Effects of Drought and Flooding on Growth and Physiology of Cinnamomum camphora Seedlings

In the context of climate change, future patterns of precipitation are expected to increase the intensity and frequency of drought and flooding stress. This is also likely to result in more frequent flooding-drought alternation events. Drought and flooding stress can have negative effects on tree morphology, physiology, and biochemistry, which can potentially pose long-term threats to tree survival and further disrupt the stability of forest ecosystems. However, it remains unclear how trees would cope with these stressors and their alternations through growth and physiology responses. Potted seedlings of C. camphora were grown under a rainout shelter in the field with four water treatments for 40 days: well-watered (WW), drought stress (DS), flooding stress (FS) and flooding-drought alternation (FDF). Growth, leaf gas exchange, water potential, and biochemical traits were measured. Results show different seedling growth patterns under drought and flooding stress. Drought increased the root-to-shoot ratio (+25%) but flooding favored leaf growth (+33%). Decreases in photosynthesis under drought and flooding were mainly related to stomatal limitations, accompanied by abscisic acid accumulation under drought but not under flooding. Drought reduced water potential, and flooding-drought alternation only decreased water potential in its drought phase. Flooding treatment had no effect on water potential. Drought treatment increased the proline concentrations (+74%) and carbon isotopic composition (+3.7%), but all treatments had no effect on the concentrations of elements in leaves. Drought stress led to carbon depletion in both stem and root, whereas flooding stress primarily induced carbon depletion in the root. Flooding-drought alternation was accompanied by complex physiological responses, including physiological recovery when the stress (flood, drought) was relieved. Our results have shown the different effects of drought and flooding on the growth and physiology of C. camphora seedlings, emphasizing the need to consider specific water stress conditions in future studies and providing a theoretical basis for better management of this tree species in urban areas under variable rainfall patterns.

Automated summary

In the context of climate change, future patterns of precipitation are expected to increase the intensity and frequency of drought and flooding stress, leading to more frequent flooding-drought alternation events. The effects of these stressors on tree morphology, physiology, and biochemistry can pose long-term threats to tree survival and disrupt forest ecosystems. The study examined how C. camphora seedlings cope with drought, flooding, and alternation of the two through growth and physiological responses. Results showed different growth patterns under drought and flooding, with drought favoring root growth and flooding favoring leaf growth. Stomatal limitations were the main cause of decreased photosynthesis under both drought and flooding, accompanied by abscisic acid accumulation only under drought. Drought reduced water potential, while flooding-drought alternation decreased water potential only during the drought phase. Drought stress led to carbon depletion in both stem and root, while flooding stress primarily induced carbon depletion in the root. The study emphasizes the need to consider specific water stress conditions in future research and provides a basis for better management of C. camphora in urban areas under variable rainfall patterns.