Mountain peatlands in Hawaii show dynamic vegetation and North Pacific hydroclimate over the Holocene: molecular-isotopic evidence

Authors: David Beilman*, University of Hawaii, Charly Massa, University of Hawaii, Jon Nichols, LDEO Columbia University
Topics: Paleoenvironmental Change, Pacific Islands, Earth Science
Keywords: Hawaii, North Pacific, mountain ecosystems, wetlands, carbon, n-alkanes, isotopes
Session Type: Poster
Day: 4/5/2019
Start / End Time: 3:05 PM / 4:45 PM
Room: Lincoln 2, Marriott, Exhibition Level
Presentation File: No File Uploaded

Organic sediment cores from montane peatlands in Hawaii from two contrasting island locations were studied for multi-proxy evidence of ecological and hydroclimatic change. Substantial carbon accumulation and the onset of organic matter stabilization began around 10 ka BP (thousands of years before present) under wet conditions at both sites. Variable rates of peat formation occurred at both sites including fast rates of in carbon accumulation during the early Holocene that resulted in significant belowground carbon storage today of from 100-144 kg C m-2. Changes in sedimentary n-alkane chain length distributions, in the context of a growing library of modern leaf waxes from native Hawaii plants, show dynamic vegetation inputs over the Holocene. Although tropical mountain wet forests are often viewed as being generally stable relative to high-latitude counterparts, it is clear that litter inputs were not consistently from a single plant type or types, but shifted dynamically in their dominance in response to climate. Hydrogen stable isotope ratios in sedimentary C29 n-alkanes show negative departures in both mountain records that are consistent with increases in storm-derived rainfall. Differences in the hydrogen stable isotopes and the rate of carbon accumulation between the contrasting locations, both in timing and in absolute value, suggest that late Holocene aridification in Hawaii was driven by changes in winter storm activity.

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