Hormetic effects of abiotic environmental stressors in woody plants in the context of climate change

Woody plants contribute to the stability and productivity of terrestrial ecosystems and are significantly affected by climate change. According to the concept of environmental hormesis, any environmental stressors can cause hormesis, that is, stimulation in low doses and inhibition in high doses. Numerous studies have demonstrated plant hormesis under low doses of various abiotic stressors. However, the hormetic responses of woody plants to abiotic stressors from climate change are insufficiently studied. This review analyses data on the stimulating effects of low doses of climate stressors in experiments and in real ecosystems. Numerous laboratory and field experiments show that single and combined exposure to various climate stressors (temperature, humidity, and elevated carbon dioxide concentrations) can cause hormesis in various species and functional types of woody plants, which can be accompanied by hormetic trade-offs and preconditioning. In addition, there is evidence of climate hormesis in woody plants in ecosystem conditions. Field experiments in various ecosystems show that elevated temperatures and/or precipitation or elevated carbon dioxide concentrations causing hormesis in dominant tree species can stimulate ecosystem productivity. Moreover, climate hormesis of the growth and reproduction of dominant forest tree species contributes to the spread of forests, that is, climate-driven ecological succession. The main commonalities of climate hormesis in woody species include: (1) Low-dose climate stressors cause hormesis in woody plants when strong (limiting) stressors do not affect plants or these limiting stressors are mitigated by climate change. (2) Hormesis can occur with the direct impact of climatic stressors on trees and with the indirect impact of these stressors on plants through other parts of the ecosystem. (3) Climate stressor interactions (e.g., synergism, antagonism) can affect hormesis. (4) Hormesis may disappear due to tree acclimatization with consequent changes in the range of tolerances to climate factors. This review highlights the need for targeted studies of climate hormesis in woody species and its role in the adaptation of forest ecosystems to climate change.