Comparison of Sungkai Tree-Ring Components and Meteorological Datafrom Western Java, Indonesia

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Comparison of Sungkai Tree-Ring Components andMeteorological Data from Western Java, Indonesia

Yumiko Watanabe∗1, Shigeki Tamura∗1, Takeshi Nakatsuka∗2, Suyako Tazuru∗3,Junji Sugiyama∗3, Bambang Subiyanto∗4, Toshitaka Tsuda∗3, and Takahiro Tagami∗1

∗1Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto UniversityKyoto 606-8502, Japan

E-mail: yumiko@kueps.kyoto-u.ac.jp∗2Graduate School of Environmental Studies, Nagoya University

Nagoya 464-8601, Japan∗3Research Institute for Sustainable Humanosphere, Kyoto University

Gokasho, Uji, Kyoto 611-0011, Japan∗4Center for Innovation, Indonesian Institute of Sciences

Jl. Gatot Subroto No.10, Jakarta 12710, Indonesia[Received October 10, 2012; accepted January 7, 2013]

In order to explore the potential of tree-ring compo-nents as climate proxies in Asian tropical area, weperformed a systematic comparison between temporalvariations in meteorological data – precipitation, rela-tive humidity and sunlight hours – and those in tree-ring parameters – ring width, mean earlywood vesselarea and δδδ 18O – in a sungkai disk collected from west-ern Java, Indonesia. Ring width shows a significantpositive correlation with precipitation in the last dryseason prior to growth period. Ring width is also cor-related inversely with sunlight hours in the last dryseason. Mean earlywood vessel area shows a signif-icant, positive correlation with precipitation and rel-ative humidity during the rainy season of growth pe-riod. The δδδ 18O and δδδ 13C time series of alpha-cellulosesamples, which divide each ring into three parts – ear-lywood, inner latewood and outer latewood – vary, fur-thermore, from 22 to 28 and from −−−28 to −−−24 ,respectively. δδδ 13C results show distinct annual cycles,for which values of earlywood are highest, graduallyfollowed by a decrease. Although δδδ 18O has no suchseasonal pattern, annual-averaged δδδ 18O records showan inverse correlation with precipitation and relativehumidity in the rainy season of growth period. As de-scribed above, multi-components of sungkai tree ringsare expected to be useful in paleoclimate reconstruc-tion on a seasonal scale.

Keywords: tree ring, ring width, vessel area, stable iso-tope geochemistry, α-cellulose

1. Introduction

The tropic plays a very important role as a globalheat engine that transports heat from the low to highlatitudes. Climate anomalies in the tropics, such as El

Nino-Southern Oscillation (ENSO), thus affect world-wide through teleconnection. The tropics is, accordingly,a crucial region for elucidating the global climate system.The history of meteorological observation is, however,only a few centuries long and available data is concen-trated in Europe and eastern North America (Parker et al.,2000). In order to quantitatively reconstruct the climateof the tropics, we need to establish a paleoclimate proxythat supplements instrumental records effectively.

As a paleoclimate proxy, tree-ring reconstruction hasthe great advantage of exact dating with an annual-resolution (McCarroll and Loader, 2004). Previous stud-ies have shown that tree-ring components, e.g., ringwidth, δ 18O in αcellulose and wood density, are usefulproxies in reconstructing paleoclimate. Paleoclimate re-construction based on tree rings is, however, very lim-ited in the tropics because it is difficult there to acquirelong-lived wood samples with annual tree rings. Thereare only small number of studies, especially in Indone-sia, such as D’Arrigo et al. (1994) and Poussart et al.(2004). D’Arrigo et al. (1994) show that the tree-ringwidth of teak is an effective proxy for ancient precipita-tion or dry season ENSO prior to growth period. Annual-averaged oxygen isotopic ratios of α-cellulose in two Ja-vanese teaks, in contrast, have high reproducibility, sug-gesting that teak δ 18O reflects external climate forcing,i.e., precipitation and/or relative humidity (Poussart et al.,2004).

In order to assess the reliability of tree-ring componentsas climate proxies in this study, we systematically com-pared between temporal variations in meteorological data– precipitation, relative humidity and sunlight hours – andin three parameters – ring width, mean earlywood ves-sel area and δ 18O – in sungkai tree rings collected fromwestern Java, Indonesia. Sungkai is a good candidate forreconstructing the paleoclimate in annual/seasonal reso-lution for the following reasons: it has distinct tree ringseven though it is a tropical tree species, it is a fast-growing

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Watanabe, Y. et al.

(a) (c)

(b)

Fig. 1. (a) Location of Serang, western Java, Indonesia. (b) Monthly precipitation at Serang (data from Badanmeteorologi, klimatologi, dan geofisika; BMKG). (c) SungkaiNAN7 disk sample. The boxed section is utilized forisotopic measurement.

tree (Ogata et al., 2008) although it is not so long-lived,and it is widely distributed in the Malay Peninsula, Suma-tra, Borneo and Java (Ogata et al., 2008).

2. Material and Methods

The sample analyzed is sungkai (Peronema canescensJack), which is closely related to teak (Tectona grandisLinn f.). This sample was collected from a site in Serang,western Java, Indonesia (Fig. 1a). As shown in Fig. 1b,monthly-averaged air temperature remains fairly constantthrough the year at Serang. In contrast, precipitationrecords for Serang show a large seasonal cycle, which os-cillated between the dry season from approximately Mayto October and the wet season from November to April, inconjunction with Intertropical Convergence Zone move-ment (Fig. 1b). The seasonal cycle of precipitation formsannual growth rings in sungkai.

Our sungkai sample was cut down in December of2004. The disk sample, which is named SungkaiNAN7(Fig. 1c), had 25 tree rings, showing that its growthspanned the interval from 1980 to 2004. The outsidering was primarily composed of conduits, showing thatthe ring was formed at the onset of the rainy season, i.e.,just before the felling in December of 2004. The tree-ring growth year is defined herein as the calendar year inwhich growth begins. We investigated the correlations be-tween tree-ring components and climate parameters dur-

ing 1988-2004 because the growth rate before 1987 ishigher than the rate after 1987.

We measured four components – ring width, mean ear-lywood vessel area, δ 13C and δ 18O – in SungkaiNAN7,as described below.

Ring width and mean earlywood vessel area: TheSungkaiNAN7 disk was scanned using a high-resolutionscanner (Fig. 1c). The digital image acquired was thenemployed for the measurement of ring width and meanvessel area in earlywood by using software from AdobePhotoshop and ImageJ (W. S. Rasband, ImageJ, U. S. Na-tional Institutes of Health, Bethesda, Maryland, USA1).In order to exclude the influences of anisotropic growth,we measured the area of the tree ring, then divided it bythe inner circumference, which was measured by ImageJ,to estimate the averaged ring width. Measured earlywoodvessel area was divided by the number of vessels to esti-mate mean earlywood vessel area.

δ 18O and δ 13C analyses in α-cellulose: Each tree ringwas divided into three parts, i.e., earlywood, inner late-wood and outer latewood. α-cellulose from each sam-ple was extracted by chemical procedures modified afterLoader et al. (1997), Nakatsuka et al. (2004); details aredescribed by Harada et al. (in preparation). Briefly, theextraction has three chemical procedures, as follows: [1]organic solvent extraction in acetone for 1 hr in an ul-trasonic bath [2] delignification consisting of a bleaching

1. http://rsb.info.nih.gov/ij/

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