Responses of Pinus massoniana and Pinus taeda to freezing in temperate forests in central China

Abstract

Masson pine (Pinus massoniana Lamb.), a native species widely distributed in temperate forests in central China, and Loblolly pine (Pinus taeda L.), an exotic tree species introduced to China from southeastern United States, are dominant evergreen conifers that play a pivotal role in maintaining forest structure and functions for the region. We examined the effects of freezing on these species with chlorophyll fluorescence and electrolyte leakage using both field- and laboratory-based experiments in September 2009 and January 2010, respectively. We found that freezing could cause a greater impact on the Loblolly pine than the Masson pine. Although the two species showed similar values of F _v /F _m and electrolyte leakage before freezing, the Masson pine needles showed lower F _v /F _m and higher electrolyte leakage ratios than those of the Loblolly pine when treated in low temperatures (−15 to 0°C). We also found that cold-acclimation was crucial for both species to adapt to low temperatures with the F _v /F _m ratio decreased approximately by 80% in the first freezing hour for the non-acclimated needles of both species while the cold-acclimated needles showed little changes in the F _v /F _m ratio. This finding is also supported by our measurements of electrolyte leakage. These results suggest that the Loblolly pine could be more susceptible to freezing damages than the Masson pine in central China.

Keywords:

• Chlorophyll fluorescence
• cold-acclimation
• electrolyte leakage
• freezing damage
• Loblolly pine
• Masson pine
• pigments
• soluble sugar content
• superoxide dismutase activity

Acknowledgements

We thank Dr Mats Hannerz and an anonymous reviewer for their constructive comments and suggestions on revising the manuscript. We gratefully acknowledge Dr Hengzhi Huang for reading the manuscript and providing valuable comments and Dr Nicholas S. Skowronski for improving the English language of the manuscript. We also thank Mr Denglong Ha, Mr Tao Zhang, and Ms Dan Liu for their field assistance. This research was partially supported by the National Key Research and Development Program (2010CB833500 and 2012CB417103). The Chinese Academy of Sciences also supported Ming Xu's work through the Bairen Program.