title: Earlywood and Latewood Stable Carbon and Oxygen Isotope Variations in Two Pine Species in Southwestern China during the Recent Decades.
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 δ13CEWand δ13CLWinP. kesiya, while δ13CEWwas significantly higher than δ13CLWinP. armandii. For bothP. kesiyaandP. armandii, δ13CEWwas highly correlated with previous year's δ13CLW, indicating a strong carbon carry-over effect for both pines. The intrinsic water use efficiency (iWUE) in the earlywood ofP. armandiiwas slightly higher than that ofP. kesiya, and iWUE of both pine species showed an increasing trend, but at a considerably higher rate inP. kesiya. Respective δ13CEWand δ13CLWseries were not correlated between the two pine species and could be influenced by local environmental factors. δ13CEWofP. kesiyawas positively correlated with July to September monthly mean temperature (MMT), whereas δ13CEWofP. armandiiwas positively correlated with February to May MMT. Respective δ18OEWand δ18OLWinP. kesiyawere positively correlated with those inP. armandii, indicating a strong common climatic forcing in δ18O for both pine species. δ18OEWof both pine species was negatively correlated with May relative humidity and δ18OEWinP. armandiiwas negatively correlated with May precipitation, whereas δ18OLWin 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.
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences Menglun, China.
authors.forename: Pei-Li
authors.initials: PL
authors.lastname: Fu
authors.affiliation: Institute of Geography, University of Erlangen-Nürnberg Erlangen, Germany.
authors.forename: Jussi
authors.initials: J
authors.lastname: Grießinger
authors.affiliation: Institute of Geography, University of Erlangen-NürnbergErlangen, Germany; World Agroforestry CentreNairobi, Kenya.
authors.forename: Aster
authors.initials: A
authors.lastname: Gebrekirstos
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences Menglun, China.
authors.forename: Ze-Xin
authors.initials: ZX
authors.lastname: Fan
authors.affiliation: Institute of Geography, University of Erlangen-Nürnberg Erlangen, Germany.
authors.forename: Achim
authors.initials: A
authors.lastname: Bräuning
keywords: Asian summer monsoon; intra-annual resolution; intrinsic water use efficiency; stable carbon isotope; stable oxygen isotopes; subtropical pine species