Physiological and growth strategies of two Cariniana species in response to contrasting light availability

Cariniana legalis and C. estrellensis are tropical emergent trees of the Lecythidaceae family that occur naturally in different forest ecosystems and belong to different ecological groups. With the aim of providing information to better manage these two congeneric Cariniana species in secondary forest enrichment plantations, an experiment was conducted using potted plants for comparing the physiological and growth responses of young C. legalis and C. estrellensis plants under contrasting light radiation availabilities. Considering that these two congeneric species occur naturally in different forest ecosystems and belong to different ecological groups, we tested the hypothesis that young plants of C. legalis have more plastic responses of photosynthetic light response curves, anthocyanin content, growth and biomass allocation to contrasting light environments than C. estrellensis. Plants were grown for 105 days under three light conditions (26, 10 and 1 mol photons m⁻² day⁻¹), simulating the daily total photosynthetic photon flux density (PPFD) in large and small canopy gaps and in the forest understory, respectively. The photosynthetic responses to contrasting light availabilities were very similar for both species. Higher values for anthocyanin reflectance index (ARI), leaf mass per area (LMA), and changes in biomass allocation indicate that C. legalis has a greater capacity for acclimation to contrasting light environments than did C. estrellensis. In addition, a greater number of smaller leaves in C. legalis could be an advantage in the understory of forests subjected to constant changes in canopy openness through the opening and closing of small- and medium-sized canopy gaps. From a practical point of view, seedlings of C. estrellensis should be planted in more open forests with less dynamic changes in canopy gaps, and seedlings of C. legalis should be planted in forests with more fluctuations in the opening and closing of small and large canopy gaps.