Journal of Tropical Ecology



Impact of severe drought associated with the 1997–1998 El Niño in a tropical forest in Sarawak


Michiko  Nakagawa a1c1, Kenta  Tanaka a1, Tohru  Nakashizuka a2, Tatsuhiro  Ohkubo a3, Tsuyoshi  Kato a4, Teizou  Maeda a3, Kaori  Sato a5, Hideo  Miguchi a6, Hidetoshi  Nagamasu a7, Kazuhiko  Ogino a8, Stephen  Teo a9, Abang Abudul  Hamid a10 and Lee Hua  Seng a10
a1 Center for Ecological Research, Kyoto University, Kamitanakami-Hirano, Otsu, Shiga 520-2113 Japan
a2 Center for Ecological Research, Kyoto University, CREST, JST
a3 Faculty of Agriculture, Utsunomiya University, Ibaraki, Japan
a4 Faculty of Agriculture, Kyoto University, Kyoto, Japan
a5 Faculty of Natural Science, Niigata University, Niigata, Japan
a6 Faculty of Agriculture, Niigata University, Niigata, Japan
a7 Kyoto University Museum, Kyoto University, Kyoto, Japan
a8 Faculty of Environmental Science, Shiga Pre. University, Shiga, Japan
a9 Forest Research Center, Sarawak, 93762 Kuching, Sarawak, Malaysia
a10 Forest Department Sarawak, 93660 Kuching, Sarawak, Malaysia

Abstract

The impact of the unusually severe drought associated with the 1997–1998 El Niño on tropical forest dynamics in Sarawak, Malaysia was examined. Mortality during the non-drought period (1993–1997) in a core plot (1.38 ha) was 0.89 % y−1, while that during the drought period (1997–1998) in the same plot and a peripheral plot was 6.37 and 4.35 % y−1, respectively. The basal area lost in the drought interval was 3.4 times that of the annual incremental basal area in 1993–1997. Drought mortality was higher for the smaller trees, though it was less size dependent than the non-drought mortality. Dipterocarpaceae, which is the dominant family in the study plot, had a mortality 12–30 times higher in the drought than the non-drought period. There were no significant differences in mortality among the topographic types. From the results of a log-linear model (multi-factored contingency table), the death of trees was correlated with size class, indicating a change in the size-class structure of the forest. Thus, both the species composition and structure are totally affected by such an episodic drought even in a per-humid tropical forest.

(Accepted November 6 1999)


Key Words: disturbance; drought; El Niño; forest dynamics; mortality; size structure; tropical forest.

Correspondence:
c1 Center for Ecological Research, Kyoto University, Kamitanakami-Hirano, Otsu, Shiga 520-2113 Japan. E-mail: miko@ecology.kyotoo-u.ac.jp.