Earlywood and Latewood Stable Carbon and Oxygen Isotope Variations in Two Pine Species in Southwestern China during the Recent Decades

Pei-Li Fu; Jussi Grießinger; Aster Gebrekirstos; Ze-Xin Fan; Achim Bräuning

doi:10.3389/fpls.2016.02050

Earlywood and Latewood Stable Carbon and Oxygen Isotope Variations in Two Pine Species in Southwestern China during the Recent Decades

Front Plant Sci. 2017 Jan 10:7:2050. doi: 10.3389/fpls.2016.02050. eCollection 2016.

Authors

Pei-Li Fu¹, Jussi Grießinger², Aster Gebrekirstos³, Ze-Xin Fan¹, Achim Bräuning²

Affiliations

¹ Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences Menglun, China.
² Institute of Geography, University of Erlangen-Nürnberg Erlangen, Germany.
³ Institute of Geography, University of Erlangen-NürnbergErlangen, Germany; World Agroforestry CentreNairobi, Kenya.

Abstract

Stable isotopes in wood cellulose of tree rings provide a high-resolution record of environmental conditions, yet intra-annual analysis of carbon and oxygen isotopes and their associations with physiological responses to seasonal environmental changes are still lacking. We analyzed tree-ring stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotope variations in the earlywood (EW) and latewood (LW) of pines from a secondary forest (Pinus kesiya) and from a natural forest (Pinus armandii) in southwestern China. There was no significant difference between δ¹³C_EW and δ¹³C_LW in P. kesiya, while δ¹³C_EW was significantly higher than δ¹³C_LW in P. armandii. For both P. kesiya and P. armandii, δ¹³C_EW was highly correlated with previous year's δ¹³C_LW, indicating a strong carbon carry-over effect for both pines. The intrinsic water use efficiency (iWUE) in the earlywood of P. armandii was slightly higher than that of P. kesiya, and iWUE of both pine species showed an increasing trend, but at a considerably higher rate in P. kesiya. Respective δ¹³C_EW and δ¹³C_LW series were not correlated between the two pine species and could be influenced by local environmental factors. δ¹³C_EW of P. kesiya was positively correlated with July to September monthly mean temperature (MMT), whereas δ¹³C_EW of P. armandii was positively correlated with February to May MMT. Respective δ¹⁸O_EW and δ¹⁸O_LW in P. kesiya were positively correlated with those in P. armandii, indicating a strong common climatic forcing in δ¹⁸O for both pine species. δ¹⁸O_EW of both pine species was negatively correlated with May relative humidity and δ¹⁸O_EW in P. armandii was negatively correlated with May precipitation, whereas δ¹⁸O_LW in both pine species was negatively correlated with precipitation during autumn months, showing a high potential for climate reconstruction. Our results reveal slightly higher iWUE 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.

Keywords: Asian summer monsoon; intra-annual resolution; intrinsic water use efficiency; stable carbon isotope; stable oxygen isotopes; subtropical pine species.