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Harvard Forest Symposium Abstract 2019

  • Title: Deciduous larch at the southern edge of Siberian boreal zone response to climate—Part I: carbon budgets in a regional to global context
  • Primary Author: JiaLin Liu (Harvard University)
  • Additional Authors: J. William Munger (Harvard University)
  • Abstract:

    Siberia is a much more forested area than North America and Scandinavia. While the Siberia is greatly dominated by deciduous larches instead of evergreen conifers such as spruces and pines. However, few studies have characterized larch’s carbon exchanges, budgets and unique functional traits in a regional to global contexts. We present flux measurements from a larch site located in the southern edge of Siberian boreal ecozone. Ecosystems at the margin of Siberia are critical but remains vulnerable due to climate forcing, permafrost thawing, and ecosystem shifting. We find net carbon exchanges from larches are influenced by the seasonality of permafrost active layer, air temperature and humidity, and soil water availability. During periods when surface soils are fully thawed, larches are significant carbon sinks. In spring-thaw and fall-freeze transitions, there is weak carbon uptake at mid-day. While net carbon exchanges are near zero when the soil is completely frozen. We apply an empirical ecosystem functional model to quantify functional relationships between larch’s carbon balance and microclimatic drivers and extrapolate its carbon budgets over time and space. Functional traits in larches are very distinct from spruces and pines. Larches are stronger carbon sinks than evergreens due to their highest forest productivity with the lower respiration budgets. Carbon sinks in two Siberian larch subtypes show diverse magnitudes. A single site is unlikely representative of the regional baseline. Altogether, this study has crucial implications for the understanding of the global carbon cycle. Contributions of boreal larches to the regional and global carbon budgets are stronger than had been previously recognized. Next-step-work should account uncertainties incorporated with age dependence, interannual variability, and spatial heterogeneity in the boreal larch ecosystem, to uncover mechanism associated with climate-fire-vegetation-carbon feedbacks in controlling the dominance of larch in Siberia.

  • Research Category: Forest-Atmosphere Exchange