Dynamic Holocene Vegetation and North Pacific Hydroclimate Recorded in a Mountain Peatland, Moloka‘i, Hawai‘i

An organic sediment core from the montane peatland Pēpēʻōpae on the Island of Molokaʻi, Hawaiʻi was studied for multi-proxy evidence of ecological and hydroclimatic change. Following a period of soil development, substantial carbon accumulation and the onset of organic matter stabilization began around 10 ka BP (thousands of years before present) under wet conditions. Continuous but variable peat formation was sustained throughout the Holocene, including maxima in carbon accumulation around 9 and 3 ka, that has resulted in a belowground carbon storage today of 144 kg C m-2. We used sedimentary n-alkane chain length distributions to reconstruct bog vegetation in the context of 14 species of modern bog plant n-alkanes. The peat was not formed by litter inputs from a single plant type or types, but inputs shifted dynamically in their dominance in response to climate. We generated a new chronology for previously-published pollen data from the study site, which showed a similar tempo and response of vegetation change in the forests upwind of the peatland. Hydrogen stable isotope ratios sedimentary C29 n-alkanes show negative departures around 9ka and 3ka consistent with increases in storm-derived rainfall.

Abstract licence: CC BY

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