The combined analysis of stable carbon and oxygen is a promising way to investigate tree physiological responses to environmental changes. However, there are only few studies that investigated the tree-ring carbon and oxygen isotope variations in subtropical and tropical areas in southwestern China.

Researchers from Xishuangbanna Tropical Botanical garden (XTBG) and University of Erlangen- Nürnbergv analyzed the tree-ring stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotope variations in the earlywood and latewood of two pine species (Pinus kesiya and Pinus armandii) from secondary forest and the natural forest. They aimed to study whether the earlywood and latewood of the two pine species differed in their δ¹³C and δ¹⁸O and investigate whether there were differences in intrinsic water use efficiency (iWUE) of pine species from the secondary forest and the natural forest and their response to elevated CO_2.

The researchers found a strong carry-over effect for δ¹³C in both secondary forest pine species P. kesiya and natural forest pine species P. armandii. There was no significant difference between earlywood and latewood for either δ¹³C or δ¹⁸O in P. kesiya. Both δ¹³C and δ¹⁸O in the earlywood of P. kesiya were significantly higher than those of latewood in P. armandii. The results showed that P. armandii had slightly higher intrinsic water use efficiency (iWUE) than that of P. kesiya.

Water use efficiency of both pine species increased, but with a higher rate in P. kesiya. δ¹³C variations in earlywood and latewood represented a site-specific or species-specific climate signals. δ¹⁸O variations showed strong coherence. δ¹⁸Oin earlywood of both pinespecies was negatively correlated with May relative humidity, whereas δ¹⁸Oin latewood of both species had a strong significant autumn precipitation signal.

The results revealed slightly higher intrinsic water use efficiency in natural forest pine species than in secondary forest pine species, and separating earlywood and latewood of for δ¹⁸O analyses could provide seasonally distinct climate signals in southwestern China.

  The study entitled “Earlywood and latewood stable carbon and oxygen isotope variations in two pine species in southwestern China during the recent decades” has been published in Frontiers in Plant Science.

Contact

FAN Zexin  Ph.D Principal Investigator

Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China
E-mail: fanzexin@xtbg.org.cn