Lake Matano (2°29.1'S 121°20'E) in central Sulawesi, the deepest and one of the largest lakes in Indonesia, provides an excellent opportunity to reconstruct long-term hydrological and vegetation changes at the heart of the Maritime Continent within the tropical Western Pacific Warm Pool. We measured the carbon isotopic composition of terrestrial leaf waxes (δ13Cwax) in new sediment cores from Lake Matano to understand regional variations in vegetation and their interactions with local and high latitude climate forcings during the past 53 kyr. Variations in δ13Cwax record the expansion and contraction of C3 versus C4 vegetation as well as changes in plants' carbon and water use efficiency and, by inference, regional hydroclimate. During Marine Isotope Stages 1 and 3, more negative δ13Cwax values indicate that closed-canopy C3 rainforests predominated in Sulawesi, reflecting a wetter, less seasonal climate. In contrast, more positive δ13Cwax values record a terrestrial ecosystem with more abundant open canopy vegetation and possible expansion of C4 grasses between 29 and 14 ka BP, indicating that during Marine Isotope Stage 2, including the Last Glacial Maximum, the climate was more arid, likely with increased precipitation seasonality, in central Sulawesi. Comparison of our record with other paleovegetation and paleohydrological records from Sulawesi and nearby islands suggests coherent long-term hydrological changes in central Indonesia that appear to be sensitive to high latitude climate across glacial-interglacial boundaries. However, variations in the amplitude of the response of vegetation to these glacial-interglacial forcings highlight the importance of regional topographic control on climate and vegetation and suggest an important role for higher elevations in maintaining rainforest refugia during regionally arid time intervals when C4 savannas and grasslands expanded at lower elevations.
Bibliographical noteFunding Information:
We acknowledge financial support from the National Science Foundation ( NSF-EAR-1144623 ) to James M. Russell. We thank Anders Noren, Nigel Wattrus, Sinyo Rio, and Gerald Tamuntuan for field assistance, and PT Vale Indonesia for logistical support during our field work. Rafael Tarozo, Yongsong Huang, Bronwen Konecky, and Kassandra Costa are thanked for laboratory assistance and for discussions on interpretations of these data. Research permits to conduct fieldwork on the Malili Lakes were granted by the Indonesian Ministry of Research and Technology (RISTEK). We also thank two anonymous reviewers who provided substantial feedback on an earlier version of the manuscript and two other reviewers for the later version of the manuscript.
© 2015 Elsevier B.V.
Copyright 2015 Elsevier B.V., All rights reserved.
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