expected, fast growers contributed disproportionately to λ: they had a 12-42% higher elasticity and a two times larger loop elasticity than slow growers. Similar disproportionate fitness contributions of fast and slow growers are expected for other long-lived tree species of which individuals experience different growing conditions for long periods of time.

Our results illustrate the need to account for persistent growth variation among individuals in tree growth predictions, demographic models and life history studies.