A long vegetation history from lowland Irian Jaya, Indonesia

Abstract

This paper reports the pollen analysis of a 10 m core from a mire at 780 m altitude and 2°S latitude on ultrabasic soils on a northern coastal range of New Guinea. The area is almost undisturbed by humans and the record is believed to cover about 60,000 yr B.P. The results show that montane forest grew around the site continously through the Late Pleistocene with a distinct increases in higher-altitude taxa from 25,000 to 10,500 yr B.P., the time of glacial maxima elsewhere. The invasion of the site by lower-altitude forest, which commenced at 10,500 yr B.P., was reversed after a few hundred years, and was not finally completed until about 7000 yr B.P. The results show that vegetation in the region has been sensitive to climatic change, the Pleistocene ecology being consistent with a temperature change of about 3–4°C. Times of change agree with other tropical areas even though the site climate was probably affected by changing sea levels. However, the tropical forest demonstrates overall long-term stability in which changes in dominance may reflect minor shifts in disturbance and tree longevity. A distinctive record of fine charcoal occurs after 10,900 yr B.P. but not at any level prior to that time. This shows that the forest was continously fire free for a very long time. the charcoal is probably an indication of anthropogenic disturbance which may correlate with the spread of agricultural innovation in lowland New Guinea. An increase in secondary species after 7000 yr B.P. may be a result of minor anthropogenic activity or the result of warmer conditions and shorter tree life in the lower-altitude forests.