In high-altitude temperate forests, freeze-thaw cycles damage the hydraulic transport function of woody species by inducing embolisms in xylem conduits. Winter embolism may have severe negative effects on plant performance during the subsequent growing season if the impaired hydraulic transport function cannot be restored.
Some tree species mitigate the negative impacts of frost-induced xylem cavitation by restoring impaired hydraulic function via positive pressures. Positive pressures generated in the root and/or stem of some species (hereinafter referred to as ‘root pressure’ and ‘stem pressure’) are effective mechanisms for refilling of winter-embolized vessels. But some other species can generate neither root pressure nor stem pressure.
Two researchers of the Institute of Applied Ecology (IAE), the Chinese Academy of Sciences (CAS), Dr. YIN Xiaohan, Prof. HAO Guangyou and their international colleague Frank Sterck at the Wageningen University recently studied hydraulic traits and xylem anatomical characteristics of 18 tree species in Changbai Mountain Broad-leaved Korean pine (Pinus koraiensis) mixed forest. These species belong to three functional groups, that is, species that can generate both root and stem pressures (RSP), species that can generate root pressure only (RP), and species that do not generate positive xylem pressure (NP).
The researchers found that the three functional groups diverged substantially in hydraulic efficiency, resistance to drought-induced cavitation and resistance to frost fatigue. The divergence in xylem anatomical characteristics at both the tissue and pit levels also caused trade-offs between frost fatigue resistance, hydraulic efficiency and hydraulic safety across species groups. “Most notably, RSP and RP were more resistant to frost fatigue than NP, but this was at the cost of reduced hydraulic conductivity for RSP and reduced resistance to drought-induced cavitation for RP,” the researchers said.
The finding of this study provides a new perspective on exploring environmental adaptation mechanisms of temperate tree species.
The study, entitled “Divergent hydraulic strategies to cope with freezing in co-occurring temperate tree species with special reference to root and stem pressure generation” has been published in New Phytologist.
The study is financially supported by the National Natural Science Foundation of China, the National Key Research and Development Program of China.