Response of water use efficiency of Cryptomeria japonica to climate change in Lushan Mountain, Jiangxi Province of eastern China

  Objective  This study aimed to theoretically support the scientific assessment of the carbohydrate-water coupling connection of Cryptomeria japonica.

  Method  The water use efficiency (WUE) of Cryptomeria japonica was calculated using the tree-ring stable carbon isotope method in this study. Additionally, average temperatures (T), precipitation (W), average wind speeds (Ws), solar radiation (Rs), the drought index (SPEI, SPI, WI), and other climate change-related indicators were used to analyze the WUE of Cryptomeria japonica and its adaptation to climate change.

  Result  (1) From 1969 to 2018, the sequence of ¹³C values of Cryptomeria japonica tree rings in Lushan Mountain, Jiangxi Province of eastern China showed a downward trend; the variation range was −23.09‰ to −25.67‰, and the annual average was −24.55‰; the inter-annual value of Cryptomeria japonica WUE showed an upward trend; the variation range was 91.06 to 118.89 μmol/mol, with an annual average of 102.37 μmol/mol. (2) Correlation analysis revealed that the WUE of Cryptomeria japonica in Lushan Mountain was significantly correlated with the temperature in July, September to November of the previous year, February to June, and September to November of the current year, and significantly negatively correlated with the wind speed in July to December of the previous year and January to December of the current year. However, the solar radiation, precipitation, SPEI, WI, and SPI of each month had no significant impact on the WUE of Cryptomeria japonica on Lushan Mountain. (3)The multiple regression model analysis showed that the WUE of Cryptomeria japonica on Lushan Mountain was mainly related to Ws₁ (wind speed in January of the current year), T₃ (average temperature in March of the current year), T₉ (average temperature in September of the current year), T₋₉ (average temperature in September of the previous year), and Ws₁₂ (wind speed in December of the current year).

  Conclusion  T and Ws are the primary climatic variables affecting WUE of Cryptomeria japonica. The WUE of Cryptomeria japonica on Lushan Mountain is not significantly affected by W, Rs, or the drought indicators (SPI, SPEI and WI).