TREE-RING RESEARCH on TECTONA GRANDIS in NORTHERN THAILAND Nathsuda Pumijumnong, Dieter Eckstein & Ute Sass from a Network O

IAWA Journal, Vol. 16 (4),1995: 385-392

TREE-RING RESEARCH ON TECTONA GRANDIS IN NORTHERN THAILAND by Nathsuda Pumijumnong, Dieter Eckstein & Ute Sass Institute for Wood Biology, University of Hamburg, Leuschnerstrasse 9 1,0-2103 I Hamburg, Germany

SUMMARY

From a network of teak chronologies in northern Thailand, 75 trees with in one province were evaluated regarding their climatic signal. The raw tree-ring series revealed a high mean sensitivity of 0.50 and a moderate first-order autocorrelation of 0.48. The first principal component of the standardized data explained 44% of the total variation in the tree-ring data, indicating a considerable climatic influence on tree growth. The climate-growth relationship suggested that growth of teak in this study area is mainly controlled by rainfall from April to June. Thus, there is some promise that the whole network of teak chronologies in northern Thailand can contribute to reconstructing climate over at least the last three centuries. Key words: Teak, Tectona grandis L., growth periodicity, climatic signal, Thailand, dendrochronology, tree rings.

INTRODUCTION

Dendrochronological studies in the tropical and subtropical forest belt were for a long time believed impossible and impractical. The increasing demand for palaeoclimatic information stimulated dendrochronologists to extend their study areas from the southern and northern temperate zones towards the equator (Baas & Vetter 1989). One of the key phenomena for climatologists is the palaeomonsoon in southeast Asia. Dendro chronological research could contribute to a better understanding of the dynamics of this Southeast Asian monsoon. Earliest studies on periodic tree growth in the tropics extend back to Brandis in 1850 in India (Liese 1986). Later, Coster (1927) investigated the periodicity of diam eter growth for more than 200 tree species in Southeast Asia. A dendrochronological approach was first applied by Berlage (1931) on teak in Java. Most recently, promising results were reported for various tree species including Pinus and Podocarpus in Thai land (Buckley et al. 1995), teak in Indonesia (Jacoby & D' Arrigo 1990; D' Arrigo et al. 1994; Murphy 1994), Peronema canescens in Sarawak (Ohta, pers. comm.), and with various tropical tree species in India (Bhattacharyya et al. 1992). Our project is an attempt to establish a network of teak chronologies in northern Thailand and to evalu ate its potential for climate reconstruction.

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Fig. 1. Teak forest in the dry (top) and in the rainy season (bottom).

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STUDY AREA AND STUDY MATERIAL

Twenty-nine natural stands of teak were selected throughout the mountains of north ern Thailand, and cores taken from approx. 400 individual trees. Cross sections were obtained from a few fallen trees (Pumijumnong et al. 1995). The elevation of the tree sites is between 200 and 1000 m a.s.l.; the topography is from flat to extremely steep. Teak grows weIl in those areas where a dry season alternates with abundant rainfaIl (Fig. 1). In northern Thailand the southwest monsoon brings rain with a monthly aver age of 167 mm from April/May to October; from November to March it is dry with only 23 mm of rainfall per month (Fig. 2).

300 ~------~~

250 50

40 C ~ ~ 30 ~ g, E 20 ~

J F M A M J J A S 0 N D J F M A M JAS J 0 N D

Fig. 2. Annual distribution oftemperature (line) and rainfall (bars) in the Phrae province. Mean annual temperature is 26.3°C; mean annual sum of rainfall amounts to 1084 mrn.

At several meteorological stations, we obtained monthly total rainfaIl (1911-1990) and monthly mean temperature (1951-1990) data. A subgroup of 75 trees from six sites in the Phrae region were selected for preliminary den drochronological evaluation to assess the feas ibility of the whole project (Fig. 3).

Fig. 3. Map of Thailand with the whole study area (shadowed) and the Phrae province indicated.

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METHODS

Tree-ring widths were measured using program CATRAS (AnioI1983). Crossdating was conducted exclusively on the light table with plotted raw tree-ring series and with the cores under a binocular microseope. The accuracy of crossdating was subsequently checked using program COFECHA (Holmes 1983). At first this was done separately for every site, later all time-series were checked against each other. We used ARSTAN (Cook 1985, Holmes 1994) to detrend each individual series by fitting a negative ex ponential or a regression line and a relatively stiff 66-year spline. Autoregressive model ing was applied and the series were averaged, using the robust mean, to a white noise residual chronology. The climate-growth relationship was evaluated using the program RESPO (Lough 1984). It performs a simple correlation analysis and a stepwise multiple regression analysis using orthogonalized monthly precipitation and temperature data and the re sidual chronology.

Fig. 4. Surface of a seetion of a teak disk (left) and a micro-section (right).

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Tree-ring width (mm) 14

2~~~~ ______~

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990

Tree-ring index

5 r-----r_--~----_r----~--~r_--_r----_r----._----r_--_.----_,

3 , .... _.. __ ._.- ·· ,1--

Fig. 5. Crossdating of 15 tree-ring series ofteak from one site within the Phrae province. The top plot shows ring-width measurements; the lower plot shows the same series after standardization.

RESULTS

In Figure 4 the surfaee of a seetion of a teak disk together with a miero-seetion are shown. Crossdating was possible although diffieult and time-eonsuming (Fig. 5). Sev eral tree-ring series eould not be erossdated. It is obvious that the raw tree-ring series eontain mueh high-frequeney variability (mean sensitivity = 0.50) and fairly low auto eorrelation (r = 0.48). After the tree-ring measurements were detrended the average eorrelation between trees is r = 0.38 and the varianee explained by the first prineipal eomponent is 44%. For calculation of the climate-growth relationship the monthly rainfall and tempera ture is included from the previous Deeember to the eurrent Oetober from 1952 to 1990 (Fig. 6). There is a strong positive relationship between tree growth and rainfall in previous Deeember and from April to June of the eurrent year. This dependeney ean easily be illustrated by eomparing the tree-ring ehrononology with the time series of rainfall from April to June (Fig. 7). Above-average temperature generally had an ad verse effeet on radial growth of teak. The pronouneed negative eorrelation of the tem-

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Preclpit3tion 0.5 ,------0.4 0.3 I!o' 0.2 8 0. 1 iI'" 0 '"~ ·0. 1 o U ·0.2 ·0.3 ·0.4

·0.5 L.=-DC-'C-+-:-J.-n-+-::FC':'Cb--+-:-M:-ar-+cA'-p-r I-:'M""'.-y +-J:-u-n +-O-J u71+-c- Au-g-+-::--->""'o'-c,-

Tempcrature 0.5 .------0.4 0.3 -.; 0.2 8 U 01 ~ 0 h--L'--.,L---lJ-..t,-:~ .. ~"" ...----,..---h ...---\..--..,r---r '"t; ·0.1 o U ·0.2 ·0.3 ·0.4

·0.5 .Dec Jan Feb Mor Apr May Jun Jul Aug Sep Oe,

Fig. 6. Climate-growth relationship of teak in the Phrae province calculated for the period from 1952 to 1990. Growth variability explained by climate = 61 %; bars = simple correlation coef ficients, significant values hatched; line = multiple regression coefficients, significant values indicated by stars.

2.5 800

700 >< ~ 2 ~ "0 600 .§. .5 c >. 0 co '.::3 S! 1.5 500 .... c0 'a'" e 400 .~ -5 6. 01) c 300 ~ '1: § v '7 ~ 200 E-< 0.5 :c:0. 100 <

O~rrn~rrn~~~~rrn~rrnnTrrrr~~nn~rrn~rrrr~~~O 1910 1920 1930 1940 1950 1960 1970 1980 1990

Fig. 7. Comparison of the regional teak chronology of the Phrae province (thick line) and the time-series ofthe amount ofrainfall from May to lune from 1911 to 1990 (thin line).

Downloaded from Brill.com10/07/2021 11:48:30AM via free access Pumijumnong, Eckstein & Sass - Tree-rings in Tectona grandis in N Thailand 391 perature from April to June or July may well be an indirect effect, linked with the high demand of the trees for abundant rainfall during the same period. High temperature may increase the evapotranspiration and thus put the trees under drought stress.

CONCLUSIONS

The growth of teak in northern Thailand is mainly correlated with rainfall during the first half of the wet season (April through July), confirming the observation that cambial activity of most teak trees in 1994 started in April (Pumijumnong et al., unpubl.). This climate-growth relationship differs from the results of Berlage (1931) and J acoby and D' Arrigo (1990) who reported that teak in Java was relatively in sensitive to the amount of wet -season rainfall. Pant and Borgaonkar (1983), however, confirm the response of teak to rainfall in the rainy season for India. This clear signal at the beginning of the rainy season may be generally valid for the whole area of natural distribution of Tectona in the northern hemisphere. Therefore it is reasonable to begin establishing a network of teak chronologies from India to Viet nam as long as these valuable natural sources for palaeoclimatic information are still available. Such a network is already being developed (Pumijumnong et al. 1995). How ever, it is also urgently necessary to increase our knowledge and understanding of the periodic cambial activity of the trees and the sites under consideration. Prototypes of such studies were conducted by Venugopal and Krishnamurty (1987) for teak in India and Nobuchi et al. (1995) for Hopea odorata and Shorea henryana in Thailand. Such studies will result in a higher temporal resolution of the climate-tree growth relation ship and the partitioning of tree-ring width into subunits of ecophysiological meaning (Sass & Eckstein 1995).

ACKNOWLEDGEMENTS

We express OUf thanks to the Faculty of Environment and Resource Studies of the Mahidol University in Thailand, to the Royal Department of Forestry in Bangkok, Thailand, to many local fore sters for their help during the sampling expedition through northem Thailand in February 1992 as weil as to Richard Holmes and Henri Grissino-Mayer, Tueson, USA, for reading the manuscript. The German Academic Exchange Service (DAAD) financially supported this research.

REFERENCES

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