Holocene dynamics of tropical rainforest, climate, fire, human impact and land use in Sulawesi, Indonesia
Final Report Abstract
Present-day tropical montane rainforests in the area of the Lore Lindu National Park are rich in biodiversity. They are also an important source of ecosystem services for local populations inhabiting the area. Projected climate changes for this region include the strengthening of monsoon circulation and an increase in the frequency and magnitude of extreme rainfall and drought events (ENSO). The ecological consequences of these scenarios are hard to predict. Our palaeoecological and palaeoenvironmental studies provide a valuable contribution by showing how the vegetation has changed as a consequence of climate variability and human activities during the Holocene. The results from three sites along altitudinal and moisture gradients show that the upper montane rainforest composition radically changed around 6000 years ago when the Quintinia dominated forest disappeared in favour of the Podocarpaceae dominated composition we see today. Around the same time ENSO has changed, approaching the modern millennial scale amplitude and frequency. Moving downward, the mid-montane rainforest shows a unique composition, with Fagaceae having been the dominant family for at least the last 1500 years. However, the vegetation composition went through two dynamic phases characterised by the establishment of secondary forests in the area as a response to stress caused by human activities and/or long and frequent periods of drought. Fires were not part of the natural upper montane rainforest system despite the change in vegetation structure and composition, but were increasingly important at lower altitudes. The correlation between higher fire frequencies at Lake Kalimpaa and higher number of El Niño events recorded in Southeast Asia suggests that the mid-montane rainforests are more susceptible to fire when longer than normal and more frequent droughts occur. In conclusion, our results show that the present-day Podocarpaceae dominated upper-montane rainforest of Lore Lindu National Park is about 6000 years old and might be the result of increased millennial scale ENSO variability. While we have no record on when the Fagaceae dominated mid-montane rainforests was established, we could assess that the forest is more susceptible to fire during longer than normal periods of droughts. The forest seems to be more dynamic when disturbance due to more frequent El Niño events and human activities occurs.
Publications
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2012. Chapter 16: The megalithic landscape of central Sulawesi, Indonesia. Combining archaeological and palynological investigations. Dominik Bonatz, Andreas Reinecke, Mai Lin Tjoa-Bonatz (eds.): Crossing Borders in Southeast Asian Archaeology. Selected papers from the 13th International Conference of the European Association of Southeast Asian Archaeologists, Berlin, 2010. 2 vol. Singapore, NUS Press, 199-220
Kirleis W., Müller J., Kortemeier C., Behling H., Soegondho S.
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2012. Evaluating Late Holocene radiocarbon-based chronologies by matching palaeomagnetic secular variations to geomagnetic field models: an example from Lake Kalimpaa (Sulawesi, Indonesia). In: Jovane L., Herrero-Bervera E. Hinnov L.A., Housen B.A. (eds): Magnetic Methods and the Timing of Geological Processes. Geological Society, London, Special Publications, 373
Haberzettl T., St-Onge G., Behling H., Kirleis W.
