Assessing the role of light in flooding tolerance for tree species recommendation in the restoration of riparian subtropical forests

Key message The mechanisms of morpho-physiological adaptation to different conditions of light and flooding are species-specific; however, light is more responsive than flooding for two species of the genus Eugenia. The frequency of flooding in subtropical riverine forests is responsible for the occurrence of the tree species, being associated with the topographic gradient and canopy opening. Flooding tolerance may vary between species and is associated with the successional restoration group. We tested the combination of flooding and light intensity in Eugenia involucrata and Eugenia uniflora, to select ecophysiological traits for recommendation in restoration projects. The plants were initially acclimated to sun and shade conditions, and, after, both sun and shade treated plants were exposed to well-watered and partial flooding as water treatments. Gas exchange, carboxylation efficiency, chlorophyll index and morphological traits were determined after 12 days of imposition of water treatments. The combination of high light intensity and flooding reduced the stomatal conductance and transpiration of E. involucrata. It was also observed a reduction in root diameter and mass accumulation. In E. uniflora, it was observed that sun plants reduced the photosynthetic efficiency with lower carboxylation efficiency. However, E. uniflora under sun and flood treatment presented greater investment in shoot diameter and mass accumulation. In both species, no differences were observed in gas exchange in plants under flood and shade conditions. Both species can be considered tolerant to the combination of high light and flood, but due to the root hydraulic limitation of E. involucrata and the higher capacity of biomass accumulation of E. uniflora in sun and flooded treated plants, E. uniflora is more recommended in restoration projects of subtropical forests. In addition, the results indicate that the light was more responsive in relation to flooding for the evaluated species.

Automated summary

The mechanisms of morpho-physiological adaptation to different conditions of light and flooding are species-specific, with light being more responsive than flooding for the evaluated species of the genus Eugenia. Flooding frequency in subtropical riverine forests is associated with tree species occurrence, topographic gradient, and canopy opening. Flooding tolerance varies between species and is linked to successional restoration groups. Our study tested the effects of flooding and light intensity on Eugenia involucrata and Eugenia uniflora, revealing that both species are tolerant to the combination of high light and flood. However, due to differences in root hydraulic limitation and biomass accumulation capacity, E. uniflora is more recommended for restoration projects in subtropical forests. The results also highlight that light has a greater impact compared to flooding for the evaluated species.